The rapidly expanding network of roads into the Amazon is permanently altering the world’s largest tropical forest. Most of the road projects proposed lack rigorous impact assessments or even basic economic justifications.

This study analyses the expected environmental, social and economic impacts of 75 projects, totaling 12 000 km of planned road, in the region.

It finds that all projects, although in different magnitudes, will negatively impact the environment. Some 45% will also generate economic losses, even without accounting for social and environmental externalities.

The study finds that canceling economically unjustified projects would avoid 1.1 million hectares of deforestation and US$ 7.6 billion in wasted funding for development projects.

For projects that exceed a basic economic viability threshold, the authors identify those that offer better economic returns in combination with lower social and environmental impacts.

They find that a smaller set of carefully chosen projects could deliver 77% of the economic benefits at a cost of only 10% of the environmental and social damage, showing that it is possible to have efficient trade-off decisions informed by legitimately determined national priorities.