Could climate’s crop impact catch us with our plants down?

The odds that yields of maize will fall by a tenth over the next 20 years have shortened from 1-in-200 to 1-in-10. Image copyright Raman Sharma used via Flickr Creative Commons license.

The odds that yields of maize will fall by a tenth over the next 20 years have shortened from 1-in-200 to 1-in-10. Image copyright Raman Sharma, used via Flickr Creative Commons license.

With the next two decades set to see a stronger increase in demand for food than the rest of the 21st century, declining harvests would cause some serious problems. Right now crop yields are growing, but could climate trends cause them to fall by a tenth, say, over the next 10-20 years?

That’s the question David Lobell from Stanford University in California and Claudia Tebaldi from the US National Center for Atmospheric Research in Boulder, Colorado have tried to answer. They find that if the world wasn’t warming, the chance of yields decreasing by a tenth over the next 20 years would be less than 1-in-200. However, climate change has made shrinking yields more likely, shortening the odds to a 1-in-10 chance for maize and a 1-in-20 chance for wheat.

“It was surprising to see how likely it is nowadays for climate trends to significantly cut into yield progress,” David told me. “It is still more likely than not that climate will be a slight drag on progress instead of a major factor. But we can’t rule out a major slowdown, and that means we should probably think through that type of scenario to figure out how to prepare for it.”

Such near-future climate forecasts are unusual, David underlined. “Longer periods allow the signal of climate change to become clearer compared to natural variability,” he explained. “But it may simply be that most of the initial questions about climate change were about the long timescales, to decide about questions related to energy choices and emissions. Now, a lot of questions are related about how to properly adapt to the changes happening now.”

What will happen to crops is central to David’s interests as associate director of Stanford’s Center on Food Security and the Environment. “I often get asked by governments or the private sector if climate change will threaten food supply in the next couple of decades, as if it’s a simple yes or no answer,” the scientist revealed. “This was especially true of a committee I recently served on focused on social stresses from climate change in the near-term. The truth is that over a 10 or 20 year period, it depends largely on how fast things warm, and we can’t predict that very precisely. So the best we can do is put odds on things.” Read the rest of this entry »

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.

Read the rest of this entry »

IPCC: Millions of words on climate change are not enough

The latest IPCC report has highlighted that it's dead certain that the world has warmed, and that it's extremely likely that humans are the main cause. Credit: IPCC

The latest IPCC report has highlighted that it’s dead certain that the world has warmed, and that it’s extremely likely that humans are the main cause. Credit: IPCC

The most recent UN Intergovernmental Panel on Climate Change (IPCC) report saw perhaps the most severe conflict between scientists and politicians in the organisation’s existence. As its name suggests, governments take an active part in the IPCC process, whose latest main findings appeared between September 2013 and May 2014. Debate over what information makes the high-profile ‘Summaries for Policymakers’ is usually intense, but this time three graphs were dropped on politicians’ insistence. I show these graphs later in this blog entry.

At the Transformational Climate Science conference in my home town, Exeter, UK, earlier this month, senior IPCC author Ottmar Edenhofer discussed the ‘battle’ with governments on his part of the report. Another scientist who worked on the report highlighted confidentially to me how unusual the omission was.

To me, it’s more surprising that this hasn’t happened more often, especially when you look more closely at the latest report’s findings. There’s concrete certainty that warming is happening, and it’s extremely likely that humans are the dominant cause, it says. Governments have even – in some cases, begrudgingly – already signed up to temperature and CO2 emission targets reflecting this fact.

The inadequacy of those words is becoming ever more starkly obvious. Ottmar stressed that the emissions levels agreed at the United Nations’ Climate Change Conference in Cancún, Mexico, in November 2010, would likely need later emissions cuts the likes of which we’ve never seen before to avoid dangerous climate change. The latest IPCC report shines a floodlight on that inertia, which understandably cranks up the tension between researchers and politicians.

Ottmar was one of two co-chairs who led the ‘working group three’ (WGIII) section of the IPCC report that looks at how to cut greenhouse gas emissions. He stressed that the need to make these cuts comes from a fundamental difference between the risks that come from climate change and the risks of mitigation. We can heal economic damage arising from cutting emissions – reversing sea level rise isn’t so easy.

