Selective cutting doesn't threaten the survival of these trees, according to the study's authors. But the practice does mean loggers need to operate over a much larger area of rain forest, they said.
"This increases penetration inside the forest and opens new, previously untouched forests," Nasi said.
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In Cameroon, for example, well over half of all "low-access" forest now lies within 10 kilometers (6.2 miles) of a logging road, according to the World Resources Institute in Washington, D.C. Low-access forest is defined as continuous forest covering at least a thousand square kilometers (386 square miles).
As access to once remote forests grows, so does the risk of greater "bush meat" hunting, or the hunting of wild animals for food. Bush-meat hunters kill not only forest antelopes, wild pigs, and primates, but also endangered mammals such as gorillas and forest elephants.
The ITTO study found that all but one of the logging concessions surveyed said hunting was a problem.
"Bush meat provides up to 80 percent of the protein needs of local communities in the region, and hunting is largely practiced everywhere," Nasi said.
The study authors also report that many logging concessions lack adequate management plans. The researchers found that among all concessions with shorter-term logging leaseswith terms under ten yearsnone had management plans in place.
Despite these findings, the study's authors suggest central Africa can sustain more logging and that timber concessions could actually help advance conservation goals.
Logging activity on the studied concessions was relatively light, according to the researchers. They noted that, on average, only two to three trees per hectare (2.5 acres) were harvested.
Nasi said there is room to increase that level of timber harvesting per hectare: Companies could log a wider range of trees species, which in turn should reduce pressure to expand operations into virgin rain forest, he said.
"Concessionaires will be likely to harvest more species if they can sell them at a profit," he added. "The best way to intensify the harvest [locally] would be to put in place incentivesfor instance, lower taxesfor the less valuable species."
Rain Forest Biodiversity
About 8 percent of central Africa's low-access tropical forest are protected by parks and reserves. Nasi said properly managed logging concessions can help to preserve rain forest biodiversity in other areas.
One example he cited is curbing the bush-meat trade.
"[Most] logging companies do not like to see their name associated with hunting, as they make no money out of it and get only bad press," Nasi said. "So they are willing to cooperate with [nongovernmental organizations] to tackle the problem."
Nasi said successful plans are already in place. He cites the example of a 150,000-hectare (370,000-acre) concession in northeast Gabon operated by Bordamur, an Indonesian logging company. The concession sits alongside Minkébé National Park, a huge area of protected tropical forest.
In 2001 WWF (World Wildlife Fund) brokered an agreement among the company, regional authorities, and local people to exclude commercial hunters and bush-meat traders from the forest. Local villagers, meanwhile, are still permitted to hunt.
Jeff Sayer, forests conservation advisor at WWF International in Gland, Switzerland, said WWF is looking to establish similar arrangements on other concessions. The goal is to reduce hunting to sustainable levels.
"We have been criticized for this in the media on the grounds we are supping with the devil," he said. "But one cannot simply ignore realities on the ground."
Forestry is becoming increasingly important to the central African economy. In Cameroon, for example, tropical timber products generate around 20 percent of the country's export revenue.
Elsewhere, the Democratic Republic of Congo is trying to kick-start its economy after years of civil war. The country is currently opening up previously untouched areas of its vast rain forests to logging companies, a move that has attracted fierce criticism from environmentalists.
But Nasi said: "Logging will continue, like it or not. And our role is to make sure that it's done as best as possible. A properly managed timber concession is most likely to be the best bet in terms of biodiversity conservation outside protected areas."
Environmental organizations, however, are currently campaigning against plans to expand industrial logging in the Democratic Republic of Congo. The country holds by far the largest area of pristine rain forest in central Africa.
Greenpeace, the environmental nonprofit, claims that instead of helping to alleviate poverty, increased logging will fuel corruption, social conflict, and environmental destruction.
Filip Verbelen, forest campaigner for Greenpeace, said, "Experience from other countries in the Congo Basin, such as Cameroon, clearly shows that it is extremely difficult to control the multiple negative impacts of logging, such as the illegal bush-meat trade, illegal timber trade, and social conflicts. Even when multilateral agencies such as the World Bank put serious conditions in place for the forestry sector, they often turn a blind eye when implementation proves to be poor."
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