Category Archives: Soil

Waste could fertilise food cost cuts

Waste not, want not: a maize anaerobic digester Image: Alex Marshall/Clarke Energy Ltd via Wikimedia Commons
Waste not, want not: a maize anaerobic digester on a farm in the UK
Image: Alex Marshall/Clarke Energy Ltd via Wikimedia Commons

By Alex Kirby

Scientists are developing a way to squeeze the last vestiges of value from renewable energy processes by combining their waste products to produce eco-friendly fertilisers that could help slow food price rises.

LONDON, 30 August 2014 − Researchers in the UK think they may have found a way to produce fertilisers that should cut farmers’ costs and at the same time boost some types of renewable energy.

Their scheme, which involves using waste material from anaerobic digesters and ash from burnt biomass, would also cut fossil fuel use and save natural resources.

The team, based at the Environment Centre at the University of Lancaster, says their fertiliser would help to slow the rise in food prices. And they believe it would work worldwide.

The three-year project has received more than £850,000 (US$1.4 m) in funding from the UK’s Natural Environment Research Council. Research, due to start this year, will take place in labs at the university and in field trials.

The project, which includes several partners working with the university, aims to produce a sustainable, environmentally-friendlier source of soil conditioner and crop fertiliser.

Potential

It builds on research originally conducted by one of the partners, Stopford Energy and Environment Ltd consultancy, which investigated using a mixture of digestates − the waste left over after material has been through an anaerobic digester − and ash, from burnt biomass, as an alternative to existing fertilisers.

Most fertilisers now in use, such as phosphorous-based and nitrate-based products, are made using energy-intensive methods that involve the consumption of oil and gas.

Phosphate-based fertiliser relies as well on the mining of phosphate, a finite and unsustainable resource, and on a production process using various toxic chemicals.

There are already projects in several countries − including the UK − that use waste from digesters to make fertiliser.

But Professor Kirk Semple, of the Lancaster Environment Centre, who leads the project, said: “It is the mixing of anaerobic digestate with biomass ash that is important. . . This would reduce pressure on natural resources and develop a new market for problematic by-products of the bio-energy industry.

“Although the project is based here in the UK, we believe there is exciting potential to produce a sustainable alternative to existing fertiliser use across the globe.”

Nutrients

A successful digestate-ash fertiliser would reduce costs and provide additional income to biomass and anaerobic digestion operators. The Lancaster team says this could make these forms of renewable energy − which could meet more than 15% of UK energy demand by 2020 − more appealing to investors, as at the moment ash has to be expensively dumped in landfills.

They say it could help to improve food security and reduce costs to farmers as production of the new fertiliser would not be linked to the global price of oil and gas.

Previous studies by Stopford show that biomass ash and digestate can be useful nutrient sources for crops in conditions which lack them.

Professor Semple told the Climate News Network that he and his colleagues were working to ensure that the new fertiliser was entirely safe. He said: “Part of the grant will be used to chemically analyse the materials, individually and together, for metals and potentially other chemicals.”

He says commercial-scale production of a successful digestate-ash fertiliser “is some way off”. But he adds: “This project offers the first detailed interrogation of this type of soil amendment. If successful, we would then look to develop this for the commercial sector.” − Climate News Network

US corn’s gravy train faces derailment

 

A field of Maize in the Corn Belt state of South Dakota on the American Great Plains Image: Lars Plougmann via Wikimedia Commons
A ripening field of maize in the American Corn Belt state of South Dakota
Image: Lars Plougmann via Wikimedia Commons

By Kieran Cooke

The US produces enough corn in one year to fill a freight train stretching round the world, according to a recent study. But climate change and unsustainable use of water resources and fertilizers threaten this vast industry.

LONDON, 22 June, 2014 – One-third of cropland in the US is devoted to corn. It produces nearly 40% of the world’s corn, and a record harvest last year was valued at nearly $70 billion.

But now there are warnings that this mighty agricultural edifice – which supports not only farmers, but a legion of food and animal feed, transport and other companies, big and small − could be seriously damaged by a changing climate.

To make matters worse, increasingly scarce water supplies could also have an adverse effect, and so too could the intensification of growing techniques − in particular, the overuse of  fertilizers and pesticides.

A study by Ceres, a US not-for-profit group that lobbies for more environmental sustainability in the business sector, looks at the risks facing one of the country’s main industries.

Negative impact

States in the American Midwest and the Great Plains region – known as the Corn Belt − account for the bulk of corn production. But the study warns: “Record-breaking weather events – including prolonged drought, intense precipitation and high temperatures – are increasingly common in the Corn Belt and are negatively impacting corn yields and corporate profits.”

