The cure for sea sickness?

Our oceans are in trouble. Marine fisheries have collapsed all over the world; at least half of the world's fish stocks are either overfished or fished at capacity; cod stocks have been decimated. And that's not all. Californian abalone, the world's most expensive shellfish, has seriously declined. Bleached coral, oil slicks, coastal pollution, toxic algal blooms, the death of kelp forests, the odd hurricane, and widespread epidemics of ticks and viruses amongst sea creatures are but a few of the ills of the oceans listed in a new report by WWF, the conservation organisation, and IUCN, the World Conservation Union published last month.

Titled "The Status of Natural Resources on the High Seas", the report written by the Southampton Oceanography Centre calls for international agreements to be put in place to regulate the management, protection and exploitation of high seas beyond the 200 nautical-mile limit of the exclusive economic zones (EEZ) of coastal states, and to create protected marine reserves. It also coincides with work conducted by The National Center for Ecological Analysis and Synthesis (NCEAS), a think tank from the University of California, Santa Barbara, which for the past four years has had a group of marine biologists studying the declining state of the world's oceans.

The group has been looking at protected marine reserves where fishing is banned; now, the scientists have presented their findings which support the creation of more fishing-free zones.

Getting to that conclusion has not been easy. The idea of creating reserves that are off-limits to fishermen led to widespread controversy and ill feeling. "The proposal to establish MPAs [marine protected areas] has resulted in fisheries officials being hung in effigy by their friends, the firing of scientists from local Fisheries Management Commissions, and the patrolling of reserve boundaries by armed guards," says Professor Stephen Palumbi, one of the members of the group, and head of the Department of Organismic and Evolutionary Biology at Harvard University, in Boston, Massachusetts.

"Fishermen are often wary of reserves because they see them as taking away from rather than contributing to their livelihoods," adds Dr Callum Roberts, who works with Professor Palumbi at Harvard. "Sceptical fishermen demand proof before implementation that they will work. The catch-22 is that without setting reserves up, such proof cannot be obtained."

Yet it is fishermen who stand to benefit most from marine reserves. One of the first to be created was the Leigh Marine Reserve at the northern tip of North Island in New Zealand. It was established in 1977 and covers roughly five square kilometres. Though small, it had a dramatic impact on marine life and on the attitude of many local fishermen towards reserves. Twenty years on, snapper populations are 40 times higher within the reserve, spiny lobster numbers up by 10 per cent, kelp forests have begun to recover and fishing catches near the reserves have also increased.

Dr Roberts cites a second, more recent, example. Georges Bank in the Gulf of Maine was once one of the most productive fishing grounds in the world. Decades of intensive fishing led to a series of fishery collapses. In 1994 three areas, totalling 17,000 square kilometres, were closed to certain types of fishing.

Although the fish recovered, an unexpected benefit was the restoration of the scallop population. NCEAS has now collated results from more than 100 marine reserves and shown that inside them, population densities are 91 per cent higher, the average size of animals is one-third higher and species biodiversity is one-fifth greater. These results held were independent of the reserves' size. This peak in biodiversity and species numbers occurred within a couple of years of protection being introduced, and have lasted for at least 40 years.

The problem is that for fishermen to be happy, the abundance within the reserves needs to spill over into the unprotected areas. Dr Louis Botsford, from the Department of Wildlife, Fish and Conservation Biology at the University of California, Davis, has been using computer models to calculate the right size and shape of a marine reserve. Most marine life goes through a larval stage; Professor Palumbi estimates that the dispersal distance of larvae is between 50 and 100 km. But fishing reduces the number of individuals so far that the population cannot sustain itself at the same numbers. Marine reserves counteract this problem. "However, the effectiveness of these reserves depends on their spacing and the distance the larvae disperse," says Dr Botsford. If species only disperse a short distance, there is no problem in terms of replacing the species within the reserve.

But a large reserve will only allow species whose larval dispersal distance is less than the width of the reserve to replace their parent populations. Dr Botsford suggests creating networks, or necklaces, of small reserves along 35 per cent of any affected coast. His models show that while very large reserves could sustain populations within the reserve, a network of small reserves is better for maintaining populations in general. Professor Palumbi adds that the span of a reserve network should be up to 10 times greater than the maximum dispersal range for the species being protected by the network ­ that's in the order of 500 to 1,000 km.

Yet there is evidence that reserves benefit fishermen too. Fish populations outside reserves off the coast of South Africa increased by almost one-fifth as fish migrated into unprotected waters; lobsters are now found in sizable numbers in the Florida Keys, after they migrated from their protected zone in the Everglades National Park, and larvae from the reserves can repopulate areas outside.

According to Dr Stephen Gaines, from the Marine Science Institute at the University of California, Santa Barbara, such a network of reserves is the best approach, not just because of conservation and fishing implications, but because it serves as an insurance policy against acts of God ­ or human error ­ such as hurricanes and oil spills.

He believes that many species take at least 20 years to recover from catastrophic disturbances, and calculates that reserve planners should set aside 50 per cent more of the sea and coastline than they intend to, in order to sustain population levels over the long term and through catastrophes.

Currently, less than one per cent of our seas are protected. In May 2000 Bill Clinton signed an executive order to increase and expand marine reserves. But it is still uncertain whether George Bush will uphold this agreement. Without protection we stand to lose not just fishing jobs and fish and chips, but a wealth of marine creatures ­ from sharks to the humble scallop.