Tag Archives: drought

Horn of Africa Famine: Millions at Risk

Horn of Africa Famine: Millions at Risk in “Deadly Cocktail” of War, Climate Change, Neoliberalism.

The United Nations has called an emergency meeting to discuss the Horn of Africa drought, which it says has already claimed tens of thousands of lives. Famine was declared in two regions of Somalia on Wednesday where 3.7 million people are in need of urgent humanitarian assistance. Another eight million people need food assistance in neighboring countries including Kenya and Ethiopia. United Nations Secretary-General Ban Ki-moon calls the situation a “catastrophic combination of conflict, high food prices and drought” and has appealed for immediate aid. We go to Nairobi for an update from Kiki Gbeho of the U.N. Office for the Coordination of Humanitarian Affairs. We also speak with Christian Parenti, author of “Tropic of Chaos: Climate Change and the New Geography of Violence.” “This was predicted long ago by people on the ground,” Parenti says. “It’s a combination of war, climate change and very bad policy, particularly an embrace of radical free market policies by regional governments that mean the withdrawal of support for pastoralists, the type of people you saw with their dead cattle.” [includes rush transcript]

Climate Change Evaporates Part of China's Hydropower

Climate Change Evaporates Part of China’s Hydropower: Scientific American.

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WATER FALL: Unusually low water levels in many Chinese rivers has contributed to a big drop in hydropower production. Image: Tomasz Dunn/Flickr

SHANGHAI — China has set ambitious goals for itself to develop hydropower to help mitigate the risks of climate change, but increasing extreme weather events likely rooted in climate change are now sabotaging the goals’ foundations.

The latest blow came in September, when many major rivers across China ran into an unusual shrinkage, with less than 20 percent water remaining at some stretches. As a result, the nation’s hydroelectric generation dropped by almost a quarter compared with last year. There has been an ever-widening decrease in power each month since July, according to a recent government statement.

As water stocks in key hydro stations decline, the regular dry season is approaching. The resulting stress on hydroelectric generation will last into next year, the statement said.

The Chinese government has yet to explain why the water flows slumped. But experts blamed it on climate change, warning of more future droughts in areas traditionally blessed with water.

If this expectation comes true, it will hamper China’s hydropower sector, which contributes most of the country’s carbon-free electricity. It will also threaten a national strategy in transmitting electricity from resource-rich western China to feed the country’s power-hungry manufacturing sector, most of which is in the east.

For Guangdong province, located on China’s east coast, this threat has already turned into a daily reality. Since its western neighbors this year failed to send as much electricity as usual, the manufacturing hub, with a capacity to produce more than half of the world’s desktops and toys, is forced to conserve electricity.

Turbines left high and dry
China Southern Power Grid, the region’s electricity distributor, attributed the energy shortage partly to the evaporation of hydropower.

As of July, on average, not even half of its installed hydropower capacity found water to turn turbines, the company’s statistics show. And several major hydro stations, built as part of the west-to-east electricity transmission plan, failed to do their jobs.

Goupitan, the largest hydroelectric generator in Guizhou province, reportedly produced only 10 percent of its normal output per day, due to shrinking water flows. And in another hydro station called Longtan, located in the Guangxi region, this year’s missing rain dropped its reservoir’s water level to a point dozens of meters lower than previous years.

“This will definitely negatively affect our hydroelectric production from now to next summer,” said Li Yanguang, who is in charge of public relations in the power station. Asked whether next summer — a regular rainy season — could make the situation better, Li answered in a cautious tone.

“This totally depends on weather,” he said. “We can’t predict that.”

Hydro growth plan sticks despite falling power output
But Lin Boqiang, one of China’s leading energy experts, is confident that the nation’s hydroelectric generation may just go in one direction: getting worse.

“If climate change caused this year’s water flow decreases, which I think it did, and then its impact [on rivers] will be a long term. It will take a toll on China’s hydroelectric output, and also push up the cost of using it,” explained Lin, who directs the China Center for Energy Economics Research at Xiamen University.

