What 1458 studies have to say about the impact of marine reserves [+ infographic]

When Marissa Baskett, a professor at UC Davis, was asked to review the latest research on marine reserves, she knew it would be a big task – but perhaps not a 1458-studies big task. That’s how many papers Baskett and former Sea Grant/NOAA Fisheries Fellow Lewis Barnett started with to write a new Annual Review, in which they assess what’s currently known about the impacts of marine reserves on ecosystem dynamics and species evolution.

The review heralds a newly accessible area of marine reserve research. “There have been reviews in the past on the ecological side, and some on fisheries effects,” says Barnett. “There’s been almost nothing reviewing the evolutionary responses.”

This is because marine reserves are just starting to reach the age where scientists can begin to see community-wide impacts and, for short-lived species at least, generational trends. Baskett says this kind of big-picture, long-term view is critical for helping managers predict fishery and conservation outcomes. 

Early research on single species alone – often commercially valuable fish – has not been enough to predict the ecosystem outcomes of marine reserves. For example, while it’s well-established that most harvested species become older, larger and more fecund within a reserve, their prey species may decrease, causing a trophic cascade that impacts other species. On evolutionary scales, while the absence of fishing pressure could ease selection for smaller fish, it could also, in time, select for lower dispersal away from the safety of reserve boundaries.

The catch in predicting these types of impacts, Baskett and Barnett agree, is that many of the theories scientists have posited on marine reserve dynamics have yet to be tested in the field. Many reserves were established relatively recently, during the last 15 years, and tracking the interactions of multiple species in a vast ocean is a herculean challenge for any scientist.

“Connectivity between networks is one example where we have had more time and opportunities to develop the theory than collect the data,” says Barnett, referring to the idea that networks of marine reserves may be more effective than isolated individual reserves. “We don’t quite have the empirical testing yet to show that there’s a network effect.”

The authors see this marriage of theory and data as the challenge for the next twelve years of marine reserve research, and the best way forward to helping managers and stakeholders achieve the economic and conservation results they want from their oceans.

“We’re getting a better handle on when we can say, ‘In these cases we expect [a change], and in these cases we don’t,” says Baskett. “We’ll know what to look for.”

Marissa Baskett is an Associate Professor of Environmental Science at Policy at UC Davis and former California Sea Grant awardee. Lewis Barnett is a post-doctoral scholar at the University of Washington and NOAA Fisheries, following his two-year graduate fellowship with Sea Grant.