Historical carbon emissions and uptake from the agricultural frontier of the Brazilian Amazon

Abstract

Abstract. Tropical ecosystems play a large and complex role in the global carbon cycle. Clearing of natural ecosystems for agriculture leads to large pulses of CO 2 to the atmosphere from terrestrial biomass. Concurrently, the remaining intact ecosystems, especially tropical forests, may be sequestering a large amount of carbon from the atmosphere in response to global environmental changes including climate changes and an increase in atmospheric CO 2 . Here we use an approach that integrates census-based historical land use reconstructions, remote-sensing-based contemporary land use change analyses, and simulation modeling of terrestrial biogeochemistry to estimate the net carbon balance over the period 1901-2006 for the state of Mato Grosso, Brazil, which is one of the most rapidly changing agricultural frontiers in the world. By the end of this period, we estimate that of the state's 925 225 km 2 , 221 092 km 2 have been converted to pastures and 89 533 km 2 have been converted to croplands, with forest-to-pasture conversions being the dominant land use trajectory but with recent transitions to croplands increasing rapidly in the last decade. These conversions have led to a cumulative release of 4.8 Pg C to the atmosphere, with ;80% from forest clearing and 20% from the clearing of cerrado. Over the same period, we estimate that the residual undisturbed ecosystems accumulated 0.3 Pg C in response to CO 2 fertilization. Therefore, the net emissions of carbon from Mato Grosso over this period were 4.5 Pg C. Net carbon emissions from Mato Grosso since 2000 averaged 146 Tg C/yr, on the order of Brazil's fossil fuel emissions during this period. These emissions were associated with the expansion of croplands to grow soybeans. While alternative management regimes in croplands, including tillage, fertilization, and cropping patterns promote carbon storage in ecosystems, they remain a small portion of the net carbon balance for the region. This detailed accounting of a region's carbon balance is the type of foundation analysis needed by the new United Nations Collaborative Programmme for Reducing Emissions from Deforestation and Forest Degradation (REDD).

A Contemporary Carbon Balance for the Northeast Region of the United States

“…Of the forage consumed by livestock, 83% of the carbon is assumed to be released to the atmosphere as animal respiration each month and 17% of the carbon is added to reactive soil organic carbon as manure. 20 For the corresponding nitrogen in forage, 50% is added to reactive soil organic nitrogen as manure and 50% is added to the soil ammonium pool as urine. For urban/ suburban areas, new temperate broadleaved deciduous trees and temperate needle-leaf evergreen trees are assumed to grow from seedlings based on the comparable parametrizations of the natural forest types.…”

Can preferential credit programs speed up the adoption of low-carbon agricultural systems in Mato Grosso, Brazil? Results from bioeconomic microsimulation

“…(INPE 2015). While overall deforestation has significantly decreased since then, recent forest clearance seems to be on the rise again (Fearnside 2015) and land clearing and subsequent soil tillage continue to cause large amounts of GHG emissions (Galford et al 2011). Favorable climatic conditions allowing for two growing seasons per year, together with the introduction of improved seeds and techniques for dealing with soil acidity, transformed Mato Grosso into a major player in soybean, maize and cotton production (World Bank 2009).…”

Quantifying the relative importance of greenhouse gas emissions from current and future savanna land use change across northern Australia

“…These include census-based historical land use reconstructions and land use statistics, satellite estimates of biomass change through time (Baccini et al, 2012), satellite-monitored fire activity and burn area estimates associated with deforestation (van der Werf et al, 2010). In addition, there is increasing use of ecosystem models coupled with remote sensing to estimate emissions from LUC (Galford et al, 2011).…”

“…Much of these GHG emissions are from the Brazilian Amazonia, an agricultural area that has been expanding since the 1990s. However, over the last decade, the rate of tropical forest deforestation in this region has decreased from 16 000 km 2 in the early 2000s to ∼ 6500 km 2 by 2010 (Lapola et al, 2014), but at the expense of the Brazilian Cerrado, a vast savanna biome of some 2.04 million km 2 , where clearing rates have been maintained (Ferreira et al, , 2016Galford et al, 2013). Given the suitability of the Cerrado topography and soils for mechanised agriculture, the Cerrado may become the principal region of LUC in Brazil (Lapola et al, 2014).…”

“…Zenone et al, 2011). In tropical regions, there is a focus on transitions from forest to pasture and from forest to crops for food or bioenergy production (Galford et al, 2011;Wolf et al, 2011;Sakai et al, 2004).…”