Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

Rewilding's social-ecological aims: Integrating coexistence into a rewilding continuum

This paper presents results from a grounded theory study of rewilding aims, addressing calls for broad scale studies of rewilding to contribute to the development of guidelines. The grounded theory draws from a broad set of data sourced from rewilding organizations, case studies, and research. Expressions from the data relating to rewilding aims and outcomes were coded. The results demonstrate the intentions for rewilding to affect systemic, ecological, and socio-cultural change. Outcomes to support rewilding aims are also identified. The aims and outcomes are presented under these headings in a social-ecological framework which offers a shared vision for rewilding. The significance of this research is that it demonstrates rewilding's multi-disciplinarity and engagement with systemic or transformative change. It addresses a perceived paradox between rewilding intervention and non-human autonomy, demonstrating that rewilding is not necessarily about removing human influence but affecting coexistence through more-than-human collaboration. A revised rewilding continuum integrating coexistence is proposed.

What moves large grazers? Habitat preferences and complementing niches of large herbivores in a Danish trophic rewilding area

Large herbivores (≥45 kg) fulfill key ecological functions. Since the Late Pleistocene megafauna diversity and abundances have declined sharply, with profound consequences for ecosystems. On this background the concept of trophic rewilding has emerged and is increasingly applied to restore natural disturbance regimes and trophic interactions, ultimately aiming to recreate self-sustaining, dynamic and diverse ecosystems. Effects of such efforts (e.g., more heterogeneous habitats) are evident, but herbivore space use, and the resulting distribution of effects on vegetation remain poorly understood. Here, we examine habitat selection of semi-feral water buffalos (Bubalus bubalis), horses (Equus ferus) and cattle (Bos taurus) in a Danish rewilding area. We modelled space use with remote sensed covariates, reflecting resources (vegetation greenness, distance to water) and infrastructure (distances to fences, paths, shelter). Seasonal differences and former land use were tested separately. We found large-herbivore space use to shift seasonally, reflecting food and water availability, and to be influenced by infrastructure and former land use. Horses reacted less to vegetation greenness and water than the two bovids. Cattle selected for green vegetation in summer, while buffalos showed the strongest association with water bodies. Overall, the three semi-feral herbivore species diverged in their habitat use both spatially and seasonally. This can be expected to translate to variable and complementary ecological impacts such as grazing, physical disturbances and habitat engineering. Such variable space use likely increases habitat heterogeneity and species richness. We therefore suggest that a diverse large-herbivore guild is key, both to understanding megafauna ecology and for successful rewilding efforts.

Where could climate-smart rewilding be located in Europe?

Climate-smart rewilding is a promising approach to ecological restoration that combines the benefits of dynamic and process-based restoration with carbon sequestration for climate change mitigation. However, little is known about suitable locations for climate-smart rewilding in Europe as there is a lack of continental scale, spatial assessments of where to rewild. We present an approach to map the potential for climate-smart rewilding in Europe by considering three dimensions: (1) Ecological potential representing the best conditions for restoring key ecological processes, (2) Carbon potential describing the potential for carbon sequestration, and (3) Land potential reflecting the societal (opportunity) costs of dedicating land to rewilding. Using these three dimensions, we map the climate-smart rewilding potential across Europe and analyse synergies and trade-offs between them. Our findings show that the potential for climate-smart rewilding is scattered across Europe with hotspots predominantly found in mountainous regions, such as the Alps and the Scottish Highlands. The Iberian Peninsula, parts of Scandinavia, the North of the UK, and the East of Europe, also show opportunities for climate-smart rewilding. The patterns highlight that high potential is not equally distributed across European countries, adding complexity to the actual implementation of measures to reach restoration targets. Furthermore, high potential areas are often characterised by a high potential for one dimension, with limited synergies between the ecological, carbon and land potential dimensions, emphasising the tension between competing land demands. The approach presented here offers valuable input for planning processes and the exploration of future scenarios.

Dracula's Menagerie Reloaded: Assessing the Relative Roles of Habitat and Interspecific Interactions in an Intact Mammalian Assemblage Using Structural Equation Modeling

Interspecific interactions play a central role in structuring animal communities and food webs. In particular, carnivores are important topdown regulators in ecological communities and the loss of carnivore species can have devastating ecosystem effects. Similarly, carnivore reintroductions are successful if the prey base is sufficient to support population growth, making the case for the importance of bottom-up regulation processes. As such, rewilding efforts targeted at restoring food webs and natural community regulation processes (trophic rewilding) have become increasingly popular. However, investigations of regulation processes in terrestrial vertebrate communities often take place in heavily altered systems, potentially biasing inference on the presence or importance of top-down versus bottom-up regulation processes. Here, we use a stable mammalian assemblage in the Romanian Carpathians to evaluate the relative importance of top-down and bottom-up processes and provide a benchmark for understanding the effects and the success of rewilding initiatives. To do so, we used camera trap data from two consecutive years in the Southern Romanian Carpathians and developed hypothesisbased interaction pathways for top-down and bottom-up regulation in a piecewise structural equation modeling (SEM) framework. Results from SEMs indicate that while both top-down (wolf and Eurasian lynx-driven) and bottom-up processes (driven by roe deer, red deer, wild boar and hare abundance) play important roles in shaping community structure, landscape characteristics (i.e., terrain ruggedness, road density, elevation, and forest cover) have a greater effect on both predators and prey. The results of this research have implications for rewilding efforts in Europe and globally. This study highlights the importance of preserving natural habitats, underscoring that effective species conservation and coexistence must go hand in hand with conserving natural spaces.

Semi-Feral Horse Grazing Benefits the Grassland Diversity of Flowering Plants Including a Pollinator-Promoting Indicator Species

European grasslands and their biodiversity are declining rapidly due to land use changes, which highlight the need to develop effective restoration strategies. This study investigates the impact of reintroducing the Swedish national horse breed (the Gotland Russ) on grassland plant diversity and evenness in abandoned agricultural landscapes in Southeast Sweden. Twelve horses were introduced into three 10-13-hectare enclosure replicates (four horses per enclosure) in a three-year (2014-2016) rewilding experiment. Plant species richness, evenness, and diversity were investigated in both grazed and un-grazed conditions. The results indicate that horse grazing significantly increased grassland plant species diversity and richness, with higher Shannon and Simpson's diversity indices in grazed areas. In addition, the abundance of white clover (Trifolium repens), a signal species beneficial to pollinators, increased significantly in grazed areas. These findings emphasize the need for integrating large herbivore grazing into ecological restoration practices. Considering the recently enacted EU Nature Restoration Law, which aims to restore 20% of Europe's degraded ecosystems by 2030, this research provides critical insights into scalable restoration methods. The implementation of restoration strategies that include large herbivores may enhance the resilience and biodiversity of European grasslands, thereby aligning with the EU's restoration goals.

Identifying Major Factors for Success and Failure of Conservation Programs in Europe

In Europe, various conservation programs adopted to maintain or restore biodiversity have experienced differing levels of success. However, a synthesis about major factors for success of biodiversity-related conservation programs across ecosystems and national boundaries, such as incentives, subsidies, enforcement, participation, or spatial context, is missing. Using a balanced scorecard survey among experts, we analyzed and compared factors contributing to success or failure of three different conservation programs: two government programs (Natura 2000 and the ecological measures of the Water Framework Directive) and one conservation program of a non-governmental organization (NGO; Rewilding Europe), all focusing on habitat and species conservation. The experts perceived the NGO program as more successful in achieving biodiversity-related aims than governmental conservation legislation. Among the factors perceived to influence the success of biodiversity conservation, several stood out: Biodiversity-damaging subsidies, external economic interests competing with conservation goals or policies conflicting with biodiversity conservation were recognized as major factors for the lack of conservation success. Outreach to raise societal interest and awareness as well as stakeholder involvement were perceived as closely related to the success of programs. Our expert survey demonstrated that external factors from economy and policy often hinder success of conservation programs, while societal and environmental factors rather contribute to it. This study implies that conservation programs should be designed to be as inclusive as possible and provides a basis for developing a standardized methodology that explicitly considers indirect drivers from areas such as economy, policy and society.

