Alarming Biodiversity Collapse in Protected Forests

Juvenile howler monkey picking berries: Alphamouse via Wikimedia Commons

In the science journal Nature this week, a piece was co-authored by more than 200 scientists from around the world—a veritable who’s-who of researchers from the world of tropical forest ecology.

The gist of the paper is alarming:

The rapid disruption of tropical forests worldwide probably imperils global biodiversity more than any other force today.
The best hope lies in protected areas.
Yet many protected areas are not effectively protecting biodiversity.

The authors write:

Our analysis reveals great variation in reserve ‘health:’ about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally.

Comparison of ecological changes inside vs outside protected areas, for selected environmental drivers. The bars show percentage of reserves with improving vs worsening conditions: Laurance, et al, Nature 2012, DOI:10.1038/nature11318

The authors studied more than 30 different categories of species—from trees and butterflies to primates and large predators—in protected areas across the tropics in the Americas, Africa, Asia, and the Pacific. They calculated how these groups have fared in recent decades and identified the drivers of environmental change.

Lead author William Laurance of James Cook University in Australia and the Smithsonian Tropical Research Institute in Panama told me:

One of the things our study demonstrated was a sort of “mirror effect”—that the changes inside vs. outside [the reserves] tend to be positively correlated.

In other words, the reserves are only as strong as the lands surrounding them. And their power to protect biodiversity—that is, a full, healthy spectrum of lifeforms from the smallest to the largest—is threatened by activities on their borders, particularly from the illegal encroachment of colonists, hunters, and loggers.

Jaguar, an apex predator: US Fish and Wildlife Service via Wikimedia Commons

The authors found that some guilds—that is, ecological groups of plants and animals—were more at risk than others. The most sensitive guilds included apex predators, large non-predatory vertebrates, bats, stream-dwelling amphibians, terrestrial amphibians, lizards and larger reptiles, non-venomous snakes, freshwater fish, large-seeded old-growth trees, epiphytes (plants that grow on other plants, like orchids), and ecological specialists.

Several other groups were somewhat less vulnerable, including primates, understory insectivorous birds, large frugivorous [fruit-eating] birds, raptorial birds [birds of prey], venomous snakes, species that require tree cavities, and migratory species. In addition, five groups increased markedly in abundance in the reserves, including pioneer and generalist trees, lianas and vines, invasive animals, invasive plants and human diseases.

Considering that the most endangered species are living in protected areas that are themselves embedded in extremely degraded landscapes, then the picture looks even gloomier.