Science for sustainable reefs
Box 1 | Strength in diversity for coral reefs
We rely on reefs for coastal protection, fisheries and tourism. However, the true value of coral reefs is in their biodiversity, for they are the 'rainforests of the ocean'. When it comes to managing reefs, if we protect their biodiversity, their biodiversity should in turn protect us, by helping to make reefs a sustainable resource.
Ecosystems with many species are more stable over time. This is because, as conditions change, the system is more likely to have species that can cope with the new conditions. Having lots of species reduces the likelihood of a major ecological collapse. Some researchers believe that the range of species the Great Barrier Reef contains makes the system more robust overall. If conditions change, common species may become rare and rare species common, but the system as a whole survives. It’s very much in our interest to manage and care for the reef system so this keeps on happening.
The more researchers investigate what’s required to keep coral reefs healthy and resilient, the more they realise it’s about keeping coral systems intact and functioning. And that means more than just protecting the coral itself; like all ecosystems, reefs have a range of species that each play a role in maintaining the reef system. Many grazing fish, for example, are needed for a well-functioning reef. Worldwide the larger herbivorous fish are now the target of fish trappers, spear fishermen and gill netting. Scientists now know that these grazers are vital in keeping reefs clean, healthy and free of seaweed. Remove them and, if nothing else replaces them, you as good as remove the reef itself. Without the fish to mow the weed, it soon takes over from the coral.
And it’s not enough just having one or two species that do all the work. Some redundancy in the different groups that perform specific functions on a coral reef is important. This means that by having several different species that perform the same role, but respond differently to conditions, if one goes other species can still do the job. For example, in Caribbean coral reef systems, overfishing removed most of the grazing fish. Their function was then carried out by sea urchins for a while; when disease caused mass death among the urchins, a lack of other species to do the job meant that many of the reef systems collapsed.
Box
Box 2. The Great Barrier Reef MPAs: How effective are they?
Related sites
Why is biological diversity important? (Australian Government Department of the Environment, Water, Heritage and the Arts)
Coral reefs (Earthbeat, Australian Broadcasting Corporation)
Resilience (Stanford University, USA)
Posted September 2009