Aquaculture Magazine

April / May 2015

Does aquaculture add resilience to the global food system?

Aquaculture is the fastest growing food sector and continues to expand alongside terrestrial crop and livestock production.

By Max Troell, Rosamond L. Naylor, Marc Metian, Malcolm Beveridge, Peter H. Tyedmers, Carl Folke, Kenneth J. Arrow, Scott Barrett, Anne-Sophie Crépin, Paul R. Ehrlich, Åsa Gren, Nils Kautsky, Simon A. Levin, Karine Nyborg, Henrik Österblom, Stephen Polasky, Marten Scheffer, Brian H. Walker, Tasos Xepapadeas, and Aart de Zeeuw*

Selected Excerpts from Proceedings of the National Academy of Sciences 111(37):13257-13263. The entire article can be accessed at 


Using portfolio theory as a conceptual framework, we explore how current interconnections between the aquaculture, crop, livestock, and fisheries sectors act as an impediment to, or an opportunity for, enhanced resilience in the global food system given increased resource scarcity and climate change. Aquaculture can potentially enhance resilience through improved resource use efficiencies and increased diversification of farmed species, locales of production, and feeding strategies. However, aquaculture’s reliance on terrestrial crops and wild fish for feeds, its dependence on freshwater and land for culture sites, and its broad array of environmental impacts diminishes its ability to add resilience. Feeds for livestock and farmed fish that are fed rely largely on the same crops, although the fraction destined for aquaculture is presently small (~4%). As demand for high-value fed aquaculture products grows, competition for these crops will also rise, as will the demand for wild fish as feed inputs. Many of these crops and forage fish are also consumed directly by humans and provide essential nutrition for low-income households. Their rising use in aquafeeds has the potential to increase price levels and volatility, worsening food insecurity among the most vulnerable populations. Although the diversification of global food production systems that includes aquaculture offers promise for enhanced resilience, such promise will not be realized if government policies fail to provide adequate incentives for resource efficiency, equity, and environmental protection.

Aquaculture’s Role in the Global Food System

Freshwater fish comprise the majority of aquaculture production today. These fish are raised in ponds, lakes, canals, cages, and tanks and benefit from a wide range of inputs, technology, and management. Although increasing competition for land and freshwater is driving expansion of aquaculture into marine environments, this trend is not ubiquitous. In many regions, increased production costs and constraints on suitable inshore coastal sites (e.g., those sheltered from wind and wave exposure, aligned with existing environmental regulations, and free of competition with housing and tourism) are resulting in continuous expansion of terrestrial aquaculture, primarily in existing agricultural areas. These pressures are also leading to the intensification of production methods, with greater use of comercial feeds. In other areas, shortages of agricultural land and saturation of sheltered inshore sites is forcing aquaculture further offshore. In Africa, where the need for aquaculture development is greatest due to falling per capita fish supplies, the lack of an enabling policy environment and weak value chain linkages have constrained sector growth despite suitable land and freshwater for expansion.

A Portfolio Perspective

In applying portfolio theory to developments in the global food system, one might think of the targeted return as the aggregate output of crops, livestock, and fish (wild capture and aquaculture) needed to meet human demands. Risks associated with food production systems involve not only temporary declines in productivity but also extensive or irreversible changes in the natural resource base that can undermine long-term productivity. The risk is captured by the variation and trend in food production and prices, because prices reflect fluctuations in supply and demand. The degree of food price volatility is indicative of the global food system’s resilience to a wide range of stressors, such as pest and pathogen outbreaks, extreme weather events (droughts, floods, temperature extremes), climate variability [e.g., El Nino-Southern Oscillation (ENSO) events], and other market shocks related to changes in the energy and financial sectors or in macroeconomic conditions. Over the longer run, price changes reflect the food system’s resilience to slower-moving variables, such as freshwater and soil depletion, changes in mean climate conditions arising from elevated greenhouse gas concentrations, and population growth. A pattern of higher and more variable prices over time would suggest deteriorating resilience in world food supplies, whereas a pattern of stable prices would indicate a more robust and resilient system.

