Page 463 - Environment: The Science Behind the Stories

said that if the people return, the fishing bans will be reassessed reserve, and fishing improved outside the reserve. At two
and that in the meantime, the bans will save the region’s fish coral reef sites in Kenya, commercially fished species and
from being depleted by industrial fleets from other countries. keystone species were up to 10 times more abundant in the
protected area as in the fished area. At Leigh Marine Reserve
Reserves can work for both fish and fishers in New Zealand, snapper increased 40-fold, and spiny lob-
sters were increasing by 5–11% yearly. Spillover from this
Over the past two decades, data from marine reserves around reserve improved fishing and ecotourism, and local residents
the world have been indicating that reserves can work as win- who once opposed the reserve now support it. Since that
win solutions that benefit ecosystems, fish populations, and time, further research has shown that reserves create a four-
fishing economies. A comprehensive review of data from fold increase in catch per unit effort in fished areas surround-
marine reserves in 2001 revealed that just one to two years ing reserves and that they can greatly increase ecotourism by
after their establishment, marine reserves: divers and snorkelers.
On Georges Bank, once commercial trawling was halted
• Increased densities of organisms on average by 91%. in 1994, populations of many organisms began to recover. As
• Increased biomass of organisms on average by 192%. benthic invertebrates began to come back, numbers of ground-
fish such as haddock and yellowtail flounder rose inside the
• Increased average size of organisms by 31%.
closed areas, and scallops increased by 14 times. Moreover, fish
• Increased species diversity by 23%. from the closure areas appear to be spilling over into adjacent
waters, because fishers have been catching more groundfish
That year, 161 prominent marine scientists signed a “consen- from Georges Bank as a whole since the late 1990s. From
sus statement” summarizing the effects of marine reserves. these and other datasets, increasing numbers of scientists,
Besides boosting fish biomass, total catch, and record-sized fishers, and policymakers are advocating the establishment of
fish, the report stated, marine reserves yield several benefits. fully protected marine reserves as a central management tool.
Within reserve boundaries, they:

• Produce rapid and long-term increases in abundance, How should reserves be designed?
diversity, and productivity of marine organisms.
• Decrease mortality and habitat destruction. If marine reserves work in principle, the question becomes how
best to design reserves and arrange them into networks. Studies
• Lessen the likelihood of species extirpation.
are modeling how to optimize the size and spacing of reserves
Outside reserve boundaries, marine reserves: so that ecosystems are protected, fisheries are sustained, and
people are not overly excluded from marine areas (Figure 16.24).
• Can create a “spillover effect” as individuals of protected Scientists are asking how large reserves need to be, how many
species spread outside reserves. there need to be, and where they need to be placed to take best
• Allow larvae of species protected within reserves to “seed advantage of ocean currents. Of several dozen studies that have
the seas” outside reserves. estimated how much area of the ocean should be protected in
no-take reserves, estimates range from 10% to 65%, with most
The consensus statement was backed up by research into falling between 20% and 50%. Most scientists feel that involv-
reserves worldwide. At Apo Island in the Philippines, bio- ing fishers directly in the planning process is crucial for coming
mass of large predators increased eightfold inside a marine up with answers to all these questions. If marine reserves can be

Small Medium
reserve reserve
Large
Fish dispersal reserve
distances

Figure 16.24 Marine reserves of different sizes may have varying effects on ecological communities
and fisheries. Young and adult fish and shellfish of different species can disperse different distances, as indi-
cated by the red arrows in the figure. A small reserve (left panel) may fail to protect animals because too many
disperse out of the reserve. A large reserve (right panel) may protect fish and shellfish very well but will provide
relatively less “spillover” into areas where people can legally fish. Thus medium-sized reserves (middle panel)
may offer the best hope of preserving species and ecological communities while also providing adequate fish to
people. Source: Adapted from Halpern, B.S., and R.R. Warner, 2003. Matching marine reserve design to reserve objectives. Proceed-
462 ings of the Royal Society of London B 270: 1871–1878, Fig 1. Used by permission of The Royal Society and the author.

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