"What is exciting is that while remote protected areas seem to be protected quite well simply because they are inaccessible, protected areas located in areas of high human pressure also seem to be maintaining their legal boundaries," Lucas Joppa of Duke University told environmentalresearchweb.

Joppa and colleagues Scott Loarie and Stuart Pimm looked at protected areas in the Amazon, Congo, South American Atlantic coast and West Africa. "The first two are the last remaining moist tropical forest wilderness areas in the world, while the last two are biodiversity 'hotspots' – areas with high biological diversity as well as intense human pressure," said Joppa.

While the two wilderness regions had very low levels of fragmentation around their protected areas and low levels of deforestation, the hotspot regions were markedly different.

"Protected areas in both regions showed a marked decrease in deforestation at their boundaries, but the West Africa region showed very low levels of fragmentation outside of protected areas, simply because deforestation was so high that no forest was left to fragment," said Joppa. "The South American Atlantic Coast region, however, showed high levels of fragmentation outside of protected areas, meaning that the opportunities to connect those fragments is potentially quite significant."

But there is one major caveat – while the two wilderness areas have many large protected areas, the researchers say that the two hotspot regions don’t have enough protected areas, and many of those areas are too small to conserve species effectively.

According to the team, protected areas are generally protecting against deforestation but major geographical considerations come into play. "This geographic variation must be incorporated into the way that the global network of protected areas is considered," said Joppa. "Also, we could find no evidence that management category within a region shaped our results. This should calm fears that the distribution of management categories somehow affects the way protected area boundaries interact with deforestation."

Since every protected area is different, other studies have found it hard to generalize results. Previous attempts have been limited either by an inability to analyse more than a few protected areas at a time or a lack of appropriate data. To try to address this lack of generality, the team used large-scale datasets on vegetation and protected areas to examine how deforestation and fragmentation occur in and around protected areas as a function of distance.

"Deforestation and fragmentation are two major contributors to species endangerment, and are also the two most easily measured ecological variables on a large scale," said Joppa. "Performing the analysis in this way allowed us to gain a generalized view of trends across regions that has been lacking from previous studies."

Now the researchers are looking to understand how protected areas perform over time by analysing deforestation data over multiple time periods from Costa Rica and Brazil. They are also examining how representative protected area networks are of the country within which they are located. "Such baseline information is currently lacking, but is vital if conservation planners are to move forward in an informed manner," said Joppa.

Colleague Marion Adeney, meanwhile, has found that distance to roads plays a critical role in the interaction between protected areas and fire, which is particularly devastating in moist tropical forests.

The researchers reported their work in PNAS.