Assessing multiple stressors on marine ecosystems in the context of the Planetary Boundaries framework

In the Planetary Boundaries framework, Biosphere Integrity is considered one of the “core boundaries” due to its vital role in the Earth system and its numerous interconnections with other boundaries (Rockström et al. 2009, Steffen et al. 2015, Richardson et al. 2023). The Planetary Boundary of Biosphere Integrity is assessed based on genetic diversity and functional integrity. While the current control variable for the genetic diversity component takes both terrestrial and marine life into account, the control variable for the functional integrity component so far only includes terrestrial life. In order to advance the representation of marine life within the boundary of functional biosphere integrity, we suggest the addition of a marine control variable that addresses the combined effect of multiple stressors on marine ecosystem health. The aim of the work presented here is to develop the basis for a multiple-stressor index that takes into account the interaction of ocean warming and ocean acidification. The index seeks to quantify the cumulative impact of anthropogenic stressors on marine ecosystems, such as kelp forests. Most species of kelp are considered foundation species due to their strong role in structuring the ecosystem. Macrocystis pyrifera (giant kelp) is the first species to be included in the development of this multiple-stressor index due to its global distribution, its important role in providing ecosystem services, and the current data availability (Roethler et al., 2025). Future work will consist of including other species and ecosystems, as well as additional stressors.References:Rockström, J., Steffen, W., Noone, K. et al. A safe operating space for humanity. Nature 461, 472–475 (2009). https://doi.org/10.1038/461472aSteffen, W. et al.,Planetary boundaries: Guiding human development on a changing planet.Science347,1259855(2015).DOI:10.1126/science.1259855 Richardson, K. et al., Earth beyond six of nine planetary boundaries.Sci. Adv.9,eadh2458(2023).DOI:10.1126/sciadv.adh2458Roethler, M. et al., Global Meta-Analysis Reveals the Impacts of Ocean Warming and Acidification on Kelps. Ecological Monographs95(3):e70034(2025). https://doi.org/10.1002/ecm.70034