Tropical climates - The Global Climate System: Patterns, Processes, and Teleconnections - page 77

has been questioned. In a 2004 study, Chappell and Agnew explored the con-
tention that, since the major droughts of the 1970s, mean annual summer rainfall
has declined. They suggest that previously published work did not take into
account ''the location of the rainfall station network each year in relation to the
spatial and temporal heterogeneity of West African Sahel rainfall.'' They went
on to suggest that the identified decline in rainfall was an artifact of changing
location and number of rainfall stations.
Clearly, there is much research remaining to be completed in the study of the
Sahel. In his review of the relationship between surface and atmosphere in the
Sahel, Taylor ( 2001 ) provides a synopsis of a climatic situation that will occupy
many researchers for years to come.
3.4.2 Amazon deforestation
The Amazon Basin of Brazil occupies some 5 million square kilometers, some
4 million of which is forested. It is an area about which much has been written,
especially since the Brazilian government's efforts to colonize the region and the
deforestation that has resulted. Essentially, the construction of highways into the
region (the Belem-Brazilia road was paved in 1974, the Cuiba-Porto Vehlo in
1984, and the Rondonia to Acre in 1986) permitted settlement that was stimu-
lated by programs to attract migrants from other parts of the country. Subsistence
farming on the poor soil of cleared forest areas was a failure and cattle pasturing
became the main land use in cleared areas. This was greatly aided by the ''right
of possession'' for whoever clears a forested area; after logging, pasture is the
easiest way to occupy an extensive area and large land tracts are often owned by
a few cattle ranchers. Brazil now has the largest commercial cattle herd in the
world and is a major exporter of beef and beef products. Beyond cattle ranching,
the planting of soybeans is also a major contributor to deforestation. Social
scientists find many problems with the events that have occurred and various
solutions have been suggested (Fearnside 1986 ; Anderson 1990 ; Amelung and
Diehl 1992 ; Hall 1997 ).
As Figure 3.10 shows, the amount of deforestation is remarkable. Through its
National Institute for Space Research (INPE), the Brazilian government moni-
tors the amount of deforestation through remote sensing. As shown in the essay
in Section 3.5 , remote sensing is of considerable importance in monitoring
tropical environments. It is largely through remote sensing that much of the
data concerning changes in the forest are derived.
Climate change resulting from deforestation can be considered at a number of
levels. First there is the global effect. A response to the burning of the forests
over a huge area is the addition of carbon dioxide to the atmosphere, with the
potential for enhancing the global greenhouse effect; then there is the removal of
the forest which serves as an oxygen source for the planet. As shown in a number
of publications, both of these concerns are difficult to evaluate and model and the