Rangelands, pastoralists and governments: interlinked systems of people and nature

Spatiotemporal variability and key factors of evergreen forest encroachment in the southern Great Plains

Woody plant encroachment has been long observed in the southern Great Plains (SGP) of the United States. However, our understanding of its spatiotemporal variability, which is the basis for informed and targeted management strategy, is still poor. This study investigates the encroachment of evergreen forest, which is the most important encroachment component in the SGP. A validated evergreen forest map of the SGP (30 m resolution, for the time period 2015 to 2017) from our previous study was utilized (referred to as evergreen_base). Sample plots of evergreen forest (as of 2017) were collected across the study area, based on which a threshold of winter season (January and February) mean normalized difference vegetation index (NDVI_winter) was derived for each of the 5 sub-regions, using Landsat 7 surface reflectance data from 2015 to 2017. Then a NDVI_winter layer was created for each year within the four time periods of 1985-1989, 1995-1999, 2005-2009, and 2015-2017, with winter season surface reflectance data from Landsat 4, 5, and 7. By applying the sub-region specific NDVI_winter thresholds to the annual NDVI_winter layers and the evergreen_base, a SGP evergreen forest map was generated for each of those years. The annual evergreen forest maps within each time period were composited into one. According to the resulting four composite evergreen forest maps, mean annual encroachment rate (km²/year) was calculated at sub-region and ecoregion scales, over each of the three temporal stages 1990-1999, 2000-2009, and 2010-2017, respectively. To understand the spatiotemporal variability of the encroachment, the encroachment rate at each temporal stage was related to the corresponding initial evergreen forest area, mean annual precipitation (MAP), and mean annual burned area (MABA) through linear regression and pairwise comparison. Results suggest that most of the ecoregions have seen a slowing trend of evergreen forest encroachment since 1990. The temporal trend of encroachment rate tends to be consistent with that of MAP, but opposite to that of MABA. The spatial variability of the encroachment rate among ecoregions can be largely (>68%) explained by initial evergreen forest area but shows no significant relationship with MAP or MABA. These findings provide pertinent guidance for the combat of woody plant encroachment in the SGP under the context of climate change.

Response of Surface Runoff and Sediment to the Conversion of a Marginal Grassland to a Switchgrass (Panicum virgatum) Bioenergy Feedstock System

The land systems between the humid and arid zones around the globe are critical to agricultural production and are characterized by a strong integration of the land use and water dynamics. In the southern Great Plains (SGP) of the United States, lakes and farm ponds are essential components in the land systems, and they provide unique habitats for wildlife, and critical water resources for irrigation and municipal water supplies. The conversion of the marginal grasslands to switchgrass (Panicum virgatum) biofuel feedstock for energy production has been proposed in the region. However, we have limited experimental data to assess the impact of this potential land-use change on the surface runoff, which is the primary water source for surface impoundments. Here, we report the results from a paired experimental watershed study that compared the runoff and sediment responses that were related to the conversion of prairie to a low-input biomass production system. The results show no significant change in the relationship between the event-based runoff and the precipitation. There was a substantial increase in the sediment yield (328%) during the conversion phase that was associated with the switchgrass establishment (i.e., the site preparation, herbicide application, and switchgrass planting). Once the switchgrass was established, the sediment yield was 21% lower than the nonconverted watershed. Our site-specific observations suggest that switchgrass biofuel production systems will have a minimum impact on the existing land and water systems. It may potentially serve as an environmentally friendly and economically viable alternative land use for slowing woody encroachment on marginal lands in the SGP.

Loss of density dependence underpins decoupling of livestock population and plant biomass in intensive grazing systems

Across the world, social-ecological rangeland systems have been transformed from a preindustrial extensive status to intensive exploitation, often leading to long-term livestock population booms, overgrazing, and rangeland degradation. To understand the regulatory mechanisms involved in such historical social-ecological transformations, we collected population data on the native sheep of the last nomadic county in the Inner Mongolia Autonomous Region (1961-2005). We detected changes in internal feedbacks (e.g., density-dependent effects) and external disturbance (e.g., winter harshness, rainfall, harvest) between the extensive and intensive management periods using regression models of sheep population growth rate and counterfactual analyses. We found that, in the extensive period, sheep populations were regulated during harsh winters by climate, while they were regulated during mild winters by negative density dependence. In the intensive period, the negative feedback of density dependence was removed through the provision of additional forage and shelter, and only winter climate and growing season rainfall regulated sheep populations. Counterfactual analyses also confirmed the irreplaceable role of density-dependence in maintaining a sustainable rangeland ecosystem. Although herders attempted to adapt to the removal of negative feedbacks by improving livestock harvest, overgrazing and grassland degradation remain a challenge in this system. We conclude that internal feedbacks within social-ecological systems should be carefully anticipated and accounted for when managing rangelands for sustainability.

