Tropical rain forests exhibit an enormous concentration of species diversity: Occupying only 6 percent of the earth’s surface, they are home to almost two-thirds of all species on earth, many of which are endemic or found only in the forests. In addition to providing food and absorbing carbon dioxide, they house many undiscovered life-saving medicinal compounds. And with the alarming rate of deforestation, they may tragically disappear in a hundred years. Obviously, preserving tropical rain forests has become paramount. But conservation management officials are faced with numerous challenges in decision making: Which areas of a tropical forest to conserve? Which parts contain the highest species diversity? And which areas should receive priority in conservation?
Conventionally, plants are divided into forest categories or communities to select areas for conservation. But this method has limitations as it tends to ignore variation of diversity within communities. On the other hand, an alternative method—macroecological modeling—takes into account diversity within a plant community. Mokany and colleagues assessed whether this approach is helpful in highlighting priority locations for conservation.
Using 527 plant community survey plots (500 – 1000m2) and environmental data, researchers developed models of species richness (total number of species) and compositional dissimilarity, which is the difference in species composition between two sites, for the over 4,000 native vascular plant species in Australia’s Wet Tropics on the northeastern coast—the largest tropical rain forest in Australia.
They then predicted both species richness and compositional dissimilarity for larger areas called grid cells, which were at least 62 times greater (62,500m2 as compared with 1000m2) than the original survey plots. Each grid cell comprised a plant community, and there were almost 1.4 million grid cells in the region. Applying a new algorithmic-based approach, they predicted the current composition of every plant community in the entire region.
The researchers then pinpointed areas of greatest conservational value: those with high concentrations of rare species, species endemic within a 30km radius, and primitive angiosperm (flowering plants) families.
Most rare species were located at higher altitudes in the forests while primitive angiosperm families were found to be more evenly spread out across the forest. The predictions revealed that communities with a large number of endemic species were concentrated in two areas of the forest. When the researchers combined all these factors along with species richness into a single conservation index, they identified two areas of high conservation value: Atherton Tablelands and Daintree rainforest.
Even though the Australian Wet Tropics are extensively studied, they suggest this method—using a conservation index—can still be applied to predict areas of conservation value in other tropical forests such as in Southeast Asia where species data is limited. Other factors such as invasive species can also be considered to locate areas where control measures need to be implemented to protect native species diversity. The researchers suggest that the different attributes can even be weighted to suit conservation requirements. The study shows that macroecological modeling will enable managers to make better decisions by channeling resources to areas of greatest priority within tropical rain forests.
Mokany K, Westcott DA, Prasad S, Ford AJ, Metcalfe DJ (2014) Identifying Priority Areas for Conservation and Management in Diverse Tropical Forests. PLoS ONE 9(2): e89084. doi:10.1371/journal.pone.0089084