Marine protected areas enhance climate resilience to severe marine heatwaves for kelp forests

Abstract Marine protected areas (MPAs) are an important tool for conserving coastal marine ecosystems, with well‐documented benefits for fished species. However, their potential to benefit non‐exploited species, such as primary producers in kelp forest ecosystems, is less well understood, particularly under escalating climate change impacts. In this study, we used four decades of remote sensing to examine the effects of 54 MPAs on kelp canopy coverage and assess how these effects influence kelp resilience to marine heatwaves. We developed a method for identifying paired reference (control) sites using historical satellite data and then used Before‐After Control‐Impact Paired Series analysis to examine whether the implementation of MPAs leads to increases in kelp coverage. In addition to examining changes in kelp coverage before and after MPA implementation, we also analysed the effect of MPAs on the resistance and recovery of kelp canopy coverage to a series of severe marine heatwaves in the North Pacific between 2014 and 2016. We found that the implementation of MPAs led to a modest positive effect with an 8.5% increase in kelp coverage compared to reference areas, though effects varied across MPAs. The positive effect of MPAs became more evident following the marine heatwaves, with kelp forests in MPAs showing greater recovery than in reference sites, particularly in southern California. Synthesis and applications . Our results provide empirical evidence of the potential role of MPAs as climate adaptation tools and highlight that well‐managed MPAs can support ecosystem stability under increasing climate stress.