State of the Planet

News from the Columbia Climate School


Agriculture and its Discontents: Greenhouse Gas Emissions

monocultureIn 1943, Norman Borlaug began his research into new varieties of wheat that could feed the burgeoning population of Mexico.  Invited by the Mexican government and funded largely by international philanthropic organizations, Borlaug’s research began what we now refer to as the Green Revolution.

Over the next 13 years, Mexico became agriculturally self-sufficient, and in 1964 began exporting wheat for the world market.  In India, the Rockefeller Foundation spread Borlaug’s new varieties and technologies, pulling India from the brink of mass famine.  In the Philippines, new varieties of rice increased production from 3.7 to 7.7 million tons per year by 1976.

There is, however, another aspect of the Green Revolution. The Green Revolution enabled a worldwide standard of agricultural production that was modeled after what was already happening in industrialized nations. This model requires heavy irrigation, intensive inputs of chemical fertilizers and pesticides, and large-scale monocultures (single-crop farms), with accompanying hypoxic zones in the seas, increased deforestation, and an increase in greenhouse gas emissions.

The ability to produce so much more food, and the export of cheap grains all over the world meant that the way in which we eat began to change.  As poverty levels fell, and feed prices fell due to excess grain production (helped by state subsidies), more people began to have access to meat. Since 1967 we’ve seen meat demand in developing countries grow by roughly 5% per year, from 11 kg/capita to 24 kg/capita.  That’s expected to rise by 57% by 2020.

More cattle means more pasture and feed land, and we’ve seen agricultural lands grow significantly in the last few decades.  According to the IPCC, agricultural lands have grown from 4,562Mha since the 1960s to 5,023Mha in 2005, now covering 40 – 50% of the world’s surface. Not surprisingly, the majority of that growth happened in the developing world. The IPCC is projecting an additional 500Mha of land will be converted to agriculture by 2050, mostly in Latin America and Sub-Saharan Africa. Unfortunately, most of that converted land is carved out of our tropical rain forests.

clearcutWe’ve seen up to a quarter of the world’s forest loss happen in the last 30 years alone. Of course, not all of that deforestation is related to agriculture and the growth of the cattle industry. But Dr. Norman Myers, of Oxford University, estimated at an FAO conference that 5% of deforestation is due to cattle ranching, 19% to over-heavy logging, 22% to palm oil plantations (largely for biofuels!), and a whopping 54% to slash-and-burn farming, often attributed to soybean and corn production. While traditional slash-and-burn agriculture was largely small-scale subsistence farming, we’ve seen an increased trend towards large-scale, mechanized commodity food production. Dr. Ruth Defries, of Columbia University, noted that in her 2006 paper “Cropland Expansion Changes Deforestation Dynamics in the Southern Brazilian Amazon” (links to PDF).  The growth of agriculture is a driving force in deforestation, reducing our carbon sinks all over the world. Indeed, deforestation presently accounts for 12 – 15% of global carbon emissions.

But what of greenhouse gas emissions associated with cultivation? The IPCC concluded in 2005 that agriculture accounted for 10 – 12% of global anthropogenic emissions, not related to deforestation. While that perhaps doesn’t seem like a huge percentage, the nature of agriculture emissions paints a different picture.

The problem of agricultural GHG emissions isn’t just how much is being emitted, but rather how potent the gases are. The main emissions are CO2, N20, and CH4. CO2 emissions happen because things in the soil rot and decay, and through that process CO2 is released into the air. However, plants also absorb CO2 and return it to the soil. So, the total release of CO2 from cultivation is really only 1% of the total global CO2 emissions.

N20 and CH4 (nitrous oxide and methane) are different, however — because methane is about 20 times more powerful in trapping heat in the atmosphere than CO2, and methane is 310 times more powerful.

The release of N2O and CH4 are largely a result of how we conduct agriculture today. N2O emissions are largely the consequence of applying too much nitrogen — a fertilizer usually chemically produced and promoted on large scales during the Green Revolution — over large areas. Not only is N2O a major greenhouse gas, but excess nitrogen often finds its way into our streams and rivers, leading to extensive areas at the mouths of rivers where there is no oxygen, and is thus fatal for animals. One of the largest is in the Gulf of Mexico.

cattleCH4 — methane — on the other hand, is largely emitted because of our appetite for meat, and especially beef. Methane is released by cattle in the form of burps and flatulence, and the storage of their manures. Methane is also emitted as organic matter decays in oxygen-deprived places, like in an underwater environment. Because of this, the cultivation of submerged rice — a crop specifically targeted for expanded cultivation in the Green Revolution – also emits a significant amount of methane emissions.

And while agriculture produces a lot of these greenhouse gases through cultivation and ranching, we also need to consider the increased reliance on farm machinery to apply fertilizers and pesticides over such large scales, and to transport grain and food from local places to very distant ones. Thus, the emissions of agricultural vehicles and building design also contribute to global GHG emissions.

The issues we’re facing for the future are serious: with our world population expected to reach 9 billion by 2050, how can we feed those to come? How can we continue to increase our agricultural yields, while acknowledging and dealing with how many greenhouse gases are released into our atmosphere? How can we scale back deforestation while rising incomes around the world imply an increasing demand for meat and cheap feed for that cattle? How do we deal with the contributions of agricultural emissions to climate change when we know also that climate change is going to alter our agricultural landscape? In a word, how do we enable sustainable development?

Whatever our solutions might be, it is clear that we’ll need creative thinking to look forward and move ahead. What do you think could be done? Comments are open below!

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David B. Benson
David B. Benson
14 years ago

Eat less meat, especially beef.

todd marsh
todd marsh
14 years ago

your treatise re methane danger presence due to cattle is laughable -methane is a natural product –co2 as well–pls note ca carbonate formations in pristine areas co2 is everpresent within earth and was being emitted long before humans emerged. As to cattle, we had more manure and flatuence present due to wandering herds as populus as fleas. Recently a 40,000 yr old baby mammoth was discovered totally intact in norther siberia(NGC) in an area then sub tropical—this 200 miles from north pole. so warming and later ice age was going on–also recent proof of 20,000 yr old glacier in hudson valley which was 5200feet deep from canada to new york harbor and gouged out huson valley and due warming became what we know as New York now

14 years ago

[…] for a small percentage — around 10% — of the carbon emissions of agriculture.  As I’ve written before, agricultural emissions are also intimately tied to deforestation, cattle-raising, and industrial […]

14 years ago

GHG & Methane production are the biggest issues that mankind is facing within the 100yrs. With a huge population explosion predicted many of the 3rd world will ramp up rice production. Rice paddies are one the biggest CO2 emitters known to man. We are in trouble!!

Justin East
14 years ago

Large-scale, mechanized commodity food production has allowed us to feed a greater percentage of the world at the expense of the environment.

Now we need to get smarter & reverse negative environmental consequences without decreasing food production.

A fantastic economic opportunity for those that have the capital to participate.

A very informative post, Tristan. Thank you.

Joseph Conrad
14 years ago

“…and a whopping 54% to slash-and-burn farming, often attributed to soybean and corn production.”

We see it for over a month every year…Indonesian slack & burn artists light up and the smoke darkens the skies in Singapore & Malaysia.

george brisbane
13 years ago

Yep, Danny hit the nail on the head. Rice paddies are terrible for co2 emissions. Yet it doesnt seem to get much of a mention in the debates