Shrinking dairy’s carbon hoofprint

After 10,500 years of farming them, does climate change mean we humans must limit our reliance on cows, or just change how we treat them? Image copyright fishhawk, used via Flickr Creative Commons licence.

After 10,500 years of farming them, does climate change mean we humans must limit our reliance on cows, or just change how we treat them? Image copyright fishhawk, used via Flickr Creative Commons licence.

Whenever I come across cows here in the southwest of the UK, usually placidly munching on a mouthful of grass, they always seem too lovable to be villains. But as we face growing twin challenges of feeding the world and fighting climate change, they’re increasingly getting a bad reputation.

Some scientists highlight reducing how much beef we eat, in particular, as an important step towards future sustainability. They say only about three or four parts in 100 of the energy in livestock feed becomes our food, while the rest is lost as manure, heat, digestive gases and slaughter by-products. Switching to more intensively farmed chicken or pork and plant-based food would be more efficient, the argument goes. It also gives a greater chance to trap carbon from waste material, which might otherwise become planet-warming greenhouse gases, as biochar that can help improve soil fertility.

A couple of years back I put this to Peter and Henri Greig who run my favourite local butchers, Pipers Farm. As they showed us round their farm Peter explained how their Red Ruby cattle can graze Devon moorland that can’t be used for crops, before moving on to pasture. While I still don’t eat a lot of beef for both environmental and health reasons, that seems a good reason for not demonising cows entirely. In fact, a paper in the June 2014 issue of the Journal of Dairy Science highlights previous research that found more grazing land exists, unusable for human food, than cropping land.

We can’t ignore what that promises for feeding the world in the future, but we can’t ignore cows’ greenhouse gas emissions either. However, rather than beef cattle, the new paper’s authors focussed on reducing levels of the potent greenhouse gas methane coming out of the digestive systems of dairy cattle. Joanne Knapp, a consultant who has researched nutrition in ruminant animals like cattle, told me her team’s interest comes in part thanks to its backers: Innovation Center for US Dairy.

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If we pass safe climate limits, it’s a long way back

University of Victoria's Andrew MacDougall in Canada's Kluane National Park Credit: Nicolas Roux

University of Victoria’s Andrew MacDougall in Canada’s Kluane National Park Credit: Nicolas Roux

If CO2 levels in the air pass the ‘safe’ limit, we’d have to take out up to four-fifths more than we originally emitted to get back under it. That’s the result from seemingly the first study to look at climate change’s reversibility with plausible scenarios, done by Andrew MacDougall from the University of Victoria (UVic), Canada. “With monumental effort and political will climate change is reversible within the millennium,” Andrew told me. “However, more carbon will need to be extracted from the atmosphere than was originally emitted to it. Meanwhile, changes in sea-level are effectively irreversible on the millennial time-scale.”

Andrew started looking at whether climate change could be undone in autumn 2012, after publishing a study showing that melting permafrost will speed up global warming. “The results were pretty grim,” Andrew said. “Combined with the failure of the political classes to implement controls on carbon emissions I began to wonder if there was a way to undo what humanity will do to the climate if we greatly exceeded the 450 parts per million (ppm) target.” That target comes because scientists say temperatures 2°C higher than the ‘pre-industrial’ average from 1850-1899 could become dangerous, and governments have agreed to keep warming below this level. Scientists also calculate that 450 CO2 molecules are allowable in every million air molecules to give us better than a 3/5 chance of temperature rises below 2°C.

After human emissions cease, current evidence suggests that natural processes would take tens of thousands of years to remove all of the fossil carbon from the atmosphere. Most of the warming will remain, even 10,000 years into the future. This sentence could be reduced by taking CO2 directly from the atmosphere, though this would be a huge effort, on the same scale as today’s fossil fuel industry according to one estimate. One method for doing that involves generating electricity by burning plants or trees that grew by absorbing CO2, and capturing and storing the CO2 from the burning. The other, known as air capture, uses machines to scrub CO2 right out of the air. However, this would need to be powered by clean energy and arguments over its cost are holding back research. Read the rest of this entry »

Speeding poor countries’ progress could halve farming emission growth

Improving agricultural productivity - particularly without increasing fertiliser use - could help cut greenhouse gas emissions from agriculture. Credit: IIASA

Improving agricultural productivity – particularly without increasing fertiliser use – could help cut greenhouse gas emissions from agriculture. Credit: IIASA

If the world’s poorer countries progress faster towards farming like richer ones the improved food availability could help fight climate change. That’s according to Austrian and Australian scientists who say that they have looked at climate change’s links to both animal and crop farming in the most depth yet.

