Managing farm ponds as breeding sites for amphibians: key trade-offs in agricultural function and habitat conservation

The ecological and biodiversity conservation values of farm dams: A systematic review

Biodiversity is in rapid decline globally with agriculture being one of the leading causes. Within agricultural landscapes, some features provide a benefit to biodiversity that is disproportionate to their spatial area. An interesting example is artificial ponds-or farm dams-which can support a large variety of taxa. Here, we present a global review of farm dam research related to biodiversity conservation objectives to provide an overview of the topics, key research insights, and the characteristics of current research. We used a three-stage process to screen literature and identified 104 relevant papers across 27 countries encompassing studies of 13 different taxa. Most of the studies were short-term (less than 5 years) with small sample sizes (less than 20 sites). Of the 104 papers, 88 were focussed primarily on ecological outcomes, such as species richness or abundance, and 15 on primary production outcomes, such as crop and livestock yield, despite addressing or measuring ecological metrics. Only one study measured both ecological and primary production outcomes. Studies frequently examined how the features of dams (79 studies) and attributes of the surrounding landscape (47 studies) impact particular species and communities. Terrestrial mammals (1 study) were under-represented in the literature with macrophytes (28 studies), macroinvertebrates (26 studies), and amphibians (19 studies) receiving the most attention. Our results reveal a growing trend towards recognizing farm dams as habitats for various taxa, including amphibians, beetles, dragonflies, and other macroinvertebrates within agricultural environments. Significant knowledge gaps exist in understanding how dam age, invasive species, and effective management practices impact the biodiversity conservation values of farm dams. Future research should emphasize enhancing biodiversity by collaborating with landholders to increase habitat through strategic vegetation planning, minimizing runoff and nutrient inflow, and restricting stock access.

Bending the curve: Simple but massive conservation action leads to landscape-scale recovery of amphibians

The global decline of amphibians is part of the global freshwater biodiversity crisis. In human-dominated landscapes, amphibian population declines are driven by multiple stressors. A better understanding of the benefits of conservation action can contribute to the halting and reversal of population declines. Our analysis of 20 y of monitoring data shows that the large-scale construction of hundreds of new ponds in northern Switzerland has halted or even reversed declining trends for the majority of amphibian species, including multiple Red-Listed species undergoing declines at the national level. This conservation success suggests that increasing habitat availability benefits threatened amphibian species despite the continued presence of stressors known to negatively affect populations.

Success stories are rare in conservation science, hindered also by the research-implementation gap, where scientific insights rarely inform practice and practical implementation is rarely evaluated scientifically. Amphibian population declines, driven by multiple stressors, are emblematic of the freshwater biodiversity crisis. Habitat creation is a straightforward conservation action that has been shown to locally benefit amphibians, as well as other taxa, but does it benefit entire amphibian communities at large spatial scales? Here, we evaluate a landscape-scale pond-construction program by fitting dynamic occupancy models to 20 y of monitoring data for 12 pond-breeding amphibian species in the Swiss state Aargau, a densely populated area of the Swiss lowlands with intensive land use. After decades of population declines, the number of occupied ponds increased statewide for 10 out of 12 species, while one species remained stable and one species further declined between 1999 and 2019. Despite regional differences, in 77% of all 43 regional metapopulations, the colonization and subsequent occupation of new ponds stabilized (14%) or increased (63%) metapopulation size. Likely mechanisms include increased habitat availability, restoration of habitat dynamics, and increased connectivity between ponds. Colonization probabilities reflected species-specific preferences for characteristics of ponds and their surroundings, which provides evidence-based information for future pond construction targeting specific species. The relatively simple but landscape-scale and persistent conservation action of constructing hundreds of new ponds halted declines and stabilized or increased the state-wide population size of all but one species, despite ongoing pressures from other stressors in a human-dominated landscape.

Spatial Differentiation of Pond Landscapes across an Urban-Rural Gradient in the Pearl River Delta Region

The impact of ponds by urbanization has been widely discussed on the landscape scale. However, relatively few studies have explored the spatial differentiation of pond landscapes across urban-rural gradients in rapidly urbanising areas. In this study, we applied the DeepLabv3+ network to perform a semantic segmentation on Google Map images to extract ponds in the Pearl River Delta (PRD) region, China; then we employed geographic information systems to analyse the ponds changes in 665 towns along an urban-rural gradient in the PRD. Results indicate that there are clear differences in landscapes between the urban core, urban, peri-urban, agricultural, and forested zone in terms of pond area and size. In total, 57.84% and 31.33% of the ponds are distributed in the peri-urban and agricultural zone, respectively; fewer ponds are present at either end of the urban-rural gradient. Owing to the legacy effects of historical land use and river systems, urban and peri-urban zone in the central and western parts of the PRD are still rich in ponds. We propose that management measures should be implemented according to the characteristics of different pond landscapes.

