非洲热带雨林继续面临挑战

The African continent contains about 30 percent of the world’s global rainforests, second only to the Amazon. Scientists and conservationists met at Oxford University to discuss changes the forests are expected to undergo in the 21^st Century.

Africa’s tropical forests face challenges from deforestation, hunting, logging and mining, as well as climate change.

“Climate change is a major issue for much of the world, but for Africa, in particular. And there’s much interest and concern around Africa’s forests, which is the second largest area of tropical forest in the world after the Amazon forest. And yet there’s been very little synthesis of the research that’s there. There’s much less known about both climate and forest and people and there interaction in Africa compared to many other regions of the world,” said Yadvinder Malhi is a professor of ecosystems science at Oxford University and director of Oxford’s Center for Tropical Forests.

He said the conference brought together experts in climate change, ecology, social sciences, economics, anthropology and archeology to discuss Africa’s rainforests.

“They’re important at an international level for many reasons. They hold a large amount of carbon. They seem to be absorbing carbon from the atmosphere, which is slightly slowing down the rate of climate change. In the case of Africa, the recycling of water. So water that falls in the Congo region gets taken up in the roots of trees and evaporated back into the atmosphere where it forms clouds and new rain,” he said.

The clouds that form over the Congo Basin actually have long range effects on water supplies and weather patterns in parts of Asia and even North America.

West and Central Africa

There’s a big difference between the forests of the Congo Basin and West Africa. Malhi says there’s been extensive deforestation in West Africa. Much of the land has been cleared for agriculture over the last 20 to 30 years.

“When we look at the Congo Basin we see a very different situation. That’s an area that is at the moment almost all intact forest and has had relatively low rates of deforestation. And the reasons why those rates have been low are varied from country to country. But in the largest area, the Democratic Republic, it’s been political instability and poor infrastructure linked to that instability that has meant that this large forest reserve has not currently really faced very heavy pressure, at least compared to forests of Asia or the Amazon,” Malhi said.

However, he said that could change with new investment and infrastructure and expansion of industrial scale plantations.

About 3,000 years ago, the Congo forests were affected by natural climate drying. Forests retreated and were replaced by grasslands.

“At the same time, around two and a half thousand years ago, Iron Age humans settled in much of the forest, cleared it with axes, with iron axes. And then they had a population collapse around a thousand years ago and the forest regrew. And this is quite a different history from the history we see in the Amazon rainforest, where there’s been pretty continuous forest over human history and earlier. And also where there was human impact it was not with iron instruments. There was no Iron Age in the Amazon,” he said.

The combination of natural climate drying and the wide scale felling of trees resulted in fewer species of trees compared to other tropical forests. However, that’s not necessarily a bad thing.

“The species that are left seem to be relatively resilient to a large extent. They can recolonize disturbed areas quite quickly. They can spread quite quickly, regrow quite quickly. So if one area gets deforested, you can still find the species elsewhere,” he said.

Food Security

Modern day deforestation is often done to make room for agriculture. The U.N. says by 2050 the world population is expected to rise to nine billion. That means a much greater demand for food. But the Oxford professor says there are ways of meeting that demand that do not require widespread deforestation. One of them is making current agricultural land much more productive.

“Much of agriculture in Africa is of very low productivity. Very low inputs of fertilizers and nutrients. You could have the current agricultural output of the Africa tropical forest region in 40 percent of its current agricultural land, leaving 60 percent of the land available for forests if the agriculture was intensified. So, it’s not a simple tradeoff between more food means more land and therefore less forests,” he said.

Malhi says once all the information from the conference is analyzed, recommendations will be made to governments, U.N. agencies and others. They’re expected to include proposals for protecting remaining rainforests, better land management for agriculture and new research into the effects of climate change.

The conference ran from January 4-6.