Home to almost 15 percent of the world’s plants and animals, Brazil is the most biologically diverse country on the planet (Le­winsohn and Prado 2005). While the great Amazon rainforest is probably its most well known ecosystem, Brazil’s Atlantic Forest and Cerrado regions are considered hotspots, some of the earth’s most biologically rich places. Additionally, the Pantanal in southern Brazil is the world’s largest wetland (about the size of Colorado). Within the Amazon, Brazil sustains over half of the world’s remaining tropical rain­forest. Unfortunately, it also has the world’s highest rate of forest destruc­tion (seven football fields per minute; Laurance et al. 2001). Roads are key to this destruction and are providing conduits for logging, forest fragmenta­tion, and access deep into the heart of the Amazon.

Brazil has an ecological research base which exceeds that of any other tropical country. This year, Brazil hosted the annual meeting of the Soci­ety for Conservation Biology and the journal Conservation Biology dedicated an entire special section on Brazilian conservation. In this paper, I review the research on the ecological impacts of roads in the Amazon and comment on the state of conservation in this mega-diverse country. With over $40 billion in planned infrastructure improvements in the next decade, Brazil’s natural heritage is at risk as roads chip away at the largest rainforest on Earth.

Deforestation
The environmental and social costs of roads in Brazil did not gain attention until the building of the trans-Amazo­nian highway. Originally built for military purposes, by 1984 some 160,000 migrants were colonizing the interior Amazon each year (Shankland 1993). While develop­ment agencies hoped to bring lifestyle-improving economic activities to inacces­sible areas, they quickly found they had no control over the volume and nature of migration (Dobias and Talbott 2001). Four years later, a fifth of the surrounding rainforest had been destroyed and 85 percent of the indigenous population had died from violence and disease (Shankland 1993). Following the construction of the trans-Amazonian highway, annual deforestation rates increased from a background level of 1,216 km2 per year in 1976 to 13,955 km2 per year in 1984 (Fearnside 1987).

The most obvious result of the trans-Amazonian highway was intensive logging and conversion of the rainforest to ranches and cropland. Several studies have since documented increased deforestation following Amazon road building (Fearn­side 1987, Carvalho et al. 2001, Laurance et al. 2001, Nepstad et al. 2001, Steininger et al. 2001). In fact, Laurance et al. (2002) reported that highway proximity was the “single most important predictor of deforestation.” Furthermore, more than two-thirds of the deforestation in the Amazon has occurred within 50 km of major paved highways (Nepstad et al. 2001).

Fragmentation
In addition to deforestation, much of the remaining Amazon is fragmented and prone to edge effects. One study found that edge effects impacted an area more than 150 percent larger than the area actually deforested (Skole and Tucker 1993). An additional million hectares of forest are selectively logged each year as well (Nepstad et al. 1999). Fragmented forests experience dramatic changes in forest dynamics, structure, composition, and microclimate resulting in a high vulner­ability to drought and fire (Laurance et al. 2000). If this trend continues, Nepstad et al. (2001) warns that forest conversion could transform half of the Amazon into fire-prone scrub vegetation and cattle pastures.

Fragmented forests directly affect wildlife as well. For example, a study found that Amazonian birds rarely crossed a road that received only 6-10 vehicle passes a day (Laurance et al. 2004). Even overgrown sections of the road were rarely crossed by solitary understory bird species. Another study found that closing roads showed a potential to restore bird movement: mixed-species flocks readily crossed a closed road while avoiding open roads (Develey and Stouffer 2000).

Overhunting
Road building allows greater hunter access and can have dramatic effects on wildlife populations. Roads reduce transportation costs and create a commer­cial demand for forest resources beyond local subsistence needs (Lorenzen and Almeida 2005). Intensive hunting can completely extirpate game species that have low reproductive rates. For example, Peres (1991) reported that populations of the endangered Humboldt’s wooly monkey were “quickly wiped out once access is opened by new roads.”

