Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

The interweave of people and place: biocultural diversity in migrant and indigenous livelihoods around Mount Cameroon

In order to further understanding of the links between biological and cultural diversity, this study examined the role of forest species and biodiversity in the livelihoods of indigenous Bakweri villagers and migrants to the Mount Cameroon region. Surveys of resources consumed and sold by 118 households were undertaken in five villages over the course of one year. The contributions of different habitats and management systems (compounds, farms, fallow, forest) and species (native and introduced; cultivated and wild-harvested) to local livelihoods were evaluated. The study showed that indigenous households depend to a much greater extent upon a range of habitats and species than migrant households, particularly for subsistence. Indigenous resource management systems grow from historical relationships between people and place, and promote resilience, well-being and adaptation in an area long characterized by environmental, social, political, and economic uncertainty. The managed landscapes of indigenous villages can contribute to broader conservation efforts in the region, including those associated with the newly established Mount Cameroon National Park