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Gully development following agricultural land use change is well documented in many tropical developing countries. However, the impact of specific agricultural intensification practices on gully formation, such as the construction of unpaved roads and contour terracing, remains poorly understood. We studied gully formation in catchments with sugarcane agriculture to inform sustainable agricultural management in Brazil. Through field surveys in ten first-to second-order catchments, we mapped erosional features and described gullying along an incision gradient from rill, to ephemeral and permanent gullies. We documented formation of >130 erosional features that concentrated mainly (96%) on dirt roads along the outer margins of streamside vegetation and bordering transitions from hillslope to hollow. We further established a slope-contributing area threshold for gullying, highlighting high susceptibility to gully formation on dirt roads and contour terraces. Key implications of our findings include targeted enhancements of riparian buffers that extend beyond concave topographies as well as the use of topographic thresholds as a benchmark for gully formation along dirt roads in Brazilian sugarcane fields.

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Sugarcane is a widespread bioenergy crop in tropical regions, and the growing global demand for renewable energy in recent years has led to a dramatic expansion and intensification of sugarcane agriculture in Brazil. Currently, extensive areas of low-intensity pasture are being converted to sugarcane, while management in the remaining pasture is becoming more intensive, i.e., includes tilling and fertilizer use. In this study, we assessed how such changes in land use and management practices alter emissions of greenhouse gases (GHG) such as CO2, N2O and CH4 by measuring in situ fluxes for one year after conversion from low-intensity pasture to conventional sugarcane agriculture and management-intensive pasture. Results show that CO2 and N2O fluxes increased significantly in pasture and sugarcane with tillage, fertilizer use, or both combined. Emissions were highly variable for all GHGs, yet, cumulatively, it was clear that annual emissions in CO2-equivalent (CO2-eq) were higher in management-intense pasture and sugarcane than in unmanaged pasture. Surprisingly, tilled pasture with fertilizer (management-intensive pasture) resulted in higher CO2-eq emissions than conventional sugarcane. We concluded that intensification of pasture management and the conversion of pasture to sugarcane can increase the emission factor (EF) estimated for sugarcane produced in Brazil. The role of management practices and environmental conditions and the potential for reducing emissions are discussed.

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In Brazil, the cultivation of bioenergy crops is expanding at an accelerated rate. Most of this expansion has occurred over low-intensity pasture and is considered sustainable because it does not involve deforestation of natural vegetation. However, the impacts on the water quality of headwater streams are poorly understood, especially with regard to the influence of land use patterns in the watershed. In this study, we investigated the effects of land-use conversion on the water quality of streams draining sugarcane fields and examined whether the preservation of forested areas at the top of the headwaters would help mitigate the negative impacts of intensive agriculture. Water samples were collected in two paired catchments in southeastern Brazil, which is one of the largest sugarcane production regions in the world. Our results show significant differences in the water quality of streams predominantly draining the pasture or the sugarcane field. Several parameters commonly used to indicate water quality, such as the concentrations of nitrate and suspended solids, were significantly higher in the sugarcane than in the pasture stream. Differences in water quality between the streams draining predominantly pasture or sugarcane fields were accentuated during the wet season. The preservation of forests surrounding the headwater streams was associated with overall better water quality conditions, such as lower nitrate concentrations and temperature of the stream water. We concluded that forest conservation in the headwater agricultural catchments is an important factor preventing water quality degradation in tropical streams. Therefore, we strongly recommend the preservation of robust riparian forests in the headwaters of tropical watersheds with intensive agriculture. More studies on the effects of best agricultural practices in bioenergy crops can greatly improve our capacity to prevent the degradation of water quality in the tropical waterways as intensive agriculture continues to expand in this region of the world.

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Brazil has a unique position in the world. It is one of the few countries that can be one of the most important producers of food, fiber and biofuel and at the same time maintain its mega biodiversity endowment and vital ecosystems services properly running. This is a challenge that only can be achieved by recognizing the importance of agribusiness sector to the Brazilian economy, but also that ecosystems have limits and we should not endless expand agriculture in the name of "development". Ecosystem services have to be recognized also as a "development" to be kept for the next generations. Agriculture only exists where ecosystems are able to maintain its basic functioning. Therefore, a well preserved nature it is the most precious asset of agriculture.

O Brasil encontra-se em uma posição privilegiada diante do mundo. É um dos únicos países que pode ao mesmo tempo ser um importante produtor de alimentos, fibras e biocombustíveis e manter sua mega biodiversidade relativamente intacta e serviços ambientais vitais funcionando apropriadamente. Este é um desafio enorme que pode ser obtido através do reconhecimento da importância que o setor agropecuário brasileiro tem para o país, mas ao mesmo tempo reconhecendo também que os ecossistemas têm limites naturais e não devemos expandir nossa fronteira agrícola indefinidamente em nome do "desenvolvimento". Os serviços ambientais prestados pelos ecossistemas devem ser valorizados e também reconhecidos como um tipo de "desenvolvimento" a ser mantido para as próximas gerações. A agricultura somente existe onde os ecossistemas são capazes de manter suas funções básicas de funcionamento. Portanto, o maior capital da agricultura é a natureza minimamente preservada.

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Several geopolitical factors, aggravated by worries of global warming, have been fueling the search for and production of renewable energy worldwide for the past few years. Such demand for renewable energy is likely to benefit the sugarcane ethanol industry in Brazil, not only because sugarcane ethanol has a positive energetic balance and relatively low production costs, but also because Brazilian ethanol has been successfully produced and used as biofuel in the country since the 1970s. However, environmental and social impacts associated with ethanol production in Brazil can become important obstacles to sustainable biofuel production worldwide. Atmospheric pollution from burning of sugarcane for harvesting, degradation of soils and aquatic systems, and the exploitation of cane cutters are among the issues that deserve immediate attention from the Brazilian government and international societies. The expansion of sugarcane crops to the areas presently cultivated for soybeans also represent an environmental threat, because it may increase deforestation pressure from soybean crops in the Amazon region. In this paper, we discuss environmental and social issues linked to the expansion of sugarcane in Brazil for ethanol production, and we provide recommendations to help policy makers and the Brazilian government establish new initiatives to produce a code for ethanol production that is environmentally sustainable and economically fair. Recommendations include proper planning and environmental risk assessments for the expansion of sugarcane to new regions such as Central Brazil, improvement of land use practices to reduce soil erosion and nitrogen pollution, proper protection of streams and riparian ecosystems, banning of sugarcane burning practices, and fair working conditions for sugarcane cutters. We also support the creation of a more constructive approach for international stakeholders and trade organizations to promote sustainable development for biofuel production in developing countries such as Brazil. Finally, we support the inclusion of environmental values in the price of biofuels in order to discourage excessive replacement of natural ecosystems such as forests, wetlands, and pasture by bioenergy crops.

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