Net Carbon Fluxes From Forest Clearance and Regrowth in the Amazon

Abstract

Abstract. Estimates of net carbon exchange resulting from forest clearance and regrowth were made for three areas in the Brazilian and Bolivian Amazon. The study areas, ranging in size from 600 to 10 000 km 2 , include communities that practice a range of land uses from small-scale, rotational agriculture to long-term pasture. Carbon emissions from deforestation were estimated based on rates of deforestation derived from Landsat satellite data and published estimates of mature forest biomass. Estimates of carbon uptake by secondary forest regrowth were based on area estimates from the satellite data and biomass estimates from field surveys. Estimates of carbon emissions from the clearance of secondary forest were included. The total carbon emissions were partitioned into that immediately released by biomass burning during clearance and that from subsequent decomposition and burning of felled biomass. A range of net carbon fluxes from secondary forest regrowth and clearance was estimated by extrapolating land-use patterns in each study area to the entire area of deforested landscape in Amazonian Brazil and Bolivia, and by varying average biomass accumulation rate of regrowing forest and fallow period.Over 60 km 2 of forest were cleared from 1988 to 1995 in each of the Brazilian study areas, and over 940 km 2 were cleared from 1986 to 1996 in the Bolivian study area. This resulted in 30-200 Mg C/yr emitted from biomass burning during deforestation. If the carbon that is committed to subsequent burning and decomposition of felled biomass is included, total committed emissions of 75-650 Mg C/yr resulted from deforestation in each study area. The carbon uptake by secondary forests was 33-435 Mg C/yr. However, emissions from the reclearance of secondary forests were nearly as large: 17-365 Mg C/yr. Extrapolation of these results to the Brazilian and Bolivian Amazon suggests that, at the national level, carbon uptake by secondary forests offset less than one-fifth of the carbon emissions from deforestation. Despite differences in land-use pattern, average fallow period, and rate of biomass accumulation used in the extrapolation, net carbon uptake by secondary forests was consistently small when compared to the total emissions from deforestation.

Climate Change: Financing Global Forests

“…16 This is generally achieved 9 Joosten andCouwenberg (2007) 10 Hirsch et al (2004);Steininger (2004) 11 Sajwaj et al (2008) 12 Nepstad et al (1999) 13 Nepstad et al (1994) 14 Giambelluca et al (2003) 15 As defined by IPCC (2000) 16 UNEP-WCMC FRIS (2008) through planting, seeding or assisting natural regeneration of the structure, productivity and species diversity of the forest originally present. ARR activities sequester carbon from the atmosphere and increase forest carbon stocks.…”

Challenges to estimating carbon emissions from tropical deforestation

“…In the Brazilian Amazon, for example, the reclearing rates of secondary forest may rival the primary forest clearing rates (Hirsch et al, 2004). Steininger (2004) also estimated significant carbon emissions from the reclearing of secondary forests in the Amazon.…”

Modeling landscape dynamics in an Atlantic Rainforest region: Implications for conservation

“…The transformation of mature forest to secondary forests is a common process in the tropics (Brown and Lugo, 1990;Gehring et al, 2005;Mayaux et al, 2005;Wright, 2005), and has profound ecological effects, particularly related to CO 2 balance (Steininger, 2004) and species conservation (Chazdon, 2003;Wright and Muller-Landau, 2006;Gardner et al, 2007a). The secondary forest of Atlantic Rainforest can sustain a high diversity of birds (Dunn, 2004;Becker and Agreda, 2005;Uezu et al, 2005), small mammals (Wu et al, 1996;Pardini et al, 2005), frogs, reptiles (Dixo, 2005;Gardner et al, 2007b;Ficetola et al, 2008) and plants (Martin et al, 2004;Bernacci et al, 2006), thus those forests play an important role in species conservation.…”