Read the rest of this entry »

Climate change-boosted disease could endanger China’s food supply

Wheat ear infected with Fusarium ear blight (FEB), giving the ear a pinkish color. The disease could be set to increase in countries like China and the UK with climate change, Bruce Fitt and his teammates have found, suggesting resistant varieties should be developed. Photo credit: CIMMYT.

Wheat ear infected with Fusarium ear blight (FEB), giving the ear a pinkish color. The disease could be set to increase in countries like China and the UK with climate change, Bruce Fitt and his teammates have found, suggesting resistant varieties should be developed. Photo credit: CIMMYT.

As the planet warms, China’s wheat crops will be threatened by more frequent epidemics of ‘fusarium ear blight’ (FEB), scientists in the UK and China have projected. Bruce Fitt from the University of Hertfordshire in Hatfield, UK, and his teammates forecast levels of the disease in the Anhui and Hubei provinces from 2021-2050. Whereas in the worst affected regions in 2001-2010 around one-sixth of all ears were infected, this was the lowest disease level the researchers found in their future scenario. In the worst-hit areas, FEB infected more than a third of all ears. “This has implications for crop breeding because it takes 10-15 years to breed a new cultivar,” Bruce told me. “If you know the disease is going to become more important then you need to get on and start breeding now rather than waiting until the disease hits you.”

Today, over a billion people don’t have enough to eat, and further population growth and climate change are set to put the world’s food supplies under even greater strain. To help ease that pressure, Bruce and other scientists are working to understand and help improve control of crop diseases like FEB. While some crop diseases will worsen in the future, not all will, he stressed. “For example, you might have a disease that is spread by rainsplash in summer and then it’s predicted that there will be far less rainfall in summer,” he explained. “Then you would expect that with climate change the importance of that disease would diminish.” If governments, farmers and seed suppliers know which diseases are likely to get worse, they can prioritise developing strategies to contol them, like breeding disease resistant varieties.

To make useful forecasts for which diseases will worsen, scientists build models that include weather data, how crops grow and how the disease pathogen spreads through the crop. “In this particular instance the wheat is susceptible only at flowering,” Bruce said. “It may be in flower for a few days. If it doesn’t get the pathogen inoculum and the right weather conditions at that time it will not get the disease.” Climate change can both alter flowering times and the chances of warm, wet weather that make infection more likely. When wheat gets infected, even if it can be harvested it is more likely to contain poisonous mycotoxins. “If it’s full of mycotoxins then it can’t be eaten by man or beast, so it’s just wasted,” Bruce added. Read the rest of this entry »

Weather extremes take twin crop and disease toll

Using MODIS data of red and infra-red emissions from the Earth's surface Assaf Anyamba and his colleagues can track conditions including temperature and levels of plant growth. In this shot the Normalized Difference Vegetation Index (NDVI) for southeast Australia from September to November 2010 shows that plants were thriving after a bout of extremely cool, wet weather. Image copyright: PLOSone, used via Creative Commons license, see reference below.

Using MODIS data of red and infra-red emissions from the Earth’s surface Assaf Anyamba and his colleagues can track conditions including temperature and levels of plant growth. In this shot the Normalized Difference Vegetation Index (NDVI) for southeast Australia from September to November 2010 shows that plants were thriving after a bout of extremely cool, wet weather. Image copyright: PLOSone, used via Creative Commons license, see reference below.

The wet and dry weather extremes the world felt between 2010 and 2012 caused wild variations in farm output and encouraged serious diseases spread by insects like mosquitoes. That’s according to scientists from NASA and the US Department of Agriculture (USDA) who studied severe droughts and rainfall that happened in six places during this period. Harvests in the four drought-stricken regions fell to as little as one-fifth of normal levels, but grew dramatically in the two rain-soaked areas, almost doubling in one case. But wet or dry, extreme conditions favoured certain species of mosquitoes (also known as vectors) that went on to cause outbreaks of illnesses like the potentially-fatal Rift Valley Fever. “Extreme weather events can have both negative and positive impacts,” observed NASA’s Assaf Anyamba. “For example eastern Australia and South Africa had bumper harvests of some crops but at the same time had outbreaks of vector-borne disease.”

