Impacts of tropical agriculture on biodiversity across spatial scales

The conversion of natural habitats to agriculture is a key driver of the global extinction crisis, with the future of biodiversity increasingly reliant upon agricultural policymakers. Understanding the impacts of agriculture on biodiversity and how best to manage farming to avert biodiversity loss are thus critical issues. At local spatial scales, conversion drives reductions in evolutionary distinct species, and phylogenetic and functional diversity. Yet, impacts may be minor compared to impacts at larger spatial scales. Impacts of farming on biodiversity will be determined by the rate of change in species over space, which is shaped by processes that cause species composition between sites to become more similar or more different. These processes may happen simultaneously and at multiple spatial scales: teasing apart their prevalence is a frontier in ecology and critical to understanding the true impacts of farming on total diversity in a region. Our project investigated how and by what mechanism agriculture affects processes of species turnover among sites that ultimately determine diversity across large scales. At the extremes, there are two management possibilities: 'land-sharing' with low-intensity farming, versus 'land-sparing' with high intensity farming over a smaller land area that allows intact natural habitat to be preserved. However, which strategy is best across spatial scales? Understanding diversity loss or retention under each strategy at different spatial scales would provide a more direct solution to the problem. Our project focused on the effects of cattle farming on birds, dung beetles and carbon stocks in Colombia - an ideal location for the study as Colombia has the highest avian species richness in the world, including several Endemic Bird Areas, and large climatic and topographic variability. A total of 969 bird species were registered across several endemic areas and habitats. This is, to our knowledge, the single largest breeding bird species dataset ever collected for a region. Analyses of the 969 bird species obtained from 3357 unique visits to 848 points across Colombia indicates that species with range limits at topographic barriers and species with narrow elevational ranges show elevated sensitivity to forest clearing. Additionally, lowland species show elevated sensitivity. We also registered 204 dung beetle taxa - at least two of these are expected to be new to science - and collected carbon stock data for 341 forest sites connected to the bird and dung beetle sampling. The study represents a major international advance in our understanding of the impacts of farming and mechanisms driving diversity changes across spatial scales.

Our bird and dung beetle species lists, and distribution data, will be used to update the national Biodiversity Information System of Colombia (SiB-Col). We have obtained sorely missing baseline data from several remote locations that are important for conservation and management. In addition, our wood specific gravity data will greatly enhance our power to predict carbon stocks at multiple scales. In this way, the project may provide a foundation for sustained biodiversity conservation efforts by identifying unique landscapes requiring targeted conservation action. For example, where biodiversity and carbon co-benefits are high. Our results are relevant for the scientific community, policy and decision makers, and investors in the carbon market alike. The project could help strengthen national policies to protect both forest cover and biodiversity. The dung beetle specimens are stored in the Entomological Collection of the Humboldt Institute and will serve as a reference collection.

The conversion of natural habitats to agriculture is a key driver of the global extinction crisis, with the future of biodiversity increasingly reliant upon agricultural policymakers. Understanding the impacts of agriculture on biodiversity and how best to manage farming to avert biodiversity loss are thus critical issues. At local spatial scales, conversion drives reductions in evolutionary distinct species, and phylogenetic and functional diversity. Yet impacts may be minor compared to impacts at larger spatial scales. Impacts of farming on biodiversity will be determined by the rate of change in species over space (beta-diversity), which is shaped by processes that cause species composition between sites to become more similar (biotic homogenization) or more different (biotic heterogenization). These processes may happen simultaneously and at multiple spatial scales: teasing apart their prevalence is a frontier in ecology and critical to understanding the true impacts of farming on gamma (overall) diversity. This project will be the first to determine how and by what mechanism agriculture affects processes of beta-diversity (turnover) among sites that ultimately determine gamma diversity across large scales. At the extremes, there are two management possibilities:'land-sharing' with low-intensity farming, versus 'land-sparing' with high intensity farming over a smaller land area that allows intact natural habitat to be preserved. But which strategy is best across spatial scales? Understanding the spatial scaling diversity loss or retention under each strategy would provide a more direct solution to the problem. Our project will focus on the effects of cattle farming on birds in the Tropical Andes of Colombia -a zone of critical conservation importance that transcends eight Endemic Bird Areas. This study would represent a major international advance in our understanding of the impacts of farming and mechanisms driving diversity changes across spatial scales.