Rising temperatures are sure to have a big impact on China’s grain output and food security over the next 20 to 50 years.
Climate changehas two main positive effects on grain output; northward migration of crops and less frost damage. By lifting average temperatures above 10°C for more of the year, climate warming has lengthened the growing season, and the biggest change is being felt in the middle latitudes of the North China Plain, a major region for wheat, maize and dry-rice farming.
Climate warming has already moved crop boundaries north to varying extents. Benefits are visible in Hebei, where a more northerly boundary for winter wheat planting has raised yields by roughly 25% in wheat growing areas and furthermore, rice farming has also moved north.
Warmer weather is also reducing frost damage to crops, and the area suitable for late-maturing crops will expand. However, it is not all good news. Extreme weather linked to climate change could cancel out the effect of increased yields, resulting in lower grain harvests.
When it comes to negative effects, drought is the prime culprit. Climate expert Zhang Cunjie has predicted that total precipitation in northern China will fall over the next 10 years. Although small localized increases may take place in some years, overall north China will remain dry. Meanwhile, south China will suffer crop damage from high temperatures and worsening summer droughts. Although the south enjoys plenty of precipitation, it is not evenly spread over the year, or geographically.
Moreover, in recent decades, China has suffered frequent regional floods due to heavy rainfall, though uncontrolled deforestation has also played a role, with consequent financial losses.
Widespread outbreaks of pests and diseases are another problem of warmer weather as it helps them survive, breed and spread. Agricultural pests and diseases currently affect 20 billion hectares of land each year and cut grain output by about 9%. Climate warming itself will also affect the growth and quality of crops. Without new, adaptive technologies, crops will grow faster, and will be lower quality, stripping away some of the positive effects of a longer growing season. For example if temperatures increase by 1°C, rice needs 2 weeks less to grow. One outcome, less tilling time, would mean fewer, smaller grains of rice, and a lower overall harvest. Wheat and corn would be similarly affected.
Several measures can be taken to counteract these problems. Technological improvements and crop strains that are more resistant to high temperatures, drought, floods, disease and pests are essential. More construction of agricultural infrastructure, and research and popularization of water-saving in agriculture are also needed.
Higher temperatures will mean that double cropping can be carried out further north, and wider application of double cropping will help increase rice harvests. The introduction of new crop varieties, and technological advances would result in more significant increases in national grain output. In a scenario of comprehensive adaptation to climate change, by 2020 China’s grain output will have increased by 28.6%. Growth will be seen in five grain-growing areas, with particularly large increases in the north and north-east, where grain harvests as a percentage of national totals will increase from 31.1% in the base year to 39.4%.
The gLawcal team
(Source: China Dialogue)