Geography Reference
In-Depth Information
tropical rainforest biota and climate. They typically are politically marginalized minor-
ity populations with high fertility rates and little or no access to external health care,
schools, and lending institutions.
Although many farmers live in permanent villages, they rotate fields every three to
five years, followed by a decade of abandonment and rejuvenation. Although this frag-
mented ownership pattern requires laborious trekking between their soccer field-sized
plots, it serves a positive adaptive function by dispersing the risks inherent to farming
over several microenvironments. To prepare a field, farmers first clear the forest with a
machete or hand axe. They ignite the downed slash when the temperature and humidity
conditions are optimum, usually prior to an afternoon rain. The ensuing conflagration
reduces the freshly cut trees and understory to a layer of nutrient-rich ash. They cultiv-
ate this enriched topsoil for the next three to five years. Little or no effort is expended
on fertilizer, weeding, or irrigation. Additional field maintenance such as fencing and
furrowing is atypical (Fig. 11.8). This low upkeep reduces the labor input, allowing time
for opportunistic hunting and transplanting of tree crops such as the plantain (banana).
The high monthly rainfall quickly leaches the nutrients into the soil and eventually be-
low the rooting zone. Without supplemental fertilizer or the copious infusion of organic
matter characteristic of a natural forest, soil fertility drops to the point where, within
four to six years, the farmer abandons the plot to begin the process anew at another
location. Since shifting cultivators grow mostly starch and vegetables, they add protein
by raising pigs, dogs, cats, and chickens. These animals require minimal care and feed
because they scavenge for rice husks, roots, insects, and other foods that humans can-
not digest.
Shifting cultivation is a land-use paradox. On one hand, it requires extensive terrain,
since most of the land is in regenerative fallow condition. On the other hand, it requires
less labor and technology. This strategy predates all others, having been employed in
tropical mountains since the early Neolithic (or Stone) Age, 10,000 years B.P. Although
it does alter the tropical rainforest, compared to other agricultural techniques there is
lower net loss of biodiversity, soil erosion, and forest fragmentation. Shifting cultivat-
ors often maintain a healthy forest mosaic with high species diversity that is slowing
gaining recognition as an excellent form of “human impacted” land offering signific-
ant conservation value (O'Brien 2002). However, it is increasingly blamed for the en-
vironmental decline of tropical mountain rainforests, though in many locations, such as
mountainous northern Honduras (Jansen 1998), northern Thailand (Renaud et al. 1998),
and southwestern China (Jianchu et al. 1999), the supposed environmental change is
both poorly documented and inadequately understood. In the case of Xishuangbanna,
a biologically diverse enclave in southwestern China, new government policies inten-
ded to help shifting cultivators transition to mixed farming actually accelerated forest
degradation. When a “Household Responsibility System” freed farmers of government
interference, their reversion to slash-and-burn cultivation decreased the amount of land
under production, creating a richer forest mosaic. Where soil erosion and forest decline
do occur, the damage is due less to the technique of shifting plots than to increasing
population pressures resulting from internal growth and external immigration (Renaud
et al. 1998). With more mouths to feed, the farmers have little choice but to shorten
the regenerative fallow periods and increase field size. Both accelerate clearing and in-
crease soil erosion, because the forest recovery period is shortened. In the highlands
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