While the road density of the Amazon is only 0.0085 km/km2, Amazonian hunt­ers are willing to wander far from the road to kill preferred game species (Peres and Lake 2003). Accordingly, Peres and Lake (2003) found that populations of preferred species were much lower close to access points (roads and rivers). Furthermore, Peres and Lake (2003) argue that 100 percent of the Amazon would be accessible to hunters if road densities increased to 0.119 km/km2. This is particularly disturbing because what appear to be pristine forests from satellite images may be absent of key wildlife species.

Roadkill
In addition to building new roads, a current trend in Brazil is to pave existing roads. Paving roads allows access throughout the wet season, as well as increasing travel speed. With increased access and speeds, roadkill also increases. Recent re­search is exploring wildlife/vehicle collisions. Gordo et al. (2005) collected roadkill on a remote Amazon highway where only 200 cars pass each day. Over five years, they collected over 2,400 birds and mammals killed on a 120 km stretch of road. Studies in other parts of Brazil also found high rates of roadkill following road pav­ing (e.g., Coehho et al. 2005, Bueno et al. 2005). Proposed strategies for mitigating wildlife/vehicle collisions include signs and driver education (Bueno et al. 2005) as well as wildlife passages and speed reducers (Coelho et al. 2005).

Challenges
Since the building of the trans-Amazonian highway, dozens of studies have documented the social and environmental impacts of roads in Brazil. The lessons are being applied around the world, except, unfortunately, in Brazil. In December 2004 Peru and Brazil agreed to build the transoceanic highway, which would stretch from Peru’s Pacific ports across the Andes and Amazon to the Atlantic (Brandon et al. 2005). Additionally, the government’s Avanca Brasil (Advance Brazil) program includes $40 billion for infrastructure in the Amazon to meet a perceived need to transport soybeans (Laurance et al. 2002). It would include paving over 7,500 km of highways and greatly expanding the Amazon road network (Laurance et al. 2002).

Avanca Brasil will nearly double the forest area within 50 km of a paved road and result in an estimated 120,000 - 270,000 km2 of deforestation in the coming 2-3 decades (Nepstad et al. 2001). In addition to deforestation, Avanca Brasil will ex­pand the logging industry, increase forest fire, and affect indigenous and biological reserves (Nepstad et al. 2001). While the official justification is to reduce the cost of transporting soybeans, the deforestation and other impacts may not be worth the benefits to this small segment of society.

Hope for the future
The predicted loss of the integrity of the Amazon may be averted. Pressure from the international community and foreign investors can greatly influence plan­ning and environmental assessment (Laurance et al. 2002). Additionally, coopera­tive resource management programs supported by wealthy nations and non-governmental organizations may help. Some 350 indigenous and environmen­tal groups work in Brazil, and many of these are oriented towards sustainable development or indigenous commu­nities (Anon 1999). Additionally, an international initiative for Amazonian conservation entitled, “Pilot Program to Conserve the Brazilian Amazon” includes land use planning, extractive and Amerindian reserves, ecological corridor systems, applied research, and capacity building for local governments (Laurence et al. 2000).

Conclusion
It has been well documented that increased transportation infrastructure accelerates migration and deforestation in the Amazon. The Amazon’s popula­tion has increased ten fold since the 1960s, and it has the highest defores­tation rate in the world. While some road construction has been prevented through environmental protest, the pressure to build roads continues. With only one percent of the Amazon of­ficially protected (Peres and Lake 2001) and an estimated 80 percent of Amazon timber harvested illegally without any environmental control (Abrzmovitz 1998), it is essential that roads be prevented in the most pristine places. Hopefully, decision makers will chose a sustainable path for the most biologi­cally diverse forest in the world.

— Adam Switalski is Wildlands CPR’s Science Coordinator and recently attended the Society for Conservation Biology annual meeting in Brazil and witnessed firsthand the impacts of roads in the Amazon.

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