Introduction - The Global Climate System: Patterns, Processes, and Teleconnections - page 19

For their part, social scientists have become much more engaged in
research efforts to distinguish between the impacts of physical processes
on various socioeconomic sectors of society and those impacts that have
actually resulted from decision-making processes. They are also active in
trying to identify as well as develop ways to use climate and climate-related
information to address a wide range of local to global societal needs.
1.3.4 Problem societies
The phrase ''problem societies'' refers to climate and climate-related factors
that affect the ability of society to interact effectively with the climate system.
Accepting the fact that there are many things about the behavior of the atmo-
sphere that we do not yet know or understand, it is also important to note that
there is a considerable amount of usable information that we do already know
about the interactions between human activities and the climate system.
Nevertheless, societies knowingly still engage in activities that increase their
vulnerability or reduce their resilience in the face of a varying climate system.
Human activities can alter the physical characteristics of climate from local
to global levels. In addition, societal changes can make them more vulnerable
to a variable climate. Policy makers at various levels of government know-
ingly make decisions (explicitly or implicitly) about land use in areas that are
prone to climate-related hazards, e.g. deforestation, increasing soil erosion,
decrease in soil fertility, destruction of mangroves, over-fishing, chemical
emissions to the atmosphere, the drying out of inland seas, and so forth. These
decisions set societies up for the impacts of varying and extreme climate and
weather conditions, and are the underlying causes of many climate-related
problems. For example:
Tropical deforestation is occurring wherever such forests exist, such as in South
America, sub-Saharan Africa and Southeast Asia. Research shows that in the
Amazon basin, for example, 50 percent of the rain that falls there is the result of
evapotranspiration from the vegetation therein.
As productive land becomes scarce, people are forced to inhabit increasingly
marginal areas for agricultural production or for livestock rearing. As a result of,
for example, moving up hillsides and mountain slopes, the cultivation of the soils
leads to an increase in soil erosion and to sediment loading of nearby streams,
rivers, and reservoirs. In time the land may have to be abandoned, leaving eroded
hillsides exposed to the vagaries of nature.
Land use in arid and semiarid areas can be very destructive, if care is not taken for
agricultural and livestock rearing activities. As land is cleared of vegetation to grow
crops, it is left vulnerable to wind and water erosion. Irrigated lands need to be
drained properly to avoid salinization of the soils or waterlogging.