Fossil fuels for transport, industry and 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 changing land use by clearing of forests to grow grain and fodder.

The Intergovernmental Panel on Climate Change, the United Nations sponsored body to objectively guide global 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 nine billion by 2050, would increase the demand for food, and hence, demand for land to grow food. While forestland is being rapidly cleared to grow 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 write in the journal, Scientific Reports, “protein conserving plant alternatives to meat that rigorously satisfy key nutritional constraints while minimising cropland, nitrogen fertiliser and water use and greenhouse gas emissions.”

A first victim of clearing land for agriculture is forest cover, the allimportant resource that drains CO2 from the atmosphere. In the context of the degradation that is taking place in the Amazon basin, Carlos Nobre, a climate scientist at the University of São Paolo, has been 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 global 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, is eight 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 nine billion tonnes of greenhouse gas emissions against just seven 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 per cent of global methane emissions, a greenhouse gas that has a global warming effect 23 times greater than CO2, and 65 per cent 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 per cent 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 400-3,000 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 per cent of the world’s grain produce is used for feeding animals.

In sum, about 26 per cent of the world’s land is used for grazing livestock and another 33 per cent 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 per cent 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 eight 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.

Horse dung

The entry of the internal combustion engine and 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, 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 green house gases emitted may have been comparable with the CO2 from the motor car.

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 pasture land use while saving 35-50 per cent of their diet related needs for cropland, nitrogen, and green house gas emission, but increase their diet related irrigation needs by five-15 per cent,” the paper says. Despite higher water needs (for crops like rice against meat sources like poultry); the diet-shift has a clear advantage.

There would be cultural challenges in changing dietary habits and adapting to a 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.