Providing food and other products to a growing human population while safeguarding natural ecosystems and the provision of their services is a significant scientific, social and political challenge. With food demand likely to double over the next four decades, anthropization is already driving climate change and is the principal force behind species extinction, among other environmental impacts. The sustainable intensification of production on current agricultural lands has been suggested as a key solution to the competition for land between agriculture and natural ecosystems. However, few investigations have shown the extent to which these lands can meet projected demands while considering biophysical constraints. Here we investigate the improved use of existing agricultural lands and present insights into avoiding future competition for land. We focus on Brazil, a country projected to experience the largest increase in agricultural production over the next four decades and the richest nation in terrestrial carbon and biodiversity. Using various models and climatic datasets, we produced the first estimate of the carrying capacity of Brazil's 115 million hectares of cultivated pasturelands. We then investigated if the improved use of cultivated pasturelands would free enough land for the expansion of meat, crops, wood and biofuel, respecting biophysical constraints (i.e., terrain, climate) and including climate change impacts. We found that the current productivity of Brazilian cultivated pasturelands is 32–34% of its potential and that increasing productivity to 49–52% of the potential would suffice to meet demands for meat, crops, wood products and biofuels until at least 2040, without further conversion of natural ecosystems. As a result up to 14.3 Gt CO2 Eq could be mitigated. The fact that the country poised to undergo the largest expansion of agricultural production over the coming decades can do so without further conversion of natural habitats provokes the question whether the same can be true in other regional contexts and, ultimately, at the global scale

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Resumo -O objetivo deste trabalho foi determinar o risco de deficit hídrico para a cultura da cana-de-açúcar em diferentes regiões brasileiras, com foco nas áreas de expansão. Para tanto, utilizou-se o modelo CSM-Canegro, para simular a produtividade da cana-planta de 12 meses, em 30 localidades. A partir dos valores estimados de produtividades potencial e atingível (produtividade sem irrigação), definiram-se as classes de risco de deficit hídrico de acordo com os níveis de eficiência climática, dada pela razão entre essas produtividades. O modelo simulou o efeito dos diferentes tipos de solo e datas de plantio sobre a produtividade, o que possibilitou caracterizar o risco de deficit hídrico associado à cultura. A região de maior risco é Petrolina, PE, enquanto as regiões de menor risco são as similares a Recife, PE, e Araguaína, TO.Termos para indexação: Saccharum, DSSAT, eficiência climática, produtividade potencial, risco climático, zoneamento climático. Simulation of the water deficit risk in sugarcane-crop expansion regions in BrazilAbstract -The objective of this work was to determine the water deficit risk for sugarcane crop in different Brazilian regions, focusing on crop-expansion regions. For that, the CSM-Canegro model was used to simulate the 12-month plant cane crop yield in 30 locations. From the estimated values for potential and attainable (without irrigation) yields, the water deficit risk classes were defined according to the climatic efficiency given by the ratio between these yields. The crop model simulated the effect of different soil types and planting dates on the yield, which made possible to characterize the water deficit risk associated to the crop. The region with the highest risk is Petrolina, state of Pernanbuco, whereas the regions with the lowest risk are those similar to Recife, state of Pernanbuco, and Araguaína, state of Tocantins.Index terms: Saccharum, DSSAT, climatic efficiency, potential yield, climatic risk, climate zoning. IntroduçãoA cana-de-açúcar (Saccharum spp.) é uma das culturas de maior importância social, econômica e ambiental, tendo atingido uma produção de 600 milhões de toneladas em 8,5 milhões de hectares no Brasil, país que é o maior produtor mundial da cultura (Veiga Filho et al., 2008). Em constante expansão, em razão da frota crescente de veículos flexfuel e do preço atrativo do açúcar, a cultura é a principal matéria prima para produção de etanol e açúcar. As maiores áreas produtoras estão nas regiões Centro-Sul e Nordeste, e o Estado de São Paulo é o maior produtor, com mais de 50% da produção do país (Companhia Nacional de Abastecimento, 2013). As áreas de expansão concentram-se na maior parte no Triângulo Mineiro e no oeste de Minas Gerais, em Goiás e no Mato Grosso do Sul (Instituto Nacional de Pesquisas Espaciais, 2013), e em algumas regiões localizadas no interior nordestino.Os principais fatores ambientais que influenciam a produtividade de cana-de-açúcar são a temperatura do ar e a disponibilidade hídrica. A temperatura afeta vários processos meta...