Floods in 2010/11 caused millions of dollars worth of crop losses in many areas. Lands were also degraded, and erosion increased. The following year there was drought, when the rains didn’t arrive and temperatures soared.

“The 2012/13 drought exemplified the vulnerability of the US corn supply chain to extreme weather,” the study says.

The bulk of US corn output goes either to animal feed or to the production of ethanol fuels, with only 10% going to food processing.

According to the report: “The 2012/13 drought had unusually severe financial impacts for many companies in the US corn value chain, hitting the meat and grain trading sectors particularly hard.

“Impacts ranged from interruptions to corn supply − which affected meat processing and ethanol refining activities − to operational challenges linked to insufficient water for manufacturing facilities, to low Mississippi river water levels that restrict transport of agricultural goods.”

While the percentage of corn production shipped abroad is relatively small, the US is still the world’s biggest corn exporter. Shortages or rising prices can have an adverse impact on the developing world, with the potential for outbreaks of serious social unrest.

The study points out that extreme weather events in recent years have resulted in large-scale price volatility. This in turn has led to what it calls riskier growing practices, with farmers and the big agricultural conglomerates seeking to cash in on rises in the market by using ever more fertilizer and pesticides on their lands.

The US government’s recent National Climate Assessment said the negative effects of climate change, such as higher temperatures and drought, would outweigh any positive impacts in the Midwest and Great Plains.

The Ceres study says corn is particularly sensitive to higher temperatures, and much of the corn is grown in regions where water supplies are already limited. In future, corn growing might have to move to cooler and more water-abundant areas further north.

Northward shift

“Higher temperatures and increased water stress mean that increased irrigation for corn will be required. Given limited water supply in parts of the Great Plains region, a northward shift in corn acreage is predicted, increasing the risk of stranded agricultural assets, such as processing, storage and transportation infrastructure.”

Costs, to the agricultural industry and to the US government are mounting. In 2012-13, the government’s Federal Crop Insurance Programme paid out a record $10.8 billion to farmers, mostly for reasons related to the drought.

Ceres says farmers and the large conglomerates that control increasing amounts of agricultural land must learn to farm more sustainably. In many cases, this means a less intensive crop regime.

There should be more measured use of fertilizers and pesticides. More efficient irrigations methods and charging systems that encourage less water use should also be implemented.

More mixed cropping should be introduced in order to preserve soil fertility, the report recommends. And companies should examine their supply chains, and pressure the farming sector to put in place better land practices.

Perhaps most controversially, Ceres has a simple message that is likely to cause a storm of anger across the Corn Belt: buy less corn. – Climate News Network

How nature affects the carbon cycle

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By Tim Radford

In Australia and the Arctic, scientists say, they have found unexpected ways in which natural processes are helping to compensate for global warming.

LONDON, 1 June – The great drylands of the planet – and they cover almost half of the terrestrial surface – may be bigger players in the carbon cycle than anyone had suspected. The world’s semi-arid regions may absorb huge volumes of carbon dioxide from the atmosphere whenever it rains enough.

A greening semi-arid ecosystem in Australia's Northern Territory, a key factor the record 2011 global land carbon sink following prolonged La Niña rainfall and long-term vegetation changes  
Image: Eva van Gorsel (CSIRO)

A greening semi-arid ecosystem in Australia’s Northern Territory, a key factor in the record 2011 global land carbon sink following prolonged La Niña rainfall and long-term vegetation changes

Image: Eva van Gorsel (CSIRO)

Benjamin Poulter of Montana State University and colleagues report in Nature that they used a mix of computer-driven accounting methods to work out where the carbon goes after fossil fuel burning emits extra carbon dioxide into the atmosphere. Decades of meticulous measurement confirm that, overall, carbon dioxide levels are increasing inexorably, and the world is warming accordingly.

But inside this big picture is a lot of seasonal and inter-annual variation. So climate scientists, when they try to work out what all this means for future climates, need to understand the carbon cycle better.

The assumption has always been that the most important terrestrial consumers of carbon dioxide were the tropical rainforests. But the match of terrestrial biogeochemical and atmospheric carbon dioxide and global carbon budget accounting models by 13 scientists from the US, Europe and Australia has revealed a different story.

In 2011 more than half of the terrestrial world’s carbon uptake was in the southern hemisphere – which is unexpected because most of the planet’s land surface is in the northern hemisphere – and 60% of this was in Australia.

Natural brake

That is, after a procession of unusually rainy years, and catastrophic flooding, the vegetation burst forth and the normally empty arid centre of Australia bloomed. Vegetation cover expanded by 6%.

Human activity now puts 10 billion tonnes of carbon into the atmosphere annually, and vegetation in 2011 mopped up 4.1 billion tonnes of that, mostly in Australia.

