State and change in carbon pools in the forests of tropical Africa

Authors

  • GREG GASTON,

    1. US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333, USA,
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  • SANDRA BROWN,

    1. US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333, USA,
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  • MASSIMILIANO LORENZINI,

    1. Food and Agriculture Organization of the United Nations, Forestry Department, Viale delle Terme di Caracalla, 00100 Rome, Italy
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  • K. D. SINGH

    1. Food and Agriculture Organization of the United Nations, Forestry Department, Viale delle Terme di Caracalla, 00100 Rome, Italy
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SANDRA BROWN tel +1/ 541 754 4346, fax +1/ 541 754 4799british@heart.cor.epa.gov

Abstract

To improve estimates of the state and change in C pools due to changes in land use in tropical forests of Africa, we combined spatially explicit estimates of biomass C density, obtained by modelling in a geographical information system (GIS), with new data on the area of forests (woody formations with a minimum of 10% crown cover) reported at subnational units for 1980 and 1990 by the Food and Agriculture Organization (FAO). Estimates of the biomass C densities for grass/shrub savannas were also included using a simple model based on precipitation. The total C pool in above– and below–ground forests and grass/shrub savannas of Africa for 1980 was 50.8 Pg (1015g), with aboveground forest biomass accounting for 75% of the total, below–ground forest biomass for 21%, and grass/shrub savannas for 4%. Area weighted mean biomass C densities were about 180 Mg ha–1 for lowland moist forests, 82 Mg ha–1 for all forests, and 6 Mg ha–1 for grass savannas. The total change in the aboveground forest C pool for the decade 1980–90 due to changes in land cover and use was estimated to be a decrease of 6.6 Pg C. Of this total, 43% was due to deforestation and 57% due to biomass reduction by other human activities. Six countries, mostly in central Africa, accounted for more than 73% of the total change in the C pool. The difference between state and change of C pool estimates made at the subnational scale and those made at the national scale proved to be insignificant across the region as a whole (2% for pools and – 1% for change in pool) but potentially important to individual countries (from + 36% to – 39% for pools and from + 43% to – 57% for change in pool). The differences between the two approaches may reflect a better match of the areas being deforested with the biomass C density of forests being cleared.

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