Global biodiversity has declined between 2% and 11% during the 20th century primarily due to land-use change, according to a large multi-model study published in Science. Led by the German Centre for Integrative Biodiversity Research (iDiv) and the Martin Luther University Halle-Wittenberg (MLU), the study compared thirteen models to assess the impact of land-use change and climate change on biodiversity metrics and ecosystem services. This analysis provides a comprehensive estimate of the global decline in biodiversity over the past century.
The researchers found that land-use change has been the largest driver of biodiversity change, as stated by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES). The study found that global biodiversity may have declined by 2% to 11% due to land-use change alone, based on calculations from seven different models and four biodiversity metrics. By including all world regions in their model, the researchers were able to address criticisms of other approaches that may have had fragmented or biased data, providing a more accurate estimate of global biodiversity trends.
In addition to the decline in biodiversity, the study also revealed mixed trends for ecosystem services in the past century. While provisioning ecosystem services, such as food and timber production, significantly increased, regulating ecosystem services, like pollination and carbon sequestration, moderately declined. The researchers used five models to analyze the impact of land-use change on ecosystem services, highlighting the complex relationship between human activity and the benefits nature provides.
Looking towards the future, the study projected that climate change could become the main driver of biodiversity loss by the mid-21st century, in combination with land-use change. Assessing three scenarios from sustainable development to high emissions, the researchers found that biodiversity loss is likely to occur in all world regions due to the combined impacts of land-use and climate change. While there are variations across regions, models, and scenarios, the overall downward trend in biodiversity loss remains consistent.
The purpose of these long-term scenarios is not to predict future outcomes, but rather to understand alternatives and guide decision-making towards more positive outcomes. The authors stress the importance of implementing policies that effectively protect biodiversity and ecosystem services. While the most sustainable scenario assessed in the study did not encompass all possible protective measures, such as increasing protected areas or large-scale rewilding, it demonstrates the need for renewed efforts to address human-caused biodiversity change.
By assessing the impacts of concrete policies on biodiversity, the researchers aim to identify the most effective strategies for safeguarding and promoting biodiversity and ecosystem services. Despite uncertainties in modeling, the study emphasizes the inadequacy of current policies to meet international biodiversity goals and the urgent need for proactive measures to address one of the world’s most significant challenges.
