Annual temperature variation influences the vulnerability of montane bird communities to land‐use change

Abstract

Understanding how and why species respond to land-use change is one of the central challenges in conservation biology, yet the causes of variation in the responses of species to land-use change remain unclear. We tested whether adaptation to different abiotic environments influenced the vulnerability of bird communities to agricultural expansion in the Himalayan mountain range, which exhibits a strong east-west gradient in annual temperature variation. We did so by surveying bird communities in forest and agriculture at opposite ends of that gradient. We contrasted metrics of species richness, diversity, community composition and forest dependency across land-use types and regions, and tested whether species' thermal sensitivity influenced their response to the replacement of forest with agriculture. Agricultural land in the relatively aseasonal east harboured significantly fewer bird species than did forests, a pattern that is starkly reversed in the highly seasonal west. For species common to both regions, eastern populations used forest ~35% more than did western populations. While western species were less constrained by temperature than eastern species, western species with narrow thermal tolerances were also more forest dependent. Selection across a stark environmental gradient on a common species pool appears to have altered the vulnerability of Himalayan birds to forest loss, with communities in the relatively aseasonal east much more sensitive to forest conversion than those in the west. Adaptation to local environmental conditions appears to mediate species' responses to land use change, with thermal specialists more vulnerable to forest loss than species with greater thermal tolerances. Species' responses to global change may differ predictably along abiotic gradients even within a single region or biodiversity hotspot, and such variation must be addressed in conservation planning.

Interactive impacts of climate change and land‐use change on the demography of montane birds

“…2). Other species traits, such as size and social and migratory behavior, did not emerge as important predictors of survival trends, indicating that adaptation to the thermal environment—rather than other species traits—influences the responses of species to anthropogenic habitat change, which is supported by prior work from the Himalayan mountain range (Srinivasan et al 2019). Given that across species, body mass was not associated with differences in survival rates in primary and logged forest, it is likely that temperature differences between primary and logged forest primarily influence fitness and survival indirectly (through, e.g., food availability) rather than through direct physiological pathways such as thermal tolerance (which are strongly tied to body size and surface area:volume ratios).…”

Topography and human pressure in mountain ranges alter expected species responses to climate change

“…If these patterns are consistent in other mountain landscapes and trends continue, species richness may continue to increase in mountains globally. Some evidence suggests that montane species may be more tolerant of land-use change than lowland species because they evolved in more variable climates and may thus be more adapted to cope with temperature changes arising from habitat modification (e.g., increased temperatures following logging) [46][47][48] . This could provide further rescue effects from pressure related to human activities.…”

Tropical and Mediterranean biodiversity is disproportionately sensitive to land-use and climate change

“…In particular, tropical biomes have a lower degree of seasonality than temperate and high-latitude biomes. Species that have evolved to tolerate the narrower range of climatic and other environmental conditions within tropical biomes are likely to be more sensitive to environmental changes than those that evolved in areas with greater environmental variability 36,37 . Indeed, responses to both climate and land-use change have been shown to be most negative in areas of low climatic seasonality or among species inhabiting these areas 18,27,38 .…”