There remains a great deal of uncertainty about the carbon cycle and how the soils and the trees manage the extra carbon. Nobody knows what will happen to this extra carbon now in the hot dry landscapes of Australia: will it be tucked away in the soil? Will it be returned to the atmosphere by subsequent bushfires? As scientists are fond of saying, more research is necessary.

But this is an example of negative feedback: as carbon dioxide levels and temperatures rise, the green things respond, and slow the acceleration of both. This is quite different from the positive feedback that follows when Arctic ice – which reflects sunlight – melts and gives way to blue water which absorbs solar energy, thus accelerating the melting.

But even the slow disaster of the polar regions could be accompanied by an ameliorating process. British researchers report in Nature Communications that the ice sheet meltwaters may be rich in iron. A boost of iron would stimulate phytoplankton growth, which means more carbon dioxide could accordingly be absorbed from the atmosphere.

Feeding the oceans

The scientists collected meltwater from a Greenland glacier in the summer of 2012, and then tested it to discover significant quantities of what geochemists call “bio-available” iron.

So, in another example of those cycles of the elements that make the world go round, ice that scrapes over rock also delivers vital nutrients to the sea, for marine plants to take up yet more carbon dioxide and flourish more vigorously in the oceans and keep the planet a little cooler.

The Greenland research gives scientists a chance to estimate more accurately the delivery of this dietary supplement to the oceans: they reckon somewhere between 400,000 and 2.5 million tonnes a year in Greenland and somewhere between 60,000 and 100,000 tonnes in Antarctica. Or, to put it more graphically, it would be like dropping 3,000 fully-laden Boeing 747s into the ocean each year.

“The Greenland and Antarctic ice sheets cover around 10% of the global land surface,” said Jon Hawkings, of the University of Bristol, UK. “Our finding that there is also significant iron discharged in runoff from large ice sheet catchments is new. This means that relatively high concentrations are released from the ice sheet all summer, providing a continuous source of iron to the coastal ocean.” – Climate News Network

Buried carbon causes deep concern

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Hidden menace: a vast store of organic carbon lies beneath the wind-blown soil of the Great Plains Image: Zorin09 via Wikimedia Commons

Hidden menace: a vast store of organic carbon lies beneath the wind-blown soil of the Great Plains
Image: Zorin09 via Wikimedia Commons

By Tim Radford

Deep beneath the Great Plains of America, a vast buried store of organic carbon has been discovered by scientists − a hidden record of bygone climate, and a potentially serious danger to the future climate

LONDON, 30 May − Geographers in the US have found a new factor in the carbon cycle, and – all too ominously – a new potential source of the greenhouse gas carbon dioxide. They have identified huge deposits of fossil soils, rich in organic carbon, buried beneath the Great Plains of America.

The discovery is evidence that the subterranean soils could be a rich store, or sink, for ancient atmospheric carbon. But if the soil is exposed – by erosion, or by human activities such as agriculture, deforestation or mining – this treasure trove of ancient charred vegetation, now covered by wind-blown soils, could blow back into the atmosphere and add to global warming.

Erika Marin-Spiotta, a biogeographer at  the University of Wisconsin-Madison, and her colleagues report in Nature Geoscience that what is known as Brady soil – ancient buried soil − formed more than 13,500 years ago in Nebraska, Kansas and other Great Plains states.

Glacial retreat

It now lies more than six metres below the surface, and it was buried by a vast deposit of loess – wind-blown dust – about 10,000 years ago, when the glaciers began to retreat from North America.

The significance is not that it survived the end of the Ice Age and the colonisation of the Great Plains by grazing animals, but in the fact that it is there at all, at such depths. Calculations about the world stock of soil carbon have focused on the topsoil, and the role of root systems, decaying vegetation, microbes and fungi in the natural carbon cycle. Now the climate scientists who play with models of the carbon cycle will have to think again.

“There is a lot of carbon at depths where nobody is measuring,” said Dr Marin-Spiotta. “It was assumed that there was little carbon in deeper soils. Most studies are done only in the top 30 centimetres. Our study is showing that we are grossly underestimating carbon in soils.”

The researchers have enough evidence to put together a picture of a stormy past in an almost empty continent. The tract of prairie that now contains the Brady soil was never glaciated. As the glaciers retreated from the rest of the continent, the climate warmed, the vegetation regime changed, and it became scorched by wildfire − “an incredible amount of fire” according to the report’s author.

Thick band

Before the ash, charred wood, and singed fibres and stalks of the prairie grasses could begin to decompose and turn back into carbon dioxide, it was covered by the accumulating loess. It now exists as a metre-thick band of dark soil far below the surface − a hidden record of bygone climate.

