Environmental▼News from another use. The decimation of Thailand’s mangroves to create shrimp farms is just one example of why this can be a problem, Wada says. Freshwater and saltwater wastewater from fish farms can also pollute both land and water. Escaped farm fish can wreak environmental havoc, too, Wada says. Salmon and tilapia from farms have bred with native stocks on almost every continent, he says. Scientists are concerned that escaped salmon could alter the genetic diversity of stocks of wild salmon with interbreeding, says Cathy Roheim, a professor in the University of Rhode Island’s Department of Environmental and Natural Resource Economics. Some of the research under way to decrease the environmental pressures caused by aquaculture includes efforts to raise saltwater fish in freshwater or saltwater with very low salinity, according to the Harbor Branch Oceanographic Institution of Ft. Pierce, Fla. U.S.
researchers are also investigating technologies for developing closed aquaculture systems that do not release polluted water and aquaculture methods that use energyefficient technologies, such as solar power. However, much of the current technology for sustainably improving the efficiency of aquaculture tends to be capital-intensive, says Christopher Delgado of IFPRI, lead author of the report. Many of the developing countries in which the majority of the growth in aquaculture is expected can’t afford expensive technologies, he says. The WorldFish Center is one of the organizations investigating inexpensive ways to increase the efficiencyand thereby reduce the environmental impactof aquaculture, Williams says. Fish can be selectively bred to increase rates of growth; their food can be enhanced so that they use it more efficiently; and farm management can be improved, she says. In Africa, for ex-
ample, researchers have bred strains of Nile tilapia that grow 100% faster, which has brought down prices. By identifying which fish are captured and raised using approaches that are less damaging to the oceans and environment, labels such as the Marine Stewardship Council’s MSC logo, which designates sustainably managed fisheries, can play an important role. David Freestone, chief counsel at the World Bank, urges developed countries to support these labels. However, developing countries may not have the resources required to put effective management systems in place, Roheim warns. “It takes a lot of money to gather data on current populations of fish, estimate maximum sustainable yield, create management regulations with someone to enforce them, work with all stakeholders of the fishery, protect marine mammals and other sea life, and so on,” she says. —KELLYN BETTS
Swedish engineers have virtually eliminated polluted runoff from Hammarby Sjöstad, the largest residential and commercial development in the city of Stockholm, thanks to a built-in system of infiltration beds and settlement tanks. Gutters and small canals that run through the parks between the apartment buildings collect clean rainwater from roofs and lawns for later use on gardens. Polluted runoff from streets and parking lots runs into tanks, where particles settle out, after which it flows into filtration beds, which remove nutrients. The cleansed water then streams into the canals and out into Hammarby Lake. The runoff controls are just one part of a plan to cut pollution and water and energy use by 50%, compared to residences and businesses built in 1990, for the redevelopment of this 1.5-square-kilometer industrial brownfield site. Energy is provided from solar and hydrogen fuel cells, bio-gas from the sewage
VICTORIA HENRIKSSON
Swedes showcase runoff-free development
plant, two power plants that run on garbage and bio-fuels (pine needle oil), and a heat exchanger that extracts heat from treated wastewater. A pilot sewage treatment plant that treats only toilet and “gray”, or washing water, opened October 16.
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The sludge from the plant will not have the high levels of metals and other pollutants that plague sludge from industrial sources. Read more about Hammarby Sjöstad at www. hammarbysjostad.stockholm.se. —JANET PELLEY
