Science in Society Archive

Industrial Agriculture and Global Warming

Peter Saunders European Parliament Briefing, 20.10.04

We all imagine farming as being very different from industry. One consists of pastures green and fields of golden corn, the other of dark satanic mills belching smoke into the sky. But farming is becoming industrialised. In developed countries, and more and more in the third world as well, traditional agriculture is being replaced by new methods that require large inputs of fertilisers, herbicides and pesticides, that depend on large scale irrigation, and that consume large quantities of fuel both in growing the food and in delivering it to consumers who may be thousands of miles away.

Now we can't go on like this, for at least two reasons. First, the world's supply of oil is drying up. It's obviously hard to say exactly how long it will last, but estimates from experts including British Petroleum and OPEC suggest between 25 and 50 years. More oil fields may be found, or we may get better at extracting it from existing fields, but that's the scale of the problem. And we can't assume that the third world will continue to use so much less than we do.

Even if we find more oil, there remains the problem of global warming. As I'm sure you know, there is now a consensus among almost all the experts in the field that over the 21 st century the mean temperature of the Earth will rise by no less than 2 C and possibly as much as 5.8 C.

And as the models are improved, that top figure itself is being revised upwards. The Hadley Centre in the UK now estimates that the rise might be as much as 8 C, and the difference is that they have been taking into account the effect of changes in vegetation, both through the destruction of the rain forests (with the accompanying release of carbon into the atmosphere) and through changes in vegetation caused by the global warming itself.

That last is very important, by the way, because it's an example of what is known in control theory as positive feedback. A rise in the Earth's temperature leads to a change in vegetation, for example the loss of rain forests that hold water and carbon. This leads to a rise in temperature, which changes the vegetation even further, and so on. You might ask where this ends, and the answer is that nobody knows. But the US National Research Council was sufficiently concerned that they commissioned a Committee on Abrupt Climate Change, and their report, published a couple of years ago, is not reassuring.

There have certainly been abrupt climate changes in the past. At the end of a period called the Younger Dryas, about 11,500 years ago, there was a sudden rise in temperature over most of the Earth. The only really accurate data we have are from ice cores in Greenland, and there the temperature went up by 8 C in a decade. That's right – a decade, not a century.

And if you think a bit of global warming might be nice for those of us who live in Northern Europe, I'd just remind you that one expected consequence would be the switching off of the Gulf Stream, which is what keeps us as warm as we are. The reason is that if the Arctic and Greenland ice sheets melt, the surface water in the North Atlantic would become less salty and wouldn't sink as it cools, making it like the North Pacific where there is no similar warming current. The ice sheets are melting and the North Atlantic is becoming less salty, so there's another warning.

The Intergovernmental Panel on Climate Change says we can expect a considerable increase in heat waves, storms, floods, and the spread of tropical diseases into temperate areas. It also predicts a rise in sea levels up to eighty-eight centimetres this century, which will affect (by seawater intrusion into the soils underlying croplands and by temporary and also permanent flooding) something like 30% of the world's agricultural lands. Things are getting serious.

Agriculture inevitably makes a contribution to greenhouse gases, as does just about every human activity. You and I breathe out carbon dioxide all the time. But the effect of modern industrial agriculture is very much greater. Currently it is responsible for 25% of the world's carbon dioxide emissions, 60% of methane gas emissions and 80% of nitrous oxide. It's going to be hard to get fossil fuel consumption down, and agriculture has an important contribution to make which need not compromise our food supply.

The most energy-intensive components of modern industrial agriculture are the production of nitrogen fertiliser, farm machinery and pumped irrigation. They account for more than 90% of the total direct and indirect energy used in agriculture and are essential to it. It has been estimated that to produce a tonne of cereals or vegetables by means of modern agriculture requires 6 to 10 times more energy than by using sustainable agricultural methods.

Through the action of denitrifying soil bacteria, land conversion is leading to the release of around half a million tonnes a year of nitrogen in the form of nitrous oxide. Nitrous oxide is up to 300 times more potent than carbon dioxide as a greenhouse gas, though fortunately atmospheric concentrations of nitrous oxide are currently less than one-thousandth that of carbon dioxide. Around 70 million tonnes a year of nitrogen are now applied to crops, contributing as much as 10% of the total annual nitrous oxide emissions of 22 million tonnes. With fertiliser applications increasing substantially, especially in developing countries, nitrous oxide emissions from agriculture could double over the next 30 years.