The researchers calculate that, altogether, there could be as much as 2.7 billion tonnes of potentially reactive carbon below the Great Plains. And what happened in the Plains, could have happened in many other parts of the world. The implication is that such deposits could exist anywhere, and could just as easily be a potential contributor to global warming  if disturbed. – Climate News Network

Soils may absorb less CO2 than thought

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Ferdynand Ruszczyc's The Soil: The part played by the world's soils in accounting for carbon dioxide is pivotal Image: Via Wikimedia Commons

Ferdynand Ruszczyc’s The Soil: The part played by the world’s soils in accounting for carbon dioxide is pivotal
Image: Via Wikimedia Commons

By Tim Radford

Researchers believe that natural processes are not as efficient in absorbing carbon dioxide and putting a brake on global warming as they had previously thought.

LONDON, 2 May – Scientists from the US, China and Ireland may have settled one big question about climate change: don’t rely on the soil microbes to help damp down the temperatures. They report in Science that as carbon dioxide levels rise, and temperatures increase, so does the turnover of carbon in the soil.

That means the hope that global warming must mean more energetic plant growth and therefore greater carbon uptake in the soil, in a cycle that engineers like to call negative feedback, looks a bit forlorn.

Kees van Groenigen of Northern Arizona University and colleagues analysed results from 53 different studies of soil carbon measurements in forests, grasslands and farmers’ fields around the world to see how CO2 affects plant growth, soil activity and soil carbon.

They found that extra carbon dioxide in the atmosphere meant more input into the soil – nearly 20% more – but it also meant more turnover, up by more than 16%.

So if more went in, more was released, because the teeming microscopic fauna that inhabit the soil, recycle nutrients and redistribute plant nourishment also became more active.

“Our findings mean that nature is not as efficient in slowing global warming as we previously thought,” said Dr van Groenigen. “By overlooking this effect of increased CO2 on soil microbes, models used by the Intergovernmental Panel on Climate Change may have overestimated the potential of soil to store carbon and mitigate the greenhouse effect.”

Forests’ role

The finding is – as all scientific findings tend to be – provisional, but it does help explain why so much research into the great soil carbon question has been inconclusive. The interplay of increasing carbon dioxide, plants and soil has been under question for years: yes, there is a fertilization effect, for instance, but it may not pay off in more food from food crops.

And the Arizona analyses offer perspective on or even gain substance from other very recent findings. For instance, the fertility of the soil is a factor in the great forest conundrum: are forests sinks or sources of carbon in the atmosphere?

An international team of researchers report in Nature Climate Change that after an analysis of data from 92 studies, they found that forests that flourish in soils that are fertile – rich in nutrients – seem to be able to lock away 30% of the carbon they take from the atmosphere by photosynthesis. But in less fertile places, the plants have to work harder to find nourishment.

“In general, nutrient-poor forests spend a lot of energy – carbon – through mechanisms to acquire nutrients from the soil, whereas nutrient-rich forests can use that carbon to enhance biomass production,” said Marcos Fernandez-Martinez of Spain’s Centre for Ecological Research and Forestry Applications.

And in the same month, a study in the journal Ecology Letters found that feedback from tiny soil-dwelling creatures was the single biggest uncertainty in the great feedback question.

“Soil microbes are responsible for one of the largest carbon dioxide emissions on the planet, about six times higher than fossil fuel burning,” said Oskar Franklin of the Institute for Applied Systems Analysis in Austria.

Microbial methane

In theory, growing forests should soak up that carbon dioxide released by the soil microbes – but as the temperature warms, soil conditions may change – and the feedback effects become harder to predict.

And soil microbes also produce a greenhouse gas that is, molecule for molecule, even more potent than CO2. Swiss and German scientists report in Nature Geoscience that warming temperatures and greater soil activity in the world’s wetlands could end up releasing not just more soil carbon but a lot more methane – 34 times more effective than CO2 as a greenhouse gas over a century, but 84 times more over 20 years – into the atmosphere.

They took a close look at the electrochemical reactions that play off in soil bacteria: wetlands are rich in peat, and when wet the soil bacteria are starved of oxygen, and in no position to release methane. But global warming could change that equation.

The European study clarifies some of the geochemistry of the world’s wetlands. “It also shows that reversible electrochemical processes have the potential to have a large effect on the environment,” said Andreas Kappler of the University of Tubingen, who is also secretary of the European Association of Geochemistry.

“There are uncertainties as to the exact extent, but we estimate that between an extra 10% up to an extra 166% of methane could be released. It also shows that these are fragile ecosystems and that slight changes in their geochemical conditions could have dramatic consequences for the environment.” – Climate News Network

Wetland emissions mean more methane

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More methane is leaking from tundra and other high-latitude environments than scientists had realised Image: Kat Spence via Wikimedia Commons

More methane is leaking from tundra and other high-latitude environments than scientists had realised
Image: Kat Spence via Wikimedia Commons

By Alex Kirby

Methane emissions are rising globally because wetlands – especially in northern latitudes – are releasing more than anyone had realised, a team of researchers based in Canada says.