Social-ecological system resilience of debris flow alluvial fans in the Awang basin, China

Debris flow alluvial fans (DFAFs) are vulnerable, although they can be used as a natural resource. The relationships between different factors related to DFAF systems and between these factors and systems are important both for identifying the risks and opportunities presented by DFAFs and for tracking system status. In this regard, resilience may be used to characterize the status of a DFAF. This study aimed to explore the processes and mechanisms of interactions among the social, economic, and ecological factors related to DFAF with respect to resilience, and to discuss potential problems in a representative DFAF. Based on the site condition and characteristics of the Awang DFAF (China) in the period 1996-2017, we formed a comprehensive indicator evaluation framework by analyzing disturbance, function, and feedback. We also established a model for evaluating resilience by integrating the analytic hierarchy process (AHP) - an entropy evaluation method (EEM) and set pair analysis (SPA). The results showed that the system of the studied DFAF was dynamically stable. The domination of the ecological system was subsequently superseded by social and economic resilience. While disturbance had direct and immediate effects, coping ability was cumulative and characterized by hysteresis at a particular response time. Overall, resilience fluctuated within an acceptable range rather than linearly increasing or decreasing. This analysis illuminated the dynamic processes of DFAFs and contributed to the understanding and planning of system trade-offs and degraded-land utilization.

Preventing rangeland degradation: a shared problem for Australia and China

Rangeland degradation continues in Australia, China and elsewhere. The stocking rate/animal production relationship has been a successful concept for pastoralists wanting to avoid degradation and/or raise incomes. However, there are no means available of alerting pastoralists to the approach of critical thresholds that would ‘flip’ rangelands into alternative states when grazing-stressed. Critical threshold forecasting for avoiding degradation (and seizing restoration opportunities) could be made available online. Research has yet to find, assemble and test the set of indicators needed to forecast the approach of critical thresholds envisaged in State-and-Transition thinking. Forecasting at paddock, property and regional scales would have to involve high-performance computing because the thresholds will be space and time dependent. The case for Australia and China to contribute cooperatively to this research effort rests on the large number of contrasting rangeland ecosystems across the two countries that represent rangelands globally. A proven history of past collaboration is extant with existing research programs on plant population dynamics, landscape patchiness/leakiness and soil biota status, and their responses to the separate and combined effects of climate and grazing animals. The road to adoption would involve partnerships with pastoralists throughout the process, remote sensing to identify approaching thresholds in real time, application of high-performance computing and possibly artificial intelligence, and packaging of forecasts for different socio-economic rangeland systems.

Commentary: on the under-valuing of Australia’s expertise in drylands research and practice globally

Global drylands are a significant driver of earth system processes that affect the world’s common resources such as the climate. Their peoples are also among the first to be widely affected by global changes such as land degradation and climate change. Yet drylands are a source of many social and technical innovations, globally, as well as in Australia. As a major developed dryland nation, Australia has previously played a major role in extending these innovations to the rest of the world. The nation has reaped reputational and commercial benefits through major research and practice contributions to dryland agriculture, water management and governance, remote area services, indigenous partnerships, dryland monitoring systems, and ‘desert knowledge’ innovation. Australian researchers continue to contribute to various relevant international processes, yet recognition and support for this within Australia has dropped off markedly in recent years. We analyse the Australian government’s investment in research and in overseas aid for drylands over the last two decades, and explore trends in government’s active involvement in major international processes related to land. These trends are short-sighted, overlooking potential economic benefits for Australian enterprises, and undermining Australia’s stance and scientific leadership in dryland systems globally. In this commentary, we argue that it is time for the trends to be reversed, as this is an area of comparative advantage for Australian diplomacy with significant returns on investment for Australia, both direct and indirect, especially when most emerging economies contain substantial drylands. We identify four major pathways to obtaining benefits from science diplomacy, and four interrelated actions within Australia to enable these – to place a higher emphasis on science diplomacy, to re-forge a bipartisan recognition of Australian drylands expertise, to establish a dedicated Dryland Information Hub, and to create a network of relevant science and technology advisors.

