(7 - 21%) and forest (8 - 21.5%) for semi-arid climates where the changes in vegetation were caused mainly by variability in precipitation, drought, natural succession, forest fires, and change in human population (Tsegaye et al. 2010; Tefera 2011). Bush/shrub covers can be found in a wider range of climates because it is relatively less sensitive to changes in climate (Chuai et al. 2013). The study area experienced an increase in bush/shrub and a decrease in grass and forest (Table 4). Compared to previous studies of other areas, the study area follows the general trend for the changes in vegetation during the given observation period.
Developed and crop land are mainly considered types of land cover associated with human activities. Human activities, such as agriculture, settlements, road construction and commercial development, are important factors that directly affect land-cover changes. Human intervention has more effect on land-cover change than climate change because the effects of climate change take a long period of time to impact land-cover changes (Seto and Shepherd 2009). Both human population and groundwater have decreased in the study area. For example, the population for the study area decreased from 1348 people in 1970 to 678 people in 2009 (US Census Bureau 2010). Groundwater has decreased since the 1970 level. The study area also experienced a decrease in precipitation from 425.5 - 379.2 mm but an increase in temperature from 11.0 - 11.9°C, which might suggest that the study area climate is gradually moving towards the more arid side of a semi-arid environment. We suspect that a harsher environment for crop production and increased deficit in available water for human activities has already occurred in the study area.
(7 - 21%) and forest (8 - 21.5%) for semi-arid climates where the changes in vegetation were caused mainly by variability in precipitation, drought, natural succession, forest fires, and change in human population (Tsegaye et al. 2010; Tefera 2011). Bush/shrub covers can be found in a wider range of climates because it is relatively less sensitive to changes in climate (Chuai et al. 2013). The study area experienced an increase in bush/shrub and a decrease in grass and forest (Table 4). Compared to previous studies of other areas, the study area follows the general trend for the changes in vegetation during the given observation period.Developed and crop land are mainly considered types of land cover associated with human activities. Human activities, such as agriculture, settlements, road construction and commercial development, are important factors that directly affect land-cover changes. Human intervention has more effect on land-cover change than climate change because the effects of climate change take a long period of time to impact land-cover changes (Seto and Shepherd 2009). Both human population and groundwater have decreased in the study area. For example, the population for the study area decreased from 1348 people in 1970 to 678 people in 2009 (US Census Bureau 2010). Groundwater has decreased since the 1970 level. The study area also experienced a decrease in precipitation from 425.5 - 379.2 mm but an increase in temperature from 11.0 - 11.9°C, which might suggest that the study area climate is gradually moving towards the more arid side of a semi-arid environment. We suspect that a harsher environment for crop production and increased deficit in available water for human activities has already occurred in the study area.
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