Parallels and discrepancies between non-native species introductions and human migration

Biological invasions and human migrations have increased globally due to socio-economic drivers and environmental factors that have enhanced cultural, economic, and geographic connectivity. Both processes involve the movement, establishment, and spread of species, yet unfold within fundamentally different philosophical, social and biological contexts. Hence, studying biological invasions (invasion science) and human migration (migration studies) presents complex parallels that are potentially fruitful to explore. Here, we examined nuanced parallels and differences between these two phenomena, integrating historical, socio-political, and ethical perspectives. Our review underscores the need for context-specific approaches in policymaking and governance to address effectively the challenges and opportunities of human migration and harm from biological invasions. We suggest that approaches to studying the drivers of biological invasions and human migration provide an excellent opportunity for transdisciplinary research; one that acknowledges the complexities and potential insights from both fields of study. Ultimately, integrating natural and social sciences offers a promising avenue for enriching the understanding of invasion biology and migration dynamics while pursuing just, equitable, and sustainable solutions. However, while human migration is a clear driver of biological invasions, drawing on principles from biological invasions to understand past and current human migration risks oversimplification and the potential for harmful generalisations that disregard the intrinsic rights and cultural dynamics of human migrations. By doing so, we provide insights and frameworks to support the development of context-specific policies that respect human dignity, foster cultural diversity, and address migration challenges in ways that promote global cooperation and justice. This interdisciplinary approach highlights the potential for transdisciplinary research that acknowledges complexities in both fields, ultimately enriching our understanding of invasion biology and migration dynamics while pursuing equitable and sustainable solutions.

Rewilded horses in European nature conservation - a genetics, ethics, and welfare perspective

In recent decades, the integration of horses (Equus ferus) in European rewilding initiatives has gained widespread popularity due to their potential for regulating vegetation and restoring natural ecosystems. However, employing horses in conservation efforts presents important challenges, which we here explore and discuss. These challenges encompass the lack of consensus on key terms inherent to conservation and rewilding, the entrenched culture and strong emotions associated with horses, low genetic diversity and high susceptibility to hereditary diseases in animals under human selection, as well as insufficient consideration for the social behaviour of horses in wild-living populations. In addition, management of wild-living horses involves intricate welfare, ethics and legislative dimensions. Anthropocentric population-control initiatives may be detrimental to horse group structures since they tend to prioritise individual welfare over the health of populations and ecosystems. To overcome these challenges, we provide comprehensive recommendations. These involve a systematic acquisition of genetic information, a focus on genetic diversity rather than breed purity and minimal veterinary intervention in wild-living populations. Further, we advise allowing for natural top-down and bottom-up control - or, if impossible, simulating this by culling or non-lethal removal of horses - instead of using fertility control for population management. We advocate for intensified collaboration between conservation biologists and practitioners and enhanced communication with the general public. Decision-making should be informed by a thorough understanding of the genetic makeup, common health issues and dynamics, and social behaviour in wild-living horse populations. Such a holistic approach is essential to reconcile human emotions associated with horses with the implementation of conservation practices that are not only effective but also sustainable for the long-term viability of functional, biodiverse ecosystems, while rehabilitating the horse as a widespread wild-living species in Europe.

Dependence of Europe's most threatened mammals on movement to adapt to climate change

Current rates of climate change and gloomy climate projections confront managers and conservation planners with the need to integrate climate change into already complex decision-making processes. Predicting and prioritizing climatically stable areas and the areas likely to facilitate adaptive species' range adjustments are important stages in maximizing conservation outcomes and rationalizing future land management. I determined, for the most threatened European terrestrial mammal species, the spatial adaptive trajectories (SATs) of highest expected persistence up to 2080. I devised simple spatial network indices for evaluation of species in those SATs: total persistence; proportion of SATs that offer in situ adaptation (i.e., stable refugia); number of SATs converging in a site; and relationship between SAT convergence and persistence and protected areas, the Natura 2000 and Emerald networks, and areas of low human disturbance. I compared the performance of high-persistence SATs with a scenario in which each species remained in the areas with the best climatic conditions in the baseline period. The 1000 most persistence SATs for each of the 39 species covered one fifth of Europe. The areas with the largest adaptive potential (i.e., high persistence, stability, and SAT convergence) did not always overlap for all the species. Predominantly, these regions were located in southwestern Europe, Central Europe, and Scandinavia, with some occurrences in Eastern Europe. For most species, persistence in the most climatically suitable areas during the baseline period was lower than within SATs, underscoring their reliance on adaptive movements. Importantly, conservation areas (particularly protected areas) covered only minor fractions of species persistence among SATs, and hubs of spatial climate adaptation (i.e., areas of high SAT convergence) were seriously underrepresented in most conservation areas. These results highlight the need to perform analyses on spatial species' dynamics under climate change.

De-extinction beyond species: Restoring ecosystem functionality through large herbivore rewilding

This perspective positions rewilding as a novel approach to ecosystem restoration, emphasising the restoration of natural processes to create self-willed ecosystems. Central to European rewilding is the de-domestication of cattle and horses to act as functional analogues of the extinct aurochs and wild horses. This de-extinction pathway shifts the focus from the loss of species to the loss of their ecological roles caused by human actions commencing millennia ago. The focus on restoring functional effects provides a strong policy rationale for large herbivore de-domestication, aligning with nature-based solutions to address environmental challenges. This alignment requires a pragmatic approach that prioritises the restoration of ecosystem functions over genetic purity and offers flexibility and scalability in rewilding efforts. I argue that creating a new category of 'ecosystem engineer' livestock is more effective than seeking wild status for these animals. As they are released into recovering ecosystems, de-domesticated large herbivores are recreating their ecological roles, 'life-spheres' and interactions. These processes open new avenues in both extinction discourse and ecological theory and encourage us to explore how de-extinct species can drive the recovery of European ecosystems.

Advancing terrestrial ecology by improving cross-temporal research and collaboration

Ecology spans spatial and temporal scales and is inclusive of the history of life on Earth. However, research that occurs at millennial timescales or longer has historically been defined as paleoecology and has not always been well integrated with modern (neo-) ecology. This bifurcation has been previously highlighted, with calls for improved engagement among the subdisciplines, but their priority research areas have not been directly compared. To characterize the research agendas for terrestrial ecological research across different temporal scales, we compared two previous studies, Sutherland and colleagues (2013; neoecology) and Seddon and colleagues (2014; paleoecology), that outlined priority research questions. We identified several themes with potential for temporal integration and explored case studies that highlight cross-temporal collaboration. Finally, a path forward is outlined, focusing on education and training, research infrastructure, and collaboration. Our aim is to improve our understanding of biodiversity patterns and processes by promoting an inclusive and integrative approach that treats time as a foundational concept in ecology.

Avian Island Radiations Shed Light on the Dynamics of Adaptive and Nonadaptive Radiation

Understanding the mechanisms underlying species formation and differentiation is a central goal of evolutionary biology and a formidable challenge. This understanding can provide valuable insights into the origins of the astonishing diversity of organisms living on our planet. Avian evolutionary radiations on islands have long fascinated biologists as they provide the ideal variation to study the ecological and evolutionary forces operating on the continuum between incipient lineages to complete speciation. In this review, we summarize the key insights gained from decades of research on adaptive and nonadaptive radiations of both extant and extinct insular bird species. We present a new comprehensive global list of potential avian radiations on oceanic islands, based on published island species checklists, taxonomic studies, and phylogenetic analyses. We demonstrate that our understanding of evolutionary processes is being greatly enhanced through the use of genomic tools. However, to advance the field, it is critical to complement this information with a solid understanding of the ecological and behavioral traits of both extinct and extant avian island species.

Framing challenges and polarized issues in invasion science: toward an interdisciplinary agenda

In a hyperconnected world, framing and managing biological invasions poses complex and contentious challenges, affecting socioeconomic and environmental sectors. This complexity distinguishes the field and fuels polarized debates. In the present article, we synthesize four contentious issues in invasion science that are rarely addressed together: vocabulary usage, the potential benefits of nonnative species, perceptions shifting because of global change, and rewilding practices and biological invasions. Researchers have predominantly focused on single issues; few have addressed multiple components of the debate within or across disciplinary boundaries. Ignoring the interconnected nature of these issues risks overlooking crucial cross-links. We advocate for interdisciplinary approaches that better integrate social and natural sciences. Although they are challenging, interdisciplinary collaborations offer hope to overcome polarization issues in invasion science. These may bridge disagreements, facilitate knowledge exchange, and reshape invasion science narratives. Finally, we present a contemporary agenda to advance future research, management, and constructive dialogue.

Preventing extinction in an age of species migration and planetary change

International and national conservation policies almost exclusively focus on conserving species in their historic native ranges, thus excluding species that have been introduced by people and some of those that have extended their ranges on their own accord. Given that many of such migrants are threatened in their native ranges, conservation goals that explicitly exclude these populations may overlook opportunities to prevent extinctions and respond dynamically to rapidly changing environmental and climatic conditions. Focusing on terrestrial mammals, we quantified the number of threatened mammals that have established new populations through assisted migration (i.e., introduction). We devised 4 alternative scenarios for the inclusion of assisted-migrant populations in mainstream conservation policy with the aim of preventing global species extinctions. We then used spatial prioritization algorithms to simulate how these scenarios could change global spatial conservation priorities. We found that 22% (70 species out of 265) of all identified assisted-migrant mammals were threatened in their native ranges, mirroring the 25% of all mammals that are threatened. Reassessing global threat statuses by combining native and migrant ranges reduced the threat status of 23 species (∼33% of threatened assisted migrants). Thus, including migrant populations in threat assessments provides a more accurate assessment of actual global extinction risk among species. Spatial prioritization simulations showed that reimagining the role of assisted-migrant populations in preventing species extinction could increase the importance of overlooked landscapes, particularly in central Australia, Europe, and the southwestern United States. Our results indicated that these various and nonexhaustive ways to consider assisted-migrant populations, with due consideration of potential conservation conflicts with resident taxa, may provide unprecedented opportunities to prevent species extinctions.

Global synthesis indicates widespread occurrence of shifting baseline syndrome

As environmental degradation continues at local, regional, and global levels, people's accepted norms for natural environmental conditions are likely to decline. This phenomenon, known as shifting baseline syndrome (SBS), is increasingly recognized as a likely major obstacle to addressing global environmental challenges. However, the prevalence of SBS remains uncertain. We conducted an extensive systematic review, synthesizing existing research on people's perceived environmental baselines. Our analysis, based on 73 case studies, suggests that SBS is a widespread global phenomenon, occurring across diverse socioeconomic, environmental, and cultural settings. We observed that younger individuals tend to hold lower environmental baselines across various environmental contexts, including climate change, natural resource depletion, biodiversity loss, and pollution. An upward shift in perceived environmental baselines among younger generations was rarely observed. These results underscore the challenge that SBS poses when policy and management responses to environmental degradation are influenced by perceived natural environmental norms.

Expanding European protected areas through rewilding

Rewilding seeks to address biodiversity loss by restoring trophic interactions and fostering self-regulating ecosystems. Although gaining traction in Europe and North America, the extent to which rewilding can meet post-2020 protected-area targets remains uncertain. We formulated criteria to map suitable areas for rewilding by identifying large tracts of land with minimal human disturbances and the presence of key mammal species. We find that one-quarter of Europe, approximately 117 million hectares (ha), is compatible with our rewilding criteria. Of these, 70% are in cooler climates. Passive rewilding opportunities, focused on managing existing wilderness, are predominant in Scandinavia, Scotland, the Iberian Peninsula, and notably in the Baltic states, Ireland, and southeastern Europe. Active rewilding opportunities, marked by reintroduction of absent trophic guilds, are identified in Corsica, Sardinia, southern France, and parts of the Netherlands, Denmark, Sweden, and Norway. Our mapping supports European nations in leveraging land abandonment to expand areas for nature conservation, aligning with the European Biodiversity Strategy for 2030. Nevertheless, countries with limited potential for rewilding should consider alternative conservation strategies.

Economics of rewilding

Rewilding, a concept often defined as an open-ended approach to ecological restoration that aims to establish self-sustaining ecosystems, has gained much interest in recent conservation science and practice. The economic dimensions of rewilding remain understudied, despite repeated calls for research, and we find that synthetic or programmatic contributions to the scientific literature are still missing. Here, we mined Scopus and Web of Science databases through a systematic review, looking for "rewilding" with various economic terms in the peer-reviewed literature, in the English language. We then screened out a 257 references-rich corpus with 14 variables, including the position of rewilding regarding positive and negative economic effects in specific sectors, and geographical or ecological foci. Our corpus amounts to ca. 40% of recent rewilding literature, with a clear emphasis on European study sites and the economic consequences of rewilding initiatives. Rewilding studies often refer to positive economic impacts on tourism and hunting, e.g., through higher income and employment rates, although very few studies properly quantify these. Conversely, most authors find rewilding harms farming, which is threatened by abandonment and damages by wildlife, raising interest in potential EU subsidy regimes. We highlight the surprising paucity of rewilding literature truly focusing on economics and/or providing detailed quantification-with remarkable exceptions. While rewilding's ecological relevance is no longer in question, demonstrating its economic benefits and sustainability will undoubtedly help scaling up. Thus, we advise rewilders to systematically measure and report investments and outcomes of rewilding initiatives, and to adopt common standards for cost and benefit assessments.

Freshwater megafauna shape ecosystems and facilitate restoration

Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross-ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food-web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature's contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human-megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna.

Environmental DNA metabarcoding reveals temporal dynamics but functional stability of arthropod communities in cattle dung

Terrestrial invertebrates are highly important for the decomposition of dung from large mammals. Mammal dung has been present in many of Earth's ecosystems for millions of years, enabling the evolution of a broad diversity of dung-associated invertebrates that process various components of the dung. Today, large herbivorous mammals are increasingly introduced to ecosystems with the aim of restoring the ecological functions formerly provided by their extinct counterparts. However, we still know little about the ecosystem functions and nutrient flows in these rewilded ecosystems, including the dynamics of dung decomposition. In fact, the succession of insect communities in dung is an area of limited research attention also outside a rewilding context. In this study, we use environmental DNA metabarcoding of dung from rewilded Galloway cattle in an experimental set-up to investigate invertebrate communities and functional dynamics over a time span of 53 days, starting from the time of deposition. We find a strong signal of successional change in community composition, including for the species that are directly dependent on dung as a resource. While several of these species were detected consistently across the sampling period, others appeared confined to either early or late successional stages. We believe that this is indicative of evolutionary adaptation to a highly dynamic resource, with species showing niche partitioning on a temporal scale. However, our results show consistently high species diversity within the functional groups that are directly dependent on dung. Our findings of such redundancy suggest functional stability of the dung-associated invertebrate community, with several species ready to fill vacant niches if other species disappear. Importantly, this might also buffer the ecosystem functions related to dung decomposition against environmental change. Interestingly, alpha diversity peaked after approximately 20-25 days in both meadow and pasture habitats, and did not decrease substantially during the experimental period, probably due to preservation of eDNA in the dung after the disappearance of visiting invertebrates, and from detection of tissue remains and cryptic life stages.

