Australasian Science: Australia's authority on science since 1938

Nature Arks Are Sinking

By Stephen Luntz

A Nature study of 60 tropical reserves established to protect bio­diversity reveals that many are experiencing high rates of extinction.

“More and more countries are trying to increase the amount of land covered by protected areas, and we always say we’re not doing enough or we’re not protecting enough. But if existing protected areas are often struggling to do their intended job, how can we assist them?” says co-author Prof Corey Bradshaw, Director of Ecological Modelling at the University of Adelaide.

More than 200 scientists assessed 30 categories of species, or taxa, and found that most reserves were providing some benefit relative to unprotected areas around them. Nevertheless, the majority of taxa in about half the reserves are on the decline.

Many reserves are poorly protected, with encroachment either from poachers and loggers or from invasive species. While loss of forest cover makes ecological decline obvious, introduced species often produce drastic but less visible ecological effects.

Bradshaw notes that even well-protected reserves suffer if logging reaches their boundaries. “The main conclusion is that what happens outside the reserve affects the inside by proxy. Protected areas do not act as islands buffered from the sea of degradation surrounding them.”

With 85% of the reserves losing surrounding forest cover, the effects were stark. Surprisingly, Bradshaw says that the size of the reserve seemed to be less important than whether activity nearby was limited.

“We need to fight internal and external threats and provide more support for protected areas in their local environment. Such efforts will ensure protected areas are made more resilient against future threats such as climate change,” Bradshaw says.

Bradshaw says internal upgrades such as fences and species control must happen along with limitations to the damage around the borders. “It is a case-by-case assessment as to which you put money into. Most of these reserves are in developing countries, so the costs are really small by western standards, but there is usually a very small budget from local sources. Compared to the cost of buying land, increased management can be quite valuable.”