Assaf and his coworkers help provide ways for the US government to closely monitor the whole world to see where droughts or wet periods might be happening. One way Assaf does this is with a pair of ‘eyes in the sky’ – NASA’s Terra and Aqua satellites. Each carries a Moderate Resolution Imaging Spectroradiometer, or MODIS, which precisely records the colours of the Earth’s atmosphere and surface, including those we can see and reaching far beyond. Scientists use the infra-red data it collects to track surface temperatures, while a combination of red and infra-red can tell them how leafy places are. From these, NASA makes this awesome ‘NDVI’ map of how well vegetated crop-growing regions across the world are, while the USDA includes them in monthly Rift Valley Fever risk reports.

While it’s important to know the impacts of extreme weather, not all countries are able to measure them. But from 2010 to 2012, the MODIS records captured the most intense set of weather they had recorded since Terra’s launch in 1999. The US, Russia, east Africa and southwest Australia endured droughts, and rain drenched South Africa and southeast Australia. Assaf and his team noticed that this weather was influencing both farming and disease in these cases, and decided to look at ‘the big picture’. “We wanted to showcase this connectedness as an example of the mixed bag of impacts anomalous weather conditions impose on society at large,” he explained. Read the rest of this entry »

The climate challenges that my morning toast poses

Britain's wheatfields could become even more productive as the world warms - but that will have implications for further greenhouse gas emissions and fairness to countries less well positioned. Image credit: Tim Gage used via Flickr Creative Commons license

Britain’s wheatfields could become even more productive as the world warms – but that will have implications for further greenhouse gas emissions and fairness to countries less well positioned. Image credit: Tim Gage used via Flickr Creative Commons license

It may seem that nothing could be simpler than toast, but next time I see a slice pop up I’ll also see an emblem of the world’s future. That’s thanks to a UK study exploring the problems surrounding growing enough wheat for flour and other foods as the world warms and has ever more people in it. The issue is especially tangled, Mirjam Röder and her University of Manchester teammates show, as adapting farming for the future will likely increase greenhouse gas emissions, driving further warming. “Climate change and food security are two issues which can’t be decoupled,” Mirjam told me. “The same applies for mitigation and adaptation.”

Mirjam is part of the “Climate change mitigation and adaptation in the UK food system” project, led by Alice Bows-Larkin and backed by Manchester’s Sustainable Consumption Institute. One concern the project reflects is that without adaptation farming will probably be the industry worst hit by climate change, with worldwide productivity falling as temperatures rise. Meanwhile, farming also releases about one-tenth of the greenhouse gases we humans emit overall. “These are largely emissions other than CO2, such as nitrous oxide and methane, mainly occurring from natural processes,” Mirjam said. “They are much harder to reduce and control. Then of course global society is challenged by increasing global food demand. So we face a triad of challenges in the food system: we need to reduce emissions, while food demand is increasing and the sector is impacted by climate change.”

Alice and Mirjam’s team looked at wheat because it makes up almost a third of all cereals grown in the world. “Global wheat demand is projected to increase by about 30% by 2050,” Mirjam. “If we don’t find methods to reduce them, total emissions from producing more wheat will rise.” As well as gases released directly by bacteria and other soil microorganisms, emissions from wheat farming arise from the energy needed to produce nitrogen fertiliser. Whether growing more wheat or dealing with rising temperatures, farmers will need more fertiliser, driving more emissions and therefore further warming. Read the rest of this entry »

Heat drives Pakistani migration

Shahdadpur, Sanghar district, Pakistan: Residents collecting their belongings on a higher ground outside village during floods. Though they may be displaced temporarily, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her team find high temperatures are more likely to drive permanent migration. Image credit: Oxfam International

Shahdadpur, Sanghar district, Pakistan: Residents collecting their belongings on a higher ground outside village during floods. Though they may be displaced temporarily, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her team find high temperatures are more likely to drive permanent migration. Image credit: Oxfam International

Excessive rainfall rarely drives Pakistanis to permanently leave their villages, even when it causes hardship like the flooding that hit around a fifth of the country in 2010. Yet they do consistently move in response to extreme temperatures, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her colleagues have found. She says the finding is a first stage in establishing if, how, and why people’s choices are affected by climate and climate change. “This is a useful step in order to be able to predict migration flows and inform local governments how might they better prepare in terms of the delivery of resources and investing in infrastructure given the occurrence of extreme weather events,” she told me.

