The environmental consequences of climate-driven agricultural frontiers

atmosphere is beyond the scope of this study, it is highly likely that developing such regions for agriculture will have significant impacts on greenhouse gas emissions that need to be bal- anced against the benefits of increased food supply and constrained by sound environmental policies. Biodiversity impacts The biodiversity impacts of the climate-driven frontiers occur where the frontiers intersect with important ecosystems and habitats (Table 3). Among global priorities for biodiversity conservation, 56% of global biodiversity hotspots, 22% of Endemic Bird Areas (EBAs) and 13% of Key Biodiversity Areas (KBAs) intersect with climate-driven agricultural frontiers (ensemble median RCP8.5 2060–2080; see Table 3). Biodiversity hotspots that have the larg- est intersection with frontiers are the Tropical Andes, the Mountains of Central Asia, the Horn of Africa and the Chilean Winter Rainfall and Valdivian Forests. Species’ ranges may move in response to climate change, causing changes in patterns of bio- diversity, at the same time as frontiers are opening. To test the effect of frontiers on future, as well as present, patterns of biodiversity, the ranges of all global restricted range birds, a set of high conservation priority species found in hotspots, KBAs and EBAs, were modelled [59]. These results show that the number of restricted range birds impacted by frontiers increases in the future from 409 species to 491 species under RCP8.5 representing 20% of the 2,451 global restricted range bird species and 409 to 362 under RCP4.5 (Table 3). Thus, range shifts due to

climate change accentuate the intersection of frontiers with suitable climate for rare species, as both crop suitability and suitable climate for species move upslope. However, this effect Fig 2. Soil organic carbon content in top 1 meter of soil (103 kg ha-1) in areas of climate-driven agricultural commodity frontiers using RCP8.5 2060–2080 climate projections (blue color ramp). Areas with >50% GCM agreement commodity frontiers are shown. Existing agricultural land cover >10% of each pixel is represented in light brown. https://doi.org/10.1371/journal.pone.0228305.g002 The environmental consequences of climate-driven agricultural frontiers PLOS ONE | https://doi.org/10.1371/journal.pone.0228305 February 12, 2020 8 / 19