Proof  TITLE Geophysical Monograph Series XXX XXXXXXXXXXXXXXXXXXXXXXXXXXX 0.029/2008GM000737 Road Impacts in Brazilian Amazonia Alexander Pfaff,  Alisson Barbieri, 2 Thomas Ludewigs, 3 Frank Merry, 4 Stephen Perz, 5 and Eustaquio Reis 6 We examine the evidence on Amazonian road impacts with a strong emphasis on context. Impacts of a new road, on either deforestation or socioeconomic outcomes, depend upon the conditions into which roads are placed. Conditions that matter include the biophysical setting, such as slope, rainfall, and soil quality, plus externally determined socioeconomic factors like national policies, exchange rates, and the global prices of beef and soybeans. Infuential conditions also include all prior infrastructural investments and clearing rates. Where development has already arrived, with signifcant economic activity and clearing, roads may decrease forest less and raise output more than where development is arriving, while in pristine areas, short-run clearing may be lower than immense long-run impacts. Such differences suggest careful consideration of where to invest further in transport.  Sanford School of Public Policy, Duke University, Durham, North Carolina, USA. 2 Cedeplar, Federal University of Minas Gerais, Belo Horizonte, Brazil. 3 The World Bank, Brasilia, Brazil. 4 Woods Hole Research Center, Falmouth, Massachusetts, USA. 5 Department of Sociology and Criminology and Law, University of Florida, Gainesville, Florida, USA. 6 Instituto de Pesquisa Economica Aplicada, Rio de Janeiro, Brazil. . INTRoDUCTIoN The roads of Brazilian Amazonia are often portrayed in a melodramatic fashion. For decades, pictures have shown dirt paths, smoldering forest remains, poor people, and perhaps a message: these are unpaved roads; imagine what paving and capital investment could do! Such “visual cost-beneft Q2 Q2 analysis,” not surprisingly, conveys some truths but not all. When deforestation occurs, it does indeed affect ecosys- tems. Roads increase access to forest and clearing follows, with ecological impacts: providing suitable habitat for some species but reducing and fragmenting other habitats, degrad- ing streams and water quality, fostering the spread of exotic invasive species, causing wildlife mortality and species loss, and even bringing about local climate change [Trombulak and Frissell, 2000; Forman et al., 2003; Fearnside, 2007]. All are important potential impacts of forest loss discussed expertly in other parts of this book. This chapter is based on people-focused research from across Amazonia and over time. We present the view that roads differ in their forest impacts, and forest loss is not their only impact. While on average new road investments in- crease deforestation, it must be recognized that a road’s for- est impact depends on the context in which the investment in lowering transport cost occurs. Further, loss of forest is not the only consideration, as there are numerous impacts of roads on the Amazonian ecosystem and on human welfare. We refer to work at different scales. This chapter’s au- thors, and certainly the larger group whose research we cite, analyze scales from the household to the village, county, state, Brazilian Amazônia Legal, country of Brazil, and the Q 1 2008GM000737-KE-Pfaff.indd Manila Typesetting Company 09/22/2009 08:00PM