LONDON, 1 May – The bad news is that global emissions of methane appear to be rising. The worse news is that scientists believe there’s much more to come in the form of releases from many of the world’s wetlands.

Methane is emitted from agriculture and fossil fuel use, as well as natural sources such as microbes in saturated wetland soils. It is a powerful greenhouse gas, and in the short term it does much more damage than the far more abundant carbon dioxide.

Just how much more damaging it is is something scientists keep updating. There is now international agreement that methane is 34 times more potent than CO2 over a century, but 84 times more over a much shorter timespan – just 20 years. And two decades can be crucial in trying to slow the rate of climate change.

Professor Merritt Turetsky, of the department of integrative biology at the University of Guelph, Canada, is the lead author of a paper published in the journal Global Change Biology.

The paper is based on an analysis of global methane emissions examining almost 20,000 field data measurements collected from 70 sites across Arctic, temperate and tropical regions.

More to come

Professor Turetsky and her colleagues report that a recent rise in atmospheric methane probably stems from wetland emissions, suggesting that much more will escape into the atmosphere as northern wetlands continue to thaw and tropical ones to warm.

The study supports calls for improved monitoring of wetlands and human changes to them. It also urges better methods of detecting different types of wetlands and different methane release rates between flooded and drained areas.

The amount of atmospheric methane had remained relatively stable for about a decade, but concentrations began to rise again in 2007.

Scientists assumed that wetland methane release was largest in the tropics, said Professor Turetsky. “But our analyses show that northern fens, such as those created when permafrost thaws, can have emissions comparable to warm sites in the tropics, despite their cold temperatures. That’s very important when it comes to scaling methane release at a global scale.

“Not only are fens one of the strongest sources of wetland greenhouse gases, but we also know that Canadian forests and tundra underlain by permafrost are thawing and creating these kinds of high methane-producing ecosystems.”

Moisture the key

Most methane studies focus on measurements at a single site, said one of her co-authors, Narasinha Shurpali, from the University of Eastern Finland. “Our synthesis of data from a large number of observation points across the globe is unique and serves an important need.”

The team showed that small temperature changes can release much more methane from wetland soils to the atmosphere than scientists had believed. Whether climate change will increase methane emissions will depend on soil moisture, said Professor Turetsky.

Under warmer and wetter conditions, much more methane is likely to be emitted. If wetland soils dry out from evaporation or human drainage, though, emissions will fall – but not without other problems, like wildfires breaking out on drying peatlands.

Another study co-author, Kim Wickland, of the United States Geological Survey, said: “This study provides important data for better accounting of how methane emissions change after wetland drainage and flooding.”

She said emissions varied between those from natural wetlands and those from areas which had been disturbed or managed. – Climate News Network

More CO2 limits plants’ protein output

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The Mojave desert: As CO2levels rose, it took up unexpectedly large amountsofthe gas Image: Rennett Stowe via Wikimedia Commons

The Mojave desert: As CO2 levels rose, it took up unexpectedly large amounts of the gas
Image: Rennett Stowe via Wikimedia Commons

By Tim Radford

With increasing warmth drying more of the Earth, arid soils may absorb more carbon dioxide – but that in turn is likely to limit protein production.

LONDON, 12 April – As global temperatures rise, more than one third of the land surface may become more arid. Although there will be changes in rainfall patterns, heat – and the attendant evaporation of the soil – could extend ever drier conditions to more and more farmland and cities, according to research in the journal Climate Dynamics.

The new study – which excludes Antarctica – is led by Benjamin Cook, a climate scientist both with the University of Columbia’s Lamont-Doherty Earth Observatory and the US space agency Nasa. It is based on climate simulation, and forecasts that 12% of the land surface will be subjected to drought by 2100 just through changes in rainfall. Throw in the increased heat, though, and the drying effect will be spread to 30% of the land.

Even those regions that might be expected to get more rain will be at greater risk of drought. This would be very bad news for the wheat, corn and rice belts of the south-western US and south-eastern China.

“For agriculture, moisture in the soil is what really matters,” said Cook’s co-author, Jason Smerdon. The research confirms previous studies, and the more recent warnings from the Intergovernmental Panel on Climate Change, and other studies, have predicted that extremes of temperature will be bad news for farmers anyway, with yields  likely to be affected.

But nothing in climate research is simple. The extra warming will be a direct consequence of ever-higher levels of carbon dioxide in the atmosphere. A study in Nature Climate Change has just revealed that arid zones offer an unexpected source of what engineers call negative feedback.