Volatility in aggregate food prices depends on variations in crop, livestock, and fish prices and on the correlations among these prices based on interactions in output and input (feed and fertilizer) markets. On the output side, crop, livestock, and fish systems are vulnerable to distinctive pest and pathogen stressors, and the sectors tend to be geographically dispersed. Although yields from individual sectors may be positively correlated in the face of climate change/variation and volatility in energy prices, they are not perfectly so, and yield variation resulting from pest and pathogen outbreaks are not typically correlated between sectors. Product markets are also linked via consumer choice: a price increase in one commodity (e.g., meat) causes consumption of substitutes (e.g., fish) to rise. The correlates between food sectors are more complex when considering feed inputs for livestock and aquaculture. Given that a large share of livestock and aquaculture systems rely on grain and oil crops for feeds, a jump in these crop prices will lead to a corresponding rise in the cost of cultured fish or meat products, albeit to differing degrees.

What do the data in Fig. 2 suggest about the global food portfolio and the role of aquaculture in this portfolio? First, they show that aquaculture prices, on average, have been less variable than other food commodities and thus appear to add some degree of stability to the global food system. Second, the fact that prices of crops, livestock, and fish products move closely together indicates that the markets are highly integrated. The diversity and substitution among food products, as well as the reliance of the meat and fish sectors on crop-based feeds and also fishmeal and fish oil, will fundamentally determine the risks and returns to the world’s food portfolio over the course of the century.

Diversity in Food Products

At the global scale, increasing the diversity of food production activities by adding a robust aquaculture sector can improve the resilience of the world’s food system as long as it does not deplete resources or pollute the environment in ways that reduce yields in aquaculture or the productivity of other food sectors. A more diverse food system essentially increases the substitution possibilities in production and consumption, adding flexibility to the system that can help buffer Price volatility and improve resource use efficiency. Diversity can be measured at varying levels of disaggregation. For example, a more diverse mixture of products within any given food sector (grains, vegetable oils, meat, fish) will generally result in a more stable price index because fluctuations in the price of any single product (e.g., rice, soy, poultry, or salmon) will not be perfectly correlated with the prices of all other commodities in that sector. Moving one step down, diversity within a given species, comprising many thousands of varieties for some species such as rice or maize, can provide important functional diversity for ecological resilience, but may have little impact on price stability in the short run if individual varieties are not distinguished in the market. Over the long run, ongoing losses of species diversity are likely to challenge the future capacity of the global food system to adapt to changing climate, resource, and cultivation conditions and thus to meet human needs.

Dependence on Feeds

The share of aquatic species raised on supplemental feed inputs continues to rise over time and accounted for almost 70% of total aquaculture production in 2012. Aquaculture’s dependence on feeds, derived from a wide variety of food-quality and human-inedible coproducts from crop, livestock, and fisheries sectors, has important implications for the resilience of the world’s food system and aquaculture’s contribution to it (fig. 3). Utilization of diverse feed resources—especially when they differ from those used in terrestrial animal farming or those consumed directly by humans for food—can increase the net returns to the global food system and provide stability by allowing substitution in feed ingredients when supplies and prices dictate. Individual aquaculture species differ in their demand for feed and feed ingredients. For example, mollusk species such as mussels and oysters, which account for ~23% of global farmed seafood production, are not fed; instead, they use natural ecosystems for food (e.g., detritus, plankton) that otherwise are not directly exploitable by humans. These filter-feeding species also help to reduce eutrophication and other threats to coastal ecosystems caused by nutrient enhancement. By contrast, in 2010, up to two-thirds of the world’s farmed finfish and crustaceans were dependent on comercial pelleted diets. Because virtually all of farmed fish and shellfish species are cold blooded and physically supported by water, they are more efficient feed converters and have higher edible yields than most terrestrial animals.

