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Trade agreements could help to protect human rights, critical ecosystems, and the climate—but only if sustainability becomes a cornerstone of international trade. The EU-Mercosur trade agreement fails to meet our three tenets of sustainable trade agreements: (1) inclusion of local communities, (2) transparency mechanisms to trace commodities and provide open-access information, and (3) enforcement to legally uphold sustainability commitments.

Changes in land systems generate many sustainability challenges. Identifying more sustainable land-use alternatives requires solid theoretical foundations on the causes of land-use/cover changes. Land system science is a maturing field that has produced a wealth of methodological innovations and empirical observations on landcover and land-use change, from patterns and processes to causes. We take stock of this knowledge by reviewing and synthesizing the theories that explain the causal mechanisms of land-use change, including systemic linkages between distant land-use changes, with a focus on agriculture and forestry processes. We first review theories explaining changes in land-use extent, such as agricultural expansion, deforestation, frontier development, and land abandonment, and changes in land-use intensity, such as agricultural intensification and disintensification. We then synthesize theories of higher-level land system change processes, focusing on: (i) land-use spillovers, including land sparing and rebound effects with intensification, leakage, indirect land-use change, and land-use displacement, and (ii) land-use transitions, defined as structural non-linear changes in land systems, including forest transitions. Theories focusing on the causes of land system changes span theoretically and epistemologically disparate knowledge domains and build from deductive, abductive, and inductive approaches. A grand, integrated theory of land system change remains elusive. Yet, we show that middle-range theories – defined here as contextual generalizations that describe chains of causal mechanisms explaining a well-bounded range of phenomena, as well as the conditions that trigger, enable, or prevent these causal chains –, provide a path towards generalized knowledge of land systems. This knowledge can support progress towards sustainable social- ecological systems.

Deforestation associated with agricultural expansion, particularly that of extensive cattle ranching, remains a pressing challenge for sustainable development and climate mitigation efforts in South America. In response to these challenges, national and local governments, as well as private and non-governmental actors, have developed new forest conservation governance mechanisms. In addition to reducing deforestation for agricultural expansion, it is hoped that these policies may lead to the intensification of existing agricultural regions, thereby contributing to global food availability and continued rural development. The objective of this study is to understand the timing and spatial patterns of crop and pasture intensification in agriculture-forest frontiers in the context of changing conservation policies and rural development. We focus on Mato Grosso, the largest soy and cattle producing state in Brazil, which spans the Cerrado and Amazon biomes and has experienced among the highest levels of deforestation for agricultural expansion globally. Using econometric analysis of remotely sensed and agricultural survey data, we find that cropland and pasture intensification are both linked to increasing forest conservation restrictions and broader supply chain development. However, the effect of conservation restrictions on intensification is lower in regions where there is more forest remaining. While crop and pasture area dynamics are often coupled in agriculture-forest frontiers, crop intensification does not appear to have contributed to pasture intensification through animal feed production. Intensification of crop and pasture areas was associated with temporary, immediate reductions in local deforestation, but crop intensification was associated with increased deforestation over longer time periods. These results suggest that targeted investments in supply chain infrastructure in the Amazon frontier could promote intensification and relieve pressure to clear fo

© 2018 Elsevier Ltd Changes in land systems generate many sustainability challenges. Identifying more sustainable land-use alternatives requires solid theoretical foundations on the causes of land-use/cover changes. Land system science is a maturing field that has produced a wealth of methodological innovations and empirical observations on land-cover and land-use change, from patterns and processes to causes. We take stock of this knowledge by reviewing and synthesizing the theories that explain the causal mechanisms of land-use change, including systemic linkages between distant land-use changes, with a focus on agriculture and forestry processes. We first review theories explaining changes in land-use extent, such as agricultural expansion, deforestation, frontier development, and land abandonment, and changes in land-use intensity, such as agricultural intensification and disintensification. We then synthesize theories of higher-level land system change processes, focusing on: (i) land-use spillovers, including land sparing and rebound effects with intensification, leakage, indirect land-use change, and land-use displacement, and (ii) land-use transitions, defined as structural non-linear changes in land systems, including forest transitions. Theories focusing on the causes of land system changes span theoretically and epistemologically disparate knowledge domains and build from deductive, abductive, and inductive approaches. A grand, integrated theory of land system change remains elusive. Yet, we show that middle-range theories – defined here as contextual generalizations that describe chains of causal mechanisms explaining a well-bounded range of phenomena, as well as the conditions that trigger, enable, or prevent these causal chains –, provide a path towards generalized knowledge of land systems. This knowledge can support progress towards sustainable social-ecological systems.