🌺 Tropical forests ravaged by logging can still have thriving ecosystems

By Linn Winge

Photo by Marco Marques / Unsplash

Most of our world’s tropical forests have been used for selective logging and only 30% remain pristine. The logged forests are labeled “degraded” and until now ecologists haven’t been exactly sure how timber extraction changes ecosystems. Tropical forests degraded by logging may be far richer in animal and plant life than previously believed.

Yadvinder Malhi together with his colleagues at the University of Oxford used tens of thousands of camera traps in order to estimate the population density of bird and mammal species in the highly biodiverse states of Sarawak and Sabah in Malaysia, New Scientist explains. After that, the team used the body mass of these animals to calculate the energy flow in both degraded and pristine forests. This reflects the total energy consumption across the food chain.

“You can think of energy flow as the measure of health or vitality of an ecosystem,” Malhi explained to New Scientist.

The tests found that in logged forests, birds and mammals consume 2.5 times more energy than they do in pristine forests.

“We really weren’t expecting anywhere near this increase,” says Malhi. “This shows that these degraded forests that are often considered lost and get little attention are actually incredibly ecologically valuable.”

Almost all of the species found in the old pristine forests were also found in the disturbed forests and most of them had a higher population density.

“Degraded” tropical forests aren’t prioritized in conservation efforts as much as pristine jungles and it is easier for governments or companies to convert them into agriculture as they are assumed to be less ecologically valuable, says Malhi. “This study shows this is actually quite a dangerous idea, as many of these degraded forests are just as vibrant, or even more vibrant than old-growth forest.”

The research team believes that the plants in degraded forests are able to prioritize growth over security - making them focus on competing for new light instead of producing toxins to fend off herbivores. More light reaches the ground through the diminished canopy cover, generating more food on the ground for deer, wild pigs and elephants.

“The whole forest gets more edible and more tasty,” says Malhi.

Despite the positive outcome of this study, it doesn’t mean that logged forests are superior to pristine ones. Sadly, with the loss of many big trees these forests have less biomass overall and they are likely to be worse at other key factors needed to maintain wider ecosystems - like, for example, generating rain.

Malhi believes that the broad term “degraded” should be reconsidered, and that these vast swathes of resilient tropical forest must be better protected, New Scientist writes.

“In terms of much of the ecology, those logged forests are not lost. They’re holding vast amounts of ecology, biodiversity and ecological function,” he says.

You can read the whole study in Nature: DOI: 10.1038/s41586-022-05523-1