Disturbing forests damages natural diversity

It is not enough just to conserve forest.

It may be just as important not to disturb any of it.

New research suggests that selective logging, hunting and other kinds of damage can do serious harm to the biodiversity within the remaining forest.

Jos Barlow, an ecologist at the University of Lancaster in the UK, and colleagues report in Nature that they looked at the records of 1,538 plant species, 460 birds and 156 species of dung beetle in the Amazonian state of Pará in northern Brazil, to build up a picture of biodiversity in a patchwork of forest and farmed land.

Brazil’s forest code requires landowners to maintain 80% of the forest cover. But what happens to the other 20% can dramatically reduce the conservation value of the remaining forest, they found. They even put a figure to this notional loss.

Photo: Mustafiz Mamun

Photo: Mustafiz Mamun

The impacts of the disturbance were the equivalent in damage to the astonishing variety of forest life, of the loss of between 92,000 and 139,000 square kilometres of primary forest. This is roughly an area the size of Greece.

And even when deforestation really is limited to 20% of the forest, the forest that remains keeps only 46% or at best 61% of its value in terms of the conservation of species.

“We provide compelling evidence that rainforest conservation initiatives must address forest disturbance as well as deforestation,” Professor Barlow said.

“Without urgent action, the expansion of logging operations and the spread of wildfires fuelled by human-induced climate change mean that tropical forests are likely to become increasingly degraded, conserving only a fraction of the breath-taking diversity they once harboured.”

And his co-author Gareth Lennox of Lancaster said: “Tropical forests are one of Earth’s most precious biological treasures. By focusing on the extent of forests that remain and ignoring their health, current national and international conservation strategies are inadvertently placing that treasure in jeopardy.” Pará is home to one in ten of the world’s birds, many of them found only in the region.

Frequent warnings

Researchers have repeatedly warned that climate change puts biodiversity at risk, especially in the tropical forests, themselves at risk from global warming that will have consequences that could in turn accelerate forest loss and the biodiversity of life sheltered by those forests, embracing both vegetation and the creatures that depend on the vegetation.

Photo: Mustafiz Mamun

Photo: Mustafiz Mamun

The scientists – from Britain, Brazil, Sweden and Australia – sampled 36 catchment areas of between 30 and 60 square kilometres each: of these, five were entirely deforested, and 31 contained various levels of remaining forest. They then within these catchments more closely examined 175 primary forest plots. Of this selection, only 30 showed no evidence of disturbance by logging, fire or hunting.

Then, having made their counts of specified plants, birds and dung beetles, they made their extrapolations. And their calculation of equivalent biodiversity loss – that is, the area of forest that would have protected the lost creatures – was at least 92,000 sq km, and possibly an area bigger than Greece.

“Even this lowest estimate is greater than the area deforested across the entire Brazilian Amazon between 2006 and 2015,” they write. “These results demonstrate an urgent need for policy interventions that go beyond the maintenance of forest cover to safeguard the hyper-diversity of tropical forest ecosystems.”