Challenges, solutions and research priorities for sustainable rangelands

Australia’s rangeland communities, industries, and environment are under increasing pressures from anthropogenic activities and global changes more broadly. We conducted a horizon scan to identify and prioritise key challenges facing Australian rangelands and their communities, and outline possible avenues to address these challenges, with a particular focus on research priorities. We surveyed participants of the Australian Rangeland Society 20th Biennial Conference, held in Canberra in September 2019, before the conference and in interactive workshops during the conference, in order to identify key challenges, potential solutions, and research priorities. The feedback was broadly grouped into six themes associated with supporting local communities, managing natural capital, climate variability and change, traditional knowledge, governance, and research and development. Each theme had several sub-themes and potential solutions to ensure positive, long-term outcomes for the rangelands. The survey responses made it clear that supporting ‘resilient and sustainable rangelands that provide cultural, societal, environmental and economic outcomes simultaneously’ is of great value to stakeholders. The synthesis of survey responses combined with expert knowledge highlighted that sustaining local communities in the long term will require that the inherent social, cultural and natural capital of rangelands are managed sustainably, particularly in light of current and projected variability in climate. Establishment of guidelines and approaches to address these challenges will benefit from: (i) an increased recognition of the value and contributions of traditional knowledge and practices; (ii) development of better governance that is guided by and benefits local stakeholders; and (iii) more funding to conduct and implement strong research and development activities, with research focused on addressing critical knowledge gaps as identified by the local stakeholders. This requires strong governance with legislation and policies that work for the rangelands. We provide a framework that indicates the key knowledge gaps and how innovations may be implemented and scaled out, up and deep to achieve the resilience of Australia’s rangelands. The same principles could be adapted to address challenges in rangelands on other continents, with similar beneficial outcomes.

Alternative strategies for management of feral goats: implications for natural resource management policies in New South Wales rangelands

Feral goats (Capra hircus) are increasing in abundance and distribution in the semi-arid and arid rangelands of New South Wales, and elsewhere in the southern rangelands. They present a conundrum for natural resource managers and policy-makers as they can be both an agricultural and environmental pest and an economic resource for landholders. This paper presents an economic analysis of a range of alternative approaches to feral goat management and assesses their implications for natural resource management policies. ‘Opportunistic harvesting’ and ‘value-added’ strategies (the latter involving use of a paddock to increase the liveweight of feral goats before slaughter for meat) returned positive net benefits to landholders, whereas the strategy of ‘no management’ resulted in a negative net benefit if the overall stocking rate was held constant. The erection of goat-proof boundary fencing to enhance production from domestic livestock generated negative net benefits unless increases in stocking rates of domestic livestock could be achieved within the exclusion fencing through improved grazing management. The use of goat-proof fencing to establish an individual paddock for domestic livestock production returned positive net benefit for landholders but also required increases in domestic stocking rate to be competitive with the best feral goat harvesting strategy. The ‘opportunistic harvesting’ and ‘value added’ strategies are thus likely to be adopted by producers without financial incentive and could result in positive resource conservation outcomes if goat prices encourage harvesting. The ‘no management’ strategy will most likely promote resource degradation and should be discouraged. Strategies involving goat-proof fencing are likely to provide positive net benefits for landholders and achieve positive natural resource outcomes if associated with improved grazing management, and reduced density of feral goats outside the exclusion fencing. It is concluded that resource conservation benefits of feral goat control strategies may be positive, negative, or neutral depending on the management strategy adopted, the extent of goat-proof fencing, and the price of meat from feral goats. It is, therefore, difficult to rely on the commercial harvesting of feral goats to achieve resource conservation objectives. Public funds could be better used to support education and training in grazing management and provide incentives for achievement of measurable natural resource outcomes than to support infrastructure establishment for the harvesting of feral goats on private properties.

Global assessment of the non-equilibrium concept in rangelands

The non-equilibrium concept of rangeland dynamics predicts that the potential for grazing-induced degradation is low in rangelands with relatively variable precipitation. To date, evidence in support of the non-equilibrium concept has been inconsistent. Using a standardized protocol, including a newly developed global map of rainfall variability, we reviewed the incidence of degradation in relation to rainfall variability across 58 published studies. We distinguished between (1) zonal degradation (i.e., degradation independent of water and key resources), (2) degradation in the presence of key resources, and (3) degradation in the presence of water. For studies not affected by proximity to permanent water or key resources, we found strong support for the non-equilibrium concept for rangelands. Zonal degradation was absent at CV (coefficient of variation) values above 33%, which has been proposed as a critical threshold. Grazing degradation was almost entirely restricted to areas with relatively stable annual precipitation as expressed by a low CV, or to rangelands with key resources or water points nearby. To better understand rangeland dynamics, we recommend that future studies use globally comparable measures of degradation and rainfall variability. Our work underlines that rangelands with relatively stable rainfall patterns, and those with access to water or key resources, are potentially vulnerable to degradation. Grazing management in such areas should incorporate strategic rest periods. Such rest periods effectively mimic natural fluctuations in herbivore populations, which are a defining characteristic of non-degraded rangelands occurring under highly variable precipitation regimes.

