14 Marine Protected Areas
14 Marine Protected Areas
- Ray Hilborn
- and Ulrike Hilborn
What are marine protected areas?
p. 104↵One of the crown jewels of marine ecosystems is the Great Barrier Reef (GBR) off the northeast coast of Australia. The reef stretches along 2,600 km of the Queensland coast and consists of 900 islands and 2,900 reefs. It is a World Heritage Site with some of the highest biodiversity in the world. It is also one of the most protected marine areas in the world. The Great Barrier Reef Marine Park Act of 1975 established most of the GBR as a park, protected by the Great Barrier Reef Marine Park Authority (GBRMPA). As of 2011, 33% of the area is closed to extractive activities such as fishing; in the other areas a blend of activities is permitted.
The four primary human activities in the GBR are tourism, recreational fishing, commercial fishing, and shipping. The GBRMPA relies on a technique called marine spatial planning or ocean zoning to separate them to reduce conflict. Essentially, portions of the reef are set aside for each activity and some sections are entirely closed, even to tourism. Marine spatial planning is increasingly advocated as a better way to manage marine ecosystems, and the GBR is often held up as a prime example of how spatial planning can work both to protect marine ecosystems and to provide for sustainable use.
p. 105↵Would it were this simple. Threats to the biodiversity of the GBR include (1) climate change, particularly increasing temperatures, ocean acidification, and rising sea level; (2) pollution, primarily sediment and nutrient runoff from agricultural areas on the mainland; (3) oil spills; (4) invasive species and outbreaks of coral-eating predators; (5) fishing; and (6) habitat damage from fishing gear, boat anchors, and shipping accidents. The problems associated with climate change are so profound that no actions the GBRMPA or the Australian government can take would have a significant effect. Land use policies on the mainland are also outside the direct control of the GBRMPA, but the Authority does actively engage with other agencies to try to minimize the pollution issue, and a number of agreements have been made to achieve this. The threat from oil spills generated by exploration and drilling has been eliminated by a complete ban on oil exploration or production within the GBR, and the zoning system minimizes the impacts of fishing and habitat damage.
Marine protected areas (MPAs) are areas of the ocean closed to some forms of human activity. Fishing is most commonly regulated, but oil exploration, oil drilling, seabed mining, and tourism are also potentially restricted. Establishing an MPA does not necessarily mean total protection. While some MPAs may be completely protected, there are degrees of protection associated with the general status of an MPA. Trawling and dredging that harms plants and animals attached to the bottom are most commonly restricted. Commercial fishing with different kinds of gear may also be banned, along with recreational fishing with hook and line or any combination of fishing methods. Tourism can be restricted by prohibiting anchoring or by banning human presence altogether.
The term marine protected area is not terribly specific, and sometimes it simply means an area with higher levels of protection than its surroundings. Perhaps more relevant to overfishing is the term marine reserve, which usually denotes areas closed to all forms of fishing.
p. 106What do marine protected areas protect?
The 2010 Deepwater Horizon oil spill in the Gulf of Mexico illustrates that most MPAs don’t protect the ecosystem from most major threats. Oil can wash hundreds of miles. MPAs provide no protection from ocean acidification, warming seas, and sea level rise, nor do they protect from land-based pollution causing dead zones and silt from runoff, or from the major threat of exotic species, or even from illegal fishing. The current implementation of MPAs simply protect marine ecosystems from fishing. So perhaps we are collectively a bit smug when we say we have “protected” the ocean with an MPA.
How much of the world’s oceans are now closed to fishing?
Closed areas have a long tradition in fisheries management, from the ancient form of traditional community-based management to Western style top-down fisheries management agencies. Any map of permitted fishing activities would look like a crazy quilt. Some areas will be closed to fishing for the protection of spawning stocks or juveniles and some to avoid by-catch; in others one type of fishing gear will be prohibited to provide an advantage for another. However, areas closed to all fishing, the true marine reserves, represent only a small portion of the world’s oceans.
Several international agreements have targets to set aside 10%–20% of the oceans for MPAs, and many countries have their own specific targets for their own marine regions. Overall, as of 2007, only 1.6% of national economic zones are in MPAs and only 0.2% are in marine reserves.
