Rice cultivation suffering from climate change

Researchers at the University of Stuttgart-Hohenheim, Germany, believe that progressive climate change is threatening rice cultivation. More frequent drought periods restricting the large amounts of water the plant needs and rising sea levels are impacting on harvests. Nevertheless, Professor Folkard Asch, an expert on rice at the university, maintains that rice cultivation cannot be restricted, since rice is a staple food for around half the world’s population.

While rice cultivation contributes to global warming by emitting considerable amounts of methane gas, one must not forget that the rice farmers are first and foremost victims of climate change, Asch stresses. He warns that sea-level rise is a particularly serious problem and adds that saltwater can penetrate the fields, especially in the regions close to the coast. Rice plants are then under considerable stress, resulting in harvest losses and even fields that are no longer of any use.

Ash warns that in addition, increasing aridity in other regions is causing a greater requirement for irrigation. “The farmers in the upstream areas take more water from the river, which lowers its water level and renders that of the river delta insufficient,” he explains. “This already presents problems in the Mekong Delta. This is why we need more water-saving cultivation methods, for example with a seasonal draining of the fields.”

Growing rice at higher altitudes is not a solution

Elsewhere, global warming can also prove beneficial to rice cultivation, and today, the plant can be grown at altitudes of above 1,800 metres as well, Asch explains. Numerous countries with higher-lying regions in Africa and America, such as Madagascar, Rwanda, Peru or Bolivia could take advantage of this, although rice varieties, stock-keeping and irrigation would have to be correspondingly adapted, he stresses. However, Asch does not believe that the new cultivation areas could make up for the failed harvests in other regions.

Methane escaping from rice paddies

Of course the rice farmers themselves could also contribute to slowing down global warming themselves, although Asch maintains that their potential is comparatively limited. It is a fact that up to 25 per cent of world-wide methane production can be traced back to wet rice agriculture. However, he points out that in many regions of the world that are permanently flooded, there is no alternative to growing rice, which is an aquatic plant, as a staple food. “Large areas of Africa and Asia are only suited to grow rice. And just like moors or marshland, even without rice cultivation, they would still emit methane,” says Asch.

Cultivation systems involving only seasonal flooding present a slightly different picture. “Here, it is easier to integrate dry phases that alter the aeration state of the soil, thus limiting the formation of methane,” Asch explains. Intensive efforts to disseminate such methods have already been in progress for years.

(Universität Hohenheim/wi)