Rapidly expanding road networks are causing large-scale damage to forests but proper infrastructure planning and implementation could actually turn them into a net positive for the environment, argue researchers writing in the journal Nature.

William Laurance and Andrew Balmford highlight the severe environmental impacts of roads in wilderness areas, including fostering illegal logging, poaching, colonization, and land speculation.

“More than 95% of deforestation, fires and atmospheric carbon emissions in the Brazilian Amazon occur within 50 kilometers of a road,” they write, noting that 100,000 kilometers of roads now crisscross the Amazon. “The Belém-Brasília Highway, completed in the early 1970s, now cuts a 400-kilometer-wide swathe of cleared forest and secondary roads through the Amazon.”

“Loggers, miners and other road builders are putting roads almost everywhere, including places they simply shouldn’t go, such as wilderness areas,” added Balmford in a statement. “Some of these roads are causing environmental disasters.”



Deforestation for agriculture and cattle ranching follows a fishbone pattern along roads in the Brazilian Amazon. Landsat image courtesy of Google Earth



Laurance and Balmford say that roads in agricultural areas can boost farm yields and access to markets, improving farms efficiency and profitability. However increased profitability often drives agricultural expansion into wilderness areas, especially tropical forests, wetlands, and grasslands.

Therefore Laurance and Balmford propose a “global ‘road-zoning’ project” to map what areas should be off-limits to roads and what areas should be prioritized for road improvement.

“We are convinced that increasing agricultural yields will lessen the impact of farming on natural ecosystems only if coupled with effective land-use planning,” they write.

“We believe that a collaborative, global zoning exercise is needed to identify where road building or improvement should be a priority, where it should be restricted and where existing roads should be closed. A multidisciplinary team could integrate and standardize satellite data on intact habitats with information on transport infrastructure, agricultural yields and losses, biodiversity indicators, carbon storage and other relevant factors. Much of this information has been recorded or can be extrapolated from current data sources.”

Once the analysis is complete, the results could be made available in the form of high-resolution maps for policymakers and others involved in planning roads.

“It is much easier for policy-makers to influence patterns of road development than to affect more socially complex problems such as population growth and overconsumption,” they write. “Roads can be re-routed, cancelled or delayed. Large road projects are often funded by taxpayers, investors or international donors who can be surprisingly responsive to environmental concerns.”



Logging road in Borneo



Properly planned roads could benefit the environment by attracting people away from sensitive areas while at the same time boosting rural livelihoods from activities not linked to habitat conversion or degradation. In some areas, alternative forms of transport — like railways or boats — might ultimately make more sense, according to Laurance and Balmford.

“Trains and boats move people and products but limit the human footprint by stopping only at specific places.”

They conclude that “keeping roads out of natural areas is one of the most tractable and cost-effective ways to protect crucial ecosystems.”

William F. Laurance and Andrew Balmford. A global map for road building. 308 | NATURE | VOL 495 | 21 MARCH 2013

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