The growth of agriculture is also leading to increasing emissions of methane. We are raising far more cattle, often on land which was once covered with forests, and we are feeding them on a high protein diet, which makes them emit even more methane than do grass-fed cattle. Even the fertilisation of grasslands with nitrogen fertilisers can both decrease methane uptake by soil bacteria and increase nitrous oxide production, thereby increasing atmospheric concentrations of both these gases . The expansion of rice paddies has also seriously increased methane emissions. Rain-fed rice produces far less methane than inundated rice fertilised with nitrogen fertiliser.

We are now encountering diminishing returns on fertilisers. The Food and Agricultural Organisation of the United Nations (FAO) admitted in 1997 that wheat yields in both Mexico and the USA had shown no increase in 13 years. In 1999, global wheat production actually fell for the second consecutive year to about 589 million tons, down 2% from 1998. Overuse of fertilisers also renders the soil less fertile in the long run, so that fertilisers become less effective.

Pesticides too are becoming less effective. Weeds, fungi, insects and other potential pests are amazingly adaptable. Five hundred species of insects have already developed genetic resistance to pesticides, as have 150 plant diseases, 133 kinds of weeds and 70 species of fungus. The reaction today is to apply ever more powerful and more expensive poisons, but this is inevitably a losing battle.

Nor is the answer genetic modification, which we are constantly being told has the potential to transform agriculture. Mind you, the lobbyists always talk about the potential, not real accomplishments, and at least in the UK we are told that we need it not so we can have a secure food supply, but in case someone else gets in first and we fall behind in the agrochemical business.

Genetically modified crops, contrary to what we are told, do not increase yields. They require more inputs, including more herbicides, whose use they are supposed to reduce significantly . They lead to profits, but only for the manufacturers, not for the farmers and certainly not for the consumers.

And they pose dangers which have never been properly assessed, largely because the only organisations with the resources to assess them properly do not consider it to be in their interests to carry out the work. No one knows for sure what will be consequences of introducing, by a very crude technique, a specific gene (or rather a specific piece of DNA, which is not the same thing) into the genome of a very different creature. It's something we should certainly be trying to find out – but not by rushing transgenic crops into production and letting the genes loose in the environment.

The problems that GM solves are often merely consequences of industrial agriculture anyway. Let me give you one example. In Southeast Asia, where rice is the staple crop, they have been genetically modifying rice to be resistant to bacterial blight. On the face of it, that sounds like an advance. But while bacterial blight has been around for a long time, it's only recently become a serious problem. When you grow rice in the traditional way, in small paddy fields alongside other crops, and with each village growing a slightly different variety, you may get an occasional outbreak, but it won't spread. Industrial agriculture means you use large fields, you don't intercrop, and you grow a single variety of rice throughout a large region. Just the conditions in which bacterial blight and all sorts of other nasties can prosper.

What is more, they had trouble finding a variety of rice from which they could isolate the gene they wanted, so if bacterial blight becomes resistant, they'll be no further ahead, and the result could be disaster for the farmers and the people who depend on them.

We must not throw away the knowledge and experience that has been accumulated by millions of farmers over several thousand years. But we can go beyond what they have learned because we have modern science to help us. If only a fraction of the money being devoted to developing GM crops were spent on improving traditional methods, think how much progress we could make.

Why don't we? Well, first of all, we are. There is work being done and it is succeeding. Just to cite one example, it's been shown that you don't have to genetically modify sweet potatoes to make them pest resistant; you only have to adapt an intercropping system that's traditionally been used in parts of Africa. Naturally the GM lobby claimed it wouldn't work in South Africa, but it does.

But because that sort of research doesn't lead to patents, companies aren't going to do it. Even universities and government laboratories are less keen than they used to be on carrying out work that won't generate royalties for them. And, unusually, GM allows companies actually to own and control varieties, so there is a big incentive to do by GM what you might have done by other, less hazardous, means.

We are told that industrial agriculture is efficient, by which is meant that it produces crops for less money. Well, I don't know how the sums work out if you add in the hidden costs like degradation of land, pollution of rivers, and so on. But even if the claim is correct, think how the efficiency comes about. Industrial agriculture is less labour intensive, but it relies heavily on oil and oil products. Now just about everyone agrees we are going to run out of oil; the only question is when. I haven't heard anybody say there is a shortage of human beings on the planet. What sort of efficiency is it that arises by replacing a resource that we have lots of by one that is rapidly being exhausted?

Industrial agriculture contributes significantly to climate change and it depends on a resource that won't always be there. We have to move to a modern, low input, sustainable agriculture. And the proper role of science is to help us achieve this, not to make a fast buck for a few biotech companies.

Peter Saunders, King's College, London.

Article first published 20/10/04

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