Assessing ambitious nature conservation strategies within a 2 degree warmer and food-secure world

Global biodiversity is projected to further decline under a wide range of future socio-economic development pathways, even in sustainability oriented scenarios. This raises the question how biodiversity can be put on a path to recovery, the core challenge for the CBD post-2020 global biodiversity framework. We designed two contrasting, ambitious global conservation strategies, Half Earth (HE) and Sharing the Planet (SP), and evaluated their ability to restore terrestrial and freshwater biodiversity and to provide ecosystem services while also mitigating climate change and ensuring food security. We applied the integrated assessment framework IMAGE with the GLOBIO biodiversity model, using the Middle of the Road Shared Socio-economic Pathway (SSP2) with its projected human population growth as baseline. We found that both conservation strategies result in a reduction in the loss of biodiversity and ecosystem services globally, but without additional measures to achieve effective climate mitigation they will be insufficient to restore biodiversity. The HE strategy performs better for terrestrial biodiversity protection (biodiversity intactness (MSA), Red List Index, geometric mean abundance) in currently still natural regions, reflecting global conservation priorities. The SP strategy yields more improvements for biodiversity in human-used areas, aquatic biodiversity and for regulating ecosystem services (pest control, pollination, erosion control), reflecting regional priorities. However, conservation only scenarios show a considerable increase in food security risks (especially in Sub-Saharan Africa) compared to the baseline and limited reduction of global temperature increase. Only when conservation strategies are combined with climate change mitigation efforts and additional actions especially in the agricultural and energy system into a portfolio of integrated sustainability measures, both conservation strategies result in restoring biodiversity to current values or even some improvement, while keeping global warming below two degrees and keeping food security risks below baseline. Minimizing food wastes and reducing consumption of animal products will be crucial.