Climate change affecting crops
By Zhu Bao (China Daily)
Updated: 2004-05-24 10:18

Agricultural researchers are being called upon to put more efforts into research on the effects of high temperatures and pests in order to adapt Chinese farming to the warming climate and prevent food security crises.

Lin Erda, a senior researcher with the Agro-meteorological Institute under the Chinese Academy of Agricultural Sciences, made the appeal as a number of related policy-makers have not taken the issue seriously. As a result, little work has been done to address the adaptation of Chinese farming to the changing climate.

Global warming, according to Lin, has both positive and negative effects on farming, but there could be a more negative influence in the long run, which may lead to a food security crisis if no immediate efforts are made to confront these problems.

Research conducted by five Chinese and British scientists in 2001 and 2002 showed that higher carbon dioxide (CO2) levels in the atmosphere, which resulted from human activities, may increase the growth and yields of crops.

This is mainly through their effects on the crop's photosynthetic processes, since higher levels of CO2 mean that plants absorb more of it - a process known as CO2 fertilization.

However, higher temperatures generally decrease yields by speeding up a plant's development so that it matures sooner, thus reducing the period available to produce yields.

Higher temperatures often also exacerbate stress on water resources that are essential for crop growth, and warmer and wetter conditions also tend to affect the prevalence of pests, diseases and weeds.

Climate change enables crops to grow in places they are not currently grown and in different time periods than usual. It also reduces yields to below an economical threshold for the farmer.

Further, the high frequency of natural disasters like floods and droughts associated with climate change can make the situation even worse.

It has been estimated that by 2030, grain production in China might decrease by up to 10 per cent because of the change in temperatures. The output of the three major crops in China - rice, wheat and maize, all expect to see reductions.

The maize planted in North China is a summer variety, and the effects of higher temperatures combined with the resulting increase in evaporation and poor irrigation due to less rainfall are expected to shorten the growing period and thus reduce overall yields.

Climate change is also expected to have a more adverse impact on spring wheat than on winter wheat.

Spring wheat yields are likely to decrease by about 30 per cent, and winter wheat by about 14 per cent by 2080.

Lin stressed that policy-makers must have a long-term outlook, work must be done to further develop farming technology to cultivate high-temperature and pest-resistant crops, and develop water-conserving agricultural practices.

According to Lin, China started research on climate change in 1991, and has become a global leader in the research of climate change impacts and adaptation in the agriculture sector.

However, more needs to be done, and a national plan must be made to encourage research on new high-temperature and pest-resistant crop species, Lin said.

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