28 JUNE 2018 • WORLD AQUACULTURE • WWW.WAS.ORG This article asserts the thesis that 1) the rapid development of aquaculture is the only way to avert future world hunger, 2) the only form of food production that can accommodate this large world population growth is integrated multi-trophic aquaculture (IMTA), 3) to develop IMTA food production on this scale, it will be necessary to eliminate the regulatory barriers that impede entry of new aquaculture ventures, and 4) even if technical and regulatory obstacles can be overcome, large-scale IMTA will not emerge unless sufficient capital is allocated to finance the new business enterprises that are necessary. Increasing Food Demand According to the United Nations another 2.9 billion people must be fed in the world by 2050. In addition, the rising middle class in developing countries is creating new demand for animal protein. The salient question is: where will the new food come from to meet the rapidly emerging demand? The Bren School of Environmental Science and Management (University of California at Santa Barbara) has concluded that production of this additional demand for food by conventional agriculture would generate an unacceptable level of greenhouse gases, exceed the global fresh water supply and require new land the size of South America. Because the supply of arable land is shrinking, not expanding, the world cannot farm its way out of hunger. World fisheries are at their sustainable limits. For these reasons, terrestrial agriculture and natural fisheries cannot supply the large amounts of animal protein that will be required soon. Dean Steve Gaines of the Bren School reports that good aquaculture that minimizes social disruption and environmental damage produces animal protein with the least environmental impact of any other form of animal production by a wide margin. Scientists at Bren also calculate that the amount of ocean surface required to produce sufficient amounts of farmed fish is equivalent to only the area of Lake Michigan. Therefore, ocean space is unlikely to limit the expansion of fish and shellfish production. Unfortunately, growth of conventional aquaculture now faces major regulatory and capital constraints. Given these constraints, one must ask: where will the protein needed to feed future occupants of our planet come from? Even if regulatory constraints are removed, another critical question is: where will we get the financial capital to build the facilities to produce this large amount of fish and shellfish? Consider the alternative. Global consumption of animal protein averages 63 kg per capita annually. At this level of consumption, we will need to produce Integrated Multi-Trophic Aquaculture and the Future of Food George S. Lockwood 200 million t more edible fish protein per year to feed the world population in just over 30 years. Assuming a generous 50 percent fillet yield, an annual production of 400 million t more fish will be required. This necessary increase in production cannot be achieved by present aquaculture systems. With an average protein retention of 20 percent for many aquaculture species, 2 billion t more plant protein will be needed annually to feed this amount of fish. Assuming 50 percent protein in these grain products, the new additional plant protein required will be 4 billion t more than is now produced annually. If advances in fish and shellfish genetics and the science of fish nutrition advance to allow grain to supply all necessary protein in fish feeds to fill this need, it is unlikely that terrestrial agriculture can produce sufficient amounts of grain. Global grain production in 2012 was 2.2 billion t, increasing at an average of 1.3 percent per year. If this growth rate continues over the next 32 years, world grain production would be 3.7 billion t or 1.5 billion t more than is currently being produced. Even with these favorable assumptions, this increase falls far short of the new required amount of 4 billion t of grain to feed the new fish production. These approximate calculations are likely to be optimistic and understate the amount of grain protein that will be necessary to produce the volume of fish and shellfish the world will require. To fill the global demand for additional animal protein, aquaculture will have to 1) produce seafood protein from lower amounts of plant protein in feeds through improvements in nutrient retention, 2) lower costs of production so that consumer prices are affordable, allowing aquaculture products to compete with other animal proteins, and 3) reduce greenhouse gas emissions (including from transportation) to acceptable levels. There is only one way meet these requirements. Integrated Multi-Trophic Aquaculture (IMTA) In recent years much attention has been devoted to IMTA production. These systems are designed to use waste metabolic products of the main species being cultured as a nutrient source to grow other species. For example, dissolved ammonia and carbon dioxide released from metabolizing aquatic animals can become nutrients for aquatic plants located nearby. These plants then become commercial crops for sale or become feed for aquatic animals within the system. This cycle mimics nature. In IMTA systems, nutrients are recycled to grow multiple species of plants and animals. This nutrient recycling provides greater use of feed inputs into the system. For example, mussels and macroalgae grown near salmon net pens capture suspended solids and dissolved nutrients to produce two additional commercial crops. Production of the additional demand for food by conventional agriculture would generate an unacceptable level of greenhouse gases, exceed the global fresh water supply and require new land the size of South America. The world cannot farm its way out of hunger.
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