The danger ‘laughing gas’ poses to the planet

The 2021 Nobel Prize for Physics recognising the research of three climatologists, Syukuro Manabe, Klaus Hasselmann and Giorgio Parisi has brought under sharp focus the threat of global warming. The Nobel Committee said that it was sending a message with its prize announcement just weeks before the CoP26 climate summit in Glasgow, Britain, as global warming sets off alarm bells around the world.

The International Panel for Climate Change has predicted dramatic changes in climate patterns in the current century and this will inevitably adversely affect food production. If one juxtaposes the global population increase with changes in ambient temperature, a grim scenario emerges. Current projections suggest that global temperature will rise by 1.8-4 degree Celsius even as the global population inches towards 10 billion.

While discussing anthropogenic global warming, one must take into account primarily carbon dioxide, the centrepiece of Manabe’s research at Princeton University, USA, occurring primarily because of industrial activities, including automobile exhaust. But more insidious is the emission of nitrous oxide, a gaseous product from urea hydrolysis, a chemical process when applied urea molecules react with soil moisture, which contributes to almost 35% global warming.

This gas, commonly known as “laughing gas” (Dinitrogen monoxide), is a byproduct of unbridled use of urea in ramping up both wheat and rice production. Dinitrogen monoxide is a major scavenger of stratospheric ozone leading to global warming and is 310 times more effective in its heat-trapping capacity compared to carbon dioxide. The average life span of this gas is 120 years. It is a serious environmental hazard that steep ramp-up of nitrous oxide in the stratosphere coincided with the green revolution of the 1960s. A consequence of the unbridled urea use is soil degradation and groundwater pollution due to high residues of nitrates which makes water non-potable.

Of the 328.43 million hectares of India’s geographical area, more than 120.40mha have degraded soils, mostly in Punjab, the “cradle” of the green revolution. When high food production is targeted through excessive use of N-fertilizers like urea, soil microbes convert N in the fertilizer urea into nitrous oxide at a faster rate than normal. This has been a major factor leading to global warming with all its attendant environmental consequences. The unseasonal rains (like what India experienced in September) is also an offshoot of this phenomenon.

Glasgow meet

The conference delegates, being totally silent on the havoc that carbon dioxide can do to enhance global warming, came forward to propose the “Global Methane Pledge” on November 2. In this context, one must understand what is methane (CH4 – 4 subscript please). There was consensus among the delegates that of the three principal “Green House Gases”(CHG) which can substantially contribute to global warming, the pecking order is as follows – carbon dioxide (CO2), nitrous oxide (N2O) and (CH4). The Global Methane Pledge is the single biggest pledge the US and European Union governments have made which is expected to limit global warming to 1.5 degree Celsius above the pre-industrial level.

In other words, both the US and EU nations, the two largest natural gas consumers, have agreed to cut the emission of methane, which could reduce global warming by just 0.2 degree Celsius by 2050. Why have they left out the insidious nitrous oxide? The answer is, the pressure of the fertilizer lobby, which propped up modern, highly chemical-centric farming, euphemistically called the “green revolution.”

Combating the ill effects of the green revolution: Food and food security is of paramount importance to life on earth and which is most threatened by global warming. Future food security will be dependent on a combination of the stresses, both biotic and abiotic, imposed by climate change, variability of weather within the crop-growing season, development of cultivars more suited to different ambient and soil-substrate conditions, intelligent soil management, with specific reference to nutrient (fertiliser) management, and the ability to develop effective adaptation strategies which allow these cultivars to express their genetic potential to the fullest, under changing climate conditions.

These may appear as challenges that may be impossible to address, because of the uncertainty in our ability to predict future climate changes. However, these challenges also provide us the opportunities to enhance our understanding of soil-plant-atmosphere interaction, and how one could utilise this knowledge to enable us to achieve the ultimate goal of enhanced food security across all areas of the globe. It is in this context that we must look at the possibility of utilising “Crop Wild Relatives”, which offers tremendous scope.

Those plant species which are very closely related to field crops, including their progenitors, have the potential to contribute beneficial traits for crop improvement, such as, resistance to an array of biotic and abiotic stresses, and to enrich the gene pool, leading ultimately to enhanced crop yield, thereby aiding humanity’s relentless search for the production of more food to meet the ever-growing needs of a burgeoning population are called “Crop Wild Relatives”. In fact, CWRs have tremendous potential to sustain and enhance global food security, thereby contributing enormously to humanity’s well-being. Therefore, their search, characterisation, and conservation in crop breeding programmes assume great importance.

The global concern over the potentially devastating impacts of climate change on biodiversity and food security, when juxtaposed with the burgeoning global population, implies immediate measures be taken to conserve CWRs and derive from them potentially usable genes to enhance crop yield. CWRs are a key tool to address the limits of genetic variation in domestic crops to adapt them to climate change. However, the extension of their conservation and promotion of more systematic exploitation is hindered by a lack of understanding of their current and potential value, their diversity and practically how they might be conserved and exploited- an important and very urgent task Indian agricultural research fraternity must immediately address.

(The writer is a former Professor, National Science Foundation, The Royal Society, Belgium & Senior Fellow, Alexander von Humboldt Research Foundation, Germany)