Environmental Concerns and Stewardship Behaviors Among Rural Landowners: What Supports Farmers and Non-farmers in Being Good Stewards?

Intensive agriculture is a main factor of biodiversity and ecosystem services loss globally. It is therefore of great importance to understand how rural landowners are managing their lands and how environmental stewardship behaviors could be strengthened. Farming and non-farming rural landowners are often considered a homogenous group. In reality, however, they vary by their histories, attitudes, interests, and resources. While many rural landowners manage their lands with environmental values in mind, others may struggle to do so. Ignoring this diversity poses the risk that planning and policy for sustainable agriculture are less effective than they could be. Hence, it is of interest to understand the variety of environmental perceptions and stewardship behaviors across these varied groups. To help addressing this knowledge gap, we conducted a survey of 1,200 farming and non-farming rural landowners, using Ontario as a case study. We specifically investigated whether farming landowners differed from non-farming landowners in expressed environmental concerns and stewardship behaviors, as well as what the roles are of participation in conservation incentive programs, demographic factors, and landholding characteristics. We analyzed survey answers with logistic regression and text analysis. Our results suggest that farming landowners are generally less environmentally concerned than non-farming landowners. However, it appears that this difference may be less driven by farm ownership than by contextual factors, such as landowner age and participation in conservation programs. Participation in conservation programs was more pronounced for non-farming landowners and was associated with higher likelihood of environmental concerns and engaging with stewardship behaviors. In contrast, higher age emerged as predictor of lower environmental concerns. In addition, we found that cost factors and knowledge needs were important barriers for stewardship behaviors across farming and non-farming rural landowners. Based on our results, we are making recommendations for increasing the effectiveness of agricultural sustainability planning and policy in Ontario, focusing on reducing financial and knowledge barriers to pro-environmental land management behaviors.

Avian Use of Dairy Farm Ponds and Landowners’ Perceptions of Their Management for Wildlife Conservation

Farm ponds are among the last remaining lentic wetland habitats in human-dominated agricultural and suburban landscapes. However, their wildlife value and farmers’ willingness to maintain them for the conservation of regionally declining biodiversity are often both poorly documented. The objectives of this study of 61 dairy farm ponds located in Southern Quebec (Canada) were to (1) describe their biophysical features and birds’ use, (2) determine habitat and landscape characteristics that influence the bird community, and (3) assess the willingness of farmers to support wildlife use. The studied ponds were small (0.17 ha) and had rectangular shape with rocky/muddy steeply slopes (21°), surrounded by 3 m wide riparian strips and pastures, hayfields, and fallows. They were located about 300 m from farmhouses, buildings, streams, and adjacent ponds. A total of 1963 individuals belonging to 46 bird species were observed. The abundance of all bird species, of species with declining populations, and of crop damaging species were positively related to the area of fallow land and to the width of riparian strips; the areas of cereals and of mixed-wood forest had a negative influence. Only two habitat variables had influence on species richness: the width of riparian strips (+) and the distance to the closest farm buildings (–). Most pond landowners (>80%) were in favour of increasing wildlife use if they were given access to associated financial support and logistical assistance. Wider riparian strips and adjacent uncultivated field margins are recommended.

Chronic Exposure to Two Gestagens Differentially Alters Morphology and Gene Expression in Silurana tropicalis

