Valuation of Nursery Areas
In principle, a picture of the potential economic value associated with the nurseries in the coastal zone can be built up via the aggregation of a number of existing valuation studies. For example, a preliminary estimate of the total economic value of ecosystem services provided by global systems shows that while the coastal zone covers only 8% of the world’s surface, the goods and services provided by it are responsible for approximately 43% of the estimated total value of global ecosystem services82. While controversial83 84, this preliminary study makes it abundantly clear that coastal ecosystem services do provide an important portion of the total contribution to human welfare on this planet.
Nursery areas within the coastal areas are of inestimable value to marine organisms: without such areas, many populations would dramatically decline and some species would go extinct85 86. To humans, marine nursery areas are highly valuable as well, since many of our industries and recreational activities are based on these habitats87 88 89. Commercial and subsistence fishing, recreational fishing and coastal tourism all depend heavily on marine species that utilize nursery habitats for survival90 91 92.
A. Fisheries. The vast majority of marine species that are targets for commercial and subsistence fisheries rely on coastal or pelagic nursery areas93 94 95. While there are species that reproduce at sea and have young that remain in the open ocean while growing, the vast majority of species utilize definable nursery areas during their life cycle. Nursery areas help generate a variety of seafood products such as fish, mussels, crustaceans, sea cucumbers and seaweeds 96 97 98. Most commercially important fish species like salmon, shad, grouper, snapper, bluefish, striped bass, tunas, and invertebrates (such as shrimp, lobster, crabs, oysters, clams, mussels), utilize nursery habitats 99 100. In 1999, the world marine fisheries catch was over 70 million metric tons – most of this productivity directly dependent on nursery habitats101. The U.S. alone exported over $170 million in marine fisheries products, exemplifying the significant economic value of these resources102.
Valuation studies of food directly or indirectly supplied by coastal systems and their nursery areas have predominantly focused on the economic value of fishery products103 104. Most methods of valuing the ecological function of coastal wetlands as breeding and nursery grounds use production function approaches105. Estimates of value of nursery areas within coastal wetlands for fisheries production have ranged widely106 107. For instance, the annual market value of seafood supported by mangroves is estimated to range from $750 to $16,750 per hectare108.
Studies of specific regions and biomes may provide a more complete picture of the enormous economic value of these habitats. The Wadden Sea in northern Germany, for instance, is estimated to provide an average of 25% of the North Sea catch of plaice, sole, shrimp, dab and herring109. Coral reef-based fisheries are also valuable: the coral reef-based fisheries in Southeast Asia generate $2.4 billion per year110. In developing countries, coral reefs contribute about one-quarter of the annual total fish catch, providing food to about one billion people in Asia alone111. Marine nursery areas are also a critical foundation for much of the mariculture industry that uses wild stock to grow valuable fisheries products, from tiger prawns to bluefin tuna112 113 114.
Besides fisheries resources, at least three other types of marketable goods are supported by nurseries in coastal systems--genetic resources, medical resources and ornamental resources115. Considering these goods as well as others services provided by coastal areas, researchers have found that the conversion of nurseries can exact huge costs116. In Thailand, for instance, mangroves to shrimp aquaculture ponds reduced the total economic value of the intact mangroves by 70% in less than a decade117.
Sometimes we recognize the economic value of a natural habitat only when we’ve lost it. Wetland loss in the U.S. and other countries has spurred economists into calculating their value. While in the mid-1980s it was estimated that U.S. coastal marshes had a value of nearly $5000/hectare/year, purely due to their significance as nursery habitat, current losses are significant. For instance, every hour a chunk of wetlands the size of a football field is lost to the Gulf of Mexico118.
B. Recreational fishing. Recreational fishing is a big business in many parts of the world, and marine-based sports fishing is one of the business’ biggest sectors. Target species in recreational fishing almost invariably utilize marine nurseries. Some of the most important recreational fishing sites are in or immediately adjacent to nursery habitats themselves. This is certainly true for coral reef based recreational fisheries, which are said to generate over a $100 million annually119. It is important to note that recreational fishing also provides non-financial benefits like rest and relaxation, so its value cannot be determined solely on the basis of the revenues it generates directly. Paradoxically, development of the coastal tourism infrastructure that supports recreational fishers has been implicated in much of the loss of coastal nursery habitats120 121. At the same time, recreational fisheries are responsible for significant proportion of fisheries mortality for many species. It is an irony that an industry that so values the resource also shares the responsibility for its decline, in many cases.
C. Tourism. Global tourism has been deemed the world’s most profitable industry and coastal tourism may be its fastest growing sector122. Much of this coastal tourism centers on aesthetically pleasing landscapes and seascapes that include critical nursery habitat123. Coral reefs are estimated to provide goods and services worth a staggering $375 billion each year; much of this generated from nature-based or eco-tourism124 125. The demand for diverse and biologically rich biomes such as coral reefs increases the value of the intrinsically linked nursery habitats such as mangrove and seagrass126. In the U.S. alone, reef ecosystems with their nursery habitats support millions of jobs and billions of dollars in tourism each year127. Reef-based tourism generated over $1.2 billion in the Florida Keys alone, while in Hawaii, annual gross revenues generated from just a single, half square mile coral reef reserve exceed $8.6 million128 129 . Even temperate coastal areas with their nursery habitats are of value for tourism: the annual aggregate willingness to pay for a moderate improvement in the Chesapeake Bay’s water quality is estimated to be in the range of $10 to $100 million in 1984 dollars130.
Unregulated, uncontrolled, or inappropriate tourism can be a threat to nurseries, however. Tourism infrastructure can cause the conversion of habitat and pollution, and consumption can drive local over-fishing and degradation131. Even nature based tourism can threaten the very draw that brings people to a place when the number of tourists exceeds the carrying capacity, or when the behavior of tourists is not adequately regulated.
D. Amenity, option and existence values. Some of the world’s most valuable things have no monetary value whatsoever – as the saying goes, the best things in life are free. The seas and coasts are of great importance to people around the world, and even for those who never or rarely visit these areas, their existence value is significant132. Since nursery areas are among the biologically richest places on earth, their survival is of great importance even to those who do not directly use their resources133. Nurseries also support a whole range of other ecosystems and species the values of ecosystems that humans do regard highly, such as coral reefs and charismatic species such as whales, seals and sea turtles. The entire web of marine life is tied in some way to nursery habitats – and humans are linked to that web through consumptive, as well as non-consumptive uses. Finally, even systems upon which we place low economic value today may be of great importance and value tomorrow – because they support species that may turn out to have pharmaceutical value, or because they support species/habitat types that will become rare and endangered in the changing conditions of the future134.
While from a purely economic viewpoint, it does not matter who receives the benefits of nursery areas, from a conservation viewpoint it does. Since revenues from tourism are often not equitably captured by local people (especially in developing countries), increased tourism may not offset other activities that impact coral reefs--such as fishing. And we must recognize that coastal nurseries may present amenity and option values to local people that differ from the values perceived by tourists and other visitors.
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