Carbon sink

A 10-year experiment in the Mojave desert in the US has shown that as carbon dioxide levels increase, arid areas take up unexpectedly large amounts of the gas.

“They are a major sink for atmospheric carbon dioxide, so as CO2 levels go up, they’ll increase their uptake of CO2 from the atmosphere. They’ll help take up some of that excess CO2 going into the atmosphere. They can’t take it all up, but they’ll help,” says Dave Evans, a biologist at Washington State University.

All land surfaces absorb some carbon. Until now, most attention has been paid to the role of forests as major “sinks” of carbon. But the US experimenters marked out nine octagonal plots of the desert and blew air with current levels of CO2 over three of them, and air with 550 parts per million of CO2, the expected level by 2050, over another three. Three received no extra air at all.

Then the researchers excavated the soils to a depth of a metre to measure the absorbed carbon and were surprised by the gain in carbon during a relatively short exposure in the plots exposed to the extra carbon dioxide.

Arid and semi-arid soils account for a large proportion of the planet’s land surface: overall, they could increase carbon uptake to account for between 15% and 28% of the amount currently being absorbed by land surfaces.

Less protein

This sounds like good news, on balance. It may not be, as far as food supplies are concerned. In the same issue of Nature Climate Change a second study reports on experiments into the effects of elevated levels of carbon dioxide on wheat.

Carbon dioxide is seen as a fertiliser of plants and indeed, without it, there would be no plants. But Arnold Bloom, a plant scientist at the University of California Davis reports that, according to his experiments, elevated levels of carbon dioxide also inhibit the conversion of nitrate into protein in crops.

Wheat provides nearly one fourth of all protein in the global human diet. Other studies have shown the same effect with wheat – and also with rice, barley and potato tubers.

“When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, it becomes clear that the overall protein available for human consumption may drop by about three per cent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades,” Bloom said. – Climate News Network

Farming on sand

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It was once a rice paddy but now it's only sand Image: Kieran Cooke

It was once a rice paddy but now it’s only sand
Image: Kieran Cooke

By Kieran Cooke

The Brahmaputra river is one of the world’s mightiest rivers, with millions dependent on its waters. The river also brings misery, with flooding and erosion major problems: climate change is likely to bring more hardship. Kieran Cooke, one of the editors of the Climate News Network, has been in Assam in northeast India, meeting villagers living on the Brahmaputra’s banks.

Laupani village, Assam, 10 March – The holes are dug laboriously in the dusty, sandy soil. Krishna Maya Sharma stops her work to wipe the sweat from her lined face.

“In the old days we would plant paddy here and have enough to sell at market” says Krishna, a 42 year old mother of six children.

“Now the soil is so bad, sweet potato is the only thing that will grow. The rest of our land is ruined.”

Laupani is a village in the north of the tea state of Assam, spread along the banks of the Brahmaputra river. In the distance, the pink evening light shines on the snow capped ridges of the eastern Himalayas.

The Brahmaputra, its waters rising more than 5,000 metres up on the Tibetan Plateau and flowing for about 3,000 kilometres through China, India and Bangladesh before joining up with the Ganges and out into the Bay of Bengal, is one of the world’s major rivers, 10 kilometres wide in places.

Widespread flooding

According to a recent report by India’s Third Pole organisation, the Brahmaputra carries a volume of water exceeded only by the Amazon and Congo rivers – and greater than the combined flow of Europe’s 20 largest rivers.

The river is a lifeline to millions, delivering vital nutrients to the soils of the plains but its fast flowing waters also cause widespread misery to people like Krishna.

Floods are frequent. There is widespread erosion and massive amounts of sand washed out of the river’s banks are deposited on surrounding fields, making once verdant areas into what looks like an enormous beach. The floods also bring invasive plant species that colonise agricultural lands.

More than 40% of Assam’s geographical area is designated as being flood prone: more than 1.5 million people were displaced by floods in 2012, lives were lost and whole villages were washed away.

Sand accumulations

“The waters were so deep and stayed so long that the grass was destroyed and our cattle died because they had no fodder” says Krishna.

“The sand means our land is no good anymore – my husband has given up being a farmer and is working in construction. Many young men go away to try and find jobs, there is nothing for them here.”

Locals – the majority of whom are poor, subsistence farmers – say river flows are becoming more unpredictable, with erosion and what’s called sandcasting becoming worse.

In part the flooding caused by the Brahmaputra’s waters is a natural phenomenon which has been going on for centuries. As the river’s waters cascade down from the Tibetan Plateau and Himalayas, millions of tons of sediment is washed onto the alluvial plains of Assam and others states in India’s northeast.

Earthquake danger

There are other forces at work: the region is a highly seismic zone. In 1950 the Brahmaputra river basin suffered one of the most violent earthquakes ever recorded. The geology of the area was changed and the river level was raised dramatically, by between eight and 10 metres in places.

