The environmental consequences of climate-driven agricultural frontiers

Growing conditions for crops such as coffee and wine grapes are shifting to track climate change. Research on these crop responses has focused principally on impacts to food production impacts, but evidence is emerging that they may have serious environmental consequences as well. Recent research has documented potential environmental impacts of shifting cropping patterns, including impacts on water, wildlife, pollinator interaction, carbon storage and nature conservation, on national to global scales. Multiple crops will be moving in response to shifting climatic suitability, and the cumulative environmental effects of these multi-crop shifts at global scales is not known. Here we model for the first time multiple major global commodity crop suitability changes due to climate change, to estimate the impacts of new crop suitability on water, biodiversity and carbon storage. Areas that become newly suitable for one or more crops are Climate-driven Agricultural Frontiers. These frontiers cover an area equivalent to over 30% of the current agricultural land on the planet and have major potential impacts on biodiversity in tropical mountains, on water resources downstream and on carbon storage in high latitude lands. Frontier soils contain up to 177 Gt of C, which might be subject to release, which is the equivalent of over a century of current United States CO2 emissions. Watersheds serving over 1.8 billion people would be impacted by the cultivation of the climate-driven frontiers. Frontiers intersect 19 global biodiversity hotspots and the habitat of 20% of all global restricted range birds. Sound planning and management of climate-driven agricultural frontiers can therefore help reduce globally significant impacts on people, ecosystems and the climate system.咖啡与酿酒葡萄（wine grapes）等作物的种植适宜条件正随气候变化发生迁移。针对这类作物响应气候变化的研究此前主要聚焦其对粮食生产的影响，但越来越多证据显示，此类种植格局变化也可能带来严重的环境后果。近期已有研究在国家至全球尺度上，揭示了种植格局变迁所引发的潜在环境影响，包括对水资源、野生生物、传粉者互动、碳储存以及自然保护的影响。多种作物将随气候适宜性的变化发生迁移，但目前学界尚未明确全球范围内多种作物同步迁移所带来的累积环境效应。本研究首次针对气候变化引发的全球多种主要商品作物适宜性变化进行建模，以评估新的作物适宜区对水资源、生物多样性以及碳储存的影响。新具备一种或多种作物种植适宜性的区域，即为气候驱动型农业前沿区（Climate-driven Agricultural Frontiers）。此类前沿区总面积相当于全球当前耕地的30%以上，其对热带山地的生物多样性、下游水资源以及高纬度地区的碳储存均可能产生重大影响。前沿区土壤中储存了高达177吉吨（Gt）的碳，这些碳有可能被释放，其总量相当于美国当前一个多世纪的二氧化碳排放量。气候驱动型农业前沿区的开垦活动，将影响全球超过18亿人口所依赖的流域。此类前沿区与19个全球生物多样性热点地区（global biodiversity hotspots）重叠，同时覆盖了全球20%的狭域分布鸟类栖息地。因此，对气候驱动型农业前沿区开展合理的规划与管理，有助于减轻其对人类、生态系统以及气候系统产生的全球性重大影响。