Responses to alternative rainfall regimes and antipoaching in a migratory system

Migratory ungulates may be particularly vulnerable to the challenges imposed by growing human populations and climate change. These species depend on vast areas to sustain their migratory behavior, and in many cases come into frequent contact with human populations outside protected areas. They may also act as spatial coupling agents allowing feedbacks between ecological systems and local economies, particularly in the agropastoral subsistence economies found in the African savanna biome. We used HUMENTS, a spatially realistic socioecological model of the Greater Serengeti Ecosystem in East Africa, to explore the potential impacts of changing climate and poaching on the migratory wildebeest (Connochaetes taurinus) population, the fire regime, and habitat structure in the ecosystem, as well as changes in the size and economic activities of the human population outside the protected area. Unlike earlier models, the HUMENTS model predicted only moderate declines in the wildebeest population associated with an increasing human population over the next century, with a gradual expansion of agriculture, more poaching, and increases in fire frequency and reduced tree density. Changes in rainfall were predicted to have strong asymmetric effects on the size and economic activity of the human population and on livestock, and more moderate effects on wildlife and other ecological indicators. Conversely, antipoaching had a stronger effect on the ecological portion of the system because of its effect on wildebeest (and therefore on fire and habitat structure), and a weaker effect on the socioeconomic component, except in areas directly adjacent to the protected-area boundary, which were affected by crop-raiding and the availability of wildlife as a source of income. The results highlight the strong direct and indirect effects of rainfall on the various components of socioecological systems in semiarid environments, and the key role of mobile wildlife populations as agents of spatial coupling between the human-dominated and natural portions of ecosystems. They also underscore the fundamental importance of considering the spatial configuration of hunting refuges across the landscape in relation to human populations.

A ground cover-based incentive approach to enhancing resilience in rangelands viewed as complex adaptive systems

Inconsistencies can commonly be expected between the financial goals of rangeland grazing enterprises and public conservation goals such as maintenance of ground cover to reduce erosion. Where the State wishes to promote conservation outcomes, incentive schemes which reward these outcomes on privately managed grazing lands are an option. We describe one such scheme intended to achieve conservation outcomes and support the development of resilience in the complex adaptive (human–environmental) rangeland system through payments related to measured ground cover. A pilot program in western New South Wales has shown that the practical operation of such a program is uncomplicated and that while several theoretical issues could be further refined there is a rationale for extension of the program based on parameters and processes that are agreed by the participants. We suggest that development of such a scheme should be considered as part of the policy mix related to natural resource management and drought assistance.

Pastoralists' responses to variation of rangeland resources in time and space

We explore the response of pastoralists to rangeland resource variation in time and space, focusing on regions where high variation makes it unlikely that an economically viable herd can be maintained on a single management unit. In such regions, the need to move stock to find forage in at least some years has led to the evolution of nomadism and transhumance, and reciprocal grazing agreements among the holders of common-property rangeland. The role of such informal institutions in buffering resource variation is well documented in some Asian and African rangelands, but in societies with formally established private-property regimes, where we focus, such institutions have received little attention. We examine agistment networks, which play an important role in buffering resource variation in modern-day Australia. Agistment is a commercial arrangement between pastoralists who have less forage than they believe they require and pastoralists who believe they have more. Agistment facilitates the movement of livestock via a network based largely on trust. We are concerned exclusively with the link between the characteristics of biophysical variation and human aspects of agistment networks, and we developed a model to test the hypothesis that such a link could exist. Our model builds on game theory literature, which explains cooperation between strangers based on the ability of players to learn whom they can trust. Our game is played on a highly stylized landscape that allows us to control and isolate the degree of spatial variation and spatial covariation. We found that agistment networks are more effective where spatial variation in resource availability is high, and generally more effective when spatial covariation is low. Policy design that seeks to work with existing social networks in rangelands has potential, but this potential varies depending on localized characteristics of the biophysical variability.

Fragmentation of Australian rangelands: processes, benefits and risks of changing patterns of land use

Pastoral development of Australian rangelands has been accompanied by fragmentation of land use, which has changed the scale at which humans and livestock access patchily-distributed resources in landscapes. These changes have tended to be targeted towards achieving narrowly defined policy or land management objectives, and have ignored the broader consequences for land use. We describe the processes of rangeland fragmentation, the factors that have driven these changing patterns of land use, and current trends towards enterprise consolidation and intensification, which continue to reshape the way humans and livestock use rangelands. Although there is growing interest in intensified systems of rangeland management, some of the benefits are uncertain, and there are several risks that serve as a caution against overoptimism: (i) intensification involves multiple simultaneous changes to enterprise operations and the benefits and trade offs of each component need to be better understood; (ii) if intensification proceeds without addressing constraints to implementing these management options sustainably then overutilisation and degradation of rangelands is likely to occur; (iii) further fragmentation of rangelands (from increased internal fencing) could compromise potential benefits derived from landscape heterogeneity in connected landscapes. Adaptation by the pastoral industry continues to reshape the use of rangelands. A broad-based approach to changes in land use that incorporates risks together with expected benefits during initial planning decisions would contribute to greater resilience of rangeland enterprises.