Resistance and resilience: can the abrupt end of extreme drought reverse avifaunal collapse?

Abstract

Aim Climate change is expected to increase the frequency and intensity of extreme climatic events, such as severe droughts and intense rainfall periods. We explored how the avifauna of a highly modified region responded to a 13year drought (the 'Big Dry'), followed by a two-year period of substantially higher than average rainfall (the 'Big Wet').Location Temperate woodlands in north central Victoria, Australia.Methods We used two spatially extensive, long-term survey programmes, each of which was repeated three times: early and late in the Big Dry, and in the Big Wet. We compared species-specific changes in reporting rates between periods in both programmes to explore the resistance (the ability to persist during drought) and resilience (extent of recovery post-drought) of species to climate extremes. ResultsThere was a substantial decline in the reporting rates of 42-62% (depending on programme) of species between surveys conducted early and late in the Big Dry. In the Big Wet, there was some recovery, with 21-29% of species increasing substantially. However, more than half of species did not recover and 14-27% of species continued to decline in reporting rate compared with early on in the Big Dry. Species' responses were not strongly related to ecological traits. Species resistance to the drought was inversely related to resilience in the Big Wet for 20-35% of the species, while 76-78% of species with low resistance showed an overall decline across the study period.Conclusions As declines occurred largely irrespective of ecological traits, this suggests a widespread mechanism is responsible. Species that declined the most during the Big Dry did not necessarily show the greatest recoveries. In already much modified regions, climate extremes such as extended drought will induce on-going changes in the biota.

Vive la résistance: reviving resistance for 21st century conservation

“…When an ecological unit -for example an ecological community -experiences periodic disturbance (e.g., frequent fires, recurrent hurricanes), it might show a gradual but long-term shift in community structure, such as loss of species [51]. Such change is particularly likely when a community is subject to multiple disturbances that interact at different temporal scales, for example when drought events (multi-year) occur in fragmented landscapes (subject to decades or centuries of disturbance).…”

Climate drying amplifies the effects of land-use change and interspecific interactions on birds

“…Continuous measurements of vegetation throughout the drought were not made so that we are only able to make a direct comparison between the changes in avifauna and the vegetation for the two time periods; early in and after the Big Dry. However, we are confident of the consistency of the changes in the avifauna because these were monitored frequently throughout the Big Dry (Mac Nally et al 2009;Bennett et al 2014b). Reductions in canopy foliage, ground-litter and shrub cover during the Big Dry (Bennett et al 2013) was likely to reduce the availability of both nest-sites and food.…”

“…Species were allocated to a single guild, deemed most appropriate. For a full explanation of the selected guilds see (Bennett et al 2014b). …”

“…Bird assemblages of the box-ironbark forests of south-eastern Australia have experienced pressure from drought and vegetation loss, fragmentation and degradation (Mac Nally et al 2009;Bennett et al 2014b). We sought to determine: (1) whether there was a shift in the bird assemblages between 1995-1997 (our original pre-Big Dry surveys) and -2011.…”

Conserving migratory and nomadic species

“…While a nomad and an equivalent sedentary species could be at equally high risk from threats whilst occupying a bottleneck or refugial site, the ability of nomads to expand in distribution (and population) when environmental conditions improve may buffer them from stochastic threats over the long term as they can move on and take advantage of good conditions elsewhere (Dean 2004). However, recent work has found that the buffering effect of movements is obviated in the face of widespread habitat loss, with equal declines among migrants and non-migrants (Albright et al 2010;Bennett et al 2014). Movement itself could be risky in the sense that locations and timings of suitable resources are unpredictable and irregular (MacNally 2009).…”