Integrating α and β diversity in conservation planning.

Conservation planning has long prioritized local species richness (α diversity) but has rarely explicitly integrated species turnover (β diversity) into actionable strategies. Areas with high species turnover lack recognition and protection despite their ecological importance. We devised a simple, standardized, and scalable approach for mapping species turnover. We rasterized species ranges, then counted the range edges of each species in each grid cell. This approach enables high-resolution mapping across regions and facilitates the integration of β diversity into conservation planning. We applied this approach to the Eastern Himalayas, where 3 biodiversity hotspots abut, and used endemic bird species as our focal taxa. Our analyses revealed differences between areas of high species richness and high species turnover. Areas of high species richness were concentrated in montane forests, whereas areas of high species turnover tended to be low in mountain forests and peak in foothills and tree lines. Both areas of high species richness and high species turnover are inadequately protected. We contend that species turnover is a critical, complementary metric to species richness in understanding patterns of biodiversity. In addition, areas of high species turnover host unique species assemblages and face a dual challenge. They host peripheral populations that are more prone to local extinction, and communities within them are particularly sensitive to climate change. These vulnerabilities heighten the urgency of protecting such areas. As conservation planning evolves toward more holistic strategies that address multiple interconnected environmental challenges-such as biodiversity loss, climate change, and water security-it becomes increasingly imperative to integrate both α and β diversity into biodiversity mapping. This integration provides a more representative and ecologically robust foundation for long-term conservation planning.