The costs of global protected-area expansion (Target 3 of the post-2020 Global Biodiversity Framework) may fall more heavily on lower-income countries

One of the biggest stumbling blocks for global environmental agreements is how higher-income and lower-income countries share the costs of implementing them. This problem has become particularly acute as biodiversity and climate ambitions have increased across recent COPs (Conferences of Parties). Here, we estimate the likely distribution of costs for one of the most ambitious proposals: draft Target 3 of the Global Biodiversity Framework (GBF), which would increase coverage of protected and conserved areas (PCAs) to 30% of global land and sea area - more than triple the current value. Since the GBF does not specify where new PCAs would be placed, we use three scenarios of how Target 3 might be implemented, cost those scenarios, and then compare the mean distribution of costs across World Bank income groups. We find that in relative terms, lower-income countries could face considerably larger financial burdens than high-income countries, even though the benefits of conservation are disproportionately enjoyed by high-income countries. Lower-income countries would also face larger increases in the amount of land or sea under conservation, implying higher opportunity and establishment costs. Resolving this potential cost-sharing inequity may be a key requirement to achieve consensus on draft Target 3, and indeed on ambitious environmental proposals more generally.