Feature Paper: Selig ER, Bruno JF (2010). A global analysis of the effectiveness of marine protected areas in preventing coral loss. PLoS ONE, 5(2):e9278. doi:10.1371/journal.pone.0009278
Author Abstract: A variety of human activities have led to the recent global decline of reef-building corals [1], [2]. The ecological, social, and economic value of coral reefs has made them an international conservation priority [2], [3]. The success of Marine Protected Areas (MPAs) in restoring fish populations [4] has led to optimism that they could also benefit corals by indirectly reducing threats like overfishing, which cause coral degradation and mortality [2], [5]. However, the general efficacy of MPAs in increasing coral reef resilience has never been tested. We compiled a global database of 8534 live coral cover surveys from 1969–2006 to compare annual changes in coral cover inside 310 MPAs to unprotected areas. We found that on average, coral cover within MPAs remained constant, while coral cover on unprotected reefs declined. Although the short-term differences between unprotected and protected reefs are modest, they could be significant over the long-term if the effects are temporally consistent. Our results also suggest that older MPAs were generally more effective in preventing coral loss. Initially, coral cover continued to decrease after MPA establishment. Several years later, however, rates of coral cover decline slowed and then stabilized so that further losses stopped. These findings suggest that MPAs can be a useful tool not only for fisheries management, but also for maintaining coral cover. Furthermore, the benefits of MPAs appear to increase with the number of years since MPA establishment. Given the time needed to maximize MPA benefits, there should be increased emphasis on implementing new MPAs and strengthening the enforcement of existing MPAs.
Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.
Review: Now that we've established how many reefs worldwide have been declining (in the last Science Corner) we will look at seeing whether marine protected areas (MPAs) are effective in helping corals recover and preventing further losses of live coral cover when neighboring reefs are being damaged.
As the authors point out, MPAs have been long established to be effective in maintaining and growing fish populations, but what about their effectiveness on longer-lived animals, such as colonial reef-building corals?
This paper is important because it is one of the first papers to address health of corals in MPAs, and as pointed out by Raymundo et al. in our third review, healthy reef fish communities help to prevent coral diseases, thereby helping the entire ecosystem to function in a "give and take" whereby the health of one component ensures and reinforces the health of other components. This is important because people rely on reefs for multiple resources, so as long as all components are functioning properly, everyone can be happy since all resources will remain at sustainable levels.
To address their question (do MPAs help prevent loss of live coral cover?) the authors looked at over 8000 surveys over nearly 40 years where live coral cover was recorded by scientists. The authors then filtered sites by MPA and non-protected area and determined trends in percent live coral cover over those four decades.
Their results were a bit startling in some regards and common sense in others. For instance, in the Philippines and Indonesia, many ornamental marine fishes (for aquariums) are collected using bleach, cyanide, and other chemicals that stun the fish (often with them dying inside aquariums from organ failure months later linked to the chemical exposures) and damage or kill the live corals in which the fish hide. Food fish is often collected using dynamite, which destroys live corals below it. Additionally, in many Indo-Pacific nations, corals are harvested for building materials, with cements and lye produced from coral skeletons.
The authors are also careful to note that "protection within MPAs may not necessarily result in positive effects on coral cover. Coral loss that is driven by regional or global stressors like climate change and coral disease outbreaks seems unlikely to be mitigated by MPAs or other local management actions [14], [15]. Indeed, several studies of individual reefs or small groups of reefs have found that MPAs do not prevent coral loss and other forms of reef degradation [7], [15], [16], [17]."
However, overall, the authors found that MPAs provided a stabilizing effect on the ecology of the reef ecosystem and that all functional levels of the reef remained constant. This effect seemed to help ensure that corals remained healthy alongside fish and invertebrate communities within MPAs, whereas live coral cover declined steadily outside of MPAs.
The authors also provide a nice map of MPAs worldwide, which is certainly better than in past decades. Hopefully more MPAs are established since the take-home message is that when you protect an entire ecosystem (as with an MPA) you also protect all the individual organisms within that ecosystem. With complex ecosystems, it is heartening to know that a hands off approach (meaning, keep your hands off the resources and out of the cookie jar) helps, though regional and global effects can play a negative effect on the progress of MPAs globally, so we must still worry about global climate change.
