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Why might fish stocks be more depleted inside a marine protected area (MPA) than outside of it?

This and other mysteries are elucidated in a Center for International Forestry Research (CIFOR) study that uses a ‘realist synthesis’ approach to understand when, how, where and why the establishment of MPAs is likely to result in better environmental conditions than other ownership arrangements.

The paper brings together evidence from 31 articles about MPAs in a wide range of contexts in Africa, Asia and Latin America. In doing so, it uses fisheries as a particular lens for addressing the broader, longstanding question for natural resource management: Given the complexity and diversity of socio-ecological systems around the world, how can we devise the best ways to intervene to promote sustainability?

The answer, it seems, may rely not only on the interventions, but also on the research method from which they were devised.


Realist synthesis is an evidence review technique that seeks to unveil the links between context, mechanisms and outcomes in complex systems.

This report marks the second time realist synthesis has ever been used in a peer-reviewed study on conservation policies. The choice emerged from the co-authors’ frustrations with more conventional methods of analysis.

Quantitative systematic reviews, which use a rigorous methodology to search for, select, appraise and synthesize primary research papers on a given topic, are widely used in the natural resource governance sector.

But these kinds of reviews were developed within medical science, explains paper co-author and CIFOR Research Director Steve Lawry, and extending their use into social scientific problems can sometimes be “asking for trouble,” he says.

“Finding studies that meet the standardized data inclusion criteria of systematic reviews, knowing that society is very complex, can be a nightmare. And you can take it from me, because I’ve done a systematic review of the investment and productivity effects of better securing land rights.”

During that research process, “we looked at 25,000 studies initially, and at the end of the process we only came up with 20 studies that met the methodological standards for inclusion.”

What’s more, he says, while the review produced some interesting findings about variations in productivity increases in different regions of the world, it failed to answer a crucial question: why were these variations occurring?

“The thing is that the systematic review does not enable us to draw conclusions directly from the data about the causes of differences in outcomes across communities or regions. Contexts differ, and that matters.”

As co-author and CIFOR Consultant Rebecca McLain puts it, realist synthesis “seeks not only to describe the outcomes of policy interventions in complex systems, but also teases out how those outcomes are arrived at, and the conditions under which different outcomes have occurred.”

Essentially, she explains, “it emphasizes the need to understand what motivates people to change their behavior – or not – in a variety of situations.”


At a basic level, the researchers’ realist synthesis on MPAs revealed that the perceptions of regulatory legitimacy are critical to long-term sustainability and cost-effectiveness.

“But the story is more complicated than that,” says McLain.

Initially, the researchers envisaged the various mechanisms that influence these long-term outcomes to be operating simultaneously with each other, but somewhat independently. “But we actually found that at least three types of legitimacy – legal, social and ecological – are typically ‘bundled together’ in a way that can’t easily be disentangled,” she says.

When one or more of these aspects are weak, people will probably behave in ways that conflict with conservation goals in the MPA. When legitimacy is “robust” on all three fronts, they are much more likely to comply with the regulations, says McLain.

“In practice this means that fishers in an area where MPAs are being established not only need to recognize that the state or community imposing the restrictions has the legal authority to do so, but they also need to see the restrictions as socially acceptable and ecologically credible,” she explains.

For example, in one of the case studies the researchers analyzed, a fishing cooperative in Puerto Peñasco, Mexico, set up no-take zones for benthic invertebrates (crustaceans, mollusks, worms and other bottom feeders).

We actually found that at least three types of legitimacy – legal, social and ecological – are typically ‘bundled together’ in a way that can’t easily be disentangled

CIFOR Consultant Rebecca McLain

At first, the initiative was successful. Cooperative members voluntarily complied with the rules due to a shared belief that it would support the overall health of fisheries in the area (ecological legitimacy) and strong social capital within the group (social legitimacy). A local official made sure that outside fishers did not take from the zones (legal legitimacy).

But during the course of the initiative, the official was replaced by someone who was not interested in enforcing the reserve rules, and outsiders began fishing in the no-take zones. When cooperative members saw these actions going unpunished, they began fishing in the zones again, too. As a result, the populations of benthic invertebrates in the area actually dropped to lower levels than in control sites.

The case shows how vulnerable a system can be to the actions of just one individual and highlights the importance of identifying “weak points” like this and finding ways to protect against them.


The researchers are excited about the possibilities of applying realist synthesis to the evaluation of other policy interventions in natural resource management, offering new insights into the ways that complex systems such as fisheries and forestry work.

“It can easily be adapted,” says McLain, “as long as there are enough studies that provide enough information about the context, mechanisms that lead to behavioral change and outcomes to make a qualitative analysis possible.”

“We think it does have some real power to generate insights into common factors that contribute to the successes and the failures of policies in various contexts,” says Lawry.

This research was supported by funding from the CGIAR research program on Policies, Institutions and Markets.

For more information on this topic, please contact Steve Lawry at
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