Reevaluating suitability estimates based on dynamics of cropland expansion in the Brazilian Amazon

Abstract

Agricultural suitability maps are a key input for land use zoning and projections of cropland expansion. Suitability assessments typically consider edaphic conditions, climate, crop characteristics, and sometimes incorporate accessibility to transportation and market infrastructure. However, correct weighting among these disparate factors is challenging, given rapid development of new crop varieties, irrigation, and road networks, as well as changing global demand for agricultural commodities. Here, we compared three independent assessments of cropland suitability to spatial and temporal dynamics of agricultural expansion in the Brazilian state of Mato Grosso during 2001-2012. We found that areas of recent cropland expansion identified using satellite data were generally designated as low to moderate suitability for rainfed crop production. Our analysis highlighted the abrupt nature of suitability boundaries, rather than smooth gradients of agricultural potential, with little additional cropland expansion beyond the extent of the flattest areas (0-2% slope). Satellite-based estimates of the interannual variability in the use of existing crop areas also provided an alternate means to assess suitability. On average, cropland areas in the Cerrado biome had higher utilization (84%) than croplands in the Amazon region of northern Mato Grosso (74%). Areas of more recent expansion had lower utilization than croplands established before 2002, providing empirical evidence for lower suitability or alternative management strategies (e.g., pasture-soya rotations) for lands undergoing more recent land use transitions. This unplanted reserve constitutes a large area of potentially available cropland (PAC) without further expansion, within the management limits imposed for pest management and fallow cycles. Using two key constraints on future cropland expansion, slope and restrictions on further deforestation of Amazon or Cerrado vegetation, we found little available flat land for further legal expansion of crop production in Mato Grosso. Dynamics of cropland expansion from more than a decade of satellite observations indicated narrow ranges of suitability criteria, restricting PAC under current policy conditions, and emphasizing the advantages of field-scale information to assess suitability and utilization.

Are Brazil's Deforesters Avoiding Detection?

“…One source of suggestive evidence of the effect of PPCDAm ii on deforestation has been the rise of deforestation in other regions of Brazil (Morton et al . ) and neighboring South American nations over the same period (Graesser et al . ; de Waroux et al .…”

“…The program has been hailed for reducing deforestation in the Brazilian Amazon (Assunção et al 2012;Arima et al 2014). One source of suggestive evidence of the effect of PPC-DAm ii on deforestation has been the rise of deforestation in other regions of Brazil (Morton et al 2016) and neighboring South American nations over the same period (Graesser et al 2015;de Waroux et al 2016). However, the incomplete scope and extent of forests and deforestation monitored by PRODES means that there was also a potential for an additional response to enforcement, namely, deforestation tailored to avoid detection by PRODES.…”

Soil Carbon Dynamics in Soybean Cropland and Forests in Mato Grosso, Brazil

“…Driven by an increasing global demand for beef and grain from a growing human population (Boucher et al, ; Brown, ), tropical deforestation to date has largely been for conversion to pasture and the C consequences of such conversions have been extensively documented (De Camargo et al, ; Fujisaki et al, ; Neill et al, ; Powers et al, ). Although pasture remains a widespread use of tropical land, in the past two decades land has been increasingly converted to highly mechanized agriculture of commodity crops like soybeans (Galford et al, ; Laurance et al, ; Nepstad et al, ; Morton et al, ) and little is known about the transition to industrial soy production, which now covers large swaths of the southern Amazon and Cerrado. This transition, which is playing out on deep, highly weathered soils, may be a substantial C source to the atmosphere, but little work has attempted to quantify soil C changes, particularly the changes that occur deeper in the soil profile.…”

Production and international trade: challenges for achieving targets 6 and 11 of the Global Strategy for Plant Conservation in Brazil

“…In parallel, other innovative initiatives, such as the soybean moratorium -an agreement between non-governmental organisations and soybean retailers whereby major traders agreed not to purchase soy grown on Amazon lands deforested after July 2006 -were either successful in their early stages (deforestation due to soy expansion in the Amazon dropped to less than 1%), did not last or had collateral effects (Rudorff et al 2011;Gibbs et al 2015). It was detected that soy expansion leaked into neighbouring biomes, particularly the Brazilian Cerrado (Morton et al 2016), and it was shown more recently that deforestation due to soybean farming in Amazonia has increased again (ABIOVE et al 2017).…”