Coral reefs count among the world's most severely threatened ecosystems. The pressure of human activities, including overfishing and pollution, is leading to a decline in their biological diversity. The effectiveness of Marine Protected Areas (MPAs) for conserving the coral biodiversity has been the subject of many specific studies at local level. Nonetheless, a world-scale assessment remains necessary in order to check if the conservation objectives laid down by the international bodies, which require that 20 to 30% of the world's coral reefs must be under official protection by 2012, are complied with and justified.
The University of Auckland in New Zealand, with the aid of several international institutions including the IRD and its researchers based in New Caledonia, has been focusing its attention on this question. Large-scale databases have been built up for that purpose, covering such aspects as geographical distribution and effectiveness of MPAs, and the extent of coral reefs. They currently embrace 980 MPAs that together cover 98 650 km2 of coral reefs, representing 18.7 % of the total surface area of reef habitats.
The database takes into account many different types of protected area, according to the objectives and management procedures associated with them. Out of all the coral reefs of the world, amounting to about 527 000 km2, 5.3 % are located in marine reserves where fishing is permitted, 12 % in intermediate reserves where fishing, recreational activities and research are accepted, and 1.4 % in strictly controlled reserves where any kind of removal is forbidden. In Australia, 69 % of coral reefs are strictly protected within such protected areas, compared with 7% in the central Pacific and the western Indian Ocean and 2% in the central area of the Indian Ocean.
By considering the poaching rate as an indirect indicator of the management of these marine areas, the research team observed that of the 1.6 % of coral reefs in the world that are theoretically protected against any illicit activities, less than 0.1 % are really free from all exploitation. The effectiveness of management methods varies between countries, but it is particularly low for the zones of high coral diversity like the Indo-Pacific region or the Caribbean. The aim of setting up Marine Protected Areas is to limit the impact of human activities. However, 85% of coral reefs situated within the MPAs are prey to local threats such as sedimentation, pollution, coastal development or overfishing, including in most centres of coral diversity.
It is now established that coral reef resilience (1) depends on functional organization, for example the presence of herbivorous fish and their predators. However, these populations are often characterized by migratory movements which expose juveniles and adults alike to the risk of fishing beyond the reserve boundaries. Some fish have territories of several square kilometres. Therefore it is not possible for reserves less than 1–2 km2 in surface area (as are 40% of MPAs) to provide enough protection for several key functional groups. A critical minimum size of about 10 km2 is necessary.
The criteria of size and isolation of MPAs as well as the distribution of coral reefs in the world, the creation of a network of MPAs, each of which would incorporate reserves of 10 km2, 15 or so kilometres between each other, would involve the designation of more than 2500 new MPAs. This would correspond to more optimal protection of 25 590 km2 of reefs, amounting to 5 % of the world's coral reefs, a figure far from the objectives declared at the 2002 world sustainable development summit which would require 20 to 30% of the major ecosystems to come under protection between now, in 2006, and 2012.
Mina Vilayleck/ Serge Andréfouët
(1) The capacity of corals to return to their initial state after a disturbance.
Serge Andréfouët, IRD Nouméa, UR CoRéUs. Tel: (+687) 26 08 00 – Email : email@example.com
Mina Vilayleck, IRD Nouméa, Service Information Communication, Tel: (+687) 26 07 99 – Email : firstname.lastname@example.org
Indicators of human-induced physical disturbance on coral reef habitats
At a PNEC workshop (Programme National Environnement Côtier) at IRD's Noumea centre, research scientists studied the most frequent human-induced physical disturbances on coral reef habitats and their consequences for such habitats. They worked to identify indicators of different forms of disturbance and their impact. Most effects are the result of coastal development, tourism, harvesting, nuclear and other weapons testing, and accidents such as shipwrecks. The complexity of coral reef ecosystems prompted the researchers to investigate a multi-scale approach involving different spatial scales of observation, in order to gain a picture of the general functioning of the system. The multi-scale approach offers a perception of a system whereby successive levels of functional organization in reef communities, from the individual to the metapopulation (1), can be associated with a potential habitat that extends from the colony and out to the whole biogeographical region.
Several disturbance indicators are proposed, depending on the scale on which investigations are focusing, and considered in three classes: stony coral, reef fishes and human uses of the ecosystem. The study involved sorting different indicator options for assessing the status of the coral reef according to particular objectives (monitoring, determining the initial status or improvement of knowledge), their specificities (whether or not they identify specific disturbances) and their scale of investigation (small, meso- or large scales). In fact, indicators of human-induced disturbance are found to be usually non-specific. A serious drawback stems from the difficulty in separating signals emanating from coinciding stressors that exert their effect at different spatial scales. The research team suggest the use of a conceptual model in order to investigate a hierarchical concept of the effects of a disturbance on coral reefs.
(2) A group of partially spatially separated sub-populations of the same species.
Pascale Chabanet - UR128 - Communautés récifales et usages dans l'Indo-Pacifique, IRD Nouméa, BP A5, 98848 Nouméa cedex New Caledonia;
Tel : (+687) 26 07 23; Email : email@example.com
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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