Climate change is another factor, with a combination of rising temperatures and accumulations of what’s known as black carbon or soot in the high Himalayas and on the Tibetan Plateau causing glaciers which feed into upper reaches of the Brahmaputra to melt.

Increasingly unpredictable rainfall patterns, with periods of intense downpours, are also contributing to more volatile river flows.

Professor Jogendra Nath Sarma is a locally based geologist who has been studying the Brahmaputra for years.

“Over time different rivers in the Brahmaputra basin have merged, braiding over a very wide area. Thousands of square kilometres of land has been eaten away. Rampant deforestation is another big contributor to land erosion. “

In the past, says Professor Sarma, people would migrate to higher ground during the flood season but now, due to population growth and large scale immigration, there is nowhere for them to go.

Doubtful future

The future does not look good. According to models produced by scientists at the Indian Institute of Technology in Guwahati, Assam’s capital, climate change will result in the Brahmaputra valley region experiencing more flood events.

The Institute says that not only will river peak flows increase: so will the incidence of pre-monsoon flooding, endangering key phases of the agricultural cycle.

Talk of climate change is not of great interest to Krishna, digging holes for her sweet potato plants. She has more immediate things to worry about.

“Life is getting harder. Every time the floods come, I wonder what will happen. But where else can we go?” – Climate News Network


 

 

 

 

Tree roots ‘are natural thermostat’

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In sight of the Carpathians: Mountain forests can cool - and warm - the Earth Image: Horia Varlan from Bucharest, Romania, via Wikimedia Commons

In sight of the Carpathians: Mountain forests can cool – and warm – the Earth
Image: Horia Varlan from Bucharest, Romania, via Wikimedia Commons

By Tim Radford

Trees can influence the climate in unexpected ways, and British researchers say their roots are an important way of helping rocks to weather and drawing carbon dioxide from the atmosphere.

LONDON, 18 February – Trees have become a source of continuous surprise. Only weeks after researchers demonstrated that old forest giants actually accumulate more carbon than younger, fast-growing trees, British scientists have discovered that the great arbiters of long-term global temperatures may not be the leaves of an oak, a pine or a eucalypt, but the roots.

The argument, put by a team from Oxford and Sheffield Universities in the journal Geophysical Research Letters, begins with temperature. Warmer climates mean more vigorous tree growth and more leaf litter, and more organic content in the soil. So the tree’s roots grow more vigorously, say Christopher Doughty of Oxford and colleagues.

They get into the bedrock, and break up it up into its constituent minerals. Once that happens, the rock starts to weather, combining with carbon dioxide. This weathering draws carbon dioxide out of the atmosphere, and in the process cools the planet down a little. So mountain ecosystems – mountain forests are usually wet, and on conspicuous layers of rock – are in effect part of the global thermostat, preventing catastrophic overheating.

The tree is more than just a sink for carbon, it is an agency for chemical weathering that removes carbon from the air and locks it up in carbonate rock.

That mountain weathering and forest growth are part of the climate system has never been in much doubt: the questions have always been about how big a forest’s role might be, and how to calculate its contribution.

Keeping climate stable

US scientists recently studied the rainy slopes of New Zealand’s Southern Alps to begin to put a value on mountain ecosystem processes. Dr Doughty and his colleagues measured tree roots at varying altitudes in the tropical rain forests of Peru, from the Amazon lowlands to 3,000 metres of altitude in the higher Andes.

They measured the growth to 30 cms below the surface every three months and did so for a period of years. They recorded the thickness of the soil’s organic layer, and they matched their observations with local temperatures, and began to calculate the rate at which tree roots might turn Andean granite into soil.

Then they scaled up the process, and extended it through long periods of time. Their conclusion: that forests served to moderate temperatures in a much hotter world 65 million years ago.

“This is a simple process driven by tree root growth and the decomposition of organic material. Yet it may contribute to the Earth’s long-term climate stability. It seems to act like a thermostat, drawing more carbon dioxide out of the atmosphere when it is warm and less when it is cooler”, Dr Doughty said.

If forests cool the Earth, however, they might also warm it up. A team from Yale University in the US has reported in Geophysical Research Letters that forest fires might have had an even greater impact on global warming during the Pliocene epoch about three million years ago than carbon dioxide.

Rapid rise expected

Nadine Unger, an atmospheric chemist, and a colleague have calculated that the release of volatile organic compounds, ozone and other products from blazing trees could have altered the planet’s radiation balance, by dumping enough aerosols into the atmosphere to outperform carbon dioxide as a planet-warmer.

