Surinder Sud: Listen to the global warning

FARM VIEW

The damage caused by climate change can be mitigated through breeding new plant types.

Agriculture and climate change have a unique relationship. Each one affects the other and, in turn, also gets affected by its consequences. And, notably, the outcome is both positive and negative, though ultimately, the deleterious implications of climate change for agriculture far outweigh the small benefits that can accrue to it.

To talk about the positive aspect first, the green house effect caused by the increased concentration of carbon dioxide, an environment-unfriendly gas, has been found to enhance photosynthesis and promote plant growth. Experiments carried out to quantify the yield spurt due to the greenhouse effect had indicated even a 20-30 per cent rise in crop yield.

But the hopes generated by these findings are now waning. Recent large-scale experiments conducted in Japan and China on rice have shown that the positive impact on productivity was overestimated earlier and that the actual yield surge due to higher carbon dioxide concentrations may be only between 10 and 15 per cent. Reporting these findings at the recently held Second International Rice Congress in Delhi, the scientists also said that these gains tend to be offset or totally lost due to the harmful impact of the higher temperature caused by greenhouse gases. The rate of increase in photosynthesis has also been observed to taper off in the later stages of plant growth.

That apart, scientific opinion is also now veering around the belief that environmentalists have perhaps been too harsh in accusing paddy fields of contributing to the climate change by generating methane. It is now believed that the paddy fields, especially in the Asian region where this crop is predominantly grown, generate far less methane than was presumed earlier. Some reckon that the actual emission may be only one-third of what was projected earlier. This is because of the generally low carbon content of the soils due to continuous cropping over the decades, as also lower application of organic inputs. Of course, the nitrogenous fertilisers applied in the inundated paddy farms do emit nitrous oxide, another greenhouse gas held responsible for global warming.

However, on the whole, the potential hazards of global warming for agriculture are, indeed, dreadful. It has been observed that high temperature damages rice flowers by making them sterile, thus reducing grain formation and, hence, crop yield. Besides, heat also pushes up the water requirement of the rice crop by raising the rate of respiration of crop plants. This has obvious ecological repercussions.

What is worse "" which the basmati industry especially needs to note "" is that climate change will impair the quality of rice grains, especially its aroma. In other words, the typical flavour of the Indian basmati that sets it apart from other types of aromatic rice produced elsewhere might undergo a change for the worse if global warming continues unabated. Even the grain appearance may change.

Also worrisome from agriculture viewpoint is the changing profile, particularly positioning, of the ozone layer. As reported in the Rice Congress, indications point to growing ozone concentration near the earth's surface, especially in Asia, due to increasing use of fossil fuel-based energy. No doubt, the atmosphere's ozone layer is a boon as it protects living beings against the potential injurious impact of ultraviolet rays emitted by the sun, but this layer needs to remain high up in the sky and not close to the surface.

The increase in the surface level ozone content is deemed by plant scientists as air pollution because it has been found to adversely effect the earth's vegetative cover, including the cultivated crops. Studies in the US and Europe have confirmed the adverse effects of ozone on wheat and soyabean. Though the impact of higher ozone level on rice is believed to be relatively low, but nevertheless, it is not wholly absent. However, further studies are needed for a better understanding of this phenomenon. The Asian countries should, obviously, be more concerned over this as the need for feeding the growing population through higher rice production is much greater in this region than elsewhere.

Fortunately, there is still no need for despair over the ill-effects of climate change on agricultural production. For, it seems possible to mitigate the damage or even avert it through suitable changes in agronomic practices and by breeding new plant types and varieties that can withstand the consequences of changed climate. But action on this front brooks no delay.

sud@business-standard.com