Short-term management of kelp forests for marine heatwaves requires planning

Heatwaves are now pervasive stressors to marine ecosystems, and it is urgent to consider mitigation tools that support ecosystem resilience and persistence in the immediate future. We modeled a system of kelp, herbivorous urchin, and predatory fish to compare how potential management actions (kelp seeding, urchin removal, and fishery closures) could reduce the likelihood of a heatwave shifting a kelp forest into a degraded urchin barren state. We found that those interventions were most effective when begun alongside or before the start of a heatwave. Closing the predatory fish fishery was more effective when done earlier and for longer, while urchin removal and kelp seeding were more effective when begun alongside and continued throughout the heatwave. Kelp seeding was notably less effective than other interventions. Our results suggest the need for improved heatwave forecasting and nimble management protocols to enact mitigation actions quickly if a heatwave is forecasted or occurs.