Ozone Is Silently Killing Our Crops

You may not be aware that ozone can directly damage crops, particularly those with broad leaves. This effect is especially common in horticultural crops. Manoj Pandey, who has authored numerous science and health articles published on this platform, presents a compelling and urgent exploration of this critical issue. Here is his insightful article. 

Ozone Is Silently Killing Our Crops

Manoj Pandey

We all know that Ozone is found in abundance in an upper layer of the atmosphere - called the Ionosphere, and plays a crucial role in protecting us from the sun’s harmful ultraviolet rays. Without a sturdy Ozone layer, humans and other living beings would develop many deformities and even cancer. Environmentalists are worried that pollution has been hurting this layer so much that sometimes a hole forms in the layer, allowing the UV radiation to enter the earth.

However, when high levels of the same life-protecting Ozone gas are present on the surface of the earth (It is called surface Ozone or stratospheric Ozone), which too happens due to pollution, it can lead to a different set of problems for the health of humans, animals and plants.
 
Just to refresh our knowledge of elementary science, Ozone (formula: O3) is a gaseous substance in which three Oxygen atoms are joined together to form a molecule unlike Oxygen (O2), whose molecule comprises only two Oxygen atoms. The presence of a third Oxygen atom makes Ozone highly reactive. 

This reactive property of Ozone hurts living beings by disturbing their biological processes, even damaging the DNA. In plants, it also disturbs the mechanism of opening of small pores – called stomata - on their surface through which Oxygen and Carbon di-oxide gases move in and out. This, in turn, disturbs photosynthesis (or the process of making food by the green parts of plants). 

All such irregularities and disruptions result in less production of food and deterioration in the quality of the farm produce. 

Ozone causes direct injury to crops, especially those with broad leaves. This happens mostly with horticultural crops. 
In addition, Ozone enhances the susceptibility of crops to diseases and pests, and alters plants’ responses to other types of environmental stresses, such as drought. 

WHY RAKE UP A ROUTINE ISSUE?

You might be wondering what makes this matter topical, especially in relation to food crops, when pollution has, for years, become a part of our lives. 
The first trigger is a recent report by the Central Pollution Control Board (CPCB) that the Ozone levels in many cities have risen beyond safe levels. 
 
Industrial and vehicular pollution is primarily responsible for production of Ozone near the earth surface. This gas is produced when some of the volatile organic pollutants combine with Nitrogen Oxide (formula: NO) gas in the presence of sunlight. NO is generated in large amounts during the breakdown of nitrogenous compounds present in fuels used in industries and vehicle engines. (Some NO is also produced in natural chemical processes.) 

Yet another study has revealed that Uttar Pradesh, Maharashtra and Madhya Pradesh have a very high Ozone concentration in the surface air, especially during pre-summer and summer months.

An earlier study by the Centre for Science and Environment (CSE) had found that Ozone levels in India’s major cities were higher than the safe limits almost throughout the year.  The second concern arises from a recent study by IIT Khargpur, projecting sharp decline in foodgrain production due to high levels of surface Ozone in the Indo-Gangetic plains and the central region of the country. While the production of rice and maize might decline by six percent, that of wheat by a colossal 20 percent! 

This study validates earlier studies in which it was warned that high surface Ozone levels in some countries, including India, might lead to huge crop losses in these countries. One study says that, due to this, India has been losing crop yields worth millions of dollars every year. Some experts say that Ozone-led crop losses have silently been causing production shortfalls at regional and global levels. 

Add to this a third, and a fourth, reason: While the harms caused by pollution to human health get enough media attention, and people get concerned about their health and that of their dear ones, the harms to crops remain unsung. The irony is that while humans, even if only the rich ones, can move to safer places or safeguard their habitats from pollution, food crops grown in large areas cannot be moved or grown in closed spaces. (The same holds true for forests, but let us focus our attention on food crops in the present discussion.)
 
Besides, it has been found that surface Ozone pollution does not remain confined to cities but spreads to villages and distant farms. In fact, it is more likely to arise in farms because the environmental conditions there (such as high levels of humidity, solar heat, and sunlight) favour its formation out of the pollutants transported there by winds. 

It has also been reported that many new, high-yielding crop varieties are more susceptible to Ozone pollution as compared to older varieties. Experts argue that surface Ozone has been nullifying some of the gains of modern farming achieved due to new technologies and better farming practices. 

HOW CAN FARMERS OZONE-PROOF THEIR FOOD CROPS? 

Sadly, individual farmers do not have much choice. Since surface Ozone pollution cannot be confined to a small area (at least, not at present), common farmers are helpless against its onslaught. 

It has been documented that, globally, areas with high crop density are under increasing stress due to growing temperature and climate change, soil and water pollution and new strains of diseases and pests. Ozone stress adds to that burden, and often has a cause-effect relationship with other stresses. In India, wheat and rice crops are considered more stress-prone as compared to other crops. You can imagine the impact of this stress on the food production when you consider that these two crops constitute three-fourths of total quantity of foodgrain produced in India. 

Though specific studies on the harm to crops due to high Ozone concentration are available, agronomic practices that can reduce local Ozone formation, and crop management based on Ozone tolerance, are yet to be implemented on a large scale. In simple terms, we do not have the option of replacing Ozone-sensitive crops with those tolerant to it, and changing the way we cultivate our crops. In India, where there is massive resistance to crop substitution in view of deepening ground water levels, cropping models to adapt to high levels of surface Ozone will be extremely difficult to implement. 

One long-term solution could be the development of less Ozone-sensitive crop varieties. However, creation of new varieties with this trait while retaining high yield has a rather low probability of success. Genetic engineering might provide a solution but it would also take years to bring results.   

It would be meaningless to try to find solutions to the problem of surface Ozone for individual farmers or in isolation from other environmental factors. It is crucial to highlight the often-overlooked threat of surface Ozone not only in environmental and public health policies but also in agricultural strategies at national and global levels. 
In the meantime, both we and our crops will continue to inhale Ozone while our vehicles and chimneys emit pollutants.

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This article has been contributed by Manoj Pandy. He does not like to call himself rationalist but insists on scrutiny of apparent myths as well as what are supposed to be immutable scientific facts. Several of his previous articles can be seen under Vigyan and Swasthaya categories on this website.