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.

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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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

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.

Climate limits room at the global dinner table

Reducing tillage used to prepare soil in farming can help reduce carbon emissions without also reducing crop yields. Credit: USDA Natural Resources Conservation Service

Part two of two

Another mid-winter feast has passed since I published the first part of this round-up of research linking food and global warming, its memory still pleasantly fresh in my mind. I’d hate to have to sacrifice any of it in the future. But what if I were forced to change or shrink my menu? You might not have to make these choices today, but scientists are helping farming adapt to a changing climate. They’re facing up to a big challenge: trying to reduce emissions, while maintaining food supplies.

As well as being affected by climate change, farming also produces some of the greenhouse gases that cause it – between one-tenth and one-third of the world’s emissions. Agricultural consultant Rob Carlton and his colleagues therefore looked at four different crop farming methods in March last year to see which would emit least greenhouse gas if the whole UK adopted it. The best approach was to dig up less left over plant material than conventional farming currently does, keeping more carbon trapped in the soil. This approach importantly produced the same amount of crops as conventional methods. That’s necessary, because converting pasture to arable land to make up crop shortfalls seen with other methods releases large amounts of greenhouse gas. “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,” Rob said.

Warming brings home the value of a meal

The 2012 Plant Hardiness Zone Map unveiled by the US Department of Agriculture this year shows average annual extreme minimum temperatures based on data from 1976-2005. In this version 2012 is modified to use the same colour code as 1990. Much of the US was one 5°F (2.8°C) half-zone colder in the 1990 Plant Hardiness Zone Map compared to the latest version. Credit: US Department of Agriculture/Friend of the Earth

Part one of two

Over the past few days I’ve been lucky enough to enjoy the kind of celebrations that would have been called feasting in the past. They’ve brought home how important food is as basic fuel, a source of pleasure and a reason for friends and family to get together. This year, that importance has drawn me increasingly to research into what climate change means for our food supply. What I’ve covered only begins to scrape the surface of the effects we can expect. However, these studies highlight how life could become yet harder for farmers, and what that could cost us all.

The warming world has already noticeably changed plant growing conditions, for example shifting the regions they are suited to grow in the US. In January, the US Department of Agriculture (USDA) redrew its map of planting zones to reflect warming seen since the 1990 version. Partly due to climate change, and partly due to new technology and better weather data, many places are now one 5°F (2.8°C) half-zone warmer. At around the same time, Chinese researchers found that the phases in the seasonal cycle of crop growth in their country had shifted between 1960 and 2008. Springtime events are now 6-15 days earlier and Autumn events 5-6 days later, they found.

Beefing down farming could cut carbon

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.

Climate cycles drive civil wars

A child in a rebel camp in the north-eastern Central African Republic, one of the countries where internal conflict has been shown to be twice as likely to occur during a year when the El Niño weather pattern occurs than in La Niña years. Credit: Pierre Holtz/UNICEF CAR/Flickr

Civil war is much more likely during the warmer phase of a global climate cycle, seemingly as political tensions get literally overheated. That’s according to researchers from Columbia University, New York, who say that conflicts within a single country are twice as likely to occur during warmer El Niño years as cooler La Niña years. This is the first indication that modern societies’ stability relates strongly to climate, though the scientists warn that their findings might not be applicable to human-caused climate change. However some of the more dramatic changes in climate and society during humanity’s history have successfully been tied together. Columbia’s Mark Cane says his team’s latest findings build on those results. “What it shows beyond any doubt is that even in this modern world, climate variations have an impact on the number of civil conflicts,” Cane said Tuesday. “It’s frankly difficult to see why that won’t carry over to a world that is disrupted by global warming.”

Previous studies on whether modern climate has influenced war found only weak links between temperature over long periods, while studies on year-to-year local changes have disagreed and been criticised for having too narrow a focus. Consequently, together with Solomon Hsiang and Kyle Meng, Cane turned to the El Niño-Southern Oscillation, or ENSO, that affects weather patterns where half the world’s people live. El Niño originates from around 1°C warming in the tropical Pacific every three to seven years, bringing hotter, drier weather to the tropics. That alternates with cooler La Niña phases that provide more tropical rain, but can dry out more northern areas, as in East Africa and the southwest US this year. Consequently, the Columbia scientists were working with changes between two states on a worldwide scale that happened relatively regularly. This comes close to the “ideal but impossible” experiment of studying two Earths with different climates, they write in top science journal Nature.

Climate rhythm shift brings early calving

The Chillingham cattle are said to be the only survivors of the wild herds which once roamed freely through the forests of Great Britain. Credit: Sarah Burthe

Climate change has caused more of the British wild cattle of Chillingham to be born in winter, when the chance they will survive to reach a year old is lowest. The cattle, which have lived on a 365 acre park since the 13^th century, show that climate’s influence on biological event timing could be greater than realised. “The proportion of births in winter was correlated with the timing of the start of the plant growing season in the previous spring, when winter born calves would have been conceived,” explained Sarah Burthe from the UK’s Centre for Ecology and Hydrology. “More calves were born in winter when the plant growing season started early in the previous spring. Although more births are happening now in the winter than they were 60 years ago, winter-born calves do not do very well relative to calves that are born during summer and are more likely to die before they reach the age of one.”

Though Burthe is currently getting up a 3.30am to study birds on the Isle of May in Scotland, the Chillingham cattle’s unique story made studying the recent climate’s impact on them less gruelling for her. As well as reputedly being the only survivors of wild herds that once roamed the land, thanks partly to the encouragement of Charles Darwin information has been collected about them since 1860. The data Burthe and her colleagues used runs back from the modern herd, which numbered 93 cattle in December, to the unusually cold winter of 1947, which only 13 cattle survived. “This study would not have been possible without the amazing data collected by the Chillingham wild cattle association since 1947,” she said.