Wilding cities for biodiversity and people: a transdisciplinary framework

Accelerating urbanisation and associated lifestyle changes result in loss of biodiversity and diminished wellbeing of people through fewer direct interactions and experiences with nature. In this review, we propose the notion of urban wilding (the promotion of autonomous ecological processes that are independent of historical land-use conditions, with minimal direct human maintenance and planting interventions) and investigate its propensity to improve biodiversity and people-nature connections in cities. Through a large interdisciplinary synthesis, we explore the ecological mechanisms through which urban wilding can promote biodiversity in cities, investigate the attitudes and relations of city dwellers towards urban wild spaces, and discuss the integration of urban wilding into the fabric of cities and its governance. We show that favouring assembly spontaneity by reducing planting interventions, and functional spontaneity by limiting maintenance practices, can promote plant diversity and provide ecological resources for numerous organisms at habitat and city scales. These processes could reverse biotic homogenisation, but further studies are needed to understand the effects of wilding on invasive species and their consequences. From a socio-ecological perspective, the attitudes of city dwellers towards spontaneous vegetation are modulated by successional stages, with grassland and woodland stages preferred, but dense shrubby vegetation stages disliked. Wild spaces can diversify physical interactions with nature, and enrich multi-sensory, affective and cognitive experiences of nature in cities. However, some aspects of wild spaces can cause anxiety, feeling unsafe, and the perception of abandonment. These negative attitudes could be mitigated by subtle design and maintenance interventions. While nature has long been thought of as ornamental and instrumental in cities, urban wilding could help to develop relational and intrinsic values of nature in the fabric of cities. Wildness and its singular aesthetics should be combined with cultural norms, resident uses and urban functions to plan and design urban spatial configurations promoting human-non-human cohabitation. For urban wilding to be socially just and adapted to the needs of residents, its implementation should be backed by inclusive governance opening up discussion forums to residents and urban workers. Scientists can support these changes by collaborating with urban actors to design and experiment with new wild spaces promoting biodiversity and wellbeing of people in cities.

Ecological restoration and rewilding: two approaches with complementary goals?

As we enter the UN Decade on Ecosystem Restoration (2021-2030) and address the urgent need to protect and restore ecosystems and their ecological functions at large scales, rewilding has been brought into the limelight. Interest in this discipline is thus increasing, with a large number of conceptual scientific papers published in recent years. Increasing enthusiasm has led to discussions and debates in the scientific community about the differences between ecological restoration and rewilding. The main goal of this review is to compare and clarify the position of each field. Our results show that despite some differences (e.g. top-down versus bottom-up and functional versus taxonomic approaches) and notably with distinct goals - recovery of a defined historically determined target ecosystem versus recovery of natural processes with often no target endpoint - ecological restoration and rewilding have a common scope: the recovery of ecosystems following anthropogenic degradation. The goals of ecological restoration and rewilding have expanded with the progress of each field. However, it is unclear whether there is a paradigm shift with ecological restoration moving towards rewilding or vice versa. We underline the complementarity in time and in space of ecological restoration and rewilding. To conclude, we argue that reconciliation of these two fields of nature conservation to ensure complementarity could create a synergy to achieve their common scope.

Squamate scavenging services: Heath goannas (Varanus rosenbergi) support carcass removal and may suppress agriculturally damaging blowflies

Human-induced environmental change has caused widespread loss of species that support important functions for ecosystems and society. For example, vertebrate scavengers contribute to the functional health of ecosystems and provide services to agricultural landscapes by removing carcasses and associated pests. Widespread extirpation of native Australian mammals since the arrival of Europeans in Australia has removed many scavenging species from landscapes, while scavenging mammals such as European red foxes (Vulpes vulpes) have been introduced. In much of Australia, squamate reptiles are the largest native terrestrial scavengers remaining, where large native mammals are extinct and conservation management is being undertaken to remove invasive mammals. The contribution of reptiles to scavenging functions is not well understood. In this study, we investigated the ecosystem functions provided by large reptiles as scavengers to better understand how populations can be managed to support ecosystem services. We investigated the ecosystem services provided by vertebrate scavengers in Australian coastal mallee ecosystems, focusing on the heath goanna (Varanus rosenbergi), the only extant native terrestrial scavenger in the region. We carried out exclosure experiments, isolating the scavenging activity of different taxonomic groups to quantify the contribution of different taxa to scavenging services, specifically the removal of rat carcasses, and its impact on the occurrence of agriculturally damaging blowflies. We compared areas with different native and invasive scavenger communities to investigate the impact of invasive species removal and native species abundance on scavenging services. Our results indicated that vertebrate scavenging significantly contributes to carcass removal and limitation of necrophagous fly breeding in carcasses and that levels of removal are higher in areas associated with high densities of heath goannas and low densities of invasive mammals. Therefore, augmentation of heath goanna populations represents a promising management strategy to restore and maximize scavenging ecosystem services.

Future changes in society and climate may strongly shape wild large-herbivore faunas across Europe

Restoring wild communities of large herbivores is critical for the conservation of biodiverse ecosystems, but environmental changes in the twenty-first century could drastically affect the availability of habitats. We projected future habitat dynamics for 18 wild large herbivores in Europe and the relative future potential patterns of species richness and assemblage mean body weight considering four alternative scenarios of socioeconomic development in human society and greenhouse gas emissions (SSP1-RCP2.6, SSP2-RCP4.5, SSP3-RCP7.0, SSP5-RCP8.5). Under SSP1-RCP2.6, corresponding to a transition towards sustainable development, we found stable habitat suitability for most species and overall stable assemblage mean body weight compared to the present, with an average increase in species richness (in 2100: 3.03 ± 1.55 compared to today's 2.25 ± 1.31 species/area). The other scenarios are generally unfavourable for the conservation of wild large herbivores, although under the SSP5-RCP8.5 scenario there would be increase in species richness and assemblage mean body weight in some southern regions (e.g. + 62.86 kg mean body weight in Balkans/Greece). Our results suggest that a shift towards a sustainable socioeconomic development would overall provide the best prospect of our maintaining or even increasing the diversity of wild herbivore assemblages in Europe, thereby promoting trophic complexity and the potential to restore functioning and self-regulating ecosystems. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Unravelling the functional and phylogenetic dimensions of novel ecosystem assemblages

Human activities are causing taxonomic rearrangements across ecosystems that often result in the emergence of novel communities (assemblies with no historical representative). It is commonly assumed that these changes in the taxonomic makeup of ecosystems also inevitably lead to changes in other aspects of biodiversity, namely functional and phylogenetic diversity. However, this assumption is not always valid, as the changes in functional and phylogenetic composition resulting from taxonomic shifts depend on the level of redundancy in the evaluated community. Therefore, we need improved theoretical frameworks to predict when we can expect coordinated or decoupled responses among these three facets of biodiversity. To advance this understanding, we discuss the conceptual and methodological issues that complicate establishing a link between taxonomic rearrangements driven by human activities and the associated functional and phylogenetic changes. Here, we show that is crucial to consider the expected changes in functional and phylogenetic composition as communities are reshaped owing to human drivers of biodiversity loss to forecast the impacts of novel assemblages on ecosystem functions and the services they provide to humanity. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Navigating ecological novelty towards planetary stewardship: challenges and opportunities in biodiversity dynamics in a transforming biosphere

