THE CONSERVATION COLUMN: Protecting marine biodiversity
Marine Protected Areas (MPAs) are an important tool in conserving threatened species and commercial fisheries. But just how effective are they? Ahead of his upcoming talk at the Royal Geographical Society in March, Earthwatch scientist Dr John Cigliano shares some insights from his research in Belize…
If you are reading this article, and this website, then you love the oceans. And you probably know that the oceans we love are under serious threat. Overfishing has decimated once abundant species. For example, 16 species of shark are considered globally threatened or near threatened, and several species have declined by over 70% from their historical numbers due primarily to commercial fishing. Rising ocean temperatures are threatening temperature-sensitive species now, causing a decline in coral reefs (see Earthwatch scientist Dr David Smith’s column on 21.12.11). Ocean acidification, a reduction in pH due to increased levels of CO2 in the oceans, has already begun to negatively affect organisms that produce calcium-rich shells and skeletons, such as corals and molluscs.
These are just a few examples of the many man-made threats that are negatively and significantly impacting our oceans. The outcome of which is a reduction in marine biodiversity. And, of course, marine biodiversity is why we dive: we want to see vibrant and abundant marine life.
So what can be done to protect marine biodiversity? One important tool that marine conservationists use is a type of reserve known as a marine protected area, or MPA. The International Union for Conservation of Nature (IUCN) defines MPAs as a “clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature...”. MPAs vary in their level of protection and range from “no- take” MPAs, in which all extractive activities (such as fishing) are prohibited, to multiple-use MPAs in which various activities are allowed but regulated.
MPAs work by reducing or eliminating the significant threats to biodiversity in a particular area. But are MPAs effective? The short answer is yes, if they are enforced. Studies have shown that when the levels of biodiversity inside of no-take reserves are compared to levels outside, biodiversity is significantly greater inside the reserve. Protection from no-take reserves also lead to an increase in population density, individual size and age of organisms, and biomass (i.e., the total weight of living organisms in a given area at a given time). Overall, this results in healthier ecological communities within the reserve boundaries, which likely makes these communities more resistant and resilient to disturbances such as coral bleaching and global warming.
So if you want to experience relatively intact (I say relatively because these communities are still not truly pristine) marine ecosystems, that support the critters and habitats that you would expect to find, including top predators such as groupers and sharks, visit a marine reserve. Multiple-use MPAs, which generally consist of no-take zones and zones that allow some level of extractive activities, such as subsistence fishing, are also effective but not to the same extent as no-take MPAs.
John conducting fieldwork
While restoring marine communities is extremely important, MPAs can also function to protect and replenish commercial fish stocks within the reserve and through the migration and dispersal of adults and larvae to surrounding fished areas. This is the focus of the Earthwatch project that I and my co-researcher, Rich Kliman, are conducting in Belize. I am interested in determining whether the Sapodilla Cayes Marine Reserve (SCMR) in southern Belize will have a positive effect on the queen conch fishery in that area.
Queen conch is an important species, both economically and culturally throughout the Caribbean. The SCMR is located at the southernmost part of the Mesoamerican barrier reef and was established to protect the queen conch fishery, as well as other natural resources in the area. The MPA is a zoned reserve with two conservation zones and one preservation zone embedded in a general use zone. The preservation zone is no-entry and no-take. Entry is allowed in the conservation zones and subsistence fishing is allowed in only one of the zones. Regulated commercial fishing is allowed in the general use zone. The SCMR was established in 1996 but protection only began in April 2010.
With the help of Earthwatch volunteers, we have collected data since 2006 on queen conch abundance, density, size, age-structure, and movement, and information on queen conch veligers - the juvenile larvae of the conch - since 2007. Working with Earthwatch volunteers is invaluable because of the labour-intensive nature of the research. With their help we have been able to sample over 4400 conch and tag another 4000+ conch while conducting surveys throughout the reserve.
Crucially, because we were able to collect data before and after the enforcement of the reserve zones, we will be able to determine if the reserve is effective. The results are preliminary, and we will continue to build on them, but there are signs that the reserve is already working. We have begun to see an increase in the proportion of sub-adult and adult conch at some sites. This is important because these individuals are of harvestable size and would have been removed by fishers. Also, we found conch at a site in 2010 where we had not seen conch in the previous four years. This is significant because this site is a historical conch fishing ground, suggesting that populations are recovering after being exploited in the past. We also have data that strongly suggest that the queen conch populations are self-sustaining. That is, the larvae that flow into the reserve and settle out in the shallow water, originate from deep-water spawning grounds in or adjacent to the reserve.
MPAs are providing hope for our oceans and the communities that depend on them. To find out how you can get involved and help us with this vital research, click here.
Dr John Cigliano will be speaking at the Royal Geographical Society on 15 March. His Earthwatch lecture, entitled Protected areas: Do they improve outcomes for key species?, is sure to entertain those who enjoyed this column. Visit Earthwatch.org for tickets and information.
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