Neutral theory reveals the challenge of bending the curve for the post-2020 Global Biodiversity Framework

In October, nations of the world will begin negotiations for the post-2020 Global Biodiversity Framework under the Convention on Biological Diversity. An influential ambition is bending the curve of biodiversity loss, which aims to reverse the decline of global biodiversity indicators. A second relevant, yet less prominent, milestone is the 20th anniversary of the publication of The Unified Neutral Theory of Biodiversity and Biogeography. Here, I apply neutral theory to show how global biodiversity indicators for population size (Living Planet Index) and extinction threat (Red List Index) decline under neutral ecological drift. This demonstrates that declining indicators are not solely caused by deterministic species-specific or geographical patterns of biodiversity loss. Instead, indicators are sensitive to nondirectional stochasticity. Thus, bending the curve could be assessed relative to a counterfactual based on neutral theory, rather than static baselines. If used correctly, the 20-year legacy of neutral theory can be extended to make a valuable contribution to the post-2020 Global Biodiversity Framework.

Automated summary

This article highlights the application of neutral theory to explain the decline in global biodiversity indicators, suggesting that these declines are not solely caused by specific species or geographical patterns. It proposes considering a counterfactual based on neutral theory when evaluating biodiversity frameworks to better inform policy-making.