Piao et al. examined various climate change models extending to future projections of change, predicted future changes in water supply available, and how these components will effect agricultural production. China produces agriculture for 22% of the world population on only 11% of its arable land. Their main crops are rice, wheat and maize. Northern and Northeast China is dryer, while Southern China is wetter. Trends will vary from region to region. Precipitation trend will experience opposite trends from Northeast to South. Glaciers melting and changes in precipitation will each affect available runoff differently. These changes will be paired with projected increasing demand for water with industrial and agricultural growth. Without taking into account CO2 emmisions, overall crop production is projected to decrease. This decrease, however, will be countered with new agricultural practices and technologies. –Sky Martin
Piao, Shilong et al. 2010. The impacts of climate change on water resources
and agriculture in China. Nature 467, 43–51.
Since 1960, the climate of China has been increasing in temperature by about 0.04°C each winter and 0.01°C each summer. It is certain from models that a warming trend will occur, but uncertain whether it will increase in rate. Two models demonstrate an increase in summer warming which would increase evapo-transpiration and decrease water supplies.
Water supply is affected by both precipitation and glacier-melt. There is no general precipitation change for the country, but regional trends were found. The north and northeast have been declining in precipitation in summer and autumn with 12% lost from 1960. The South has had increasing precipitation in summer and winter. Predictions for future precipitation trends are highly uncertain. More drought and flood are predicted for Northwest China and the Lower Yangtze River and less for the northeast and the northwest of the Yangtze. One scenario predicts longer drought periods in the Northeast and less in the Northwest, while another predicts a decrease of drought in the northeast. Piao et al. suggest that more thorough studies on soil moisture and droughts in the twentieth century would help to formulate a more accurate prediction.
A decrease in glacier recovery of ice ever year is more certainly predicted than precipitation trends. This will cause more runoff in the spring and early summer, and less water in late summer for the first few decades, and result in an overall water loss of 10-67% by 2100. Runoff may peak around 2030–2050 from the reduction of ice, but will then decrease.
There are conflicting models that predict how yields will change over the next 40 years, extrapolated from data from the 1970s to 2000. Increase in temperature itself will benefit irrigated crops and hinder rain-fed crops. Rice will benefit from an expanded territory to be grown in. Temperature will also cause an increase in disease and pests’ terrain as well. Overall climate change and water shortages alone are predicted to reduce crop production by 2050: 4–14% less rice, 2–20% less wheat, and 0–23% less maize. This may be countered by the fertilization of increased CO2concentrations, but CO2 increase could be eliminated by the harms of increased ozone exposure.
Overall crop reduction due to climate change and water stress from diminished supplies and increased demand is projected for agriculture in China. It’s very uncertain how precipitation trends will affect future water supplies, but glaciers are more certainly predicted to shrink, eventually providing less water. Crop production overall will decrease, however, large technological advancements are being made and could continue to prevent or delay pressures of climate change and water shortage.