Feedback on Subject of Marine Reserve Science: Readers Respond With Variety of Views

MPA News

The December 2003/January 2004 issue of MPA News offered two essays by scientists on marine reserve research. One questioned the rigor with which reserve research has been conducted, while the other explained difficulties involved in studying reserves, including finding adequate control sites. The essays presented a dilemma: we all want the best science on reserves, but to get it will require significantly more time and money - resources that are already scarce for managers.

Readers responded to the essays with a range of views, from arguing that the state of reserve science is stronger than was depicted, to suggesting that scientists should focus more attention on other issues, like socioeconomic factors in reserve success or the effects of pollution on MPAs. Because of the amount of feedback, we have devoted a larger-than-usual portion of this month's issue to letters. Below, MPA News highlights four of the responses received.

Response #1: Moving The Discussion About Marine Reserve Science Forward

By Benjamin Halpern, Robert R. Warner, and Steven D. Gaines

It was with great interest and concern that we read the piece by Willis et al. in the last issue of MPA News (MPA News 5:6). Although we fully support healthy scientific debate, we feel that this piece misrepresents the current state of knowledge about marine reserves. This is not an issue of differing opinions about what marine reserves can and cannot do; instead it is a question of what the science of marine reserves can and cannot tell us. We appreciate the call for more rigor in marine reserve monitoring. As Willis et al. note, some reserve monitoring schemes have been poorly conceived. Nonetheless, our current state of knowledge is not nearly as dire as they depict.

Methods for evaluating reserve effects

Willis et al. claim we know little about how reserves affect fish species, since few monitoring studies show density increases greater than 100%. However, posing an arbitrary one-tailed "minimum criterion" is misguided (i.e., we cannot presume only positive effects); species should vary in their response, including some declines. More importantly, the Willis et al. approach ignores the power of synthesis. Meta-analyses of reserve effects have shown that there is a strikingly consistent increase in density, size, and diversity of exploited stocks within reserves. This is what meta-analyses do: when single studies have limited statistical power, consistency in the direction of changes across multiple studies can uncover real and significant patterns.

Willis et al. also misrepresent the significance of variable outcomes from theoretical models. Variable outcomes arise in theoretical studies because they include different assumptions or processes. Syntheses of modeling results gain power from variable outcomes. This variability focuses our attention on critical mechanisms, generates hypotheses to test empirically, and provides insight into problems that are experimentally intractable. Although we are unaware of any management decisions that have been based solely on reserve theory, the future development of these models should enhance management decisions, rather than obscure them.

Inadequate experimental design

How many studies of reserve effects have had perfect experimental designs? None, as Willis et al. point out. But enough have had designs that allowed a test for the presence and the potential effects of the five experimental shortcomings Willis et al. identify:

  1. Insufficient sample replication: Although it is theoretically possible to find a location where multiple reserves could be established to ensure proper replication, it is politically and logistically unlikely. Meta-analysis is a way to overcome this limitation.

  2. Spatial confounding (reserve sites are always in better areas than control sites): Syntheses of results from Before-After-Control-Impact (BACI) studies show that although initial conditions in reserve and control sites differ, there is no bias or trend in these differences.

  3. Lack of temporal replication: Reserve studies have monitored reserve impacts over years to decades, and these studies show a rapid response for some species and a slower response for others. On average, however, responses inside reserves typically exceed those from associated control sites.

  4. Lack of treatment (reserve) replication: Most reserves have been established in isolation rather than in networks or multiple reserves. Recent noteworthy exceptions (e.g., the Channel Islands of California) will provide such treatment replication for future studies. Until then, meta-analysis is a powerful way to overcome this limitation.

  5. Non-random placement of reserves: Again, BACI studies have shown that control sites are just as often placed in better than in worse locations. There is no a priori reason to expect a reserve effect to be positive.

Finally, while it is true that "with a sufficiently large sample size, a statistically significant difference between two sites can almost always be obtained due simply to true natural biological variability between the sites," this expectation is two-tailed (the difference could be positive or negative) unless one assumes that reserve sites always start out better than control sites (existing studies suggest this is not true). Sadly, no study of marine reserves has had the luxury of detecting statistically significant yet trivial effects, since sample sizes are consistently too small.

Lessons for reserve managers

Rather than simply instructing managers to be more rigorous in reserve design, we think it is more useful to point out the potential problems with reserve monitoring, and to suggest practical solutions.

First, because of the expected export function of reserves, there are no true controls even when habitats vary little among locations; sites outside of reserves may show increases (from export) or decreases (due to displaced fishing effort). While most existing reference areas have shown increases following the establishment of nearby reserves, many more studies are needed. Monitoring designs based upon analyses of gradients in responses as a function of distance from reserves may prove especially insightful.

Second, meta-analyses suggest the level of exploitation, life history, and trophic level of a species can strongly affect its response to protection, and monitoring schemes and expectations must take these expected differences into account. Arbitrary "minimum criteria for biological significance" ignore basic ecological principles.

