Functional Wetland Loss Drives Emerging Risks to Waterbird Migration Networks

J Patrick Donnelly,Johnnie N Moore,Michael L Casazza,Shea P Coons

doi:10.3389/fevo.2022.844278

J Patrick Donnelly, Johnnie N Moore + Show 2 more

Open Access

https://doi.org/10.3389/fevo.2022.844278

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Abstract

Migratory waterbirds (i.e., shorebirds, wading birds, and waterfowl) rely on a diffuse continental network of wetland habitats to support annual life cycle needs. Emerging threats of climate and land-use change raise new concerns over the sustainability of these habitat networks as water scarcity triggers cascading ecological effects impacting wetland habitat availability. Here we use important waterbird regions in Oregon and California, United States, as a model system to examine patterns of landscape change impacting wetland habitat networks in western North America. Wetland hydrology and flooded agricultural habitats were monitored monthly from 1988 to 2020 using satellite imagery to quantify the timing and duration of inundation—a key delimiter of habitat niche values associated with waterbird use. Trends were binned by management practice and wetland hydroperiods (semi-permanent, seasonal, and temporary) to identify differences in their climate and land-use change sensitivity. Wetland results were assessed using 33 waterbird species to detect non-linear effects of network change across a diversity of life cycle and habitat needs. Pervasive loss of semi-permanent wetlands was an indicator of systemic functional decline. Shortened hydroperiods caused by excessive drying transitioned semi-permanent wetlands to seasonal and temporary hydrologies—a process that in part counterbalanced concurrent seasonal and temporary wetland losses. Expansion of seasonal and temporary wetlands associated with closed-basin lakes offset wetland declines on other public and private lands, including wildlife refuges. Diving ducks, black terns, and grebes exhibited the most significant risk of habitat decline due to semi-permanent wetland loss that overlapped important migration, breeding, molting, and wintering periods. Shorebirds and dabbling ducks were beneficiaries of stable agricultural practices and top-down processes of functional wetland declines that operated collectively to maintain habitat needs. Outcomes from this work provide a novel perspective of wetland ecosystem change affecting waterbirds and their migration networks. Understanding the complexity of these relationships will become increasingly important as water scarcity continues to restructure the timing and availability of wetland resources.

Highlights

IntroductionConservation of migratory birds is complex, requiring knowledge of species movements between distinct regions spanning hundreds to thousands of kilometers that collectively support breeding, wintering, and stopover habitats
Water development associated with many of these sites acts as drivers of urban development and irrigated agriculture supporting metropolitan centers and agricultural economies that account for 40% of global food production (UNESCO-UN-Water, 2020)
Wetland change in SONEC was driven by functional decline as indicated by the continuous drying of semi-permanent wetlands consistent across functional groups

Summary

Introduction

Conservation of migratory birds is complex, requiring knowledge of species movements between distinct regions spanning hundreds to thousands of kilometers that collectively support breeding, wintering, and stopover habitats. Climate and landuse change are the major factors affecting migratory habitats and have substantially increased the risk of species declines globally (Spooner et al, 2018). While some birds have changed their migration chronology and range extent to align with shifting climate and land-use patterns (Hitch and Leberg, 2007; Visser et al, 2009), increasing environmental pressures are likely to outstrip the adaptive plasticity of many species (Schmaljohann and Both, 2017). Waterbirds in some regions have adapted to landscape change by utilizing agricultural food resources and flood irrigation practices to offset historic wetland losses (Elphick and Oring, 2003; Taft and Haig, 2005; Donnelly et al, 2021). Emerging impacts of climate change in these regions raise concerns over the sustainability of continental wetland networks as water scarcity triggers land-use change and ecological effects misaligned with waterbird habitat needs (Haig et al, 2019; Donnelly et al, 2020)

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