The interacting effects of climate and land-use/land-cover changes on ecological communities

Human activities continue to create land-use/land-cover (LULC) change across the Earths surface, and together with climate change, are major drivers of changes in biodiversity through time. However, the impacts of these spatiotemporally variable drivers on biodiversity change can be complex. We examined the effects of interactions between climate and LULC change on bird communities across the continental United States over nearly three decades. We analyzed temperature and precipitation data alongside data on tree-canopy, cropland, urban, and surface-water cover to understand how climate/LULC-change interactions influence species richness and abundance. Our results revealed stable or increasing trends in species richness, but a decline in overall abundance primarily from common species and a consequent increase in aspects of evenness of communities. We found that areas experiencing warming and drying climates exhibited increased species richness and slower declines in abundance. However, impacts of LULC change had contrasting effects on richness and abundance. Areas that experienced increasing tree-canopy cover over time had increasing trends in species richness, but exacerbated declines in abundance. On the other hand, areas with increasing cropland had moderated abundance declines, but more declining trends in richness. Finally, we found that the effects of climate/LULC-change interactions varied across the range of each pressure. While some interactions support a dominant role of climate change in structuring communities, others indicate that LULC change can mitigate or exacerbate the impact of climate change on biodiversity. Overall, our results highlight the importance of considering the direction and magnitude of each driver when assessing how climate and LULC interactions shape ecological communities.