Public Release: 

High stakes for biodiversity, depending on which climate change target we reach

American Association for the Advancement of Science

A new assessment finds that, by 2100, the number of plant and vertebrate species losing more than half of their natural ranges will double if global warming is limited to 2°Celsius (C), rather than 1.5°C; insects are projected to be impacted the most, with 18% losing over half of their natural ranges under the warmer scenario. The United Nations Paris Agreement aims to limit global warming to "well below" 2°C above preindustrial levels and to "pursue efforts" to limit it to 1.5°C; however, current pledges by countries are expected to exceed these targets, at 3.2°C. Here, Rachel Warren and colleagues sought to understand how these different global warming scenarios will impact the geographical areas in which a species can be found ("species range"), assessing a total of more than 115,000 terrestrial species; their study involved many organisms, including many insects, that have not previously been considered in similar global biodiversity assessments. In particular, they looked at which species are expected to lose more than half of their natural ranges by 2100. The authors report that 49% of the insects, 44% of the plants, and 26% of the vertebrates included in their study will experience dramatic reductions in their ranges if global warming maxes out at 3.2°C, compared to 6% of insects, 8% of plants, and 4% of vertebrates if warming is limited to the ideal target of 1.5°C. Notably, there are substantial benefits in achieving the more ambitious 1.5°C target rather than the 2°C target; achieving the former would halve the number of species that experience severe reductions in their ranges. The authors note some species that are more likely to be impacted than others, including several pollinators. Guy Midgley highlights this study in a related Perspective.

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