Resistance and resilience of terrestrial birds in drying climates: do floodplains provide drought refugia?

Aim Climate refugia will become increasingly important for biota as climate change causes an increased frequency and intensity of extreme events, such as drought. Floodplains are potential drought refugia because they have cooler and more mesic microclimates than adjacent areas, and greater water availability through shallower groundwater and flooding. We explored the role of floodplains as drought refugia by estimating the resistance and resilience of terrestrial birds over a 13-year drought (the ‘Big Dry’) and for 4 years following the break in the drought in floodplain and non-floodplain zones. Location Murray–Darling Basin, Australia. Methods We used Atlas of Australian Birds survey data from more than 39,000 surveys at over 28,000 sites to estimate trends in reporting rates in floodplain and non-floodplain zones for 144 bird species during extended drought (1998–2009) and in the post-drought period (2010–13). Results There was greater resistance to drought in floodplain zones: fewer species declined in floodplain zones (19%) than in non-floodplain zones (29%) during the Big Dry, and more species had elevated reporting rates (13% vs. 8%). More species showed a recovery in reporting rates in non-floodplain zones (40.3%) than in floodplain zones (15.3%) during the post-drought period, which was expected because declines during the Big Dry were more common in non-floodplain zones. There was some evidence for limitations in the resilience of floodplain avifauna, with only 17.9% of species that declined in floodplain zones during the drought subsequently recovering. Conclusions Floodplains appear to enhance resistance to drought for many bird species, and are likely to be particularly important as refugia in areas with an arid climate. However, their role in resilience is less clear. Floodplain ecosystems require long-term management to relieve pressures and to restore their ecological condition so that their role as drought refugia is maintained or enhanced.

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