Third, power analyses using known natural variation in recruitment and population size in marine species suggest that many effects of marine reserves will be difficult to detect even in the best of circumstances. This variation must be taken into account in both monitoring design and in setting time limits for marine reserve performance.


If the requirement for an adequate and appropriate experimental design for testing reserve effectiveness is multiple (and identical) reserve and control sites, measured before and after reserve creation, across multiple times, that demonstrate at least a 100% increase in some measure of interest, for all species, as Willis et al. suggest, then we will never have a good empirical test of reserve effects. Furthermore, reserves are not established as perfectly designed ecological experiments; they arise from political processes with inherent compromises. Should we then ignore reserves as a conservation and management option? We argue that this is not only conservative beyond reason, but that it also ignores the power and lessons of syntheses of both data and models. We have learned much about the science of marine reserves in the past decade, and this guides us toward areas that require further research. Importantly, we currently know enough about marine reserves to justify their use and implementation as one of several conservation and resource management tools.

For more information:
Ben Halpern, National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93106, USA. E-mail: halpern [at]

Bob Warner, Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA. E-mail: warner [at]

Steve Gaines, Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA. E-mail: gaines [at]

[Editor's note: For readers interested in the scientific literature on which Halpern, Warner, and Gaines have based the above statements, a version of this piece containing literature citations is available online.]

Response #2: The Science Of Marine Protected Areas: How Much Of It Is Useful?

By Nancy Dahl-Tacconi

Kelleher (1999) put it simply when he wrote, "The science done for an MPA has to be driven by management needs." Since each MPA is managed in a unique context, the information needed by managers varies according to the objectives and challenges of each situation.

Despite the vast range of natural and social scientific information needed by managers, the bulk of science on MPAs in the past few decades has focused primarily on two areas: issues of design (including studies on biological diversity, dispersal and migratory ranges, and minimum requirements for species viability); and patterns of abundance and distribution of economically important species (mainly studies on fisheries potential). Regrettably, studies on social dimensions of MPAs have been uncommon.

The quest to identify a "reserve effect" on fisheries resources has become increasingly trendy in recent scientific literature. The difficulties in designing and executing "good science" toward this cause have stirred up debates in the scientific community (MPA News 5:6). I agree that science should strive to be rigorous, but in the cash-strapped, politically charged, and value-laden world of MPA management, how much sleep can we afford to lose over this when there are so many other issues that need to be investigated? Lee (1993) offered us some helpful advice: "In the case of large ecosystems, pragmatism is a prime virtue: to learn what we can, and to recognize its limits."

Rigor alone does not ensure that scientific information is useful in a management context. Management is not conducted in a world that abides by the idealistic rules of appropriately replicated and controlled scientific experiments. For managers, investing valuable resources in achieving ideal experimental designs may be overkill, especially in areas where small investments in education campaigns or alternative livelihood programs can largely negate the need to conduct research on MPA effects for the purpose of convincing stakeholders of the value of protecting their marine environment.

To a manager, information is useful for changing or reinforcing someone's attitudes or behavior, including everything that any stakeholder (that also includes management staff) thinks or does in or around an MPA. That is the ultimate purpose of the application of information in an MPA management context. The two biggest contributions that scientific information can make toward improving the use of MPAs as a management tool are, first, to assist in designing and establishing areas that will be well-suited to their intended management objectives, and second, to assist in adapting management strategies to improve the likelihood of achieving those objectives.

Managers need a vast range of critical information to do their jobs effectively. In order to develop, monitor, and adapt management strategies, they need information on: awareness levels, aspirations and compliance of stakeholders; nature and extent of threatening processes; abundance and distribution of focal species or habitats; costs and benefits of management initiatives such as alternative livelihood programs or capacity building; changes in stakeholders' perceptions of social and environmental values; quality of life in adjacent communities; adequacy of various financing mechanisms; current and future political climates; trends in industrial technology; and a host of other important considerations that influence how managers make decisions and implement their programs. The vital roles of natural science, social science, and a pragmatic approach to investigating relevant issues are obvious.

Current studies on information requirements of MPA managers and how stakeholders define a "successful MPA" are exposing reasons why certain types and combinations of information are particularly useful for improving management in different contexts. Considering "context" is the key. Scientific articles on MPAs rarely mention specific management objectives or relevant contextual issues surrounding management actions at the research sites. This impedes the application of scientific information in a management setting for two reasons. Recommendations from research conducted oblivious to management realities may be irrelevant to managers. Alternatively, inappropriate presentation of potentially useful information can obscure its actual relevance.

Research that is designed, conducted and presented in a way that is relevant to the actual management goals and challenges of an MPA, and responsive to the information needs of managers, will go a long way toward improving the image and management practice of MPAs.

Message to scientists: Information on economically important species comprises just a few large drops in the bucket of information that practitioners must consider while designing areas and adapting management strategies. Scientific findings presented in the context of actual management issues will get used. The rest may not.

