Cropland expansion changes deforestation dynamics in the southern Brazilian Amazon

Abstract

agriculture ͉ carbon ͉ land use change ͉ soybean T he ''arc of deforestation'' along the southern and eastern extent of the Brazilian Amazon is the most active land-use frontier in the world in terms of total forest loss (1) and intensity of fire activity (2). Historically, the dominant pattern of forest conversion has begun with small-scale exploration for timber or subsistence agriculture, followed by consolidation into largescale cattle ranching operations or abandonment to secondary forest (3-5). Recent expansion of large-scale mechanized agriculture at the forest frontier has introduced a potential new pathway for forest loss, generating debate over the contribution of cropland expansion to current deforestation dynamics (5-9). In the nine states of the Brazilian Legal Amazon, mechanized agriculture increased by 36,000 km 2 , † † and deforestation totaled 93,700 km 2 ‡ ‡ during [2001][2002][2003][2004]. Recent gains in the area under cultivation and the productivity of locally adapted crop varieties have made Brazil a leading worldwide producer of grains such as soybeans; the agribusiness sector now accounts for more than one-third of Brazil's gross national product (10).The state of Mato Grosso alone accounted for 87% of the increase in cropland area and 40% of new deforestation during this period. Whether cropland expansion contributes directly to deforestation activity or occurs only through the intensified use of previously deforested areas has important consequences for ecosystem services (11), such as carbon storage, and future deforestation dynamics.Amazon deforestation is Brazil's largest source of CO 2 emissions (12, 13). Carbon fluxes from deforestation are a function of the area of forest loss (14-16) and related forest disturbances, such as fire (17, 18) and logging (17,19), variations in forest biomass across the basin (20), and land use or abandonment after forest clearing (3,21). Land use after forest clearing remains a major source of uncertainty in the calculation of deforestation carbon fluxes because methods to assess deforestation trends in Amazonia have not followed individual clearings over time (4,5,(22)(23)(24)(25)(26)(27)(28). The relative contributions of smallholder agriculture and large-scale cattle ranching to annual forest loss have been inferred from the size of deforestation events (5, 28), but no direct measurements have been available. Rapid growth of large-scale agriculture in Amazonia challenges the historic relationship between land use and clearing size.We determine the fate of large deforestation events (Ͼ25 ha) during [2001][2002][2003][2004] in Mato Grosso State to provide satellitebased evidence for the relative contributions of cropland and pasture to increasing forest loss during this period (Fig. 1). Our approach combines satellite-derived deforestation data, vegetation phenology information from the Moderate Resolution Imaging Spectroradiometer (MODIS; ref. 29), and 2 years of field observations to establish the spatial and temporal patterns of land use after fo...

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“…Brazil is considered to have one of the best monitoring programmes for deforestation, yet a 20% uncertainty in annual deforestation rate was found in the Mato Grosso study (Morton et al, 2011). Increased knowledge of LU after deforestation is vital as carbon losses for cropland are potentially higher than for pasture, perennial plantation or secondary forests (Morton et al, 2006). This is important not only when calculating emissions but also for improving our understanding of forces driving deforestation.…”

Interactions between repeated fire, nutrients, and insect herbivores affect the recovery of diversity in the southern Amazon

“…They are, however, increasingly encroached upon by agriculture and pasture (Fearnside 2001;Morton et al 2006), conversions that could represent a loss of 40 % of the Amazon forest by 2050 (Soares-Filho et al 2006). At the southern edge of the Amazon, reduced precipitation, more frequent fires, and acidic, welldrained soils create a boundary between tropical forest and cerrado (savanna; Oliveira and Marquis 2002).…”

Export-oriented deforestation in Mato Grosso: harbinger or exception for other tropical forests?

“…While pasture remained the predominant land use following deforestation, clearing forest for soya bean contributed about 12 per cent of Mato Grosso's deforestation for large clearings (more than 25 ha) in 2000-2005 [7,15]. Indirect deforestation, or 'leakage', pushed clearing for pasture further into the agricultural frontier as soya bean expanded into pasture, accounting for additional deforestation attributable to the soya bean boom [16,17].…”