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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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 »

Diving deep into ocean data uncovers ‘missing heat’ treasure

A new ocean reanalysis called ORAS4, here showing the difference between September 2012 sea temperatures and the average for 1989-2009 (not part of the latest study), has helped show that extra heat trapped in the atmosphere by CO2 humans are emitting is buried in the deep ocean. Credit: ECMWF

A new ocean reanalysis called ORAS4, here showing the difference between September 2012 sea temperatures and the average for 1989-2009 (not part of the latest study), has helped show that extra heat trapped in the atmosphere by CO2 humans are emitting is buried in the deep ocean. Credit: ECMWF

A newly-made picture of ocean history has backed a theory that the missing piece of a climate puzzle at the edge of space lies deep in Earth’s waters. The puzzle comes because the amount of heat energy our planet has absorbed should have warmed it more than it seems to have done. But now, using an ocean reanalysis assembled from data gathered from many sources, UK and US researchers have shown especially strong recent warming in oceans below 700m. “We have found some energy buried at depths,” Kevin Trenberth from the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. “We also have a plausible explanation for it related to changes in winds.”

In 2010, Kevin went public over his worries about a budget that didn’t balance. But rather than money, that budget tallies heat energy from the Sun entering the top of the atmosphere against energy the Earth radiates back out into space. Satellite measurements show more energy coming in than leaving, which is what causes global warming. But Kevin noticed that existing measurements showed the world hadn’t warmed as much since 2003 as this budget would suggest.

With over nine-tenths of the surplus energy coming into the Earth going into the sea, the deep ocean has always looked the likeliest hiding place for the missing heat. However, temperature data from those depths is scarce, making the theory hard to prove. Yet, in the years since Kevin pointed out the problem, scientists have gathered some clues to back that explanation. For example, some used a model that includes the complex links between the atmosphere, land, oceans, and sea ice to run five simulations of the 21st century. They found warming slowdowns on the Earth’s surface similar to what has happened in the 2000s, with the heat going into the deep oceans. But even this just underlined the importance of using measurements to see the effect directly. Read the rest of this entry »

Cause vagueness hinders climate extinction action

Stony Brook University's John Wiens and Abigail Cahill were among a team who looked at what existing research said about how climate change causes extinctions. Credit: Stony Brook University

Stony Brook University’s John Wiens and Abigail Cahill were among a team who looked at what existing research said about how climate change causes extinctions. Credit: Stony Brook University

Though human-caused climate change is making organisms extinct, we know worryingly little about how it’s happening. That’s what John Wiens and PhD students from Stony Brook University in New York State found after looking at existing research into the subject.  Among 136 studies into our changing climate’s effects on life around the world, the 11-strong team found that just seven mentioned a direct – or proximate – cause of extinction. “Understanding the proximate causes of extinction from climate change should be an urgent priority for future research,” they write in a paper published on Wednesday. “For example, it is hard to imagine truly effective strategies for species conservation that ignore these proximate causes.”

Currently, the International Union for Conservation of Nature lists 20 species as extinct worldwide or extinct in the wild potentially because of climate change. And while John’s team found there typically isn’t strong evidence for these links, there is evidence that climate has pushed many other organisms into local extinction. But while climate is the ultimate, driving, force behind their downfall, there can be direct, or proximate, causes of extinction that are less obvious. That means looking beyond overheating and rainfall changes, to include issues like disease and food availability. Change in population of other species is another common proximate cause. That could include population increases of predators or competitors that are harmful to an organism, or declines in beneficial species like prey, pollinators, and hosts for parasites.

John became interested in such causes through his personal interest in biodiversity and climate change’s threat to it. Building on that, he led a class last year for PhD students at his university on whether and how species can adapt to such changes.  “As we read papers related to this topic, the students and I realized that it was not really clear what species would need to adapt to in order to survive in a changed climate,” he told me. “Initially, we assumed that they would need to evolve to not overheat.  But, as we read and thought more about the topic, we realized that the story was much more complicated.” Read the rest of this entry »

More bird flu over the horseshoe crabs’ nests?

Sandpipers, ruddy turnstones and red knot birds crowd Delaware Bay searching for horseshoe crab eggs. Credit: Paul Williams (Iron Ammonite)/Flickr

Sandpipers, ruddy turnstones and red knot birds crowd Delaware Bay searching for horseshoe crab eggs. Credit: Paul Williams (Iron Ammonite)/Flickr

Climate change could make bird flu even more common among birds at a US hotspot for the disease. That’s what mathematical models of bird flu levels in Delaware Bay developed by biologists Pej Rohani and Vicki Brown at the University of Michigan in Ann Arbor suggest. “We’re not suggesting that our findings necessarily indicate an increased risk to human health,” said Pej. “But every single pandemic influenza virus that has been studied has included gene segments from avian influenza viruses. So from that perspective, understanding avian influenza transmission in its natural reservoir is, in itself, very important.”

Bird flu levels in Delaware Bay are at least ten times as high any other site in the world watched by scientists. That’s thanks in large part to ruddy turnstones, birds that pause there each year as they migrate between South America and the Arctic. Once in the Arctic, ruddy turnstones who spend their winters in America can meet – and share diseases – with others spending winter all over the world. During their Delaware stop-off they feed on horseshoe crab eggs, but fisherman harvest the crabs for fishing bait, while development in the area destroys the crabs’ nesting sites. This has meant fewer eggs, and in turn fewer shorebirds.

Global warming adds an extra layer to the problems facing these birds, by changing when important natural events happen. For example, birds that migrate long distances have started to make their spring journeys earlier. That could mean that ruddy turnstones arrive in Delaware Bay before all the horseshoe crabs have laid their eggs. Faced with an even more limited food supply, the birds must pack together yet closer in hunting for those that are available, creating an ideal scenario for disease transmission. 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 »

Baking sands worsen leatherback turtle survival crisis

Baby leatherback turtles face many threats, and climate change looks set to add to them. Credit: Juanma Carillo/Flickr

Baby leatherback turtles face many threats, and climate change looks set to add to them. Credit: Juanma Carillo/Flickr

As the world warms in upcoming decades less than half the current number of Costa Rican leatherback turtles will succeed in their first, vital, journey from sandy nest to sea. That’s according to a team of US researchers who have closely monitored how regular climate fluctuations affect egg and hatchling survival. That’s allowed them to show a clear relationship that they can use to predict the turtles’ future prospects, explained James Spotila from Drexel University in Philadelphia, Pennsylvania. “With the projected warming that’s going to happen in this century, these eggs and hatchlings are going to have a serious problem,” Spotila told Simple Climate. “We’ll have to do some kind of mitigation to keep these animals alive.”

James, who is also chairman of the Leatherback Trust, has been studying nesting turtles, considered “critically endangered”, at Las Baulas Park in Costa Rica for 22 years. Over that time, he and his fellow scientists had noticed more hatchlings in some years than others, and wanted to know the cause. The close watch they keep on the turtles gave them the first clues that climate played a role. “We noted that as the season would progress, and got hotter and drier, you had a reduction in hatching success of the eggs,” James said.

To find a detailed link, the scientists focused on one important nesting area in the Las Baulas Park – Playa Grande – over 6 seasons, from 2004-2010. Over that time they tracked temperature and rainfall measurements recorded at a nearby airport. But the hardest part – much of which was done by James’ Drexel colleague Pilar Santidrian Tomillo – came after the nests hatched.

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