Trophic cascades on temperate reefs: Managing for the resilience and adaptive capacity of coastal communities

Background/Question/Methods

Kelp forests are one of the most productive ecosystems on our planet providing a diversity of ecosystem goods and services that coastal communities have relied on economically and culturally for millennia. These ecosystems are also highly susceptible to top-down forcing by strongly interacting predators such as sea otters, spiny lobsters and key reef fish. Drawing on empirical examples from coastal Alaska, British Columbia, Californian and New Zealand we ask; what biotic and abiotic factors mediate the strength of coastal trophic cascades triggered by predator depletion and recovery, how have coastal communities responded to variation in these dynamics through time and space, and finally, how can our understanding of these dynamics inform conservation and management policies that support the adaptive capacity of coastal communities.

Results/Conclusions

We show that the magnitude of cascading effects can vary substantially as a function of regional oceanographic context. Furthermore, coastal communities reliant on kelp forest-associated services tend to shift their exploitation to alternative resources in response to declines driven by changing abundances of predators. We predict that the potential for adaptive exploitation of different natural resources varies as a function of economic context and lags behind the spatial redistribution of fishing effort. To improve the adaptive capacity of coastal communities we recommend that conservation and management policies, at local and federal levels, support occupational resilience through diversity in economic opportunities, co-management and designated access privileges. Furthermore, resilience requires flexible management institutions that can respond and adapt quickly to change. Finally, science must engage meaningfully with local coastal communities and be used as a process, rather than a product, to examine the tradeoffs between ecological, economic and social risk, inform co-management policies, evaluate their impacts and reassess policies as the effects of trophic cascades ripple through coastal marine ecosystems.