Intermodel comparison of biodiversity and ecosystem services projections for the Shared Socio-Economic Pathways

Abstract

Scenarios are powerful tools to envision how nature might respond to different pathways of future human development and policy choices. Potential global trajectories for drivers of ecosystem change have been recently explored by the climate-science community. However, contrarily to what is common practice in the climate change modelling community, biodiversity and ecosystem services models are rarely used together to project potential consequences on future trajectories of human development. Although targeting long-term analyses, with low sensitivity to short-term and local/regional dynamics, the shared socioeconomic pathways (SSPs) explore a wide range of human development pathways, from slow to fast rates of population growth, economic growth, technological development, trade development and implementation of environmental policies. The SSPs can be used in combination with representative concentration pathways (RCPs), which describe pathways of greenhouse gas emissions resulting in different climate change scenarios. Integrated assessment models and global climate models can translate relevant combinations of SSPs/RCPs into land-use change and climate change projections.

Here, existing biodiversity and ecosystem services models were used to translate these projections into potential impacts on nature, nature’s contributions to people, and good quality of life. Although this approach does not account for drivers of change in biodiversity and ecosystem services operating at regional and subregional scales, it enables an assessment of impacts from projected changes in land use and climate at the global scale. In contrast with previous analyses, we used a wide range of models to assess the impact across diverse dimensions of biodiversity (for example, species richness, abundance, and composition) and ecosystem services (provisioning, regulating, and cultural services). Comparable metrics for biodiversity and ecosystem services (such as essential biodiversity variables, alpha diversity, range size change) were used to harmonize outputs from models addressing each of these dimensions. Although this use of scenarios based on combinations of SSPs/RCPs continued the tradition of viewing nature as the endpoint in a linear cascade of models, it allowed us to understand how the updated projection of future human development will continue the trends in biodiversity loss of the last century, thus failing to fulfil existing global biodiversity conservation targets.