Human-induced global changes, including anthropogenic climate change, biotic globalization, trophic downgrading and pervasive land-use intensification, are transforming Earth's biosphere, placing biodiversity and ecosystems at the forefront of unprecedented challenges. The Anthropocene, characterized by the importance of Homo sapiens in shaping the Earth system, necessitates a re-evaluation of our understanding and stewardship of ecosystems. This theme issue delves into the multifaceted challenges posed by the ongoing ecological planetary transformation and explores potential solutions across four key subthemes. Firstly, it investigates the functioning and stewardship of emerging novel ecosystems, emphasizing the urgent need to comprehend the dynamics of ecosystems under uncharted conditions. The second subtheme focuses on biodiversity projections under global change, recognizing the necessity of predicting ecological shifts in the Anthropocene. Importantly, the inherent uncertainties and the complexity of ecological responses to environmental stressors pose challenges for societal responses and for accurate projections of ecological change. The RAD framework (resist-accept-direct) is highlighted as a flexible yet nuanced decision-making tool that recognizes the need for adaptive approaches, providing insights for directing and adapting to Anthropocene dynamics while minimizing negative impacts. The imperative to extend our temporal perspective beyond 2100 is emphasized, given the irreversible changes already set in motion. Advancing methods to study ecosystem dynamics under rising biosphere novelty is the subject of the third subtheme. The fourth subtheme emphasizes the importance of integrating human perspectives into understanding, forecasting and managing novel ecosystems. Cultural diversity and biological diversity are intertwined, and the evolving relationship between humans and ecosystems offers lessons for future stewardship. Achieving planetary stewardship in the Anthropocene demands collaboration across scales and integration of ecological and societal perspectives, scalable approaches fit to changing, novel ecological conditions, as well as cultural innovation. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Trophic rewilding as a restoration approach under emerging novel biosphere conditions

Rewilding is a restoration approach that aims to promote self-regulating complex ecosystems by restoring non-human ecological processes while reducing human control and pressures. Rewilding is forward-looking in that it aims to enhance functionality for biodiversity, accepting and indeed promoting the dynamic nature of ecosystems, rather than fixating on static composition or structure. Rewilding is thus especially relevant in our epoch of increasingly novel biosphere conditions, driven by strong human-induced global change. Here, we explore this hypothesis in the context of trophic rewilding - the restoration of trophic complexity mediated by wild, large-bodied animals, known as 'megafauna'. This focus reflects the strong ecological impacts of large-bodied animals, their widespread loss during the last 50,000 years and their high diversity and ubiquity in the preceding 50 million years. Restoring abundant, diverse, wild-living megafauna is expected to promote vegetation heterogeneity, seed dispersal, nutrient cycling and biotic microhabitats. These are fundamental drivers of biodiversity and ecosystem function and are likely to gain importance for maintaining a biodiverse biosphere under increasingly novel ecological conditions. Non-native megafauna species may contribute to these effects as ecological surrogates of extinct species or by promoting ecological functionality within novel assemblages. Trophic rewilding has strong upscaling potential via population growth and expansion of wild fauna. It is likely to facilitate biotic adaptation to changing climatic conditions and resilience to ecosystem collapse, and to curb some negative impacts of globalization, notably the dominance of invasive alien plants. Finally, we discuss the complexities of realizing the biodiversity benefits that trophic rewilding offers under novel biosphere conditions in a heavily populated world.

Reassessment of the risks of climate change for terrestrial ecosystems

Forecasting the risks of climate change for species and ecosystems is necessary for developing targeted conservation strategies. Previous risk assessments mapped the exposure of the global land surface to changes in climate. However, this procedure is unlikely to robustly identify priority areas for conservation actions because nonlinear physiological responses and colimitation processes ensure that ecological changes will not map perfectly to the forecast climatic changes. Here, we combine ecophysiological growth models of 135,153 vascular plant species and plant growth-form information to transform ambient and future climatologies into phytoclimates, which describe the ability of climates to support the plant growth forms that characterize terrestrial ecosystems. We forecast that 33% to 68% of the global land surface will experience a significant change in phytoclimate by 2070 under representative concentration pathways RCP 2.6 and RCP 8.5, respectively. Phytoclimates without present-day analogue are forecast to emerge on 0.3-2.2% of the land surface and 0.1-1.3% of currently realized phytoclimates are forecast to disappear. Notably, the geographic pattern of change, disappearance and novelty of phytoclimates differs markedly from the pattern of analogous trends in climates detected by previous studies, thereby defining new priorities for conservation actions and highlighting the limits of using untransformed climate change exposure indices in ecological risk assessments. Our findings suggest that a profound transformation of the biosphere is underway and emphasize the need for a timely adaptation of biodiversity management practices.

Resource partitioning in a novel herbivore assemblage in South America

Human-induced species declines and extinctions have led to the downsizing of large-herbivore assemblages, with implications for many ecosystem processes. Active reintroduction of extirpated large herbivores or their functional equivalents may help to reverse this trend and restore diverse ecosystems and their processes. However, it is unclear whether resource competition between native and non-native herbivores could threaten restoration initiatives, or to what extent (re)introduced species may influence local vegetation dynamics. To answer these questions, we investigated the diets of a novel South American herbivore assemblage that includes resident native species, reintroduced native species and introduced non-native species. We examined plant composition, diet breadth and the overlap between species to describe the local herbivory profile and the potential for resource competition. Using DNA metabarcoding on faecal samples (n = 465), we analysed the diets of the herbivore assemblage in the Rincón del Socorro rewilding area of Iberá National Park, Argentina. We compared the species richness of faecal samples, the occurrence of plant families/growth forms and the compositional similarity of samples (inter- and intraspecifically). Our results indicate species-level taxonomic partitioning of plant resources by herbivores in this system. Differences in sample richness, composition and diet breadth reflected a diverse range of herbivory strategies, from grazers (capybara) to mixed feeders/browsers (brocket deer, lowland tapir). Differences in diet compositional similarity (Jaccard) revealed strong taxonomic resource partitioning. The two herbivores with the most similar diets (Pampas deer and brocket deer) still differed by more than 80%. Furthermore, all but one species (axis deer) had more similar diet composition intraspecifically than compared to the others. Overall, we found little evidence for resource competition between herbivore species. Instead, recently reintroduced native species and historically introduced non-natives are likely expanding the range of herbivory dynamics in the ecosystem. Further research will be needed to determine the full ecological impacts of these (re)introduced herbivores. In conclusion, we show clear differences in diet breadth and composition among native, reintroduced and non-native herbivore species that may be key to promoting resource partitioning, species coexistence and the restoration of ecological function.

Meta-analysis shows that wild large herbivores shape ecosystem properties and promote spatial heterogeneity

Megafauna (animals ≥45 kg) have probably shaped the Earth's terrestrial ecosystems for millions of years with pronounced impacts on biogeochemistry, vegetation, ecological communities and evolutionary processes. However, a quantitative global synthesis on the generality of megafauna effects on ecosystems is lacking. Here we conducted a meta-analysis of 297 studies and 5,990 individual observations across six continents to determine how wild herbivorous megafauna influence ecosystem structure, ecological processes and spatial heterogeneity, and whether these impacts depend on body size and environmental factors. Despite large variability in megafauna effects, we show that megafauna significantly alter soil nutrient availability, promote open vegetation structure and reduce the abundance of smaller animals. Other responses (14 out of 26), including, for example, soil carbon, were not significantly affected. Further, megafauna significantly increase ecosystem heterogeneity by affecting spatial heterogeneity in vegetation structure and the abundance and diversity of smaller animals. Given that spatial heterogeneity is considered an important driver of biodiversity across taxonomic groups and scales, these results support the hypothesis that megafauna may promote biodiversity at large scales. Megafauna declined precipitously in diversity and abundance since the late Pleistocene, and our results indicate that their restoration would substantially influence Earth's terrestrial ecosystems.

