How Little We Know About Tropical Rainforests and the Threats to Forest Biodiversity

A spate of studies highlighted both how little we know about tropical rainforests and the threats to forest biodiversity.  In May a report from the World Wide Fund for Nature (WWF) and the Zoological Society of London (ZSL) said that wildlife populations in the tropics have declined 61 percent over the past 40 years. The Living Planet Index tracks almost 10,000 populations of 2,688 vertebrate species in the tropics and temperate regions. The report was followed in July by a Nature study which found that half of assessed protected areas in the tropics suffered an “erosion of biodiversity” over the last 20-30 years.

Rainforest in Sabah, Malaysian Borneo. Photo by Rhett A. Butler ©

Rainforest in Sabah, Malaysian Borneo. Photo by Rhett A. Butler ©

In August, a study published in PLoS ONE documented large-scale die-off of mammal populations in long-ago isolated forest fragments in Brazil’s Mata Atlantica. Examining 18 mammal species across 196 forest fragments in the Atlantic Forest, the researchers found “unprecedented rates of local extinctions,” despite the fact that they purposefully visited the “most intact and best preserved” sites in the region. On average only about 4 target mammals were found out of 18 in each forest patch. The findings undercut assumptions made by the widely used theory of species-area relationships, which predicted that around 45-80 percent of the mammals would have remained. Worryingly even some large forest patches with intact canopies had been depleted of the target mammals.  In December, a comprehensive survey of arthropods in a rainforest in Panama found that 60-70 percent of tropical forest arthropods may be yet to be described by scientists.


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