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The traditional practice of burning at the pre-harvesting of sugarcane has being phasedout in Brazil, resulting in the maintenance of a crop`s residue layer on soil surface, namely the Green Cane Trash Blanket (GCTB). New technologies for electricity and second-generation ethanol (2G) production from crop residues have raise the question on what would be the optimum amount of crop residue left on the field to keep the agronomic and environmental benefits of GCTB. To support informed decision making on sugarcane trash management, we updated, evaluated and applied a new version of the SAMUCA model to simulate the sugarcane growth and water use under the GCTB effect. The updated model was calibrated and parameterized for bare soil and GCTB conditions and evaluated across different Brazilian regions. Thirty-year simulations were then conducted with the updated model to quantify the effects of GCTB on sugarcane growth and water use where sugarcane is traditionally grown in Brazil. The updated version of SAMUCA model showed equal or superior performance when compared with widely-used process-based models for sugarcane. Based on our 30-year simulations, the GCTB exhibited a high probability to promote a beneficial effect on sugarcane yields in dry climates (> 90%), with the potential for increasing, on average, 14 ton ha -1 of fresh cane yield in Petrolina, Brazil. Although the beneficial effect on yields were not significant in humid regions, the maintenance of 12 ton ha -1 of GCTB was associated with a high probability (> 87%) in reducing the water use of sugarcane cropping system by mm, on average, potentially reducing irrigation demand in the early stages of crop development while protecting crop production under dry spell events. The new version of SAMUCA model offers as a tool for decision making on mulch management in sugarcane plantations.

To meet rising demands for agricultural products, existing agricultural lands must either produce more or expand in area. Yield gaps (YGs)—the difference between current and potential yield of agricultural systems—indicate the ability to increase output while holding land area constant. Here, we assess YGs in global grazed‐only permanent pasture lands using a climate binning approach. We create a snapshot of circa 2000 empirical yields for meat and milk production from cattle, sheep, and goats by sorting pastures into climate bins defined by total annual precipitation and growing degree‐days. We then estimate YGs from intra‐bin yield comparisons. We evaluate YG patterns across three FAO definitions of grazed livestock agroecosystems (arid, humid, and temperate), and groups of animal production systems that vary in animal types and animal products. For all subcategories of grazed‐only permanent pasture assessed, we find potential to increase productivity several‐fold over current levels. However, because productivity of grazed pasture systems is generally low, even large relative increases in yield translated to small absolute gains in global protein production. In our dataset, milk‐focused production systems were found to be seven times as productive as meat‐focused production systems regardless of animal type, while cattle were four times as productive as sheep and goats regardless of animal output type. Sustainable intensification of pasture is most promising for local development, where large relative increases in production can substantially increase incomes or “spare” large amounts of land for other uses. Our results motivate the need for further studies to target agroecological and economic limitations on productivity to improve YG estimates and identify sustainable pathways toward intensification.

The semiarid lands of Northeast Brazil represent one of the most densely populated regions of the country. Rainfall variability together with land degradation and large-scale poverty in rural areas makes this region vulnerable to droughts.Most of the agriculture in this region is rainfed and deficient rainfall leads to severe drought impacts. In this review, we examine different short-and long-term strategies directed to cope with possible impacts of droughts proposed by the government, farmers, civil society, and the private sector. These are approaches to adaptation to drought in the Northeast of Brazil, and among them, we have agricultural management and soil conservation and better management of water resources. Other actions include seasonal climate forecasts and funds transfer and credits to affected small-scale farmers. Although some of these actions are for the short term and may help to survive the drought situation, they may be only postdisaster mitigation options that do not improve adaptive capacity. They favor maladaptation and create dependency of farmers to government actions. Some experiences such as AdaptaSertão show potential benefits for small-scale farmers. We identify key challenges for moving toward a more holistic risk management approach and highlight the need to integrate actions and tools for adaptation, combining technology-based solutions with in-depth knowledge of local and regional social, economic, and cultural aspects, among them seasonal climate forecasts and drought impacts studies, among some other proactive predisaster ways, rather than reactive postdisaster actions. Adaptation strategies must increase long-term resilience of food production in the Brazilian Northeast, going beyond an individual drought event.