Insights from a 31-year study demonstrate an inverse correlation between recreational activities and red deer fecundity, with bodyweight as a mediator

Human activity is omnipresent in our landscapes. Animals can perceive risk from humans similar to predation risk, which could affect their fitness. We assessed the influence of the relative intensity of recreational activities on the bodyweight and pregnancy rates of red deer (Cervus elaphus) between 1985 and 2015. We hypothesized that stress, as a result of recreational activities, affects the pregnancy rates of red deer directly and indirectly via a reduction in bodyweight. Furthermore, we expected non-motorized recreational activities to have a larger negative effect on both bodyweight and fecundity, compared to motorized recreational activities. The intensity of recreational activities was recorded through visual observations. We obtained pregnancy data from female red deer that were shot during the regular hunting season. Additionally, age and bodyweight were determined through a post-mortem examination. We used two Generalized-Linear-Mixed Models (GLMM) to test the effect of different types of recreation on (1) pregnancy rates and (2) bodyweight of red deer. Recreation had a direct negative correlation with the fecundity of red deer, with bodyweight, as a mediator as expected. Besides, we found a negative effect of non-motorized recreation on fecundity and bodyweight and no significant effect of motorized recreation. Our results support the concept of humans as an important stressor affecting wild animal populations at a population level and plead to regulate recreational activities in protected areas that are sensitive. The fear humans induce in large-bodied herbivores and its consequences for fitness may have strong implications for animal populations.

The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene

Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large non-mammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings.

Rewilding by large ungulates contributes to organic carbon storage in soils

The concept of rewilding, which focuses on managing ecosystem functions through self-regulation by restoring trophic interactions through introduced animal species with little human intervention, has gained increasing attention as a proactive and efficient approach to restoring ecosystems quickly and on a large scale. However, the science of rewilding has been criticized for being largely theory-based rather than evidence-based, with available data being geographically biased towards the Netherlands and Scandinavian countries, and a lack of objective data on rewilding effects on soil processes and C sequestration. In response to a call for data-driven experimental rewilding projects focused on national contexts, we collected unique data on the effects of large herbivore rewilding on soil properties from eight sites in the Czech Republic. These include sites with a wide range of edaphic characteristics that were grazed by Exmoor ponies, European bison, and back-bred Bos primigenius cattle (singly or in combination) for 2-6 years on areas ranging from ≈30 to ≈250 ha. Despite the relatively short duration of rewilding actions and considerable variability in the response rate of soil properties to grazing, our results indicate improved nutrient availability (evidenced by higher nitrification rate or higher soluble nitrogen concentration) and accelerated ecosystem metabolism (higher soil microbial biomass and dissolved carbon content). On longer-grazed pastures, rewilding contributed to soil carbon sequestration associated with increased water holding capacity and improved soil structure. However, other soil properties (reduced dissolved P concentration or total P content) showed signs of low P availability in the soils of the rewilding sites. Therefore, carcass retention should be considered where possible. Our data, although limited in number and geographic coverage, allow us to conclude that large ungulate rewilding has the potential to enhance soil carbon sequestration and related ecosystem services in rewilding areas. At the same time, we urge similar monitoring as an essential part of other rewilding projects, which will ultimately allow much more robust conclusions about the effects of this management on soils.

Functional traits-not nativeness-shape the effects of large mammalian herbivores on plant communities

Large mammalian herbivores (megafauna) have experienced extinctions and declines since prehistory. Introduced megafauna have partly counteracted these losses yet are thought to have unusually negative effects on plants compared with native megafauna. Using a meta-analysis of 3995 plot-scale plant abundance and diversity responses from 221 studies, we found no evidence that megafauna impacts were shaped by nativeness, "invasiveness," "feralness," coevolutionary history, or functional and phylogenetic novelty. Nor was there evidence that introduced megafauna facilitate introduced plants more than native megafauna. Instead, we found strong evidence that functional traits shaped megafauna impacts, with larger-bodied and bulk-feeding megafauna promoting plant diversity. Our work suggests that trait-based ecology provides better insight into interactions between megafauna and plants than do concepts of nativeness.

Shorebirds-driven trophic cascade helps restore coastal wetland multifunctionality

Ecosystem restoration has traditionally focused on re-establishing vegetation and other foundation species at basal trophic levels, with mixed outcomes. Here, we show that threatened shorebirds could be important to restoring coastal wetland multifunctionality. We carried out surveys and manipulative field experiments in a region along the Yellow Sea affected by the invasive cordgrass Spartina alterniflora. We found that planting native plants alone failed to restore wetland multifunctionality in a field restoration experiment. Shorebird exclusion weakened wetland multifunctionality, whereas mimicking higher predation before shorebird population declines by excluding their key prey - crab grazers - enhanced wetland multifunctionality. The mechanism underlying these effects is a simple trophic cascade, whereby shorebirds control crab grazers that otherwise suppress native vegetation recovery and destabilize sediments (via bioturbation). Our findings suggest that harnessing the top-down effects of shorebirds - through habitat conservation, rewilding, or temporary simulation of consumptive or non-consumptive effects - should be explored as a nature-based solution to restoring the multifunctionality of degraded coastal wetlands.

Public attitudes and intentions toward engaging in reintroduction of wolves to Japan

Reintroducing apex predators is an important approach in ecosystem restoration; however, it is challenging. Wolves (Canis lupus) were exterminated in Japan around 1900, and since then, there has been a lack of top predators throughout the country. Currently, the wild ungulate population is increasing, causing agricultural and forest damage. This has triggered an ongoing debate among researchers and nongovernmental organizations on whether wolves should be reintroduced to promote self-regulating biodiverse ecosystems. We conducted a nationwide survey to examine public attitudes toward wolf reintroduction (WR) in Japan. We sent online questionnaires to 88,318 citizens across the country. Among the 12,028 respondents, excluding those with invalid or incomplete answers and unqualified respondents, we obtained and analyzed 7500 responses that were representative of Japanese citizens in terms of some key sociodemographic attributes. More respondents disagreed with WR (39.9%) than agreed (17.1%), and many respondents (43.0%) were undecided. Structural equation modeling revealed that risk perceptions affected public attitudes, implying that the greater the perceived threat of wolf attacks, the less likely people are to support WR. In contrast, attitudes toward wolves (e.g., "I like wolves.") influenced by wildlife value orientation and beliefs about the ecological role of wolves (e.g., controlling deer populations) positively affected public attitudes toward WR. Those who had a positive attitude toward WR showed intentions to engage in behaviors that support WR. Our results suggest that the dissemination of information related to the ecological role of wolves and the development of a more mutualistic mindset in people could positively influence public support for WR in Japan.

Worldwide Late Pleistocene and Early Holocene population declines in extant megafauna are associated with Homo sapiens expansion rather than climate change

The worldwide extinction of megafauna during the Late Pleistocene and Early Holocene is evident from the fossil record, with dominant theories suggesting a climate, human or combined impact cause. Consequently, two disparate scenarios are possible for the surviving megafauna during this time period - they could have declined due to similar pressures, or increased in population size due to reductions in competition or other biotic pressures. We therefore infer population histories of 139 extant megafauna species using genomic data which reveal population declines in 91% of species throughout the Quaternary period, with larger species experiencing the strongest decreases. Declines become ubiquitous 32-76 kya across all landmasses, a pattern better explained by worldwide Homo sapiens expansion than by changes in climate. We estimate that, in consequence, total megafauna abundance, biomass, and energy turnover decreased by 92-95% over the past 50,000 years, implying major human-driven ecosystem restructuring at a global scale.

Herbivory limits success of vegetation restoration globally

Restoring vegetation in degraded ecosystems is an increasingly common practice for promoting biodiversity and ecological function, but successful implementation is hampered by an incomplete understanding of the processes that limit restoration success. By synthesizing terrestrial and aquatic studies globally (2594 experimental tests from 610 articles), we reveal substantial herbivore control of vegetation under restoration. Herbivores at restoration sites reduced vegetation abundance more strongly (by 89%, on average) than those at relatively undegraded sites and suppressed, rather than fostered, plant diversity. These effects were particularly pronounced in regions with higher temperatures and lower precipitation. Excluding targeted herbivores temporarily or introducing their predators improved restoration by magnitudes similar to or greater than those achieved by managing plant competition or facilitation. Thus, managing herbivory is a promising strategy for enhancing vegetation restoration efforts.