Overall, the aquaculture sector currently provides more opportunities for efficient transformation of agriculture and fisheries resources (including byproducts and coproducts) for human protein consumption than does much of the terrestrial livestock sector. Moreover, many of the most pressing challenges associated with typical high-input terrestrial animal production systems are less severe in their aquatic analogs, as measured per unit protein produced (e.g., contributions to greenhouse gas and eutrophying emissions). In some instances, comparable threats do not arise at all (e.g., emergence of novel human disease threats such as bird flu), or if such pressures do arise, they are distributed differently across the globe (e.g., habitat degradation and loss). As a result, substituting terrestrial animal production with selected aquaculture species and systems that use feed and other resources efficiently would increase resilience to the global food portfolio, as long as the latter minimizes environmental impacts and negative spillovers to other food systems. Substitution between meat and farmed fish would depend, however, on consumer tastes and preferences, and at present, the very rapid growth of meat demand (far in excess of population growth) constitutes a challenge.


The present diversity of aquaculture systems— characterized by a wide range of cultured species, feed ingredients, and feed practices—contributes important elements of stability to the world’s food portfolio. Caution is warranted, however, in concluding that a more diverse food portfolio will enable the global food system to meet the rising demand for protein in the face of climate change, resource scarcity, and other economic and biophysical stresses. As the aquaculture sector develops and becomes more technologically sophisticated and potentially more reliant on fish/crop-based feeds, issues of social inequity are likely to develop in terms of income generation and access to fish/crops for food (vs. feed). In addition, the ability of aquaculture to add resilience to world food supplies will depend on how the sector develops in terms of species composition, feed inputs, and system design and operation and whether such development can offset the negative externalities associated with existing terrestrial crop and livestock systems (e.g., nutrient loss and greenhouse gas emissions) and capture fisheries (e.g., overfishing). If not designed and managed to minimize environmental damages and social injustices, aquaculture is likely to make the global food system less— not more—resilient. Nations encouraging aquaculture growth should thus focus on building flexible and heterogeneous production systems that derive feeds from both food-grade and non–food-grade agricultural products as efficiently and equitably as possible. Such a strategy requires the development of a diversity of aquaculture species; the promotion of coproducts from the crop, livestock, and fisheries sectors for feeds; the design of infrastructure that uses renewable energy; and the implementation of management practices that minimize wastes and environmental impacts. At the national scale, appropriate policy incentives, proper institutions, and sound industry support will be needed for a flexible and resilient global food portfolio. If the aquaculture industry seeks to dominate the global market for animal protein, it should take a leading role in promoting this strategy of resilience.

*Max Troella,b, Rosamond L. Naylorc, Marc Metianb, Malcolm Beveridged, Peter H. Tyedmerse, Carl Folkea,b, Kenneth J. Arrowf, Scott Barrettg, Anne-Sophie Crépina, Paul R. Ehrlichh, Åsa Grena, Nils Kautskyi, Simon A. Levinj, Karine Nyborgk, Henrik Österblomb, Stephen Polaskyl, Marten Schefferm, Brian H. Walkern, Tasos Xepapadeaso, and Aart de Zeeuwp 

a) Beijer Institute of Ecological Economics, Royal Swedish Academy of Sciences, SE-104 05 Stockholm, Sweden; b) Stockholm Resilience Centre, Stockholm University, SE-106 91 Stockholm, Sweden; c) Center on Food Security and the Environment, Stanford University, Stanford, CA 94305; d) The Worldfish Center, Penang, Malaysia; e) School for Resource and Environmental Studies, Dalhousie University, Halifax, NS, Canada B3H 3J5; f) Economics Department, Stanford University, Stanford, CA 94305; g) Earth Institute and School of International and Public Affairs, Columbia University, New York, NY 10027; h) Department of Biology, Stanford University, Stanford, CA 94305; i) Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden; j) Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544; k) Department of Economics, University of Oslo, Blindern, NO-0317 Oslo, Norway; l) Department of Applied Economics, University of Minnesota, St. Paul, MN 55108; m) Department of Environmental Sciences, Wageningen University, 6700 DD, Wageningen, The Netherlands; n) The Commonwealth Scientific and Industrial Research Organisation Sustainable Ecosystems, Canberra, ACT 2601, Australia; o) Department of International and European Economic Studies, Athens University of Economics and Business, GR10434 Athens, Greece; and p) Center for Economic Research and Tilburg Sustainability Center, Tilburg University, 5000 LE, Tilburg, The Netherlands.


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