There are few efforts collecting information about who has migrated and why over long periods of time, especially in areas where extreme weather occurs. But IFPRI has a long history of evaluating questions linked to food security in countries across the world, including Pakistan. From 1986-1991 its Pakistan Rural Household Survey questioned 800 households about how they lived and farmed, and it has tracked those households ever since. “Local collaborators found the original households in 2001 and 2012 and asked the head of household or an otherwise knowledgeable person what happened to each household member who resided with them in 1991,” Valerie said. “Our study is one of the first to quantify long-term migration patterns over a long period of time.”

The follow-ups recorded the long-term movements and fortunes of 4,428 people from 583 households. The researchers combined these answers with temperature and rainfall data in one ‘logit’ and one ‘multinomial logit’ model designed to let them measure the odds that people moved. “The first model allows us to answer: What are the odds of a person moving out of the household in response to extreme temperature or rainfall?” Valerie explained. “The second model allows us to distinguish moves by location and allows us to answer the following questions: What are the odds of a person moving out of the household but within the village in response to extreme temperature or rainfall? What are the odds of a person moving out of the household but out of the village in response to extreme temperature or rainfall?” Read the rest of this entry »

Fossil fuels are more than just a bad habit

The benefits fossil fuels bring make them probably the hardest addiction ever to kick. Credit: Don Hankins, via Flickr Creative Commons licence

The benefits fossil fuels bring make them probably the hardest addiction ever to kick. Credit: Don Hankins, via Flickr Creative Commons licence

I’m increasingly realising how much of a creature of habit I am. I have the same bizarre sticky brown yeast extract goo on toast for breakfast each morning. I watch films in my lounge most evenings. And I wonder: How much of my personality is just a collection of habits? What about yours, and all of ours? Could our whole society just be a giant collage of habits? And most relevant to this blog: how much of the human greenhouse gas emissions that are driving global warming come from our habits?

Recently, I’ve been keeping track of how long I spend doing things, which has been helping me swap what I think are bad habits for better ones. It’s tempting to suggest fighting climate change in a similar way. Many people talk about how we burn fossil fuels to propel our cars or run our gadgets as a bad habit, and even an addiction. But it’s more complicated than other addictions. Fossil fuels have been to our society more like food and a salary are to us individually – they’ve helped produce many of the healthiest aspects of the modern world. They’ve powered more than a century of rapid social and technological progress, and given many countries their current rich, well-fed figures.

For an article I’m writing about employment prospects in the UK’s chemical industry, I recently spotted the table below. It shows ‘gross value added’ (GVA), a measure of the money contributed to the economy, per person across the country’s different industries. It was striking to me that while bankers may get all the headlines for their wealth, the energy industry has the greatest earning power per head in the UK.

Oil and gas extraction help the "Mining and Quarry; Energy & water" sector make the largest contribution per head to the UK economy, as they employ relatively few people relative to their large economic output . Credit: Office for National Statistics

Oil and gas extraction help the “Mining and Quarry; Energy & water” sector make the largest contribution per head to the UK economy, as they employ relatively few people relative to their large economic output. The ‘total’ figure is the overall GVA for the UK, averaged across all industries. Credit: Office for National Statistics

Much like I’d quickly struggle without food or money, today sharply taking fossil fuel energy away from our societies would immediately threaten our existence. In fact, some think even the small changes already happening taste bad. Again in the UK chemical industry, there are worries that higher costs from clean energy are making it less competitive with other countries. Part of the way it would like to avoid this issue is through unconventional natural gas supplies, presumably extracted through controversial ‘fracking’ methods. Read the rest of this entry »

Continuing the fight for CO2 monitoring

  • This is part two of a two-part post. Read part one here.
Dave Keeling had to balance his work measuring CO2's rise in the air and tracking its movements through the Earth's systems with fighting to get the money to fund his work. Credit: Scripps Institution of Oceanography

Dave Keeling had to balance his work measuring CO2′s rise in the air and tracking its movements through the Earth’s systems with fighting to get the money to fund his work. Credit: Scripps Institution of Oceanography

By 1963, having directly measured a steady increase in CO2 levels over five years, Dave Keeling felt he had clearly shown the value of such non-stop monitoring. But that message hadn’t reached government decision makers. And so Dave swung into the first battle in the war to continue tracking the key greenhouse gas that has flared up repeatedly in the following decades.

