Marine Reserves and Marine Protected Areas

Marine Protected Areas (MPAs) are areas of marine habitat where human activity is managed or regulated. This management or regulation can include seasonal fisheries closures, catch limits, bans on taking reproductive individuals, or bans or restrictions on mineral extraction or waste dumping. More restrictive MPAs, in which no form of “resource” extraction—living, mineral, or fossil—is permitted, are called fully protected marine reserves, and are commonly known simply as marine reserves. They differ from MPAs in that their more comprehensive approach is designed to maintain ecosystem function.

There are approximately two dozen marine reserves in United States territorial waters, most notably within the Florida Keys National Marine Sanctuary. The largest such reserve in the United States is the 200 square mile Tortugas Ecological Reserve.

Numerous studies have demonstrated that the full protection afforded by marine reserves results in an increase in size and number of heavily exploited species within the reserve. Most reserves have generated substantial increases in short-lived, fast-growing species within five years of protection. One review of 80 different reserves found that average values of all biological measures were strikingly higher inside marine reserves compared to reference sites (either the same site before the reserve was created or equivalent sites outside the reserve). Relative to reference sites, population densities were 91% higher, biomass was 192% higher, and average organism size and diversity were 20–30% higher in reserves.

There is also growing evidence that, at least in most cases, fisheries adjacent to reserves benefit from increasing numbers of fish which migrate out beyond the reserves’ boundaries. Indeed, some researchers have argued that integrating large-scale networks of marine reserves into fishery management, could reverse global fishery declines and provide urgently needed protection for marine species and their habitats. As well, there is accumulating evidence that, among other benefits, reserves: protect important habitat, including spawning and nursery areas; provide an “insurance policy” against uncertainty and errors in fishery management; provide educational opportunities; protect or improve recreational opportunities; protect or improve opportunities for tourism; protect cultural and historical resources; and provide economic benefits to local communities.

The Problem

• The area protected in marine reserves is still a fraction of 1% of the world’s ocean, a small figure compared to the 4% of terrestrial area protected. In the United States, the area covered by national marine sanctuaries is just three per cent of the combined area covered by national forests, parks, and wildlife refuges. Marine reserves also tend to be small. The vast majority are less than 0.39 square miles in area.
• There continues to be significant opposition to MPAs in general, and marine reserves in particular, from some sectors, not least commercial and recreational fishing interests, members of which argue that reserves and MPAs are of little practical benefit and serve only to deny fisheries access to productive waters.

The Context

• Research into marine reserves has helped illuminate clearly just how pervasive are the impacts of fisheries on marine systems. Researchers consider the extent to which populations rapidly rebound in reserves as testament to the degree to which those populations had previously been depressed.
• Although reserves and MPAs have been typically established along coasts, increasingly researchers are making the case for reserves in deep sea regions, arguing that they would provide protection for species which live primarily in the high seas, as well as species-rich but increasingly threatened ecosystems such as seamounts.
• Marine reserves are not a cure-all. Most studies show that some species decline following a reserve’s establishment, presumably because they are prey for large, predatory fish whose numbers increase within reserves. Species that are not heavily exploited outside reserves tend not to increase inside them. Long-lived, slow-maturing species will probably respond to reserve protection more slowly than those with shorter life cycles.
• Without a sufficiently comprehensive network of sufficiently large reserves, protection for highly migratory species will be inadequate at best. Furthermore, they provide at best limited protection from pollution and nearby development. Finally, protected areas may undergo significant change—and areas of importance to endangered habitat and wildlife may undergo significant spatial shifts—as a result of altered conditions due to global climate change.

Further Reading

Gell, F.R. and Roberts, C.M. 2003. Benefits beyond boundaries: the fishery effects of marine reserves. Trends in Ecology and Evolution 18(9): 448-455.

Halpern, B.S. and Warner, R.R. 2002. Marine reserves have rapid and lasting effects. Ecology Letters, 5(3): 361-366.

Palumbi, S.R. 2002. Marine Reserves: A Tool for Ecosystem Management and Conservation. Pew Oceans Commission, Arlington, Virginia. 44pp.

Soto, C.G. 2002. The potential impacts of global climate change on marine protected areas. Reviews in Fish Biology and Fisheries 11(3): 181-195.