Message to managers: "Science-based" recommendations generated without regard to the actual management context should be applied with great caution. While working with scientists to design research, communicating explicit intentions for the results will help facilitate the best use of scientific information in practice.

Kelleher, G. 1999. Guidelines for Marine Protected Areas. IUCN, Gland (Switzerland).
Lee, K.N. 1993. Compass and Gyroscope: Integrating Science and Politics for the Environment. Island Press, Washington, DC (USA).

For more information:
Nancy Dahl-Tacconi, Mail to: Center for International Forestry Research (CIFOR), PO Box 6596 JKPWB, Jakarta 10065, Indonesia. Tel: +62 251 355 552; E-mail: ntacconi [at]

[Editor's note: Dahl-Tacconi is project leader for evaluations of management effectiveness at two MPAs in Indonesia, with her work supported by the US National Oceanic and Atmospheric Administration. She is also a Ph.D. candidate at the University of Queensland, Australia, studying the roles of scientific methods and participatory processes in evaluating effectiveness of MPAs.]

Response #3: No-Take Zones Are Not The Only Way To Achieve Benefits For Biodiversity and Fisheries

By Graeme Kelleher

The articles in the December/January edition of MPA News implied (by omission of mention) that benefits for both biodiversity and fisheries flow only from no-take MPAs. There is another consideration in relation to achieving biodiversity and fisheries objectives that I think deserves mention. I refer to the use of non-trawling zones in large MPAs.

I think that it would be fair to assume that many benefits to both categories of objective (biodiversity and fisheries) can flow from non-trawling zones where limited line-fishing may be permitted, especially when significant transmission of target larvae or fish occurs from the non-trawl zones into surrounding areas. The visual evidence from films and photographs showing the benthic effects of bottom trawling is very powerful. It is obvious that bottom trawling drastically changes benthic habitats and, consequently, could well have negative effects on biodiversity and may also reduce total catch of a target species.

Although demonstrating scientifically that repeated bottom trawling often reduces biodiversity is difficult and expensive, I think it is fair to assume that in many circumstances this will be the effect, just as plowing reduces biodiversity on land. Meanwhile, research is proceeding here in Australia and elsewhere on this question.

In the interest of balance, I also should mention that it is evident from fishing data on, for instance, prawn (shrimp) catches, that repetitive trawling can increase catch of a target species over time and reduce by-catch - i.e., it can reduce benthic biodiversity, but improve the fishery.

I emphasize that the above comments represent only my personal opinion.

As another of your recent articles recognizes, the recent draft re-zoning of the Great Barrier Reef Marine Park aims to increase the no-take area of the MPA from a trivial 16,100 km2 to about 113,000 km2 (MPA News 5:6). What was not emphasized is that the non-trawling areas (which include the no-take areas) will hopefully be increased from a mere 169,000 km2 to 229,000 km2. The MPA area in total is 344,400 km2.

For more information:
Graeme Kelleher, 12 Marulda Street, Arenda, Canberra ACT 2614, Australia. Tel: +61 2625 11402; E-mail: g.kelleher [at]

[Editor's note: Kelleher served as chairman and chief executive of the Great Barrier Reef Marine Park Authority from 1979 to 1994. He is now a senior advisor to the IUCN World Commission on Protected Areas.]

Response #4: Scientists Should Focus More On Threat Of Pollution

By Floor Anthoni

The appearance in MPA News of two essays by marine scientists questioning the rigor of marine reserve research attests to courage since it is not easy to say that the Emperor has no clothes. There is indeed much wrong with the claims made for perceived fisheries benefits from marine reserves. Due to a variety of reasons, much of marine science has succumbed to the "snapshot" approach, where inexperienced junior scientists make dives for a year to collect data to prove a hypothesis. These scientists are not long-term observers, and so do not notice events happening around them that could influence the outcomes of their studies, such as climatic oscillations or habitat degradation.

Meanwhile, scientists have remained largely oblivious to the major damage caused to the world's coastal seas by land-based pollution, including mud, fertilizer runoff, and sewage. (Mud, for example, has had a significant impact on the world-renowned Goat Island marine reserve here in New Zealand.) Too few scientific studies have been done on how pollution can impact marine life. Scientists must focus more of their research on this threat, and every marine protected area should have an action plan for rehabilitating the land in its catchment areas.

Marine reserves are but a small tool in the toolbox of marine conservation. To save the sea will require a fully integrated approach that looks at the causes of all the threats to the sea, not just those from fishing. I invite MPA News readers to visit the Seafriends website (, which is devoted to this philosophy.

For more information:
Floor Anthoni, Seafriends Marine Conservation and Education Centre, 7 Goat Island Rd, Leigh R.D.5, New Zealand. Tel: +64 9422 6212; E-mail: sea.friends [at]

[Editor's note: Anthoni is director of the Seafriends Marine Conservation and Education Centre, an NGO dedicated to the conservation of New Zealand seas.]