Hugo Valin from the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria, and his colleagues studied cutting the gaps between farming output in rich and poor countries. They say halving this ‘yield gap’ for crops, and reducing it by a quarter for animals, could halve the increase in worldwide greenhouse gas emissions from farming between 2000 and 2050. But they have also found that improved farming methods could raise how much food people eat, meaning that emission reductions aren’t as much as they would be otherwise.

“The widespread idea is that intensifying crop farming is beneficial to the environment because it spares land,” Hugo told me. “We show that it is more complex than this. Intensification also stimulates consumption because it allows farmers to supply more food at affordable prices.”

Farming produces about a third of all ‘man-made’ greenhouse gas emissions, though a lot of them are actually from farm animals’ belches and farts and manure. The rest come from chemical reactions of fertiliser used on crops in soil, and also gases released from soil, plants and trees when forests are converted into farmland. Four-fifths of these emissions happen in developing countries. The world’s population is set to grow from around 7 billion people today to between 8.3 and 10.9 billion by 2050. We need more food for those extra people, which will add to the greenhouse gases farming puts into the air each year. Read the rest of this entry »

Developed countries duck warming responsibility

Beijing Normal University's John Moore, Xuefeng Cui and their collegues assessed the relative impact on future warming if developed and developing countries follow the pledges to cut CO2 emissions they made at the UN climate change conference in Cancún, Mexico, in November 2010, shown here. Credit: UNclimatechange/Flickr

Beijing Normal University’s John Moore, Xuefeng Cui and their collegues assessed the relative impact on future warming if developed and developing countries follow the pledges to cut CO2 emissions they made at the UN climate change conference in Cancún, Mexico, in November 2010, shown here. Credit: UNclimatechange/Flickr

Disputes between leaders of rich and poor countries currently mean little comes from meetings where they’re meant to draw up plans to slow and stop climate change. But developed countries’ existing promises would achieve just 1/3 of any warming slowdown, even though we’re responsible for more than 2/3 of CO2 emissions before 2005. That’s according to a team of mainly Chinese researchers who have tried to settle these fights using “earth system” models, considering both natural and human factors. “Developed countries need to take more responsibility in climate mitigation by cutting more carbon emissions and helping developing countries to control carbon emission while maintaining economic development,” said Xuefeng Cui from Beijing Normal University (BNU).

At the United Nations’ Climate Change Conference in Cancún, Mexico, in November 2010, leaders agreed to try and limit the global temperature rise to 2°C higher than pre-industrial levels. They also agreed that doing this needs deep, but fair, cuts in the amount of warming-causing greenhouse gases humans emit. But they still argue about how to share those cuts. That prompted Cui and his team to make an unusual effort to use science to show what is fair.  “The arguments in the IPCC process demand some fact-based reasoning rather than just the ‘blame game’,” team member John Moore told Simple Climate. “Our study is the first interdisciplinary study by climate, social, economic, and ecological scientists and policy makers to look at the historical responsibilities and effect of future mitigation by applying state-of-art earth system models,” Xuefeng added.

Getting such a broad view meant that the team had to develop entirely new methods for their research, published online in the scientific journal Proceedings of the National Academy of Sciences of the USA on Monday. “Most scientists are interested in the real impacts rather than assigning responsibilities,” Moore said. “These are more abstract philosophical and moral points than they tend to consider.” It took a 37-strong team of scientists to develop the approach, and one of the two earth systems models, they used. Whole earth system models are needed to understand the effects plants, animals, land and oceans have on climate. Read the rest of this entry »

Beefing down farming could cut carbon

University of Exeter's Tom Powell. Credit: University of Exeter

University of Exeter’s Tom Powell. Credit: University of Exeter

If people like me in the developed world eat less steak, it could free up room for plants to reduce CO2 levels in the air driving climate change. That’s one forecast that has come from Tom Powell and Tim Lenton at the University of Exeter, who have studied how much space we’ll need for food in the future. “The impact on the environment of trying to produce the food demanded by the world’s population in the future could be disastrous, unless we make the production system much more efficient,” Tom told Simple Climate. “By far the easiest way to do this would be to cut meat eating, especially beef. Meat is likely to get more expensive as the resources needed to produce it become limited, and its environmental impact grows. Small changes to our diets and the ways we produce food have the potential to make what is currently a very environmentally damaging system a much more positive one.”

When we’re buying food, its climate impact may not be immediately obvious. But plants use the sun’s energy to take CO2 out of the atmosphere as they grow, storing that energy and CO2 in their bodies for a comparatively short time. “We can’t escape the links between our energy use, whether it’s for diet, industry or transport, and the carbon cycle,” Tom underlined. “Unfortunately, the carbon cycle also controls a sort of global thermostat, with the amount in the atmosphere as CO2 or methane influencing the climate.”

