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5.5.2. Associated Impacts of Projects that Sequester Carbon
Under a carbon market, projects that promote afforestation through plantation
forestry may be attractive to many prospective investors, given their potential
to generate profitable financial returns in addition to carbon credits (Frumhoff
et al., 1998). The potential impacts of projects that are designed to
promote afforestation through plantation forestry will vary significantly with
location, scale, use of native versus exotic tree species, and intensity of
management. Intensively managed plantations, for example, can help maintain
and improve soil properties, particularly if understory vegetation and leaf
litter is not cleared (Chomitz and Kumari, 1998), as well as providing a source
for biomass fuels and other wood products. They can have highly variable impacts
on water resources (Section 2.5.1). Plantations typically
do not appear to reduce pressure on natural forests in the humid tropics (Kanowski
et al., 1992; Johns, 1997) because these forests are not generally cleared
for the sawn wood, pulpwood, or other products that plantations provide. Kanowski
et al. (1992) suggest that fuelwood plantations might help reduce pressure
on natural woodlands in relatively arid regions. Thus, they might help to stem
desertification in some settings.
Plantation projects would have negative impacts on biodiversity if they replace
native grassland or woodland habitat or if permanent plantations of exotic species
were planted in sites where natural or assisted restoration of indigenous forests
is feasible. Many grassland ecosystems, for example, are rich in endemic species;
in the Mpumalanga province of South Africa, the expansion of commercial plantations
(Eucalyptus spp. and Pinus spp.) has led to significant declines
in several endemic and threatened species of grassland birds (Allan et al.,
1997).
In contrast, nonpermanent plantations of exotic or native species can be designed
to enhance biodiversity co-benefits by jump-starting the process of restoring
natural forests (Keenan et al., 1997; Lugo, 1997; Parrotta et al.,
1997a,b). Commercial forestry plantations can also increase biodiversity co-benefits
by adopting longer rotation times, reducing or eliminating measures to clear
understory vegetation, using native tree species, and minimizing chemical inputs
(e.g., Allen et al., 1995a,b; Da Silva et al., 1995).
Afforestation or reforestation measures could have positive or negative impacts
on local communities. Negative impacts can result if projects are implemented
on land for which communities have alternative priorities, such as agricultural
production, and if communities are not effectively engaged in all phases of
project design and implementation (Cullet and Kameri-Mbote, 1998; Section 6.6.3).
In urban or peri-urban areas, they can also produce significant local socioeconomic
benefits through improvements in air quality (McPherson, 1994).
Some observers have expressed concern that carbon-offset financing for reforestation
projects in non-Annex I countries could promote deforestation by financing the
expansion of plantations that replace natural forests whose associated emissions
would not be constrained by a national cap (German Advisory Council on Global
Change, 1998). Section 2.5.2.2 discusses possible options,
should Parties wish to constrain such projects.
Agroforestry activities can sequester carbon and produce a range of environmental
and socioeconomic benefits. For example, trees in agroforestry farms improve
soil fertility through control of soil erosion, maintenance of soil organic
matter and physical properties, increased nutrient inputs through nitrogen fixation
and uptake from deep soil horizons, and promotion of more closed nutrient cycling
(Young, 1997). Thus, agroforestry systems that incorporate trees on farms can
improve and conserve soil properties (Nair, 1989; MacDicken and Vergara, 1990),
as is the case in the AES Thames Guatemala project (Dixon et al., 1993).
Agroforestry projects also may provide local economic benefits, with farmers
gaining higher income from timber, fruits, medicinals, and extractives than
they would from alternative agricultural practices (Cooper et al., 1996).
Poorly planned and implemented agroforestry projects, however, can fail to
benefit or have negative impacts on local farmers. For example, the introduction
of labor-intensive agroforestry technologies can lead to labor competition between
agroforestry practices and traditional farming (Laquihon, 1989; Repollo and
Castillo, 1989). Poorly planned projects can also lead to excessive light and
water competition between crops and trees, as well as reducing the area available
for food crops.
The associated environmental benefits of project activities that promote assisted
regeneration of natural forests are similar to those of forest conservation.
As the forest matures, key benefits may include protection of watersheds, soil
fertility, and biodiversity. As with forest conservation or plantation forestry,
assisted forest regeneration could lead to negative social impacts if communities
are prevented from changing to preferred land uses in the future. This negative
impact also can be reduced by ensuring that the designation of areas for reforestation
is consistent with long-term regional land-use plans and that community development
priorities are effectively incorporated during project development and implementation
(Section 5.6).
There is very limited experience of LULUCF pilot projects that sequester carbon
or reduce carbon emissions from agricultural soils. There are vast areas of
degraded and desertified land in developed and developing countries, however,
where well-designed projects can add carbon to the soil while increasing agricultural
productivity and sustainability.
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