Roads are primary vectors of deforestation in the Pan Amazon

It all starts with a road. In Brazil, the federal government commissioned the construction of mule trails and telegraph lines to link their coastal cities with long-established settlements on remote Amazonian tributaries. In the Andes, communication between the highlands and the lowlands has occurred over millennia via trails that traverse the foothills using routes dictated by topography.

Most of these early roads had little impact on settlement and were associated with only a limited amount of deforestation, but most modern highways trace these routes into the wilderness. Deforestation occurs when a government sends a clear signal that it is investing in a major trunk highway; objectives vary, but have included strategies to integrate an isolated population centre, open a region to settlement and create access to a valuable mineral asset. Settlers move into a region only when there is a commitment to keeping the road accessible on a permanent basis.

There have been exceptions, particularly in Brazil in the 1980s, when the promise of future pavement did not materialize, but in general people will invest time and money in clearing the forest only when they believe they can transport their production to market. The examples are abundant and self-evident. All but six of the fifty human-modified landscapes defined in Chapter 1 are organized around a major trunk highway.

The existence and quality of secondary road networks is more important than trunk highways for determining the spatial extent and intensity of land use within a frontier landscape. Access roads change a linear deforestation vector into a two-dimensional front that can trigger a geometric expansion in the deforestation rate.

It is not sufficient just to have a secondary road network, however; it too must be open year-round in order to ensure that crops do not rot in the field. A functional secondary road network mandates investment in bridges, culverts and embankments; even more important is a budget to maintain these fragile assets in a region characterized by high seasonal rainfall.

The economic output of deforested lands is very much dependent on the quality of secondary roads because they connect ranches, farms, and plantations with the industrial infrastructure essential to agricultural supply chains, particularly grain silos, rice mills, palm-oil extraction refineries and beef-packing plants. An overemphasis on trunk highways at the expense of investment in secondary roads in consolidated frontiers is a misallocation of public investment that results in sub-optimal economic growth.

In aggregate, secondary roads require a greater investment than trunk highway systems, but the responsibility for building and maintaining these key transportation assets is almost always with under-funded local governments. Central governments have access to national budgets and international investment capital, which finance the construction of the trunk highway, but local governments must depend on limited revenues derived from local taxes or revenue transfers from the central government. Not infrequently, secondary roads are built by settlers out of necessity and constructed outside the framework of the environmental review and licensing system.

“A Perfect Storm in the Amazon” is a book by Timothy Killeen and contains the author’s viewpoints and analysis. The second edition was published by The White Horse in 2021, under the terms of a Creative Commons license (CC BY 4.0 license). See this excerpt in Spanish here and in Portuguese here.

Read the other excerpted portions of chapter 2 here: