Marine protected areas: do they work?

13 08 2010

One measure that often meets great resistance from fishermen, but is beloved by conservationists, is the establishment of marine protected or ‘no take’ areas.” Stephen J. Hall (1998)

I’m going to qualify this particular post with a few disclaimers; first, I am not involved in the planning of any marine protected areas (henceforth referred to as ‘marine parks’) in Australia or elsewhere; and second, despite blogging on the issue, I have never published in the discipline of protected area design (i.e, ‘conservation planning’ is not my area of expertise).

That said, it seems to becoming more imperative that I enter the fray and assess not only how marine parks should be designed, but how effective they really are (or can be). I’ve been asked by several conservation NGOs to provide some insight into this, so I thought I should ‘think aloud’ and blog a little mini-review about marine park effectiveness.

Clearly there is a trend to establish more marine parks around the world, and this is mainly because marine conservation lags so far behind terrestrial conservation. Indeed, Spalding et al. (2008) showed that only 4.1 % of continental shelf areas are incorporated within marine parks, and ~ 50 % of all marine ecoregions have less than 1 % marine park coverage across the shelf. Furthermore, marine protection is greatest in the tropical realms, while temperate realms are still poorly represented.

The question of whether marine parks ‘work’ is, however, more complicated than it might first appear. When one asks this question, it is essential to define how the criteria for success are to be measured. Whether it’s biodiversity protection, fisheries production, recreational revenue, community acceptance/involvement or some combination of the above, your conclusion is likely to vary from place to place.

Other complications are, of course, that if you cannot ensure a marine park is adequately enforced (i.e., people don’t respect the rules) or if you don’t actually place the park anywhere near things that need protecting, there will be no real net benefit (for any of the above-mentioned interest groups). Furthermore, most marine parks these days have many different types of uses allowed in different zones (e.g., no fishing, some fishing, recreational diving only, no boat transport, some shipping, etc., etc., etc.), so it gets difficult to test for specific effects (it’s a bit like a cap-and-trade legislation for carbon – too many rules and often no real net reduction in carbon emissions – but that’s another story).

All these conditions aside, I think it’s a good idea to present what the real experts have been telling us about marine park effectiveness from a biodiversity and fishing perspective over the last decade or so. I’ll summarise some of the major papers here and give an overall assessment at the end. I do not contend that this list is even remotely comprehensive, but it does give a good cross-section of the available evidence.

  • McClanahan & Mangi (2000): For Kenyan coral reef parks, total wet mass of catches per trap, the mean size of the trapped fish, and the number of fish species caught per trap declined as a function of the distance away from the park edge. This relationship was truncated on the unmanaged side of the park which also had smaller catches, smaller fish, and fewer species than the managed side.
  • McClanahan & Kaunda-Arara (2002): In Kenyan coral-reef lagoons on seven reefs over 6 years, most fish species within the park showed recovery after fisher exclusion.
  • Gell & Roberts (2003): In a short review, these authors conclude that reserves and fishery closures benefit species as diverse as molluscs, crustaceans and fish of many sizes, life histories and mobilities. Benefits develop within 2-5 years of marine reserve establishment and continue to build for decades. Reserves work in coral reefs, kelp forests, temperate continental shelves, estuaries, seagrass beds, rocky shores and mangroves.
  • Halpern (2003): Probably the most comprehensive review of 89 marine park studies concluded that on average, density, biomass, size of organisms, and diversity (except for invertebrate biomass and size) were higher inside reserves compared to outside (or after reserve establishment versus before) for all species and examining each functional group (carnivorous fishes, herbivorous fishes, planktivorous fishes/invertebrate eaters, and invertebrates) separately.
  • Mumby et al. (2006): In Caribbean coral reef systems, these authors showed that marine reserves benefit both grazers and their predators, but more so for algal grazers. This, in turn, benefits coral reefs by removing competing algae biomass.
  • Shears et al. (2006): In New Zealand marine parks (one with full fisher exclusion, the other with partial exclusion), legal-sized spiny lobster (Jasus edwardsii) were 11x more abundant and biomass 25x higher in the no-take marine park following park establishment, while in the partially protected marine park there was no measurable change in numbers.
  • Stelzenmüller et al. (2007): In a Mediterranean reserve system, catch-per-unit-effort (CPUE) of total fish and CPUE and length of common pandora (Pagellus erythrinus) increased close to the reserve. CPUE and length of striped red mullet (Mullus surmuletus) slightly increased also near the reserve.
  • Stewart et al. (2009): In another comprehensive review of temperate marine parks, these authors found higher density, biomass and species richness in reserves compared to adjacent exploited areas.
  • Kellner & Hastings (2009): Demonstrated that displacement of fishing into smaller areas by the establishment of marine parks can facilitate the invasion of marine pests.

