Causative Factors of Agricultural Drought

Precipitation and Land Management

The causes for agricultural drought in Latin America can be analyzed from two points of view. In the first case, drought is intrinsically related to precipitation deficit during a given period of time, which negatively affects crops and water resources (Brunini et al., 2002). Second, the poor management of agricultural lands and exploitation of natural resources have turned highly productive areas into degraded lands. The decaying of organic matter increases the risk of drought due to the decrease in water retention capacity of the soil. Also, soil compaction contributes to drought occurrence.

El Niño/Southern Oscillation

The most important meteorological phenomenon that causes large-scale droughts (both spatially and temporally) is El Niño/Southern Oscillation (ENSO) and La Niña (Alves and Repelli, 1992; Cunha et al., 2001; Marengo et al., 2001; chapter 3). In Brazil, the northern part of the northeastern

Figure 12.2 Spatial variation in precipitation distribution across Brazil.

region, the eastern part of the Amazon (tropical zone), and the southern region (extra-tropical zone) are influenced most by the ENSO phenomenon. Normally, during the positive phase of the ENSO, the northeastern region of Brazil experiences a decrease in seasonal rainfall and an increase in the intensity of the droughts, but the south of Brazil experiences an increase in precipitation (Cunha, 1999; Martelo, 2000).

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