Restoration is good, but conservation is better
3 August 2009
The damage to ecosystems caused by human activities can be reversed to some extent, but the original pristine state can rarely be restored, according to a study reported in Science last week.
Researchers have used restoration ecology as an approach to combat the negative effects of human activities, such as logging, mining or pollution for the last 40 years. But until now, scientists didn't know how effective their strategies were at restoring the biodiversity of ecosystems.
'There haven't been any systematic reviews or large studies to work out when and where restoration works,' says Professor James Bullock of the Centre for Ecology & Hydrology and co-author of the Science study.
So, to see how effective restoration projects are, Professor José Maria Rey Banayas of the University of Alcalá in Spain led a team which analysed 89 restoration studies from every continent except Antarctica.
They looked at projects covering tropical, temperate, terrestrial and aquatic systems, and chose studies that compared restored systems with degraded systems and the original pristine environment.
'You can't say "don't worry, do what you like and we'll come in afterwards and restore it." That's not going to be the case. A better approach would be to conserve pristine environments in the first place.'
Professor James Bullock, Centre for Ecology & Hydrology
The projects the team studied varied in their levels of restoration: some were classed as passive restoration, where, for example a logged area was left to regenerate on its own. They also looked at more intensive approaches like substituting damaged corals with artificial reefs. The ages of the projects Rey Benayas and his team studied ranged from less than five years old to 300 years old.
They found that on average restoration improved biodiversity by 44 per cent, with tropical terrestrial projects the most successful. But crucially levels of biodiversity in the restored systems never returned to their original pristine states.
'Conservation preserves the original biodiversity of ecosystems, which are more likely to be beneficial to people by providing essential services,' says Bullock.
Coined by the Millennium Ecosystem Assessment, the term 'ecosystem services' describes the benefits that people gain from healthy ecosystems such as fertile soil, clean water, timber and food.
'It's not clear why the tropical terrestrial projects were most successful, but it could be because there's been a lot of research into returning these systems to their original condition,' adds Bullock.
Although encouraging, the results suggest ecological restoration is not a quick fix.
'You can't say "don't worry, do what you like and we'll come in afterwards and restore it." That's not going to be the case. A better approach would be to conserve pristine environments in the first place,' says Bullock.
Although scientists have assumed that improved biodiversity is likely to mean better ecosystem services, this hasn't been tested until now. But this study shows that biodiversity and ecosystem services are directly linked. 'This is another very good reason to conserve biodiversity,' says Bullock.
Bullock says the next step is to work out how long it takes for restorations to be successful, link this to economic and social science and attempt to put a value on the services provided by natural ecosystems.
Enhancement of Biodiversity and Ecosystem Services by Ecological Restoration: A Meta-Analysis
José M. Rey Benayas, Adrian C. Newton, Anita Diaz, James M. Bullock, Science
18 February 2009; accepted 9 July 2009
Published online 30 July 2009; 10.1126/science.1172460
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