Megaherbivores provide biotic resistance against alien plant dominance

While human-driven biological invasions are rapidly spreading, finding scalable and effective control methods poses an unresolved challenge. Here, we assess whether megaherbivores-herbivores reaching ≥1,000 kg of body mass-offer a nature-based solution to plant invasions. Invasive plants are generally adapted to maximize vegetative growth. Megaherbivores, with broad dietary tolerances, could remove large biomass of established plants, facilitating new plant growth. We used a massive dataset obtained from 26,838 camera stations and 158,979 vegetation plots to assess the relationships between megaherbivores, native plants and alien plants across India (~121,330 km2). We found a positive relationship between megaherbivore abundance and native plant richness and abundance, and a concomitant reduction in alien plant abundance. This relationship was strongest in protected areas with midproductive ecosystem and high megaherbivore density but it was lost in areas where thicket-forming alien plants predominated (>40% cover). By incorporating the role of ecosystem productivity, plants traits and densities of megaherbivores on megaherbivore-vegetation relationships, our study highlights a function of megaherbivores in controlling alien plant proliferation and facilitating diverse native plants in invaded ecosystems. The study shows great potential for megafauna-based trophic rewilding as a nature-based solution to counteract dominance of plant invasions.

Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi-aquatic common hippopotamus

Megaherbivores perform vital ecosystem engineering roles, and have their last remaining stronghold in Africa. Of Africa's remaining megaherbivores, the common hippopotamus (Hippopotamus amphibius) has received the least scientific and conservation attention, despite how influential their ecosystem engineering activities appear to be. Given the potentially crucial ecosystem engineering influence of hippos, as well as mounting conservation concerns threatening their long-term persistence, a review of the evidence for hippos being ecosystem engineers, and the effects of their engineering, is both timely and necessary. In this review, we assess, (i) aspects of hippo biology that underlie their unique ecosystem engineering potential; (ii) evaluate hippo ecological impacts in terrestrial and aquatic environments; (iii) compare the ecosystem engineering influence of hippos to other extant African megaherbivores; (iv) evaluate factors most critical to hippo conservation and ecosystem engineering; and (v) highlight future research directions and challenges that may yield new insights into the ecological role of hippos, and of megaherbivores more broadly. We find that a variety of key life-history traits determine the hippo's unique influence, including their semi-aquatic lifestyle, large body size, specialised gut anatomy, muzzle structure, small and partially webbed feet, and highly gregarious nature. On land, hippos create grazing lawns that contain distinct plant communities and alter fire spatial extent, which shapes woody plant demographics and might assist in maintaining fire-sensitive riverine vegetation. In water, hippos deposit nutrient-rich dung, stimulating aquatic food chains and altering water chemistry and quality, impacting a host of different organisms. Hippo trampling and wallowing alters geomorphological processes, widening riverbanks, creating new river channels, and forming gullies along well-utilised hippo paths. Taken together, we propose that these myriad impacts combine to make hippos Africa's most influential megaherbivore, specifically because of the high diversity and intensity of their ecological impacts compared with other megaherbivores, and because of their unique capacity to transfer nutrients across ecosystem boundaries, enriching both terrestrial and aquatic ecosystems. Nonetheless, water pollution and extraction for agriculture and industry, erratic rainfall patterns and human-hippo conflict, threaten hippo ecosystem engineering and persistence. Therefore, we encourage greater consideration of the unique role of hippos as ecosystem engineers when considering the functional importance of megafauna in African ecosystems, and increased attention to declining hippo habitat and populations, which if unchecked could change the way in which many African ecosystems function.

Large mammals and trees in eastern monsoonal China: anthropogenic losses since the Late Pleistocene and restoration prospects in the Anthropocene

Massive human-induced declines of large-sized animals and trees (megabiota) from the Late Pleistocene to the Anthropocene have resulted in downsized ecosystems across the globe, in which components and functions have been greatly simplified. In response, active restoration projects of extant large-sized species or functional substitutes are needed at large scales to promote ecological processes that are important for ecosystem self-regulation and biodiversity maintenance. Despite the desired global scope of such projects, they have received little attention in East Asia. Here, we synthesise the biogeographical and ecological knowledge of megabiota in ancient and modern China, with relevant data mostly located in eastern monsoonal China (EMC), aiming to assess its potential for restoring functionally intact ecosystems modulated by megabiota. We found that during the Late Pleistocene, 12 mammalian megafaunal (carnivores ≥15 kg and herbivores ≥500 kg) species disappeared from EMC: one carnivore Crocuta ultima (East Asian spotted hyena) and 11 herbivores including six megaherbivores (≥1000 kg). The relative importance of climate change and humans in driving these losses remains debated, despite accumulating evidence in favour of the latter. Later massive depletion of megafauna and large-sized (45-500 kg) herbivores has been closely associated with agricultural expansion and societal development, especially during the late Holocene. While forests rich in large timber trees (33 taxa in written records) were common in the region 2000-3000 years ago, millennial-long logging has resulted in considerable range contractions and at least 39 threatened species. The wide distribution of C. ultima, which likely favoured open or semi-open habitats (like extant spotted hyenas), suggests the existence of mosaic open and closed vegetation in the Late Pleistocene across EMC, in line with a few pollen-based vegetation reconstructions and potentially, or at least partially, reflecting herbivory by herbivorous megafauna. The widespread loss of megaherbivores may have strongly compromised seed dispersal for both megafruit (fleshy fruits with widths ≥40 mm) and non-megafruit plant species in EMC, especially in terms of extra-long-distance (>10 km) dispersal, which is critical for plant species that rely on effective biotic agents to track rapid climate change. The former occurrence of large mammals and trees have translated into rich material and non-material heritages passed down across generations. Several reintroduction projects have been implemented or are under consideration, with the case of Elaphurus davidianus a notable success in recovering wild populations in the middle reaches of the Yangtze River, although trophic interactions with native carnivorous megafauna have not yet been restored. Lessons of dealing with human-wildlife conflicts are key to public support for maintaining landscapes shared with megafauna and large herbivores in the human-dominated Anthropocene. Meanwhile, potential human-wildlife conflicts, e.g. public health risks, need to be scientifically informed and effectively reduced. The Chinese government's strong commitment to improved policies of ecological protection and restoration (e.g. ecological redlines and national parks) provides a solid foundation for a scaling-up contribution to the global scope needed for solving the crisis of biotic downsizing and ecosystem degradation.

Browsers or Grazers? New Insights into Feral Burro Diet Using a Non-Invasive Sampling and Plant DNA Metabarcoding Approach

Ungulates play a large role in shaping ecosystems and communities by influencing plant composition, structure, and productivity. We investigated the summer diets of feral burros in two ecosystems in which they are found in the United States: a subtropical desert in Arizona and a temperate juniper shrubland in Utah. Between 24 June and 16 July of 2019, we gathered 50 burro fecal samples from each location and used plant DNA metabarcoding to determine the burros' diets. We found that during our sampling period the burros in the Sonoran Desert consumed a higher proportion of woody browse and had a narrower dietary niche breadth and lower degree of diet diversity compared to the burros in the juniper shrubland ecosystem, where the burros consumed higher proportions of graminoids and forbs and had a higher diet diversity index and broader dietary niche breadth. The burros in the Sonoran Desert relied primarily on Prosopis spp. (mesquite) and Poaceae grasses, whereas the burros in the juniper shrubland relied on a wider variety of forb and grass species, likely due to the greater variability in the forage species temporally and spatially available in that temperate ecosystem. We found that feral burros are highly adaptable with respect to diet and appear to be employing a mixed feeding strategy, similar to their ancestor, the African wild ass, to meet their nutritional needs in whichever ecosystem they are found.

