Ongoing deforestation poses a major threat to biodiversity^1,2. With limited resources and imminent threats, deciding when as well as where to conserve is a fundamental question. Here we use a dynamic optimization approach to identify an optimal sequence for the conservation of plant species in 458 forested ecoregions globally over the next 50 years. The optimization approach includes species richness in each forested ecoregion, complementarity of species across ecoregions, costs of conservation that rise with cumulative protection in an ecoregion, the existing degree of protection, the rate of deforestation and the potential for reforestation in each ecoregion. The optimal conservation strategy for this formulation initially targets a small number of ecoregions where further deforestation leads to large reductions in species and where the costs of conservation are low. In later years, conservation efforts spread to more ecoregions, and invest in both expanded protection of primary forest and reforestation. The largest gains in species conservation come in Melanesia, South and Southeast Asia, the Anatolian peninsula, northern South America and Central America. The results highlight the potentially large gains in conservation that can be made with carefully targeted investments.

持续的森林砍伐对生物多样性构成重大威胁^1,2. 在资源有限且威胁迫在眉睫的情况下，决定何时何地进行保护是一个基本问题。在这里，我们使用动态优化方法来确定未来 50 年全球 458 个森林生态区植物物种保护的最佳顺序。优化方法包括每个森林生态区的物种丰富度、生态区物种的互补性、随着生态区累积保护而上升的保护成本、现有保护程度、森林砍伐率和每个生态区重新造林的潜力。该公式的最佳保护策略最初针对少数生态区，进一步的森林砍伐导致物种大量减少并且保护成本较低。在以后的岁月里，保护工作扩展到更多的生态区，并投资于扩大原始森林的保护和重新造林。物种保护的最大成果来自美拉尼西亚、南亚和东南亚、安纳托利亚半岛、南美洲北部和中美洲。结果强调了通过谨慎有针对性的投资可以在保护方面获得巨大收益。