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Measuring shocks to the global seafood supply

By Jeff Atkins

plos ecologyESA 100 research news originally posted on the PLOS Ecology Field Reports blog on Aug 14, 2015.

Jessica Gephart, a Ph.D. candidate at the University of Virginia, presented work at the 100th meeting of the Ecological Society of America during Tuesday’s Sustainability: Agriculture/Forestry detailing the evolution of the global seafood market.

She modeled environmental and policy perturbations using a combination of network analysis and an adapted ecological perturbation model. Her work offers insights into an understudied ecological issue of global importance.

Nigerian fish sellers. (Photo courtesy of Kyle Davis)
Nigerian fish sellers. (Photo courtesy of Kyle Davis)

Global significance of seafood

In 2010, fish accounted for 16.7 percent of the global population’s intake of animal protein and 6.5 percent of all protein consumed. Moreover, fish provided more than 2.9 billion people with almost 20 percent of their intake of animal protein, and 4.3 billion people with about 15 percent of such protein. Fish proteins can represent a crucial nutritional component in some densely populated countries where total protein intake levels may be low.”

— from The State of World Fisheries and Aquaculture, 2014 (FAO UN)

By 2012, human consumption of fish exceeded 136 million tonnes — a 16% increase since 2007 and nearly 20 kg of fish per person. While seafood has become the most widely traded food commodity, it is often not included in food trade studies. With rising population, growing reliance on seafood as a dietary staple, and the increasing connectivity of global trade markets, understanding the dynamics of global seafood markets and their potential vulnerabilities is important.

Total fisheries capture (from both marine and inland waters) and aquaculture production. (from FAO UN). Total capture increases steadily till the 1990’s and then levels off, while aquaculture has increased in production steadily.

Basic ecology adapted for real world problems

The original ecological model, adapted by Gephart and her collaborators, is an ecological perturbation model outlined by Bruce Hannon in 1973 in a paper entitled “The Structure of Ecosystems.”

Conceptually, Gephart’s model is the same as Hannon’s. Hannon’s model represents the ecosystem as a network. To test the effects of perturbations, a “shock” is introduced to the system. In ecosystem terms, a shock can be a nutrient addition or pulse of phytoplankton. Then using the relationships of the nodes within the network of the ecosystem, the effects of that shock can be calculated across the ecosystem and on each node, or component, of that ecosystem represented in the model.

Gephart replaces species with countries and regions. Ecological connections between nodes become trade relationships. And energy shocks are replaced with market perturbations that would include fishery collapse, natural disasters, or the implementation of export bans.

“We distribute the shock across the network structure based on per capita GDP to take into account willingness to pay so that people who are willing to pay a higher price are sent less of the shock, said Gephart. “The GDP effect essentially intensifies the result of Central and West Africa being most vulnerable.

This network analysis employed by Gephart uses trade data from the self-reported UN Comtrade data from 1994–2012) and allows for the quantification of bilateral trade network structure. Shocks were assessed by comparing changes in national fish supplies to indices of nutritional fish dependency.

Vulnerability and exposure

Vulnerability in the analysis is defined by the IPCC vulnerability framework and is comprised of three components:

1) Exposure — Amount of shock that ends up in a region, expressed as a change in their fish availability.

2) Sensitivity — Or much the shock actually affects the people, represented in the model as a region or country’s dependence on fish

3) Adaptive Capacity — The ability of the people or the country to offset the impacts of a shock, often related to governance and infrastructure. Are there alternative ways to deal with the problem in the country?

This vulnerability framework has often been used in climate change studies, but is now being used in food security studies.

“If a country becomes exposed to a shock, what does that mean for their health and well-being?” said Gephart, “do they have alternative ways to deal with the problem? Are there solutions within in the country? We need to know how to assess that.”

By the numbers

Gephart’s analysis of global seafood market connectivity shows an average annual trade increase of 4.1% since 1994 and an 80% growth in partnerships.

This increase in globalization has advantages. Countries are able to gain access to larger markets and bolster local economies. Diets also become more diversified and regional supply shocks are able to be surmounted via imports. There is of course the downside. Increasing globalization can lead to a loss of sector jobs and increased reliance on other countries to meet food demands and nutritional needs.

The increase in network connectivity levels off from 2009–2012, likely related to the overall contraction of the market during the financial crisis. There is evidence that trade has begun to increase again. An analog for this even has already been seen. During the global grain crisis in 2007–2008, India imposed an export ban on rice that created a shortage of rice to SE Asia. Countries who were dependent on rice from India experienced shortages. Similar shocks could be felt in the seafood market as well, were a global shock to be of significant size.

Her research not only offers insight into these relationships, but also offers possible solutions. She points out that countries can limit their vulnerability by reducing reliance on net imports, diversifying food sources beyond seafood, and expanding aquaculture.

“Areas of sub-Saharan Africa produce less than 1% of global aquaculture,” says Gephart, “that number could vastly increase.”

She is quick not denigrate globalization and trade, “there are definite benefits to trade in seafood markets, but we must be aware of the need to build in resilience into the global food system and minimize vulnerabilities.”

JEFF ATKINS is a Ph.D. candidate at the University of Virginia and Field Scientist for the Shenandoah Watershed Study. His research focuses on the interaction of vegetation and landscape position to influence biogeochemical cycles within complex terrain and the effects of inter-annual climate variability on ecosystems. You can reach him via Twitter (@atkinsjeff).

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