Little shrimp, big impacts.
Cao, L, JS Diana, GA Keoleian and Q Lai. 2011. Life cycle assessment of Chinese shrimp farming systems targeted for export and domestic sales. Environmental Science and Technology http://dx.doi.org/10.1021/es104058z.
More than six million tons of shrimp are consumed globally in a year, and nearly half of that shrimp is farmed. About three quarters of all farmed shrimp is produced in Asia, with China as the largest producer. The United States is the largest importer of shrimp, followed by the European Union and Japan. Shrimp is the most valuable marine product traded globally.
More than three times the amount of shrimp is produced in the world today than in 1980. As demand for shrimp increases in markets such as the United States and Europe, many shrimp growers convert to intensive industrial aquaculture to increase production.
Aquaculture is the practice of raising fish, shrimp or other animals in a controlled water environment, often with many more individuals in the water than could be sustained in the wild. In modern shrimp aquaculture, the crustaceans hatch, grow for several weeks and mature in ponds for three to six months to reach market size.
Intensive shrimp farms often import broodstock – adults that produce fertilized eggs – that are disease resistant and highly productive year-round. During the growing phase, the shrimp are kept at a high density in the water. Feed, fertilizer and antibiotics are added to the water. The water is circulated and aerated to prevent animal deaths.
Semi-intensive farms have fewer animals in the water and fewer requirements in terms of water circulation. These farms operate on a smaller scale, require less investment in technology on behalf of the owners and are generally family enterprises.
More traditional methods of farming shrimp include growing shrimp in pools in mangrove forests, though the yield for this practice is generally low for the amount of land used. The sensitive mangrove forests are disturbed or destroyed in the process.
In China, intensively farmed shrimp are often targeted for international export, while semi-intensively farmed shrimp are more often consumed within Asia.
Shrimp farming has notable environmental impacts. Once released, the wastewater adds acid and salt to soil, often making the affected land unsuitable for plants. The released waste can also lead to eutrophication of nearby marine environments. This means that the nutrient dense shrimp waste can cause plant and algal blooms in marine environments, leading to a lack of oxygen that kills other marine species.
Shrimp are also caught in the wild, which also has environmental impacts. Shrimpers trawl for the critters in open waters. The trawlers throw away much of the marine life they catch because it is either not shrimp or not sellable on the market. Often, the waste is more than half of what they net, amounting to about two million tons a year.
Researchers conducted a life cycle assessment for both intensive and semi-intensive shrimp farming in Hainan Province, China, where intensive shrimp farming is becoming more common due to government subsidies. Life cycle assessments evaluate the energy, materials and the impact on water and land quality of a process.
In this case, the scientists studied the entire process of shrimp farming from hatching and growing to processing and distribution and mathematically compared each of the different environmental impacts. They compared global warming, soil acidification, eutrophication, energy use, and biotic resource use.
They collected information from six hatcheries and 18 farms during the pervious three years of production. The researchers interviewed the managers of each facility using a detailed questionnaire and inspected facility records. The researchers used the data to calculate the environmental impacts for both intensive – the export market to Chicago, Ill. – and semi-intensive – domestic market in Shanghai – farming practices per ton of shrimp produced.
Intensive farming had greater impacts in all of the environmental impact categories than semi-intensive shrimp farming.
In terms of water quality, the excessive nutrient run-off into surrounding waterways can cause algae blooms and aquatic plant and animal deaths. Intensive farming also made a larger contribution to soil acidification, which occurs when the waste from shrimp farms is applied to land. Intensive farming produced about twice as much greenhouse gases and required about double the amount of energy use compared to semi-intensive farming.
The period of growing the shrimp to market size – or the "grow out" phase – contributed the most to all categories of environmental impacts for both intensive and semi-intensive farms. The researchers estimated that 70 percent to 95 percent of the environmental impact of shrimp farming could be attributed to this phase due to feed production, electricity and effluent produced. Comparatively, hatching, processing and transport impacts were relatively minor. The shrimp spend most of their life cycle in this stage, which on average takes three to six months.
The researchers found that shrimp farming is less energy intensive than beef, pork, and salmon production, about the same as chicken production and less efficient than tilapia production.
Intensive shrimp farming has substantially greater environmental impacts than semi-intensive shrimp farming, according to this life cycle assessment. However, intensive shrimp farms are the fastest growing sector of shrimp production globally.
As in prior studies, the highest impacts were found in shrimp production and processing, especially for the export market.
More sustainable farming practices are suggested to reduce the environmental impacts. The researchers' recommendations mostly focus on changes in the shrimp farming process that can be made by the producers.
To make intensive shrimp farming for export more sustainable, the researchers suggest that industrial farmers develop and use feed that contains less fishmeal. One idea is to switch to plant-based feed. However, these new formulas would need to be evaluated for their ability to support healthy shrimp growth and their own environmental impacts.
The researchers also recommend policy changes. Policy makers could mandate shrimp farm waste treatment to lessen impacts on water and soil quality. Current regulations vary as to how shrimp farm waste is handled. Maintaining waste in treatment pools to decrease nutrient and salt content before release could dramatically decrease the environmental impact of shrimp farming in terms of damage to marine and plant life.
Increasing energy efficiency would help to reduce energy consumption. However, a major, national-level change in energy production policy would be needed to significantly cut greenhouse gas production due to shrimp farming. Most of the greenhouse gas production was tied to China's very heavy use of coal.
Shrimp production – not shipping – caused the greatest environmental impacts of shrimp farming. Even so, environmental impacts could be reduced further if consumers bought locally- or nationally-produced shrimp. How do shrimp-eaters tell the difference? Opt for whole shrimp instead of the headless, deveined variety and buy shrimp with minimal processing or packaging.
Diana, JS. 2009. Aquaculture production and biodiversity conservation. BioScience http://dx.doi.org/10.1525/bio.2009.59.1.7.
Food and Agriculture Organization of the United Nations (FAO). 2010. Global study of shrimp fisheries. ftp://ftp.fao.org/docrep/fao/011/i0300e/i0300e.pdf
Food and Agriculture Organization of the United Nations (FAO), Network of Aquaculture Centres in Asia-Pacific (NACA), United Nations Environment Programme (UNEP), World Bank (WB), and World Wide Fund for Nature (WWF). 2006. International principles for responsible shrimp farming. http://www.enaca.org/uploads/international-shrimp-principles-06.pdf
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