Gestagens are active ingredients in human and veterinary drugs with progestogenic activity. Two gestagens-progesterone (P4), and the synthetic P4 analogue, melengestrol acetate (MGA)-are approved for use in beef cattle agriculture in North America. Both P4 and MGA have been measured in surface water receiving runoff from animal agricultural operations. This project aimed to assess the morphometric and molecular consequences of chronic exposures to P4, MGA, and their mixture during Western clawed frog metamorphosis. Chronic exposure (from embryo to metamorphosis) to MGA (1.7 µg/L) or P4 + MGA (0.22 µg/L P4 + 1.5 µg/L MGA) caused a considerable dysregulation of metamorphic timing, as evidenced by an inhibition of growth, narrower head, and lack of forelimb emergence in all animals. Molecular analysis revealed that chronic exposure to the mixture induced an additive upregulation of neurosteroid-related (GABA_A receptor subunit α6 (gabra6) and steroid 5-alpha reductase 1 (srd5α1) gene expression in brain tissue. Chronic P4 exposure (0.26 µg/L P4) induced a significant upregulation of the expression hypothalamic-pituitary-gonadal (HPG)-related genes (ipgr, erα) in the gonadal mesonephros complex (GMC). Our data suggest that exposure to P4, MGA, and their mixture induces multiple endocrine responses and adverse effects in larval Western clawed frogs. This study helps to better our understanding of the consequences of chronic gestagen exposure and suggests that the implications and risk of high gestagen use in beef cattle feeding operations may extend to the aquatic environment.

Biodiversity Patterns of Macroinvertebrate Assemblages in Natural and Artificial Lentic Waters on an Oceanic Island

The Azorean islands have been historically affected by human activities, mainly due to the combined effects of habitat degradation and fragmentation, and the introduction of exotic species. We here aim to analyze the role of environmental characteristics and spatial descriptors in supporting regional biodiversity of macroinvertebrates by considering natural ponds and artificial tanks. After the monthly variation of macroinvertebrate assemblages was assessed in three temporary and two permanent ponds in the Azorean island of Terceira during a complete inundation-desiccation annual cycle, the assemblage differences of 12 ponds (three temporary and nine permanent ponds) and 8 closely-located artificial tanks were analyzed across a range of landscape disturbances. Macroinvertebrate assemblages were found to differ according to hydroperiod and sampled months. Although the former explained the highest variance, macroinvertebrate differentiation by hydroperiod was also dependent on the study month. Our results also revealed a consistent monthly pattern of species replacement. However, the contribution of nestedness to the macroinvertebrate β-diversity was notable when temporary ponds were close to desiccation, probably indicating a deterministic loss of species due to the impoverished water conditions of the ponds facing desiccation. When the macroinvertebrate assemblages were analyzed in relation to physico-chemical variations and spatial descriptors, the artificial tanks were not clearly segregated from the natural ponds, and only differentiated by pH differences. In contrast, those natural ponds exhibiting high concentrations of total phosphorous (likely signs of anthropization) also discriminated the ordination of ponds in a distance-based redundancy analysis, and showed impoverished assemblages in comparison with well-preserved ponds. The macroinvertebrate assemblages of the natural ponds showed a significant spatial pattern, but this spatial influence was not significant when tanks and ponds were considered together. Our results suggest that tanks may act as possible reservoirs of biodiversity during the desiccation period of temporary ponds, but are unable to establish successful populations. These fishless permanent tanks can complement the conservation of a biodiversity that is largely maintained by the pristine high-altitude natural ponds. The establishment of a guideline for conservation management that also considers the artificial tanks is necessary to benefit the local and regional Azorean macroinvertebrate diversity.

Identifying Opportunities to Conserve Farm Ponds on Private Lands: Integration of Social, Ecological, and Historical Data

In some landscapes, effective conservation of wildlife habitat requires extending beyond the boundaries of reserves and addressing stewardship of private lands. This approach could be especially valuable for the conservation of farm ponds, which are abundant and serve key agricultural functions on private lands. Though farm ponds also provide wildlife habitat, little is known about how they are managed or how values and beliefs of their owners relate to their quality. To address this knowledge gap, we collected data on pond habitat quality and management using historical aerial imagery and high-resolution Google Earth satellite imagery of the Grand River Grasslands of southern Iowa and Northern Missouri. We also collected spatially congruent social data using a mail back survey sent to 456 landowners in the region (32.7% response rate). We used mixed-effects linear regression to link indicators of habitat quality to the survey results. We found that many ponds were permanent, accessible to cattle, in early successional states, and had little wetland vegetation, indicating a scarcity of suitable habitat for wildlife. At the same time, 35–57% of survey respondents said they would be willing to change their management to benefit aquatic organisms. Our analyses indicated that higher cover of cattails correlated with ownership by respondents who regarded row crops or income from agriculture as less important and ponds tended to be temporary if owned by respondents who had many ponds. Moving forward, large landowners and those willing to manage their land to benefit wildlife may constitute a core set of future partners for conservation efforts focused on improving pond habitat in the region.