Environmental effects of the pasture-sugarcane conversion and pasture intensification

Abstract

Sugarcane ethanol is an alcohol-based renewable biofuel produced by the fermentation of sugarcane extract and molasses, and Brazil is the world's largest producer of it. Brazil is also the largest producer of sugar; hence, sugarcane agriculture in the country is quite extensive, covering an area of about 10 million ha of arable land and ranking as the third largest crop after corn and soybean. Looking back, there is no doubt that Brazil's successful use of sugarcane significantly reduced the country's oil dependency, increased energy security, contributed to a thriving economy, and positioned Brazil as a world leader in the biofuel sector. In recent years, the increases in bioethanol consumption in the country and the production of bioelectricity from sugarcane solid waste have also reduced GHG emissions considerably. However, growing concerns about the social and environmental costs associated with ethanol production at a large scale have led to the development of indicators of environmental sustainability that allow quantifying both costs and benefits of biofuels benefits to society. The criteria adopted to assess biofuel sustainability are quite comprehensive and should help society to realize the benefits of biofuels. Nevertheless, our knowledge about the impacts of sugarcane ethanol produced in Brazil is still limited, especially for water and soils, and presents a serious obstacle in assessing sugarcane biofuel sustainability. One of the premises is that land requirements for biofuel should not exert extra pressure on native ecosystems or compete with food production by using the best agricultural lands. This premise implies that the expansion of biofuel crops like sugarcane should proceed without future clearings or without advancing over food crops. One alternative that has been considered to avoid clearing of native vegetation of Brazilian biomes is to expand energy crops in degraded or underutilized pasturelands. In order to free pastureland for other uses, the same number of animal heads, including future expansions, should be accommodated in an area smaller area by stocking rates (number of animals per hectare). We called this process "pasture intensification". Land use intensification to produce increase animal production per unit of pastureland or to convert pastureland to sugarcane has to be implemented in a way that preserves basic ecosystem integrity and maximizes the provision of ecosystem services. In order to do that, a set of environmental management practices conducive to that goal are needed. Based on this previous discussion, the goal of this project is to assess the environmental consequences of two major land intensifications that are critical for Brazil and the development of the bioenergy industry in other subtropical and tropical areas: the conversion of pasturelands to sugarcane fields, and the intensification in pastureland management that, potentially, enables such conversion. Our ultimate goal is to provide a series of management practices that would preserve the environmental integrity, and maximize ecosystem services. More specifically we will address how land intensification affects the water, carbon, nitrogen and phosphorus dynamics, and how pollution (pesticides) and fragmentation from agriculture affect ecosystems functioning. In order to achieve such goal we propose the follow components of the project: (i) a set of paired field experiments where pasturelands plots will be intensified to increase the animal product output per unit area or converted to sugarcane fields with the purpose of investigating changes in nutrients and contaminants dynamics; (ii) at watershed level (100 to 1,000 ha), a series of studies to assess the effect of agricultural intensification on the landscape ecology and water cycle. (AU)