So the general conclusion is yes, marine parks benefit biodiversity and help to recover fish populations depleted from fishing (with the possibility of some unintended consequences though for community composition). There are also a host of studies looking at the socio-economic advantages/disadvantages of marine reserves that I won’t attempt to get into. It does seem however from that perspective that marine reserves are generally considered, despite initial resistance, positive components of coastal human communities.

I’ll leave you with some words by Ben Halpern in his 2003 review:

Despite the popularity of marine reserves as a management tool, few reserves appear to have been created or designed with an understanding of how reserves affect biological factors or how reserves can be designed to meet biological goals more effectively (e.g., attaining sustainable fish populations).”

CJA Bradshaw

McClanahan, T., & Mangi, S. (2000). Spillover of exploitable fishes from a marine park and its effect on the adjacent fishery Ecological Applications, 10 (6), 1792-1805 DOI: 10.1890/1051-0761(2000)010[1792:SOEFFA]2.0.CO;2

McClanahan, T., & Kaunda-Arara, B. (1996). Fishery Recovery in a Coral-reef Marine Park and Its Effect on the Adjacent Fishery Conservation Biology, 10 (4), 1187-1199 DOI: 10.1046/j.1523-1739.1996.10041187.x

Gell, F. (2003). Benefits beyond boundaries: the fishery effects of marine reserves Trends in Ecology & Evolution, 18 (9), 448-455 DOI: 10.1016/S0169-5347(03)00189-7

Halpern, B. (2003). The impact of marine reserves: do reserves work and does reserve size matter? Ecological Applications, 13 (sp1), 117-137 DOI: 10.1890/1051-0761(2003)013[0117:TIOMRD]2.0.CO;2

Mumby, P. (2006). Fishing, Trophic Cascades, and the Process of Grazing on Coral Reefs Science, 311 (5757), 98-101 DOI: 10.1126/science.1121129

Shears, N., Grace, R., Usmar, N., Kerr, V., & Babcock, R. (2006). Long-term trends in lobster populations in a partially protected vs. no-take Marine Park Biological Conservation, 132 (2), 222-231 DOI: 10.1016/j.biocon.2006.04.001

Stelzenmuller, V., Maynou, F., & Martin, P. (2007). Spatial assessment of benefits of a coastal Mediterranean Marine Protected Area Biological Conservation, 136 (4), 571-583 DOI: 10.1016/j.biocon.2007.01.002

Stewart, G., Kaiser, M., Côté, I., Halpern, B., Lester, S., Bayliss, H., & Pullin, A. (2009). Temperate marine reserves: global ecological effects and guidelines for future networks Conservation Letters, 2 (6), 243-253 DOI: 10.1111/j.1755-263X.2009.00074.x

Kellner, J., & Hastings, A. (2009). A reserve paradox: introduced heterogeneity may increase regional invasibility Conservation Letters, 2 (3), 115-122 DOI: 10.1111/j.1755-263X.2009.00056.x

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9 responses

13 08 2010

A great post. This message deserves to be spread far and wide- the amount of confusion and deliberate misinformation by some in the fishing community on the issue of MPAs needs to be countered with the evidence. Thanks Corey.

