The 1950s saw the birth of the first “Green Revolution”, with world agriculture’s move from tall- to short-stalk crop varieties and the use of pesticides, fertilisers and agricultural machinery. These changes allowed 19 developing countries to achieve food self-sufficiency. But since then, the global population has grown and pollution has worsened. The coming decades will see the world’s population increase from six to nine billion, and the achievements of the Green Revolution will be hard pressed to meet new food and environmental demands. As a result, the United Nation’s Food and Agricultural Organization has called for a new, second Green Revolution.
But what will the weapons of this new revolution be? How can it meet the challenges of increasing food production against a background of shrinking arable land and freshwater resources; the need to protect the environment and public health from the effects of fertilisers and pesticides; and the effects of climate change on agriculture? Scientists have turned to genetic engineering, aiming to transfer advantageous genes to crops and increase harvests. And the media has called it the greatest hope of the new Green Revolution.
Scientists are now able to transplant genes from other species into crops, creating entirely new species and even halving plant growth cycles. US firms Dupont and Monsanto, along with Europe’s Novartis and others, have made massive investments in gene technology research. Pioneer, a US company, has decoded three-quarters of the 80,000 genes in maize, and expects to complete the remaining quarter within five years. Monsanto is attempting to identify and patent 15% of the maize genome.
Support for genetic engineering in China is steadily increasing, and the use of genetically-modified crops to increase harvests has been welcomed by the country’s agricultural industry. China has given priority to the development of pest-resistant cotton, yellow dwarf disease resistant winter wheat, bacterial blight-resistant rice and pesticide-resistant rice; as well as developing brown-rot resistant potatoes and new strains of maize. The country is also committed to developing technology such as genetically-modified “super” pigs, cows and sheep, animal embryo transfers, animal gender-selection technology, genetically-engineered immunisations and bioreactors.
The long list of new technologies shows that for Chinese scientists, the new Green Revolution is about increasing productivity based on the contributions of molecular biology. But they ignore an equally – if not more important – contribution: that from ecology.
China produces 480 million tonnes of grain every year. Of this, 180 million tonnes are used for human consumption, and 120 million tonnes (25% of the total) becomes livestock fodder. Of this fodder, 100 million tonnes is used to feed pigs, China’s second largest consumer of grain after people. Grain production is not the issue therefore; the question is about our sources of meat and milk. A Green Revolution based on ecology should not focus on the production of grain, but of straw. It should use ecological principles to solve food and environmental problems, not polluting methods such as fertilisers and pesticides. The Green Revolution must use existing species to increase humanity’s food supply, rather than manipulating genes.
The ecological solution is not to raise grain production directly, but to utilise the 50% of China's crop weight that is currently discarded, which is mostly straw, and use it to produce more food, animal fodder and fertiliser. This will greatly increase the productivity of China’s land. The large quantities of organic fertiliser that can be produced as a by-product will increase the harvests from large quantities of low-quality and medium-quality land, indirectly increasing grain production.
China has 1.831 billion mu (around 1,221,000 square kilometres) of cultivatable land, of which 155 million mu (around 133, 000 square kilometres) are salt-affected and 1 billion mu (around 667, 000 square kilometres) is arid. Genetic engineering will not be enough to grow grain in these regions. At the same time, China produces 600 to 700 million tonnes of straw every year, which represents a fresh weight of 1.8 to 2.1 billion tonnes. This could feed 180 to 210 million tonnes of livestock, which would provide, at a conservative estimate, 72 to 84 million tonnes of meat. Assuming five portions of grain are equivalent to one portion of meat, China’s annual straw production generates the equivalent of a further 360 to 420 million tonnes of grain, a figure twice current production levels. Animals and microorganisms can convert the currently-unused straw to food and grain, something that no technology can currently do. Of course, we cannot use all of this straw, but with technological advances, using half of it would be entirely plausible. Currently, 73% of China’s straw is burnt, discarded or used in other low-efficiency ways, so there is certainly a lot of scope for its increased use.
We must also turn to China’s mobile fertiliser factories: the country’s cows and sheep. The average cow produces 25 kilograms of dung per day, and 50% of China’s straw production could feed from 360 to 420 million head of cattle: a total of 3.28 to 3.83 billion tonnes of dung per year. This entirely organic fertiliser would contain between 5.67 and 6.62 million tonnes of nitrogen, equivalent to between 28.35 and 33.10 million tonnes of ammonium sulphate. This approaches China’s total annual fertiliser production of 33.90 million tonnes, but unlike chemical fertilisers, the use of this organic fertiliser will not harm the soil or cause pollution. Tests I carried out at Shandong Agricultural University show that if the amount of organic matter in the soil is raised from 1% to 5%, the amount of fertiliser used can be cut in half and still increase productivity.
Processed straw will feed cattle and the dung will produce biogas. The sludge from biogas production can then be returned to the fields as organic fertiliser. China already has this technology, but its use is seasonal and decentralised. Straw production is difficult to centralise, and should be collected and used locally on a local level. There is already the technology to convert straw into fodder for cows and sheep.
Malnutrition is a major issue in developing countries, and meat is much more nutritious than grain. Using straw to produce meat, milk and fertilisers provides countries with necessary nutrition and organic fertiliser for their soil. All nations, particularly developing ones, should launch a new Green Revolution in which ecology plays a leading role, both solve food security issues and improve the environment.
Jiang Gaoming is a professor at the Chinese Academy of Sciences’ Institute of Botany. He is also vice secretary-general of the UNESCO China-MAB (Man and the Biosphere) Committee and a member of the UNESCO MAB Urban Group.