Global Marine Ecosystem Dynamics and Food Security: Projections from an Earth System Model

The ocean are a key source of nutrition for people around the world and an important question is - how much food can the oceans provide twenty, fifty, or hundred years from now. Any reasonable answer to this question must account for both the impacts of climate change and direct human actions, such as fishing, on ocean ecosystems. Here I present a global size-based ecosystem model which we use to quantify changes in the composition and spatial dynamics of marine communities as they respond to climate change and fishing pressure. At the foundation of this model are two general rules: (1) big things eat small things and (2) big things have more say in where they move than small things. These two rules are codified using advection-diffusion-reaction equations. Our model sits on top of an Earth System Model produced by NOAA’s Geophysical Fluid Dynamics Laboratory; specifically the Carbon, Ocean Biogeochemistry and Lower Trophics module (COBALT). COBALT provides information on the mass distribution and productivity of multiple zooplankton groups, which we use as the base of the food chain for our size-based model. Fishing effort is included as an extra size-class-specific mortality term. We use our size-based model to project potential fish catch into the future, for areas around the world, and compare our modeled data with projections on societal and human-demographic trends (i.e. increasing population sizes and nutritional requirement). These comparisons identify areas around the world where food security, from marine sources, is potentially at risk.