Some protected areas are quite large. The Great Barrier Reef was the largest until 2000, when the United States established the Northwest Hawaiian Islands National Monument. Some countries have closed very large areas to trawling. The United States has closed more than two thirds p. 107↵of its 200-mile zone to bottom contact gear, although most of this is in Pacific waters too deep to be fished, and New Zealand has closed 30% of its 200-mile zone to trawling.
What is the impact of closing areas to fishing?
The difference in abundance between areas that are fished and areas protected from fishing depends greatly on two factors—how much fishing goes on outside the reserve and the size of the reserve in relation to how much the fish move around.
Studies that compare abundance inside and outside long-established reserves typically find that fish inside are two to four times more abundant.
If a reserve is small and the fish move a lot and far away, there may be no effect at all. But if the fish don’t go far and fishing pressure is high outside, we may well find 5 to 10 times more abundance inside the protected area. The more an area is overfished on the outside, the greater the relative abundance of fish will be on the inside.
Not only will there be more fish but there will also be more species, or higher biodiversity, inside a reserve. Reserves with overfished surroundings will typically show a 30% increase in species counts, and the fishes will live to a ripe old age and trophy size—a natural consequence of not ending life early on a hook or in a net.
All well and good, but where will the fishermen go? Elsewhere, of course. And there we have a negative consequence of closed areas that can even lead to overfishing or increased by-catch outside the reserves. Such dislocation and redirecting of fishing effort can be rather disruptive to fishing communities. Longer travel means extra fuel, and extra fuel and more travel means more greenhouse gases. Longer travel also means more risk of accidents and reduced profit, which can, in the worst case, make it impossible for some types of boats to fish at all.
p. 108↵MPAs may also effectively “lock up” a portion of the fish stock and thereby lower the total sustainable yield. If that part of the stock stays inside the reserve, we can expect a proportional loss of sustainable yield to the outside fishery. If, however, the stocks outside the reserve are overfished, the eggs and larvae dispersing from the reserve can actually increase yield.
Do MPAs increase the abundance of fish?
In almost all cases we have established that there are more fish inside an effectively enforced MPA than outside it. But when it comes to how many more fish there are in the overall ecosystem, things get murky. We generally expect that when fishing moves outside the reserve, the added effort on the outside will decrease the abundance there. But to move from expectation to fact, we would need good data for inside and outside the reserve before and after exclusion. Alas, good data are sparse. In some cases we know that abundance did increase inside and outside a reserve after closure, but the studies lack controls, or data for a similar area without superimposition of an MPA. And if the establishment of an MPA just happened to coincide with good environmental conditions for everyone, we would certainly expect abundance to increase outside the reserve as well. In other cases, we know that abundance increased inside the reserves but declined outside.
In general, ecological theory expects and predicts that if overfishing is a major problem, establishing an MPA will result in more fish in the system overall. This is because eggs and larvae drift out of the reserve and reseed the adjacent overfished areas and thereby increase overall abundance.
Can MPAs solve some of the problems of overfishing?
Yes, when fisheries are overexploited and it is impossible to regulate either fishing effort or catch, MPAs are often effective p. 109↵at maintaining populations of fish within the reserves—but only if the local fishing community respects the area as protected. Both traditional and modern managers of small-scale fisheries around the world now use protected areas as one of their management tools.
In areas where a fisheries management system that prevents yield overfishing is already in place, MPAs must be seen primarily as natural parks where more pristine levels of abundance and community structure are preserved and where the ecosystem is protected from overfishing. Still, MPAs will probably have no part in preventing economic or yield overfishing.
And this is precisely why MPAs are so controversial in developed countries with established fisheries management systems. Recreational and commercial fishermen believe that heavy regulations to prevent overfishing already exist and that there is really no need for MPAs to add to their burden.
How much of the ocean should be set aside as protected from fishing?
It all depends on the objectives—what should the protected areas accomplish and for whose benefit? There are already international targets to lock up between 10% and 30% of national economic zones under various levels of protection, but most countries are very far from those targets. In countries with well-functioning systems to prevent overfishing, reserves are primarily intended to provide protection for representative habitats and their associated biodiversity, much like terrestrial national parks. For comparison, about 10% of the United States land area is located in parks. Here, as with most aspects of ecosystem-based management, the answer depends on social choices, not scientific analysis.