Biodiversity loss reduces global terrestrial carbon storage. A study using a macroecological model and empirical data shows that biodiversity declines under climate and land-use change scenarios could lead to a global loss of 7.44–103.14 PgC (global sustainability scenario) and 10.87–145.95 PgC (fossil-fueled development scenario). This indicates a self-reinforcing feedback loop where higher climate change leads to greater biodiversity loss, which in turn increases carbon emissions and climate change. Biodiversity conservation and restoration can help achieve climate change mitigation goals. Climate change and biodiversity loss are interconnected crises. Experimental studies show that more diverse plant assemblages have higher biomass production and carbon sequestration. Biodiversity loss can be a major driver of productivity loss, on par with elevated CO₂ or drought effects. Thus, biodiversity loss can affect climate change by altering carbon sequestration and storage. Despite biodiversity's role in carbon sequestration, high-level nature-based solutions often focus on increasing ecosystem extent rather than diversity. Ecosystem service models often do not account for biodiversity effects. Earth System Models (ESMs) typically use a small number of plant functional types and do not include biodiversity-productivity mechanisms. Incorporating biodiversity-ecosystem function relationships could improve model accuracy, especially over long timescales. The study used the Biogeographic Infrastructure for Large-scaled Biodiversity Indicators (BILBI) model to project plant species richness changes and linked it with empirical biodiversity-biomass relationships. The results showed that biodiversity loss leads to significant carbon storage loss, particularly in tropical regions. Under the fossil-fueled development scenario, carbon loss was higher, with losses up to 145.32 PgC. These losses could rival emissions from land-use change or melting permafrost. The study highlights the importance of maintaining and enhancing plant species diversity in natural vegetation to address climate change. However, existing initiatives often focus on ecosystem extent rather than diversity and composition. Biodiversity loss can drive carbon emissions, and maintaining biodiversity is crucial for carbon storage. The study also notes uncertainties in biodiversity-ecosystem function relationships and the need for further research to improve models and policies. Biodiversity conservation and restoration are essential for climate change mitigation, emphasizing the need to consider biodiversity's functional value rather than just area-based measures.Biodiversity loss reduces global terrestrial carbon storage. A study using a macroecological model and empirical data shows that biodiversity declines under climate and land-use change scenarios could lead to a global loss of 7.44–103.14 PgC (global sustainability scenario) and 10.87–145.95 PgC (fossil-fueled development scenario). This indicates a self-reinforcing feedback loop where higher climate change leads to greater biodiversity loss, which in turn increases carbon emissions and climate change. Biodiversity conservation and restoration can help achieve climate change mitigation goals. Climate change and biodiversity loss are interconnected crises. Experimental studies show that more diverse plant assemblages have higher biomass production and carbon sequestration. Biodiversity loss can be a major driver of productivity loss, on par with elevated CO₂ or drought effects. Thus, biodiversity loss can affect climate change by altering carbon sequestration and storage. Despite biodiversity's role in carbon sequestration, high-level nature-based solutions often focus on increasing ecosystem extent rather than diversity. Ecosystem service models often do not account for biodiversity effects. Earth System Models (ESMs) typically use a small number of plant functional types and do not include biodiversity-productivity mechanisms. Incorporating biodiversity-ecosystem function relationships could improve model accuracy, especially over long timescales. The study used the Biogeographic Infrastructure for Large-scaled Biodiversity Indicators (BILBI) model to project plant species richness changes and linked it with empirical biodiversity-biomass relationships. The results showed that biodiversity loss leads to significant carbon storage loss, particularly in tropical regions. Under the fossil-fueled development scenario, carbon loss was higher, with losses up to 145.32 PgC. These losses could rival emissions from land-use change or melting permafrost. The study highlights the importance of maintaining and enhancing plant species diversity in natural vegetation to address climate change. However, existing initiatives often focus on ecosystem extent rather than diversity and composition. Biodiversity loss can drive carbon emissions, and maintaining biodiversity is crucial for carbon storage. The study also notes uncertainties in biodiversity-ecosystem function relationships and the need for further research to improve models and policies. Biodiversity conservation and restoration are essential for climate change mitigation, emphasizing the need to consider biodiversity's functional value rather than just area-based measures.