13 08 2010

Thanks, Mark. That was my main aim when putting this together. Agreed – a lot of misinformation, especially around the time of elections.

13 08 2010


I am left wanting something more…. not to label myself from the get go but, I am interested in the idea of fisheries production being a measure of success for marine parks. This interests me because success is likely to be not only criteria dependent but, scale dependent. In regard to fisheries production, it is typically measured at a much larger scale (and arguably should be) than the more typical inside versus outside MPA comparison experimental design to measure the success of am MPA. I am no opponent of MPAs, just interested in getting good performance at as many scales as we can… and how or what other support these parks may need to achieve greater success.

In the interest of maximizing benefits and reducing costs, I think it is important to look across scales. Most of your references and conclusion on whether or not marine parks “work” appear to be based on results derived from exp. designs that are small in scale. Yet, you leave with us with a quote suggesting the need to consider effects of marine parks on populations, which in most cases, are larger than the scale of any particular park if not several parks.

History has shown that even the most well-intended solutions have created problems (many of which have been anchored to the issue of scale). In the interest of not repeating this conundrum with marine parks, it seems pertinent we look to measure the successes or pitfalls by measuring dynamics that both exist within them and ripple out of them at a variety of scales. Is greater fish production in a protected area versus an unprotected area really the work of the marine park or is it the work of the fish? My understanding is that the ‘work’ of the marine parks is to regulate fishing pressure (as well as other environment disturbances), which we know to reduce fish size and density, out of them. The question left in my mind is, how can we know everything outside of the MPA is not a little bit worse off because of it?

Not out of cynicism, just concern.

13 08 2010

All good points, Amber. This is one reason why I included the Kellner & Hastings (2009) paper which shows that concentrating fishing effort into smaller areas ex-park can lead to a higher incidence of marine pest invasion. I’m sure there are many other examples of concentrating effort leading to worse-off effects outside of reserves. Furthermore (and despite Halpern’s conclusion that size doesn’t matter, probably because of a narrow range of small-sized reserves he reviewed), Gell & Roberts conclude that the size of the reserve is imperative, and this is supported also by our recent work looking at the temporal variability of coral reef fish populations with respect to reef size.

13 08 2010
Marine protected areas: do they work? « Human Dimensions of Natural Resource Management

[...] Marine protected areas: do they work? I’m going to qualify this particular post with a few disclaimers; first, I am not involved in the … [...]

24 01 2011
Condoms instead of nature reserves «

[...] The practice of designating hallowed places as nature reserves must no longer be seen as “victories,” but rather as concessions. They are a permit issued to keep on growing as long as a small portion of the land base is left off the shopping list. The declaration by certain politicians to “protect” 12% of our land surface from exploitation is a permit to leave 88% unprotected. What they are really talking about, is licensed exploitation. It is like paying the mob not to rob your neighbourhood, so that they can ravage others. The Saxons called it Danegeld, and all it bought was time. What is magical about this 12%? Does 12% somehow represent the area of land necessary to protect wilderness and wildlife? Or is it a political figure designed to achieve a compromise between conservationists and developers? [my addendum: see my related post about reserve percentages for marine parks] [...]

5 04 2011
Does the pope where a funny hat? «

[...] blogged several times on the subject (see Marine protected areas: do they work?, The spillover effect, Interview with a social (conservation) scientist, and Failing on ocean [...]

18 06 2011
The few, the loud and the factually challenged «

[...] fishers who benefit from the free, public-good resource that they assist in maintaining (see here, here and here). The evidence is clear world-wide: marine parks benefit pretty much everything and [...]

11 01 2013
k Barnes

How can this happen?????

BP is expected to move to drill several wells in 2013 and 2014, using a floating rig similar to the Deepwater Horizon. The April 5 Adelaide Advertiser looked forward to the Bight becoming “a major oil and gas reserve for Australia, with a 100 million barrel field, worth $10 billion.”

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