Abstract
Long-term data are needed to explore the interaction of weather extremes with habitat alteration; in particular, can ‘refugia’ buffer population dynamics against climate change and are they robust to disturbances such as timber harvesting. Because forest bats are good indicators of ecosystem health, we used 14 years (1999–2012) of mark-recapture data from a suite of small tree-hollow roosting bats to estimate survival, abundance and body condition in harvested and unharvested forest and over extreme El Niño and La Niña weather events in southeastern Australia. Trapping was replicated within an experimental forest, located in a climate refuge, with different timber harvesting treatments. We trapped foraging bats and banded 3043 with a 32% retrap rate. Mark-recapture analyses allowed for dependence of survival on time, species, sex, logging treatment and for transients. A large portion of the population remained resident, with a maximum time to recapture of nine years. The effect of logging history (unlogged vs 16–30 years post-logging regrowth) on apparent survival was minor and species specific, with no detectable effect for two species, a positive effect for one and negative for the other. There was no effect of logging history on abundance or body condition for any of these species. Apparent survival of residents was not strongly influenced by weather variation (except for the smallest species), unlike previous studies outside of refugia. Despite annual variation in abundance and body condition across the 14 years of the study, no relationship with extreme weather was evident. The location of our study area in a climate refuge potentially buffered bat population dynamics from extreme weather. These results support the value of climate refugia in mitigating climate change impacts, though the lack of an external control highlights the need for further studies on the functioning of climate refugia. Relatively stable population dynamics were not compromised by timber harvesting, suggesting ecologically sustainable harvesting may be compatible with climate refugia.
Highlights
Many species face challenges of climate change interacting with habitat alteration
Sufficient data for modelling survival and abundance was available for four species that varied in body mass: C. morio (8 g), V. darlingtoni (6 g), V. regulus (5 g) and V. pumilus (4 g)
We found that apparent survival was not strongly influenced by extreme weather patterns, except for the smallest species, nor was abundance or body condition
Summary
Many species face challenges of climate change interacting with habitat alteration. Understanding how these perturbations affect life history attributes and drive population dynamics is vital for improving future conservation and management of species. Long-term data sets are needed to quantify variation in population dynamics, especially in relation to management interventions and global-climate-change induced weather extremes [1, 2, 3]. Some progress has been made in identifying drought refuges in arid environments [5], but existing proposals for evaluating the value of refugia often rely on mechanistic model frameworks [6]. Buffering of population dynamics in potential climate refugia during weather extremes is relatively underexplored
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