The latest report of the IPCC recommends eating less meat for a cooler planet, says S.Ananthanarayanan.

Fossil fuels for transport, industry and for electricity are seen as the main cause of carbon emissions and global warming. Another cause of comparable increase in the CO2 in the air, and one more amenable to control, is the changing land use, the clearing of forests to grow grain and fodder.

The Intergovernmental Panel on Climate Change, the UN sponsored body to guide objectively the world's response to the climate challenge it faces, in a special report just published, has identified human diet as the driver for the accelerating loss of green cover across the earth. A review of the report, in the journal, Nature, quotes Hans-Otto Pörtner, an ecologist working with the UN as saying, “We don’t want to tell people what to eat, but it would indeed be beneficial, for both climate and human health, if people in many rich countries consumed less meat, and if politics would create appropriate incentives to that effect.”

The report underlines the conclusion that rising population, which is slated to grow to 9 billion by 2050, would increase the demand for food, and hence demand for land to grow food. While forestland is being rapidly cleared for cultivation, for grain for human consumption, it is important to note that a large part used is for growing grain to feed animals that are bred for their meat. This is clearly less than optimal, for the reason that weight for weight of nutrition, particularly protein, the animal source uses substantially more resources than vegetable sources.

And while it would be a challenge to get the world to bid farewell to meat, Gidon Eshel, Paul Stainier, Alon Shepon and Akshay Swaminathan, from Bard College, New York, Harvard College, Cambridge and Harvard University, Boston propose a way out. They have identified "protein conserving plant alternatives to meat that rigorously satisfy key nutritional constraints while minimizing cropland, nitrogen fertilizer and water use and greenhouse gas emissions," they write, in the journal, Scientific Reports.

A first victim of clearing land for agriculture is forest cover, the all-important resource that drains CO2 from the atmosphere. In the context of the degradation that is taking place in Amazon basin, Carlos Nobre, a climate scientist at the University of São Paolo is quoted to say, that this, over 30-50 years, would lead to 50 billion tonnes of carbon staying put in the atmosphere. The figure is alarming, in the context of the current annual, world output of CO2, from the generation of power, of some 35 billion tonnes. And the estimated reduction of emission, if all power generation were from nuclear sources, of 8 billion tonnes a year.

Agriculture alone is estimated to be responsible for 12-14 billion tonnes of CO2 every year. In comparison, is a report by the Food and Agriculture Organization, which says livestock production is responsible for some 9 billion tonnes of greenhouse gas emissions, against just 7 billion tonnes by the world's transport sector.

Apart from livestock using land for pasture and consuming agricultural production, ruminant animals are responsible for 37% of global methane emissions, a greenhouse gas that has a global warming effect 23 times greater than CO2, and 65% of global nitrous oxide emissions (mainly due to manure) which has 296 times the global warming potential of CO2. The, livestock in the US is said to produce 130 times the excrement of the world's human population. In addition, livestock accounts for 64% of ammonia emissions, which can lead to acid rain. Of all the farmed animals, of which there are 55 billion worldwide, beef is the most carbon-intensive, producing 34.6 kg of CO2 per kg of meat.

Apart from carbon emissions, meat production makes things worse by record water consumption. The water consumed in producing a kilogram of beef is about 15 tonnes, compared to 400-3000 kg for cereal crops. A vast proportion of land and water, and fuel and power resources are then used up in producing cheap meat – at the cost of cost of rice and wheat, and ecological consequences worldwide. It is ironic that while meat production thus makes it difficult to produce grain, around 40% of the world's grain produce is used for feeding animals.

In sum, about 26% of the world's land is used for grazing livestock and another 33% is used to grow the crops and grain to feed them. The demands of livestock have led to deforestation, soil erosion, other effects of overgrazing and the displacement of local communities. In the Amazon, 70% of previous rainforest land is now pasture, with feed crops occupying a good part of the rest.

The IPCC report notes that diet change, with eating less meat, in developed countries, could have a huge impact of containing the degradation of forests. As the picture would show, a complete shift from animal food would save 8 billion tonnes of CO2, a level that could otherwise be reached only if all the power generation in the world shifted to nuclear – a tall order.

Alternative meat

As a first step to finding replacement of meat in diets, the group writing in Scientific Reports analyse the nutritional value and the contribution to environment pollution of different kinds of vegetable- derived foods. Statistical analysis and studies for finding the optimum mix disclose that it is possible to match the nutrition content of a meat diet by vegetable foods and yet save significantly in the use of resources. " By replacing meat with the devised plant alternatives—dominated by soy, green pepper, squash, buckwheat, and asparagus—Americans can collectively eliminate pastureland use while saving 35–50% of their diet related needs for cropland, nitrogen, and green house gas emission, but increase their diet related irrigation needs by 5-15%," the paper says. Despite higher water needs (for crops like rice, against meat sources like poultry), the diet-shift has the clear advantage.

There would be cultural challenges in changing dietary habits and adapting to new cuisine. But the shift would represent a social engineering opportunity and a pathway that is within the individual's control. It would also be less dependent on the compulsions that influence corporates and governments, whose progress towards keeping global temperature rise below 1.5°C does not appear promising.

Horse dung
The entry of the internal combustion engine and the motor car, which replaced the horse-drawn carriage, is usually blamed for the rise in CO2 in the air. What is often not appreciated is that just before the motor car entered the scene, the cities of London and Paris faced a major problem because of horse dung that covered the streets. With rising population and prosperity, carriages would have multiplied and streets would have been choked with dung. The GHG emitted may have been comparable with the CO2 from the motor car!

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