科学美国人60秒:New African Highways Have a High Environmental Price

By the end of the century, the United Nations reckons the population of Africa could hit 4.3 billion people—four times today's numbers. It's the fastest-growing spot on the planet, which inevitably means growing pains: “We're seeing a real rush, almost a feeding frenzy of foreign mining investment, and in some cases, land grabs." Bill Laurance, an ecologist at James Cook University in Australia. 

"We're living in the most active era of infrastructure and road expansion in human history. We're projected to see 25 million kilometers of new paved roads on the planet by the middle of the century, which is enough to go around the world more than 600 times." Thirty-three of those roads—spanning 53,000 kilometers—are already planned in Africa. So Laurance and his colleagues examined the pros and cons of the new projects. They measured potential benefits, like more agricultural opportunities, and weighed those gains against environmental impacts.

The research team determined that the planned roads and railways would slice through more than 400 protected areas. And if you include a 25-kilometer buffer zone on each side of the road—where Laurance says new hunting, poaching, farming, logging and mining are bound to pop up—the tally of violated protected areas rises to more than 2,000. The researchers do endorse five of the 33 roads as promising—good for humans, not so bad for the environment. And they identify the six worst planned roads, which they say probably should not be built at all. The study is in the journal Current Biology. [William Laurance et al, Estimating the Environmental Costs of Africa’s Massive ‘‘Development Corridors’’]

Laurance says we've seen the effects of rampant road-building before: "Two-thirds of the world's forest elephants have been wiped out in the last decade. And this has actually been linked pretty clearly with the expansion of the road network in the Congo already." And the first paved road through the Amazon, finished in the early 70s, is now a 400-kilometer-wide gash through the rainforest. Considering all the attention carbon emissions are getting in Paris right now, it might be worth remembering where one-sixth of the world's emissions come from: deforestation.

—Christopher Intagliata