Thanks to four new instruments called spectrophotometers, Dave had been able to use the same molecular movements that allow CO2 to absorb heat to measure it. Though his most famous site was at Mauna Loa in Hawaii, one was also installed in Antarctica. Another sailed on a ship and the final one stayed at Dave’s lab at Scripps Institution of Oceanography analysing samples collected in vacuum-filled five litre flasks from aircraft and elsewhere. Thanks to funds from 1957-1958’s International Geophysical Year a team of scientists was busy collecting a “snapshot” of CO2 data that Dave’s boss at Scripps, Roger Revelle, wanted.

So in 1961, Dave moved his family to Sweden for a year to work out exactly what the measurements were showing. He took a fellowship at the Meteorological Institute, University of Stockholm working with its new director Bert Bolin, who had earlier worked on the first computerised weather forecast. With measurements ongoing, annual ‘breathing’ cycles of rising and falling CO2 and the increasing trend underlying them became ever clearer.

Together, Dave and Bert found CO2 concentrations were going up by 0.06 ppm per month on average. Bert also undertook a series of complex calculations by hand to work out CO2 movement and cycles in its levels. In doing so he was showing how oceans, plants on land, and human fossil fuel burning contributed to the patterns that would later need computer models for fuller analysis. This, Dave felt, clearly showed why non-stop CO2 monitoring was needed rather than just snapshots. But by 1963 the shipboard spectrophotometer had come home, and Dave had also called back the one in Antarctica. And with funding cuts biting at the Weather Bureau, now part of the National Oceanic and Atmospheric Administration (NOAA), the staff at Mauna Loa fell from eight to three. And soon afterwards, a problem with Dave’s equipment proved too much for the overstretched team to fix.

“Suddenly there were no precise measurements being made of atmospheric CO2 anywhere,” he recalled. “I had seen the budget cut coming early in 1963 and had tried to prevent its terminating the CO2 program at Mauna Loa Observatory. I even went to Washington to plead for supplemental funding. This had no tangible effect, however, until the cessation of measurements actually occurred. The National Science Foundation (NSF) then found funds to pay for an additional technician at Mauna Loa. I learned a lesson that environmental time-series programs have no particular priority in the funding world, even if their main value lies in maintaining long-term continuity of measurements.” Read the rest of this entry »

Climate change can make us more violent

Civil wars, like the one in Somalia that destroyed this tank, could become more common as the world warms. Image taken by Charles Roffey, used via Flickr CreativeCommons license.

Civil wars, like the one in Somalia that destroyed this tank, could become more common as the world warms. Image taken by Charles Roffey, used via Flickr CreativeCommons license.

US economists have drawn together 45 sets of evidence spanning 10,000 years to show that warmer temperatures and more extreme rainfall can cause greater human conflict. University of California, Berkeley’s Ted Miguel says this “could have critical implications for understanding the impact of future climate change on human societies”.

“Many global climate models project global temperature increases of at least 2°C over the next half century,” Ted told me. “Our findings suggest that global temperature rise of 2°C could increase the rate of intergroup conflicts, such as civil wars, by over 50% in many parts of the world, especially in tropical regions where such conflicts are most common.”

Scientists have long puzzled over whether data backs climate as a cause of violent events such as the fall of the Roman empire. Global warming has brought an ‘explosion’ of interest from researchers, from archaeologists to psychologists, in climate-linked violence. And the types of conflict vary from fights between two people to civil wars and collapse of whole civilisations. But some studies see political, economic and geographical factors as more important than climate.

How researchers assess their data in these studies could introduce problems. For example, it can often be argued that ‘correlation does not imply causation’, meaning that links between two data sets might be caused by other factors. For example, reading ability might seem to improve as shoe size does, but one doesn’t cause the other – getting older causes both. To find any real, bizarre, link between shoe size and reading ability, you would need to look at people with the same age – or ‘control for’ age.

So Ted and his Berkeley teammates only brought together data that could be used to find causal links, although not all the original studies they started from had done this. Bringing together data from many different studies, collected all over the world, considering different types of violence, gives their findings stronger backing than each lone study. They called on records collected in many places that had taken measurements repeatedly in each place, and analysed them from scratch to reach their own conclusions. Read the rest of this entry »

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