A better Amazon road network for people and the environment

Abstract

The rapidly expanding network of roads into the Amazon is permanently altering the world's largest tropical forest. Most proposed road projects lack rigorous impact assessments or even basic economic justification. This study analyzes the expected environmental, social and economic impacts of 75 road projects, totaling 12 thousand kilometers of planned roads, in the region. We find that all projects, although in different magnitudes, will negatively impact the environment. Forty-five percent will also generate economic losses, even without accounting for social and environmental externalities. 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, we identify the ones that are comparatively better not only in terms of economic return but also have lower social and environmental impacts. We find that a smaller set of carefully chosen projects could deliver 77% of the economic benefit at 10% of the environmental and social damage, showing that it is possible to have efficient tradeoff decisions informed by legitimately determined national priorities.

Keywords: Amazon; cost–benefit analysis; deforestation; roads network.

Fig. 1.

Predicted deforestation in the 20-km buffer around selected road projects (20 y). Using historical data on tree cover loss and a spatial simulator software (DinamicaEGO), we estimated the deforestation that would be caused by each road project as the difference between predicted deforestation with and without implementation of the road. The countries are in beige and their boundaries are in gray/olive.

Fig. 2.

Distribution of economic returns (NPV over 20 y, 7% discount rate). For each proposed road, we calculated the expected economic return using the widely used Roads Economic Decision model. On the cost side, we considered initial investments and maintenance. On the benefit side, we considered reductions in vehicle operating costs and travel time. The small clear circles are outliers.

Fig. 3.

Tradeoff between economic benefits and socioenvironmental impacts. Each dot represents a road project. Projects to the left of the dashed vertical line have a negative economic return (NPV < 0). Projects below the dashed horizontal line have worse than the average socioenvironmental impact. Projects in quadrant D have a positive economic benefit and less than average socioenvironmental damage.

Fig. 4.

Cumulative economic return and impact for NPV > 0 projects. Roads with positive returns (n = 41) are sorted from the highest to the lowest ratio of economic benefit per unit of socioenvironmental damage. Projects to the right of the solid red line (not shown) are both economically and socioenvironmentally bad and should not be implemented. The cumulative economic return is represented by the blue line. The dashed and solid red lines indicate 10% and 54% of the total socioenvironmental damage score, respectively.