Better be prepared

Climate change can have serious effects on crops

Published: Saturday 15 October 2005

Better be prepared

-- The terms 'global warming' and 'climate change' have been the source of much dissension within the scientific community. Proponents of climate change argue that it will have cataclysmic impacts on crops and this in turn will affect large masses of people.

But there are some scientists who do dismiss climate change. Of course, some of them do so out of vested interests.

However, the arguments of a few skeptics certainly merit attention. These scientists dismiss climate change predictions, because they are based on simulation models. They contend that since, at present, we cannot accurately forecast the temporal or spatial vagaries of weather in a season, not much store should be laid on climate predictions, 100 years hence. They also argue that the magnitude of weather alterations forecast for the worst climate change scenario, occur even now, intra-seasonally or inter-seasonally. So, technology can be -- and is being --developed to help crops cope with such weather vagaries, they contend.

However, such skeptics miss out a crucial point: the current weather aberrations, they refer to, are limited to short durations, and the effects of one period of abnormal weather is often offset by another period of an opposing trend -- as in case of rainfall and temperature. However, when there is an overall increase in temperature, crop life is surely to get shortened. Similarly, increase or decrease in rainfall also affects crop life.

Beneficial or hazardous Then there are some scientists who argue that increase in co2 levels -- one of the causes of climate change -- has a fertilising effect on crops. But they ignore the fact that any increase in co2 will be accompanied by a rise in temperature, which will then shorten field-life of crops. It's estimated that a doubling of co2 will lead to a temperature increase of 3 c. There are also indications that rise in co2 levels will increase cloudiness, especially in the rabi (winter) season. This will be accompanied by a rise in night temperatures. This will surely be an agricultural hazard.

Overstating the problem? But climate change theories are not without flaws. Early flowering of tree species is often cited as evidence of climate change. However, one is not too sure if this due to increasing temperatures. It would be better to study flowering behaviour of plants with long gestation periods. Bamboo flowering in Assam could be an apt example. Similarly, absence of pre-monsoon and post-monsoon hail storms and reduction in thunderstorms -- another oft-cited climate change indicator -- could be due to growth of concrete jungles in place of vegetation. These vagaries could also be ascribed to the diminution of natural vegetation in rural areas, to make way for agricultural use.

The loss of some aquatic, terrestrial and avian species is often cited as evidence of climate change. But it's now well-known that surface runoff from rains often carries residues of agrochemicals along with it and leads to extinction of species. So, species extinction is not due to climate change but a result of human intervention.

Proponents of the climate change theory argue that increased mean air temperatures will increase water requirements of crops, and also increase evaporation. But they miss out a critical fact: increase in mean air temperatures will also increase the moisture holding capacity of the atmosphere. Moreover, increase in mean temperatures is unlikely to enhance evaporation because such rise would mainly be due to high night temperatures. Also, water losses due to transpiration will be less under an elevated co 2 regime -- the prime cause of increased mean temperatures.

Notwithstanding these flaws, it's better to be prepared for climate change. This will require agronomic measures such as change in sowing dates to ensure proper balance between vegetative and maturity periods of the crop. Crop rows should be tailored to ensure proper penetration of sun's rays. Mitigating climate change effects would also require help from genetic sciences. Crop varieties that can stand up to temperature vagaries have to be developed. In particular, leaves should ensure adequate penetration of sun's rays. Combating climate change will require efforts from many quarters. Are we prepared?

S Venkataraman is a retired director of the Indian Meterological Department

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