Understanding cumulative human impacts in a marine ecosystem with computational experiments

People affect marine ecosystems in many ways, such as climate change, pollution, and overfishing. Cumulative impacts refer to the combined effects of such stressors. They pose one of the biggest threats to ecosystems and biodiversity worldwide. Yet, we know little about how stressors act together in complex ecosystems. This makes it challenging to manage our coasts and seas sustainably. The CLIMAX project aims to better understand cumulative impacts through computer simulations. It introduces innovative modeling and data analysis methods that combine today’s computing power with the knowledge that ecologists have built in decades of field and laboratory studies. CLIMAX will show the potential of these new methods with a case study: human impacts in the Skagerrak and Kattegat. Here, the project tackles two pivotal environmental questions. First, we already know much about single stressors’ effects on individual species – but how do these stressors interact to create ecosystem changes like reduced biodiversity and productivity? Second, how does long-term stress affect the ecosystem's ability to withstand and recover from extreme events like marine heat waves? Marine ecosystems are remarkably stable, yet cumulative impacts can overwhelm their ability to withstand and recover from disturbance. Hence, CLIMAX’s results might improve the sustainable use and protection of marine ecosystems in Norway and elsewhere.

Cumulative impacts refer to the combined effects of multiple stressors on an ecosystem, e.g., climate change, pollution, and fishing. They are one of the biggest threats to ecosystems and biodiversity, but understanding them better remains a grand challenge in marine ecology. Modeling is a crucial component of tackling this challenge. However, current modeling approaches contradict empirical studies, suffer from data limitations, or ignore the statistical possibilities arising when ecosystem simulations are run many times. New modeling and analysis approaches are therefore needed. CLIMAX aims to 1) make a leap in the modeling of cumulative impacts and 2) exploit this methodological progress to understand how cumulative impacts emerge at the ecosystem scale. CLIMAX’s scientific potential comes from a novel combination of leading-edge computational methods and a strong foundation in the empirical literature. This integration of methods is based on three ideas. First, ecosystem models (here, Ecospace) can simulate how stressor effects identified in empirical studies might ripple through the food web. Second, ecosystem models can generate big data about the simulated ecosystem in computational experiments (running the model many times with changing inputs). Third, such big data allow for unprecedented statistical analyses of how ecosystem-scale changes might emerge in the model system. CLIMAX will develop these methods, make them available in free software, and show their scientific potential by addressing two critical research questions: 1) How might stressor interactions at the ecosystem scale emerge from known effects on individual species? 2) How do chronic stressors affect ecological resilience to short-term, extreme disturbances like marine heatwaves? By combining the best computational methods and harnessing the unprecedented computing power available today, CLIMAX has the potential to set an ambitious agenda for modeling cumulative impacts for decades to come.