Protected areas lead to long term transformation of marine ecosystems

Results from a new study in Australia affirm the ability of "no take" marine protected areas to aid the recovery of overfished ecosystems. Graham Edgar and fellow researchers from University of Tasmania found that the reefs within three marine protected areas off eastern Tasmania transformed over time into communities not otherwise seen in the regional seascape, and these changes intensified for at least 16 years.

Over time, the communities progressed towards an increasing number of large fish and rock lobsters (Janus edwardsii) and a decreasing number of grazers (i.e. sea urchins and mollusks) - although some of these changes took several years to manifest themselves. Specifically, the decline in grazers lagged five years - the time for lobsters to grow large enough to begin preying on them.

The researchers also conducted a continent wide analysis of marine protected areas and similarly found an increase in large fish in no-take reserves compared to adjacent fished regions with the changes intensifying for at least 20 years.

Bias in location of protected areas...
In their continent-wide analysis, the researchers also found that protected areas are biased towards places with poor resources for fisheries. They found that marine protected areas at the time of designation had on average 60% fewer large fish than adjacent fished sites. They suspect that this reflects the pressure of industry lobbying groups to designate protected areas in places with poor fisheries resources.

The authors argue that this could compromise marine protected areas as a tool if these areas have few large fish because they never were good for fishing in the first place. Protecting places that have never been subject to heavy fishing and never will be is akin to the bias in terrestrial ecosystems of protecting remote, high elevation places that would never have been developed.

If on the other hand, these sites had few large fish because they had been so heavily overfished before, then designating marine protected areas would allow ecosystem to recover as the study clearly shows (though it could take a long time). Unfortunately the study is not able to distinguish whether marine protected areas have been biased toward places that were heavily fished or just intrinsically poor in fisheries resources. Getting to the bottom of this question would clearly be an important focus for future research.

--Reviewed by Rob Goldstein

Edgar, G., Barrett, N., & Stuart-Smith, R. (2009). Exploited reefs protected from fishing transform over decades into conservation features otherwise absent from seascapes Ecological Applications, 19 (8), 1967-1974 DOI: 10.1890/09-0610.1