Background
As the global population continues to rise, food production will also need to increase. Unless existing agricultural land is made more productive, it is likely that increased food demand will lead to the clearing of more land for agriculture.
Satellite data indicates that there has been an increase in “global greening” since the 1980s. That suggests that large parts of the world’s agricultural land have become more productive, reducing the need for new cropland. While an earlier analysis, in 2016, claimed that the increased concentration of atmospheric CO2 was responsible for most of that productivity increase, a new study argues that land use management plays a larger role than previously thought.
Comment
There are seven regions of the world that display an increase in greening and six of them are located in major agricultural regions, suggesting that agricultural productivity has improved in those areas since 2000. The increased greening in China and India alone accounts for almost one-third of the global increase since 2000.
The greening is mainly caused by either an enlargement of forested areas, or an increase in the amount of cropland. Most of the greening in China is explained by the 42 per cent increase in forested area since 2000. China has launched a series of programmes in recent decades to conserve and expand forests, with the goal of reducing soil erosion and air pollution. At the same time, however, Chinese demand for forestry products has increased deforestation rates internationally and reduced the global effect of its domestic forestry policy.
The greening is mainly caused by either an enlargement of forested areas, or an increase in the amount of cropland. Most of the greening in China is explained by the 42 per cent increase in forested area since 2000. China has launched a series of programmes in recent decades to conserve and expand forests, with the goal of reducing soil erosion and air pollution. At the same time, however, Chinese demand for forestry products has increased deforestation rates internationally and reduced the global effect of its domestic forestry policy.
In India, most of the greening is caused by more efficient agricultural land management. In the period 2000 to 2017, cereal production increased by 26 per cent while the area under cultivation remained stable. China also increased cereal production by 43 per cent over those years, without significantly increasing the area under cultivation. The increased use of surface and groundwater irrigation, as well as heavy fertiliser use, explains most of the productivity gains achieved by those countries. It is unlikely that the current rates of fertiliser and water use can be sustained over the long term, which will necessitate the introduction of further efficiency measures.
While “CO2 fertilisation” does help plant growth, and some of the productivity gains in China and India can be attributed to it, there are limits to how helpful it will be in the long term. The effects of CO2 fertilisation are limited by the availability of nitrogen and the drawbacks from increasing the concentration of atmospheric CO2 are likely to outweigh any beneficial outcomes.
Rather than the effects of an increased concentration of CO2, the greening trend in major crop growing regions is most likely explained by the adoption of: quick-growing hybrid crops, multiple cropping, irrigation, fertiliser use, pest control, better quality seeds, farm mechanisation, credit availability and crop insurance programmes. It follows then, that further productivity gains are most likely to be achieved through the efficient use of water, fertiliser and new agricultural technology.