Monday, 21 May 2012

Protected Areas: Is bigger really better?

I'm in the midst of my revision for the exams lurking around the corner (quite literally, I have one on Thursday, one on Monday and then one on Wednesday. I am in no way prepared for the last one but I'm getting there with the others). I'm just about to start looking over my coursework for this module, "Protected Areas: Is bigger really better?" and thought, what better way to inject the information I had understood back into my brain than to educate those who might not really understand the predicament that managers face.

Why is protection needed?
Through a combination of habitat modification, non-indigenous species introductions and direct exploitation, humans have undoubtedly placed an excess amount of pressure on the Earth, and as such the protection of these affected areas is the foundation for all biological conservation strategies. A protected area (PA) is defined as being “an area of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources, and managed through legal or other effective means” (IUCN 1994). Protected areas (PAs) aim to alleviate the anthropogenic pressures mentioned above. As a result, it is imperative that areas are effectively conserved, protected and managed if we are to meet the demands of the Convention on Biological Diversity (CBD) which intends to significantly reduce the rate of biodiversity loss by 2020.


Although there has been an increase in the number of Marine Protected Areas (MPAs) globally, the ocean is still poorly represented when managing conservation priorities. Only about 1.17% of the world’s oceans are protected with approximately 6,800 designated MPAs. Land-based PAs however are expected to cover 13% of the Earth’s surface with over 120,000 designated PAs.

PA development
The development of PAs has, in recent years, taken a “no-take is best” and “bigger is better” stance, since the fundamental purpose of a PA is to preserve biodiversity. The Global Ocean Legacy programme of the Pew Environmental Group has largely driven the expansion of MPAs following their aims to establish a coherent protection network, something that has been highlighted as being highly important. Very large terrestrial PAs have typically aimed to conserve wilderness which unfortunately do not necessarily overlap with high priority areas. These areas biased towards lower quality lands and tend to have very little economic worth to humans.

Is bigger better? The SLOSS debate.
Based on the theory of island biogeography (MacArthur & Wilson 1967), an increase in size coincides with  an increase in species diversity and richness. These assumptions have been used to set baseline targets for conservation and are as such an integral part of the PA planning process. Early work suggested that larger PAs would be more beneficial to protecting biodiversity since they support larger species numbers, however since their establishment there has been an ongoing debate on the veracity of this. This is the 'SLOSS debate' (Single Large or Several Small). The outcome of the debate basically states that the "which is best" scenario largely depends on the objectives of the protected area, essentially no coherent conclusion was made!

An interesting point made was the potential for a population to recover after a catastrophe. Habitat fragmentation remains as one of the biggest threats to biological diversity since it increases the edge effect, a phenomenon whereby population densities tend to decline from the core to the peripheral habitat (or edge) due to the infiltration of human activity or natural threats which can hinder these populations. The smaller the population is, the more 'at risk' it is from extinction, however several small 'islands' of protection (depending on the extent of their connectivity) will have some level of interaction. These can act as reserve populations and help to repopulate an area. Very large protected areas (vLPAs) are expected to be so large that the risk of population extinction is very slim.

vLPAs and fisheries management
Whilst I am a (or aspiring to be at least) marine biologist maybe I should relate this whole thing to fisheries management and whether vLPAs are beneficial in this instance. As discussed by Roberts et al. (2001) it is highly unlikely that vLPAs would benefit fisheries as much as intermediate sizes. Lack of financial backing or stakeholder support would deem the implementation of these sites near impossible. Through the eyes of an eager fisherman, some marine reserves can be seen as pure gold mines since landings at these reserve edges can be exceptional due to something called "spillover". As the extent of spillover depends on boundary length and the edge-area ratio, vLPAs would not result in a high degree of spillover unless it was long in shape (rather than circular).

Target species
Protected areas need to be implemented with a species in mind. Small reserves have the capability to protect significant biodiversity in some species, such as in South African fynbos. Predators such as the African wild dog and brown bear, on the other hand, may require large areas to retain a decent proportion of their original species richness. vLPAs can encompass a species' entire range and as such as perceived as being 'better', however a tight network of highly connective reserves can achieve essentially the same thing. The (and I practised this a lot so I could actually say it correctly) Papahānaumokuākea Marine National Monument (Northwestern Hawaiian islands) is a prime example of this. For mobile species such as the giant trevally, the general consensus is that it is difficult to protect such populations due to their fluid spatial movements. By protecting important aggregation sites such as feeding or spawning sites, these populations can be protected without having to cordon off large areas.

What about cost?
In economic terms, a protected area may be seen as an investment - as such the expected benefits need to outweigh the potential costs before its implementation. A major cost involved is the displacement of fishermen from previously fished areas (should that area be closed to fishing activity). Asides from this aspect, protected areas are not cheap. Running costs of between $5 billion and $19 billion were estimated by Balmford et al. (2004) should we create enough PAs to meet biodiversity targets. Smaller reserves can be managed by small, local populations (community effort right?) whilst very large reserves suffer from the extreme demand for resources and personnel required to manage the large boundaries.

A brief summary of the advantages and disadvantages of vLPAs (in both terrestrial and marine sites) can be found below:

Support more species
Difficulties in enforcing protection over a large area.
Large protective core not affected by ‘edge-effects’
Conflict over land use and economical expenses.
Accommodate range shifts due to climate change
May not be as beneficial to fisheries as first thought.
Accommodate highly mobile/migratory species.

A few key references that I have cited here...
Balmford, A., Gravestock, P., Hockley, N., McClean, C. J., & Roberts, C. M. (2004). The worldwide costs of marine protected areas. Proceedings of the National Academy of Sciences of the United States of America, 101(26), 9694-9697

Roberts, C. M., Bohnsack, J. A., Gell, F., Hawkins, J. P., & Goodridge, R. (2001). Effects of marine reserves on adjacent fisheries. Science, 294(5548), 1920-1923.

I haven't referenced this one but it is really useful (for my revision and for those who are generally interested in marine reserves)

Roberts, C.M. & Hawkins, J.P. (2000) Fully protected marine reserves: A guide. World Wildlife Fund, Washington DC (link here:

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