In fact, the Pliocene was at least 2°C or 3°C warmer than the pre-industrial world. The Pliocene is of intense interest to climate scientists: they expect planetary temperatures to return to Pliocene levels before the end of the century, precisely because humans have cleared and burned the forests, and pumped colossal quantities of carbon dioxide into the atmosphere. The greater puzzle is why a rainy, forested and conspicuously human-free world should have been so much warmer.

“This discovery is important for better understanding climate change through Earth’s history, and has enormous implications for the impacts of deforestation and the role of forests in climate protection strategies”, Dr Unger said.

All this scholarship is concerned with the natural machinery of ancient climate change, and the Yale research was based on powerful computer simulations of long-vanished conditions that could not be replicated in a laboratory.

Meanwhile, ironically, forest scientists have had a chance to test the levels of volatile organic discharges from blazing forests because freakish weather conditions in Norway have seen unexpected wild fires in tracts of mountain forest. December was one of Norway’s warmest winter months ever. In one blaze, 430 residents were forced to evacuate. – Climate News Network

Fungus governs soil’s carbon content

FOR IMMEDIATE RELEASE

By Tim Radford

The soil stores the greater part of the Earth’s carbon. Just how much it stores is determined largely by what sort of fungi live in the roots of plants and trees, researchers have found.

LONDON, 28 January – Most of the planet’s carbon is neither in the forests nor the atmosphere. It is in the soil under your feet. US scientists think that they have identified the mechanism that keeps most of this awesome treasury of carbon locked away in the soil – or surrenders much more of it back to the atmosphere. The answer is: a fungus.

This answer matters because what happens to soil carbon is critical to predicting the planet’s future climate, according to Colin Averill of the University of Texas at Austin.

He and colleagues from the Smithsonian Tropical Research Institute in Panama and Boston University in Massachusetts report in Nature that the storage of carbon in soils is influenced by the mycorrhizal fungi that live in symbiotic relationships with plants.

In a symbiotic relationship, creatures benefit from each other, and in this case the fungi extract nitrogen from the soil, and make it available to the roots of the growing plant. Plants take carbon from the air to make their tissues; when a tree falls, or a branch breaks, or a shrub dies, most of the carbon gets back into the atmosphere through decomposition. But some gets buried, and stays in the soil

Averill and colleagues decided to look at the respective roles of two kinds of mycorrhizal fungus: one group known as ecto- and ericoid mycorrhiza (EEM), and another called arbuscular mycorrhiza (AM). The first produce enzymes that degrade nitrogen.

Out-competing microbes

That means that whenever there is organic nitrogen in the soil, the fungi take the greater share: they compete with soil microbes for the soil nutrients.  So the scientists predicted that if the EEM type was dominant, then there would be greater proportions of carbon conserved in the soil.

They then looked at all the known data about soil carbon and nitrogen in various ecosystems: the boreal forests of the north; the temperate woodlands, the tropical forests and the grasslands.

An Amanita mushroom, the fruiting body of an ectomycorrhizal fungus associated with the roots of a Hemlock tree in Harvard Forest, US Image: Colin Averill

Amanita mushrooms, part of an ectomycorrhizal fungus in the roots of a Hemlock tree in Harvard Forest, US
Image: Colin Averill

Where the proportions of arbuscular mycorrhiza were highest, the levels of soil carbon tended to be lower. In an EEM world, there could be 70% more carbon stored in the soil. Unexpectedly, they found that the relationship was independent of, and mattered far more than, the effects of net primary production, temperature, rainfall and levels of soil clay. What mattered most was the type of fungus dwelling in the roots of the forest trees, or the savannah grasses.

“Natural fluxes of carbon between the land and atmosphere are enormous and play a crucial role in regulating the concentration of carbon dioxide in the atmosphere and in turn, the Earth’s climate”, said Averill.

“This analysis clearly establishes that the different types of symbiotic fungi exert major control on the global carbon cycle, which has not been fully appreciated or demonstrated until now.”

Complex relationships

The research, once again, is a reminder that climate models depend on an understanding of how the world works, and that there is still much more to understand about planetary workings. Fungi are mostly invisible. Ceps, morels, chanterelles, truffles and field mushrooms are edible prizes that pop up from the soil, but most of the fungal action is below the soil.

The biggest single creature on the planet is not the blue whale but a fungus that covers 10 square kilometers of soil in the Blue Mountains of Oregon, in the US.

The research is a reminder of a secret kingdom buried in the first metre or so of the world’s soils, a kingdom with profound influence on the machinery of the planetary carbon cycle.

“The research is not only relevant to models and predictions of future concentrations of atmospheric greenhouse gases, but also challenges the core foundation in modern biogeochemistry that climate exerts major control over soil carbon pools,” said Adrien Finzi, of Boston University, one of the authors. – Climate News Network