Herbivory and nutrients shape grassland soil seed banks

Anthropogenic nutrient enrichment and shifts in herbivory can lead to dramatic changes in the composition and diversity of aboveground plant communities. In turn, this can alter seed banks in the soil, which are cryptic reservoirs of plant diversity. Here, we use data from seven Nutrient Network grassland sites on four continents, encompassing a range of climatic and environmental conditions, to test the joint effects of fertilization and aboveground mammalian herbivory on seed banks and on the similarity between aboveground plant communities and seed banks. We find that fertilization decreases plant species richness and diversity in seed banks, and homogenizes composition between aboveground and seed bank communities. Fertilization increases seed bank abundance especially in the presence of herbivores, while this effect is smaller in the absence of herbivores. Our findings highlight that nutrient enrichment can weaken a diversity maintaining mechanism in grasslands, and that herbivory needs to be considered when assessing nutrient enrichment effects on seed bank abundance.

Effect of global warming on the potential distribution of a holoparasitic plant (Phelypaea tournefortii): both climate and host distribution matter

Phelypaea tournefortii (Orobanchaceae) primarily occurs in the Caucasus (Armenia, Azerbaijan, Georgia, and N Iran) and Turkey. This perennial, holoparasitic herb is achlorophyllous and possesses one of the most intense red flowers among all plants worldwide. It occurs as a parasite on the roots of several Tanacetum (Asteraceae) species and prefers steppe and semi-arid habitats. Climate change may affect holoparasites both directly through effects on their physiology and indirectly as a consequence of its effects on their host plants and habitats. In this study, we used the ecological niche modeling approach to estimate the possible effects of climate change on P. tournefortii and to evaluate the effect of its parasitic relationships with two preferred host species on the chances of survival of this species under global warming. We used four climate change scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) and three different simulations (CNRM, GISS-E2, INM). We modeled the species' current and future distribution using the maximum entropy method implemented in MaxEnt using seven bioclimatic variables and species occurrence records (Phelypaea tournefortii - 63 records, Tanacetum argyrophyllum - 40, Tanacetum chiliophyllum - 21). According to our analyses, P. tournefortii will likely contract its geographical range remarkably. In response to global warming, the coverage of the species' suitable niches will decrease by at least 34%, especially in central and southern Armenia, Nakhchivan in Azerbaijan, northern Iran, and NE Turkey. In the worst-case scenario, the species will go completely extinct. Additionally, the studied plant's hosts will lose at least 36% of currently suitable niches boosting the range contraction of P. tournefortii. The GISS-E2 scenario will be least damaging, while the CNRM will be most damaging to climate change for studied species. Our study shows the importance of including ecological data in niche models to obtain more reliable predictions of the future distribution of parasitic plants.

Large herbivore diversity slows sea ice-associated decline in arctic tundra diversity

Biodiversity is declining globally in response to multiple human stressors, including climate forcing. Nonetheless, local diversity trends are inconsistent in some taxa, obscuring contributions of local processes to global patterns. Arctic tundra diversity, including plants, fungi, and lichens, declined during a 15-year experiment that combined warming with exclusion of large herbivores known to influence tundra vegetation composition. Tundra diversity declined regardless of experimental treatment, as background growing season temperatures rose with sea ice loss. However, diversity declined slower with large herbivores than without them. This difference was associated with an increase in effective diversity of large herbivores as formerly abundant caribou declined and muskoxen increased. Efforts that promote herbivore diversity, such as rewilding, may help mitigate impacts of warming on tundra diversity.

Impacts of large herbivores on terrestrial ecosystems

Large herbivores play unique ecological roles and are disproportionately imperiled by human activity. As many wild populations dwindle towards extinction, and as interest grows in restoring lost biodiversity, research on large herbivores and their ecological impacts has intensified. Yet, results are often conflicting or contingent on local conditions, and new findings have challenged conventional wisdom, making it hard to discern general principles. Here, we review what is known about the ecosystem impacts of large herbivores globally, identify key uncertainties, and suggest priorities to guide research. Many findings are generalizable across ecosystems: large herbivores consistently exert top-down control of plant demography, species composition, and biomass, thereby suppressing fires and the abundance of smaller animals. Other general patterns do not have clearly defined impacts: large herbivores respond to predation risk but the strength of trophic cascades is variable; large herbivores move vast quantities of seeds and nutrients but with poorly understood effects on vegetation and biogeochemistry. Questions of the greatest relevance for conservation and management are among the least certain, including effects on carbon storage and other ecosystem functions and the ability to predict outcomes of extinctions and reintroductions. A unifying theme is the role of body size in regulating ecological impact. Small herbivores cannot fully substitute for large ones, and large-herbivore species are not functionally redundant - losing any, especially the largest, will alter net impact, helping to explain why livestock are poor surrogates for wild species. We advocate leveraging a broad spectrum of techniques to mechanistically explain how large-herbivore traits and environmental context interactively govern the ecological impacts of these animals.

Elephant rewilding affects landscape openness and fauna habitat across a 92-year period

Trophic rewilding aims to promote biodiverse self-sustaining ecosystems through the restoration of ecologically important taxa and the trophic interactions and cascades they propagate. How rewilding effects manifest across broad temporal scales will determine ecosystem states; however, our understanding of post-rewilding dynamics across longer time periods is limited. Here we show that the restoration of a megaherbivore, the African savannah elephant (Loxodonta africana), promotes landscape openness (i.e., various measures of vegetation composition/complexity) and modifies fauna habitat and that these effects continue to manifest up to 92 years after reintroduction. We conducted a space-for-time floristic survey and assessment of 17 habitat attributes (e.g., floristic diversity and cover, ground wood, tree hollows) across five comparable nature reserves in South African savannah, where elephants were reintroduced between 1927 and 2003, finding that elephant reintroduction time was positively correlated with landscape openness and some habitat attributes (e.g., large-sized tree hollows) but negatively associated with others (e.g., large-sized coarse woody debris). We then indexed elephant site occurrence between 2006 and 2018 using telemetry data and found positive associations between site occurrence and woody plant densities. Taken alongside the longer-term space-for-time survey, this suggests that elephants are attracted to dense vegetation in the short term and that this behavior increases landscape openness in the long term. Our results suggest that trophic rewilding with elephants helps promote a semi-open ecosystem structure of high importance for African biodiversity. More generally, our results suggest that megafauna restoration represents a promising tool to curb Earth's recent ecological losses and highlights the importance of considering long-term ecological responses when designing and managing rewilding projects.

The Yale Geochronometric Laboratory and the Rewriting of Global Environmental History

Beginning in the nineteenth century, scientists speculated that the Pleistocene megafauna-species such as the giant ground sloth, wooly mammoth, and saber-tooth cat-perished because of rapid climate change accompanying the end of the most recent Ice Age. In the 1950s, a small network of ecologists challenged this view in collaboration with archeologists who used the new tool of radiocarbon dating. The Pleistocene overkill hypothesis imagined human hunting, not climate change, to be the primary cause of megafaunal extinction. This article situates the Pleistocene overkill hypothesis in a broader history of the emergence of historical ecology as a distinct sub-discipline of paleoecology. Tracing the work of the Yale Geochronometric Laboratory and an interdisciplinary research network that included Paul Sears, Richard Foster Flint, Edward Deevey, Kathryn Clisby, and Paul S. Martin, it reveals how both the methods and the meaning of studying fossil pollen shifted between the 1910s and 1960s. First used as a tool for fossil fuel extraction, fossil pollen became a means of envisioning climatic history, and ultimately, a means of reimagining global ecological history. First through pollen stratigraphy and then through radiocarbon dating, ecologists reconstructed past biotic communities and rethought the role of humans in these communities. By the 1980s, the discipline of historical ecology would reshape physical environments through the practice of ecological restoration.