Tim and Tom noted that as the number of us on the planet grows, and we get wealthier, we are demanding more energy, both as food and fuel. “This is having damaging effects on ecosystems, and even on the world’s climate as the population grows toward 9.5 billion people all aspiring to a western lifestyle,” Tom underlined. As people get richer they also eat more meat – but meat production is hugely inefficient. Only about three or four parts in 100 of the feed energy livestock eat becomes food, with the rest lost as manure, heat, methane and slaughter by-products. Today, meat consumption provides one-sixth of the energy people across the world get from their food on average. However, people in rich countries eat much more meat, getting almost one third of their energy from it. Read the rest of this entry »

Complete organic crop switch would raise UK emissions

Ploughing up pasture land for use to grow vegetables releases organic carbon as greenhouse gases. Credit: Andrew Stawarz/Flickr

Ploughing up pasture land for use to grow vegetables releases organic carbon as greenhouse gases. Credit: Andrew Stawarz/Flickr

Succeeding in the struggle to feed the increasing number of people in the world could hinder the fight against climate change if we relied on organic crop farming alone. That’s because it produces less food compared to the same area farmed using more usual methods, a team of British scientists said last week.

“Widescale adoption of organic crop production in the UK is always likely to require conversion of pasture to arable land,” agricultural consultant Rob Carlton told Simple Climate. Pasture land that livestock graze on contains more soil organic carbon than arable land, and changing over can release almost two tonnes of carbon per hectare each year. Thanks to those emissions, growing the same amount of crops in the UK with organic methods as existing farming does would produce the equivalent of three times as much CO2. But using aspects of the “environmentally-friendly” organic methods and more usual ones together might actually reduce such greenhouse gas emissions and help meet targets to slow global warming.

How we humans feed ourselves is an easy-to-overlook source of greenhouse gases that warm the planet. However in the UK it produces almost one-tenth of our emissions, Rob explained. “The UK is aiming for an 80 per cent reduction on 1990 greenhouse gas emissions by 2050 and a proportion of these cuts should come from the agricultural sector,” he said. “Globally agriculture accounts for over 14 per cent of greenhouse gas emissions, rising to 26 per cent when forestry and land use change are included. However, the need for emissions reductions should be viewed against demands on agriculture which are increasing as the population and consumption increases and farmers diversify into industrial and fuel crops.” Read the rest of this entry »

Thick ice decline could advance watery Arctic summers

NASA's shipborne ICESCAPE mission cuts a path through multiyear Arctic ice last year. This thicker form of ice is declining fastest, NASA's Joey Comiso has shown in a separate study. Credit: NASA/Kathryn Hansen

NASA's shipborne ICESCAPE mission cuts a path through multiyear Arctic ice last year. This thicker form of ice is declining fastest, NASA's Joey Comiso has shown in a separate study. Credit: NASA/Kathryn Hansen

The oldest and thickest ice in the Arctic is vanishing the fastest, data studied by NASA scientist Joey Comiso and published last month have shown. “This is alarming since it is usually the thick component that would survive the long summer melt period,” Joey told Simple Climate. “Since the thick component is declining more rapidly, the Arctic summer ice cover is more vulnerable to further decline. Assuming that the surface temperature continues to warm up as it has in the last several decades, this makes it more likely that we will have very little or no sea ice cover in the summer sooner than we previously expected.” And when the Arctic is ice-free in summer, dramatic environmental changes could follow that would speed warming further and limit the supply of fish for food.

Having long studied Arctic sea ice cover, Joey previously showed that 2007’s record smallest summer area was around one quarter smaller than the previous minimum in 2005. That “has been regarded as the event that could trigger an irreversible change in the Arctic sea ice cover”, Joey wrote in this latest research paper in the Journal of Climate. But after that low the area of thickest ice that can survive the summer melts, known as perennial ice, recovered slightly before dipping again this winter.

Intrigued by that recovery, Joey wanted to understand it. He therefore turned to data collected by tools called microwave radiometers that have been flying over the Arctic on satellites since 1979. These can collect information on the ability of different objects to emit microwave energy, or their microwave emissivity. Salt content, or salinity, influences this emissivity. As sea ice is initially around one-third as saline as sea water, microwave emissivity can be used to tell one from the other. It can also separate multiyear ice, which has survived at least two summer melt seasons, from thinner second year ice that has only survived one summer. Read the rest of this entry »