Tebaldi and Lobell (2008) applied probabilistic methods to demonstrate that
projected changes in temperature and precipitation negatively affect global crop
yields by causing a decrease in yield of about 9 % (with 95 % probability intervals
of 1.7–17 %) for barley, of 13 % (5–25 %) for maize and of 5 % (1–10 %) for
wheat. So water for agriculture is critical for future global food security. However,
continued increase in demand for water by nonagricultural uses, such as urban and
industrial uses have put irrigation water demand under greater scrutiny and
threatened food security (Hanjra and Qureshi 2010). Continued increase in demand
for irrigation water over many years has led to changed water flows, land clearing,
and therefore deteriorated stream water quality. Addressing these environmental
concerns and fulfilling urban and industrial water demand will require diverting
water away from irrigation. This will reduce irrigated area and its production and
impact on future food security (Hanjra and Qureshi 2010).
Water productivity is a concept to express the value or benefit derived from the
use of water and includes essential aspects of water management such as
production for arid and semi-arid regions (Kijne et al. 2003). Increasing water
productivity means either to produce the same yield with less water resources or to
obtain higher crop yields with the same water resources (Zwart and Bastiaanssen
2004).
1.10.3 Few Fields for Agriculture
Land-use intensity is one of the most significant forms of land cover modification,
and can have a major detrimental impact on terrestrial and aquatic ecosystems.
Agricultural land transformation and occupation have direct ecological impacts on
sites as well as on the surrounding landscape. Generally, crop production deprives
the land of most ecological value.
Many developed countries are experiencing environmental pollution due to
intensive agricultural activities, including intensive crop and livestock production.
Intensive agricultural activities have been identified as the major sources of
nonpoint source pollutants and are known to alter and impact the quality of the
receiving water bodies (Zhang et al. 2012).
There are already 3.5 Gha (Gigahectare = 109 Ha) or 23.5 % of the total land
which has been degraded to some degree (Bai et al. 2008) by a range of processes
such as accelerated soil erosion (by water and wind), salinization, nutrient/
elemental imbalance, depletion of soil organic C (SOC), and other processes which
undermine the physical, chemical, and biological quality of soil (Lal 2013b).
Urbanization, surface sealing, and brick making are other factors already affecting
300 Mha worldwide (Lal and Augustin 2011).
Over the 50-year period between 1961 and 2011, land area under agriculture
increased modestly at the rate of 8.2 million ha for agricultural land, 6.3 for
grazing land, 1.9 for cropland, and 3.0 for irrigated land. But in the recent years,
cropland has been reduced by 13 % and pasture by 4 %. According to the Food
24
L. Garcia-Mier et al.
projected changes in temperature and precipitation negatively affect global crop
yields by causing a decrease in yield of about 9 % (with 95 % probability intervals
of 1.7–17 %) for barley, of 13 % (5–25 %) for maize and of 5 % (1–10 %) for
wheat. So water for agriculture is critical for future global food security. However,
continued increase in demand for water by nonagricultural uses, such as urban and
industrial uses have put irrigation water demand under greater scrutiny and
threatened food security (Hanjra and Qureshi 2010). Continued increase in demand
for irrigation water over many years has led to changed water flows, land clearing,
and therefore deteriorated stream water quality. Addressing these environmental
concerns and fulfilling urban and industrial water demand will require diverting
water away from irrigation. This will reduce irrigated area and its production and
impact on future food security (Hanjra and Qureshi 2010).
Water productivity is a concept to express the value or benefit derived from the
use of water and includes essential aspects of water management such as
production for arid and semi-arid regions (Kijne et al. 2003). Increasing water
productivity means either to produce the same yield with less water resources or to
obtain higher crop yields with the same water resources (Zwart and Bastiaanssen
2004).
1.10.3 Few Fields for Agriculture
Land-use intensity is one of the most significant forms of land cover modification,
and can have a major detrimental impact on terrestrial and aquatic ecosystems.
Agricultural land transformation and occupation have direct ecological impacts on
sites as well as on the surrounding landscape. Generally, crop production deprives
the land of most ecological value.
Many developed countries are experiencing environmental pollution due to
intensive agricultural activities, including intensive crop and livestock production.
Intensive agricultural activities have been identified as the major sources of
nonpoint source pollutants and are known to alter and impact the quality of the
receiving water bodies (Zhang et al. 2012).
There are already 3.5 Gha (Gigahectare = 109 Ha) or 23.5 % of the total land
which has been degraded to some degree (Bai et al. 2008) by a range of processes
such as accelerated soil erosion (by water and wind), salinization, nutrient/
elemental imbalance, depletion of soil organic C (SOC), and other processes which
undermine the physical, chemical, and biological quality of soil (Lal 2013b).
Urbanization, surface sealing, and brick making are other factors already affecting
300 Mha worldwide (Lal and Augustin 2011).
Over the 50-year period between 1961 and 2011, land area under agriculture
increased modestly at the rate of 8.2 million ha for agricultural land, 6.3 for
grazing land, 1.9 for cropland, and 3.0 for irrigated land. But in the recent years,
cropland has been reduced by 13 % and pasture by 4 %. According to the Food
24
L. Garcia-Mier et al.