As Brazilian environmental scientists, we believe that the Business Feature “Drink the best and drive the rest”1 understates the serious environmental and social problems associated with Brazil's sugar-cane ethanol industry. For instance, although you say that soil erosion is a “potentially” damaging side-effect of sugar-cane cultivation, there is abundant scientific evidence already that environmental degradation from soil erosion in sugar-cane fields is widespread2. In the state of São Paulo, which is the core of the ethanol industry in Brazil, estimated rates of soil erosion in sugar-cane fields are up to 30 tonnes of soil per hectare per year. Moreover, despite laws to protect the riparian buffers that prevent soil inputs to rivers and streams, only 30% of riparian zones have been preserved in river basins.

The burning of sugar-cane fields before manual harvesting twice a year is another serious environmental problem related to the ethanol industry in Brazil. Although a law passed in 2002 by the state of São Paulo decrees that, by 2006, 30% of the sugar-cane fields with slopes lower than 12% (called mechanizable areas) should not be burned, farmers have been reluctant to replace cheap manual labour with more expensive mechanized harvesting. The deadlines imposed to reduce the burning of sugar-cane fields have been postponed several times, under pressure by sugar-cane farmers. Thus, it is likely that smoke pollution from sugar-cane fields will continue to be a major problem in São Paulo and other Brazilian states for many years, leading to further acidification of the already poor tropical soils3. Additionally, high particulate concentrations in the atmosphere from sugar-cane burning have been associated with a growing number of human respiratory diseases in sugar-cane regions4,5.

Last but not least, although the sugar-cane industry generates jobs in Brazil, working conditions, especially for manual harvesters, are extremely poor and often associated with causes of death. Thus — although we agree that Brazil's ethanol industry is “able to get better” — from an environmental and social standpoint, it is far from being as good as you portray.

We believe that the present ethanol industry and proposals for expansion of ethanol production in Brazil and worldwide should be carefully evaluated, to avoid environmental and social problems far outweighing long-term economic gains.