Section B5.4 of the SPM makes the following statement:
Depending on future socioeconomic conditions, limiting global warming to 1.5°C, compared to 2°C, may reduce the proportion of the world population exposed to a climate-change induced increase in water stress by up to 50%, although there is considerable variability between regions (medium confidence).
With respect to Water Stress, the IPCC concedes that socioeconomic conditions are at least as important as global warming. MIT researchers concluded that by 2050 "52 percent of the world's projected 9.7 billion people will live in water-stressed regions." The study found population and economic growth are the socioeconomic factors most responsible for increased water stress, resulting in an additional 1.8 billion people living in water-stressed areas.
Groundwater resources are being depleted much faster than they are being recharged in several arid areas of the world. This will cause additional water stress that is only marginally related to global warming, but substantially related to population growth and economic development.
The United Nations World Water Development Report makes similar conclusions to the MIT researchers.
Audrey Azoulay, the director-general of Unesco, noted "two-thirds of the world's forests and wetlands have been lost since the turn of the 20th century – a trend that needs to be addressed." "We all know that water scarcity can lead to civil unrest, mass migration and even to conflict within and between countries," she said. "Ensuring the sustainable use of the planet's resources is vital for ensuring long-term peace and prosperity."
The sustainable use of the planet's resources will still need to be done, even if we somehow stopped all greenhouse gas generation.
Section B5.3 of the SPM makes the following statement:
Limiting warming to 1.5°C, compared with 2.0oC, is projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereal crops, particularly in subSaharan Africa, Southeast Asia, and Central and South America; and in the CO2 dependent, nutritional quality of rice and wheat (high confidence). Reductions in projected food availability are larger at 2.0oC than at 1.5°C of global warming in the Sahel, southern Africa, the Mediterranean, central Europe, and the Amazon (medium confidence). Livestock are projected to be adversely affected with rising temperatures, depending on the extent of changes in feed quality, spread of diseases, and water resource availability (high confidence).
About 70% of the world's freshwater is used for irrigation, 20% for industry and 10% for residential, so it is clear that the future water stress will also impact crop yields. This is especially true in less developed countries where 90% of freshwater resources are used for agriculture. By 2050, agriculture will need to produce 60% more food globally, and 100% more in developing countries. These are stresses due to population growth not global warming. Crop Yields are also severely impacted by soil degradation which is not caused by global warming (but does worsen global warming). Increased population pressures make it likely that soil degradation will continue.
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