An analysis of nearly 600 previously published paleoecological records suggests that Earth’s terrestrial ecosystems are under risk of major transformation under all but the most aggressive climate mitigation scenarios. The results, say the authors, should inform policy discussions and also stimulate other applications of the recent fossil record to assess how Earth’s lands will be affected under future climate change. Terrestrial ecosystems are largely governed by the composition and structure of the plants and trees that they contain, and climate-induced changes to vegetation can greatly impact biodiversity and ecosystem services. While increases in global temperature are likely already driving changes in terrestrial ecosystems, understanding of the magnitude of this change is limited, constrained by imperfect models and direct observations. However, according to Connor Nolan and colleagues, a look back in time to the changing landscapes of the past offers an additional important means to evaluate the sensitivity of the world’s ecosystems to today’s rapidly changing climate. Nolan et al. used paleoecological records from nearly 600 locations around the world, which chronicle changes to vegetation as the world warmed following the Last Glacial Maximum (LGM) 21,000 years ago. Their analysis revealed that the warming that occurred between the LGM and the early Holocene (10,000 Before Present) — an increase of 4 to 7° Celsius — was sufficient to drive changes in terrestrial ecosystems worldwide. The authors suggest that this post-glacial warming is roughly comparable (albeit higher) to the warming expected to occur over the next century, should there not be significant reductions in atmospheric emissions, and as such, it serves as a conservative estimate of the magnitude of the ecological transformation likely to unfold throughout the 21st century. However, the landscape into which these ecosystems will transition remains elusive. Many will be wholly new and novel in composition, structure and function, and perhaps even vanishing, under sustained climate change.
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