Author Abstract: A variety of human activities have led to the recent global decline of reef-building corals [1], [2]. The ecological, social, and economic value of coral reefs has made them an international conservation priority [2], [3]. The success of Marine Protected Areas (MPAs) in restoring fish populations [4] has led to optimism that they could also benefit corals by indirectly reducing threats like overfishing, which cause coral degradation and mortality [2], [5]. However, the general efficacy of MPAs in increasing coral reef resilience has never been tested. We compiled a global database of 8534 live coral cover surveys from 1969–2006 to compare annual changes in coral cover inside 310 MPAs to unprotected areas. We found that on average, coral cover within MPAs remained constant, while coral cover on unprotected reefs declined. Although the short-term differences between unprotected and protected reefs are modest, they could be significant over the long-term if the effects are temporally consistent. Our results also suggest that older MPAs were generally more effective in preventing coral loss. Initially, coral cover continued to decrease after MPA establishment. Several years later, however, rates of coral cover decline slowed and then stabilized so that further losses stopped. These findings suggest that MPAs can be a useful tool not only for fisheries management, but also for maintaining coral cover. Furthermore, the benefits of MPAs appear to increase with the number of years since MPA establishment. Given the time needed to maximize MPA benefits, there should be increased emphasis on implementing new MPAs and strengthening the enforcement of existing MPAs.
Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.
Review: Now that we've established how many reefs worldwide have been declining (in the last Science Corner) we will look at seeing whether marine protected areas (MPAs) are effective in helping corals recover and preventing further losses of live coral cover when neighboring reefs are being damaged.
As the authors point out, MPAs have been long established to be effective in maintaining and growing fish populations, but what about their effectiveness on longer-lived animals, such as colonial reef-building corals?
This paper is important because it is one of the first papers to address health of corals in MPAs, and as pointed out by Raymundo et al. in our third review, healthy reef fish communities help to prevent coral diseases, thereby helping the entire ecosystem to function in a "give and take" whereby the health of one component ensures and reinforces the health of other components. This is important because people rely on reefs for multiple resources, so as long as all components are functioning properly, everyone can be happy since all resources will remain at sustainable levels.
To address their question (do MPAs help prevent loss of live coral cover?) the authors looked at over 8000 surveys over nearly 40 years where live coral cover was recorded by scientists. The authors then filtered sites by MPA and non-protected area and determined trends in percent live coral cover over those four decades.
Their results were a bit startling in some regards and common sense in others. For instance, in the Philippines and Indonesia, many ornamental marine fishes (for aquariums) are collected using bleach, cyanide, and other chemicals that stun the fish (often with them dying inside aquariums from organ failure months later linked to the chemical exposures) and damage or kill the live corals in which the fish hide. Food fish is often collected using dynamite, which destroys live corals below it. Additionally, in many Indo-Pacific nations, corals are harvested for building materials, with cements and lye produced from coral skeletons.
The authors are also careful to note that "protection within MPAs may not necessarily result in positive effects on coral cover. Coral loss that is driven by regional or global stressors like climate change and coral disease outbreaks seems unlikely to be mitigated by MPAs or other local management actions [14], [15]. Indeed, several studies of individual reefs or small groups of reefs have found that MPAs do not prevent coral loss and other forms of reef degradation [7], [15], [16], [17]."
However, overall, the authors found that MPAs provided a stabilizing effect on the ecology of the reef ecosystem and that all functional levels of the reef remained constant. This effect seemed to help ensure that corals remained healthy alongside fish and invertebrate communities within MPAs, whereas live coral cover declined steadily outside of MPAs.
The authors also provide a nice map of MPAs worldwide, which is certainly better than in past decades. Hopefully more MPAs are established since the take-home message is that when you protect an entire ecosystem (as with an MPA) you also protect all the individual organisms within that ecosystem. With complex ecosystems, it is heartening to know that a hands off approach (meaning, keep your hands off the resources and out of the cookie jar) helps, though regional and global effects can play a negative effect on the progress of MPAs globally, so we must still worry about global climate change.
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