Final tropical forest refuges under threat
Refuge peril About half the protected tropical forest areas in the world are losing biodiversity due to pressures both within and from outside the reserves, according to a new study.
"As the tropics are being degraded, the protected areas are increasingly becoming a very critical corner stone for any kind of effort to conserve nature in the future," says Laurance.
But, he says, many reserves are themselves vulnerable to pressure from illegal logging and clearing, fires and hunting.
Laurance and colleagues checked the health of 60 typical reserves, categorised by the International Union for the Conservation of Nature, in 36 tropical nations across the world.
They found that while half the reserves were "succeeding", the other half were "suffering" from declines in 31 biodiversity groups, including primates, top predators, and old growth trees, over the past 20 to 30 years.
This decline is despite an overall increase in protection of reserves over the same period.
The researchers also found there had been an increase in weeds, and in the incidence of human diseases in people living in the reserves.
Laurance says this is probably due to increasing populations, which provide a greater disease "reservoir", a greater number of roads that facilitate the movement of disease, and the fact that disease vectors prefer disturbed areas.
Crucially, Laurance and colleagues found that environmental degradation immediately outside the reserves was nearly as important as pressures inside the reserves.
85 per cent of reserves studied had lost some of their surrounding forest cover, says Laurance.
"This really is falling out as one of the key threats," he says. "If you get a lot of logging and fires and hunting around a reserve, you also get, to a lesser degree, those same threats tending to penetrate inside the reserve."
"We really need to think about things like having real buffer zones around reserves and trying to maintain substantial connectivity to other areas of forest."
Laurance also suggests "relatively benign land uses" around the reserves and buffer zones such as "agroforestry and mixed plantations" instead of "fire-maintained cattle pastures and slash and burn farming."
"We can't just circumscribe these protected areas, completely trash everything around them and then presume that they are going to be nice little samples of nature in the future."
Laurance says his analysis relied on the best available data, collected directly from 262 field biologists and environmental scientists who work in these reserves.
"They are the muddy-kneed types of people who work out in the field for very long periods of time," he says.
The scientists were required to answer a 10-page questionnaire with 365 questions as well as participate in face-to-face or phone interviews. In return for their work, they were offered co-authorship of the paper.
Laurance says this direct approach was chosen over a review of publications for a number of reasons.
"Firstly, there is an enormous amount of variability in the number of publications per site. If you are going to compare a site with 10 studies to that which has 3000 then you are going to have a huge sample bias," he says.
The researchers also found interviewing people was a much more efficient way to get information.
"These researchers knew this literature, but beyond that they knew things that hadn't been published yet," says Laurance. "They had synthesised and integrated and networked a lot with other researchers. They were founts of information."
"If you really wanted to have hard data you'd need $20 billion and 20 or 30 years of field work and by that time it's probably too late to do anything about the environmental crisis unfolding."