|The Global Greenhouse Regime. Who Pays? (UNU, 1993, 382 p.)|
|Part III National greenhouse gas reduction cost curves|
|10 Abatement of carbon dioxide emissions in Brazil|
By far the largest source of anthropogenic carbon dioxide emission in Brazil is deforestation, principally in Amazonia. The carbon stock of the seasonal and rainforest vegetation in Amazonia is estimated to range from 140 to 200 TC/ha; that of pasture is 10 TC/ha; and of cropland, 5 TC/ha. The forest carbon stock may be adjusted as new information becomes available on subsurface biomass of the vegetation. Changing land use also reduces soil carbon content. In pasture soil, for example, the carbon content may be about 10 per cent of the approximately 100 TC/hectare of forest soil, or about 90 TC/ha. less than in forests. (Houghton et al 1991).
Thus, assuming a deforestation rate in Amazonia of 1.8 million hectares per year, gross CO2 emissions would be 250-360 MTC (though not all appears immediately in the atmosphere). To this figure should be added emissions from deforestation in other regions of Brazil. Unfortunately, we have no estimates for this source. Although substantially smaller, these are not insignificant.
Biological processes also continually accumulate carbon from the atmosphere, as is the case with regrowth of natural vegetation on deforested areas, abandoned land, or forest plantations. The rate of natural regrowth can vary by a factor of twenty in humid tropical areas depending on the local land-use situation (Nepstad et al 1990). The scale of this countervailing sequestration is poorly understood.
Despite these uncertainties, it is clear that Brazil's annual emissions from deforestation (250-360 MTC) dwarf those of fossil fuel use (60 MTC) as well as from biomass use for energy (about 11 MTC). This fact is consistent with the observation that fuelwood use is not a major factor in overall deforestation, though it may be significant in some regions (for example, charcoal from cerrado and mangroves). The primary direct causes of deforestation are clearing for pasture and cropland, with logging often opening up the occupation process.
Focusing on Amazonia, any substantial decrease in the rate of deforestation is likely to be associated with decreased economic growth. Macroeconomic modelling suggests that for every 1 per cent reduction in deforestation regional GDP would have to fall by roughly 1.7 per cent (Reds 1991). While pessimistic, the model suggests a first approximation of the cost of CO2 abatement by halting deforestation, roughly US$4/TC according to the model's author. This low cost (equivalent to a tax of $0.50/barrel of oil) is probably an upper limit, since the model assumes historical relationships. A strategy to change these relationships should be both cheaper and allow a less drastic trade-off between economic growth and deforestation. Such a strategy must go beyond police enforcement or reducing/eliminating legal and financial incentives to deforestation, though these are important (for example, Binswanger 1991). New or modified economic activities must be developed or strengthened both in forested and deforested areas (Sawyer 1990) based on land-use zoning. Settlement and economic activity, for example, should be stabilized, consolidated, and (in many areas) intensified in the largely deforested areas along the frontier and the 'pre-frontier'. While complex, restructuring Amazonia's economy is likely to be a large, 'no regress' source of CO2 abatement.
The relationship between land-use trends and energy policy has been little explored in Brazil. The most important such interaction is fuelwood for industry and charcoal. This nexus is the most important direct energy-related source of deforestation. A key issue is whether a decisive move to put these uses on a sustainable basis is justified or whether they should be phased out.
Another important land-use issue in relation to energy arises from hydroelectricity development in Amazonia. The relative priority, rate of development, and ultimate potential may all be influenced by a strategy to minimize deforestation. The infrastructure and migrations occasioned by hydro are the key concern. Some projects may provoke deforestation. Others help to decrease it as, for example, on the Tocantins river (Moreira et al 1990). This indirect effect on carbon emissions is likely to be larger than differences in direct electricity CO2 emissions resulting from alternative scenarios of hydropower/thermal generations (as discussed above).
Two subsidiary issues also connect land-use and energy policy issues. The unavailability of electrical power to isolated communities (most especially in Amazonia) constrains economic development. Poverty, in turn, fosters more carbon-emitting and intensive resource exploitation (Poole et al 1990). Relatedly, fuels such as diesel sold for use in Amazonia are subsidized (Reds 1991). The common denominator of CO2 emissions reinforces the need to consider energy, land use and regional development together.