Projected increases in exposure to climate extremes across global vertebrate diversity hotspots

Climate change intensifies climate extremes globally, threatening biodiversity. Vertebrates vulnerable to climate extremes are identified by the International Union for Conservation of Nature (IUCN), though future changes in exposure to climate extremes for these species remain unclear. Using CMIP6 climate models under four Shared Socio-economic Pathways, we projected changes in extreme drought, heat, and precipitation frequencies globally between 1974–2014 and 2050–2090 for 1,634 terrestrial vertebrates considered threatened by climate extremes, focusing on 33 global vertebrate diversity hotspots. Results indicate substantial increases in climate extremes, with tropical regions facing the highest increases in extreme heat and drought. Hotspots with few climate extreme-threatened vertebrates often face the highest increases in climate extreme frequencies, suggesting vertebrate vulnerability within numerous hotspots is understudied. These results highlight the need to incorporate climate projections into conservation assessments, and for targeted research on climate extreme effects on tropical vertebrates, which may have lower tolerances to climatic change than temperate counterparts.

Methods
We used global standardized precipitation index (SPI) and temperature data to calculate past and future climate extreme occurrence. To this end, we used four Global Climate Models (GCM) and four Representative Concentration Pathways (RCP), for a historical and future period, from CMIP6 projections.  We analyzed changes in drought exposure across species ranges considered by IUCN to be threatened by three types of climate extremes, and across 33 global vertebrate diversity hotspots holding about 85% of global vertebrate diversity.

气候变化在全球范围内加剧气候极端事件，对生物多样性构成威胁。世界自然保护联盟（International Union for Conservation of Nature, IUCN）已识别出易受气候极端事件影响的脊椎动物，但这些物种未来面临的气候极端事件暴露程度变化仍不明确。本研究依托耦合模式比较计划第六阶段（Coupled Model Intercomparison Project Phase 6, CMIP6）下的4种共享社会经济路径相关气候模式，针对1634种被认定受气候极端事件威胁的陆生脊椎动物，以及33个全球脊椎动物多样性热点区域，预测了1974-2014年至2050-2090年间全球极端干旱、极端高温与极端降水发生频率的变化。研究结果显示，气候极端事件发生频率将大幅上升，热带地区的极端高温和极端干旱增幅最为显著。那些仅分布有少量受气候极端事件威胁脊椎动物的热点区域，往往面临最高的气候极端事件频率增幅，这表明众多热点区域内的脊椎动物易受性尚未得到充分研究。本研究结果凸显了将气候预测纳入保护评估的必要性，同时也呼吁针对热带脊椎动物开展针对性研究——相较于温带类群，热带脊椎动物对气候变化的耐受度可能更低。
方法
本研究采用全球标准化降水指数（Standardized Precipitation Index, SPI）与气温数据，计算历史与未来时期的气候极端事件发生情况。为此，本研究依托CMIP6的预估数据集，选用4个全球气候模式（Global Climate Model, GCM）与4种典型浓度路径（Representative Concentration Pathways, RCP），覆盖历史与未来两个时期。本研究分析了IUCN认定受三类气候极端事件威胁的物种的分布范围内，以及占全球脊椎动物多样性约85%的33个全球脊椎动物多样性热点区域的干旱暴露程度变化。