Giant mahogany trees lie alongside a logging road in northern Republic of the Congo.

Most of the industrial logging in central Africa targets high-value trees such as African mahoganies, which are exported for use in making furniture.

But logging companies are now increasingly harvesting other tree species as well.

"When I started working in this region in the northern Republic of Congo, 70 to 80 percent of the production was centered on just two species," said Nadine LaPorte, lead researcher of a new study on logging in the region.

"Now they go to more than ten species."

This may be a sign that some of the tree species are being overharvested, LaPorte warned.

Laws requiring that sawmills be set up locally may also contribute to the heavy logging, she added.

"I understand that they're looking at solving the problem of poverty and providing jobs to people," LaPorte said.

"But this puts pressure on the loggers to do the bad thing and take too much wood from the forest in order to satisfy the demand by the sawmills."

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