Scientists in Bolivia, Brazil, Colombia, Peru, Sweden and the US have warned that road projects planned for the Amazon basin would deforest some 2.4 million ha of rainforest, and had not undergone environmental impact assessment.
The paper, published this week in the Proceedings of the National Academy of Sciences of the US, examined some 75 road schemes with a total length of 10,000km and a total value of $27bn were planned over the next five years in Bolivia, Brazil, Colombia, Ecuador and Peru.
They say about 17% of these projects violate either environmental regulations or the rights of indigenous peoples.
"Data to support good decisions is remarkably scarce," the paper says. "Typical feasibility studies, where they exist, inadequately address environmental and social impacts and do not facilitate comparison across projects."
The environmental impact of these schemes goes beyond the land they occupy, since many will be used to support agriculture and ranching development, which will also lead to deforestation.
However, according to the scientists, the investment in the highways will not lead to net economic gain, since half are likely to be loss making. They argue that cancelling those would save as much as $7.6bn and save some 1.1 million ha of rainforest.
If governments went ahead with the least damaging schemes, on the other hand, they would gain $4bn and reduce deforestation by 90%.
The Amazon basin is a global is home to up to 15% of the world’s plant and animal species, including 30 million people, and is the largest source of fresh water in the world.
As well as playing a part in regulating the Earth’s climate systems, the rainforest stores up to 200 billion tonnes of carbon. "All of these benefits," the study notes, "depend to a greater or lesser degree on conservation of the biome in a healthy, natural state".
Image: The Amazon hosts 15% of the world’s biodiversity (Gleilson Miranda/Governo do Acre/CC BY-SA 2.0)