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

Abstract

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.

Vive la résistance: reviving resistance for 21st century conservation

“…Such factors might explain variation in resistance and resilience among otherwise ecologically similar units (i.e., ecological units with similar intrinsic attributes). For example, during a severe drought in south-eastern Australia, Selwood et al [44] and Haslem et al [45] showed that the resistance of bird communities to drought was affected by environmental variables (vegetation type and the extent of tree cover, respectively). These findings suggest that extrinsic factors amenable to conservation management (either through habitat restoration or protection) modulate resistance and resilience.…”

“…For instance, the 'climate refuge' concept is linked to both resistance and resilience [44]. Microclimates that are buffered from climatic extremes allow individuals to survive, or allow continued recruitment at the local scale, such that such locations have higher resistance to drought.…”

“…Many ecosystems are exposed to multiple interacting disturbances, such that the resistance and resilience of the biota to a given disturbance might be amplified or diminished by existing disturbance processes [45,59]. Resistance and resilience are likely to vary along natural environmental gradients [44]. Some areas can be buffered from disturbance more than their surroundings, thereby providing a more stable environment.…”

“…These approaches depend on variation in resistance and resilience being relatable to spatial data, such as remotely sensed vegetation patterns. Recent work at the community and species levels indicate that this is often the case [44,45,55].…”

Species‐specific and temporal scale‐dependent responses of birds to drought

“…Drought can impact birds by reducing breeding success (Colón, Long, & Morrison, 2017;Cruz-McDonnell & Wolf, 2016;Skagen & Adams, 2012), causing abundance shifts (Albright, Pidgeon, Rittenhouse, Clayton, Wardlow, et al, 2010;Gorzo et al, 2016;Selwood, Thomson, Clarke, McGeoch, & Mac Nally, 2015), reducing species richness , or by driving interannual range shifts or dispersive movements (Bateman et al, 2015). Drought can impact birds by reducing breeding success (Colón, Long, & Morrison, 2017;Cruz-McDonnell & Wolf, 2016;Skagen & Adams, 2012), causing abundance shifts (Albright, Pidgeon, Rittenhouse, Clayton, Wardlow, et al, 2010;Gorzo et al, 2016;Selwood, Thomson, Clarke, McGeoch, & Mac Nally, 2015), reducing species richness , or by driving interannual range shifts or dispersive movements (Bateman et al, 2015).…”