But still, from Lin’s point of view, such setbacks can’t compete with the Chinese desire for tapping more water power. China, already the world’s largest hydropower user, plans to add another 120 gigawatts by 2015 — a crucial step toward greening 15 percent of its power mix by the end of the decade.

Yang Fuqiang, a senior climate and energy expert at the Natural Resources Defense Council, agreed that China’s hydropower plan will stand, though not primarily for energy supply concerns.

Although a climate-resilient approach is factored into the designs of hydro projects, China is still likely to suffer from hydroelectric output decline, says Yang. But the nation can seek more clean energy from the sun or wind, which won’t be affected by climate change, and get the electricity generated elsewhere via a smart grid, he said, referring to an advanced transmission infrastructure China has been building.

So what’s the point of keeping hydro?

“In the future, the importance of hydro projects won’t be on power generation, but on water management,” Yang explained. “It helps control floods, ensure ships transportation and reserve water — a function that [water-scarce] China needs badly.”

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

New Research Casts Doubt on Doomsday Water Shortage Predictions

New Research Casts Doubt on Doomsday Water Shortage Predictions: Scientific American.

MELTDOWN: The melting of mountain glaciers around the world may not contribute as much to water supplies as thought, new research argues. Image: Abhishekjoshi/Flickr

From the Andes to the Himalayas, scientists are starting to question exactly how much glaciers contribute to river water used downstream for drinking and irrigation. The answers could turn the conventional wisdom about glacier melt on its head.

A growing number of studies based on satellite data and stream chemistry analyses have found that far less surface water comes from glacier melt than previously assumed. In Peru’s Rio Santa, which drains the Cordilleras Blanca mountain range, glacier contribution appears to be between 10 and 20 percent. In the eastern Himalayas, it is less than 5 percent.

“If anything, that’s probably fairly large,” said Richard Armstrong, a senior research scientist at the Boulder, Colo.-based Cooperative Institute for Research in Environmental Sciences (CIRES), who studies melt impact in the Himalayas.

“Most of the people downstream, they get the water from the monsoon,” Armstrong said. “It doesn’t take away from the importance [of glacier melt], but we need to get the science right for future planning and water resource assessments.”

The Himalayan glaciers feed into Asia’s biggest rivers: the Indus, the Ganges and the Brahmaputra in India, Pakistan and Bangladesh, and the Yellow and Yangtze rivers in China. Early studies pegged the amount of meltwater in these river basins as high as 60 or 70 percent. But reliable data on how much water the glaciers release or where that water goes have been difficult to develop. Satellite images can’t provide such regular hydrometeorological observations, and expeditions take significant time, money and physical exertion.

New methods, though, are refining the ability to study this and other remote glacial mountain ranges. Increasingly, scientists are finding that the numbers vary depending on the river, and even in different parts of the same river.

Creeping hyperbole
“There has been a lot of misinformation and confusion about it,” said Peter Gleick?, co-director of the California-based Pacific Institute for Studies in Development, Environment and Security. “About 1.3 billion people live in the watersheds that get some glacier runoff, but not all of those people depend only on the water from those watersheds, and not all the water in those watersheds comes from glaciers. Most of it comes from rainwater,” he said.

A key step forward came last year when scientists at Utrecht University in the Netherlands, using remote sensing equipment, found that snow and glacier melt is extremely important to the Indus and Brahmaputra basins, but less critical to others. In the Indus, they found, the meltwater contribution is 151 percent compared to the total runoff generated at low elevations. It makes up about 27 percent of the Brahmaputra — but only between 8 and 10 percent for the Ganges, Yangtze and Yellow rivers. Rainfall makes up the rest.

That in itself is significant, and could reduce food security for 4.5 percent of the population in an already-struggling region. Yet, scientists complain, data are often inaccurately incorporated in dire predictions of Himalayan glacial melt impacts.

“Hyperbole has a way of creeping in here,” said Bryan Mark, an assistant professor of geography at Ohio State University and a researcher at the Byrd Polar Research Center.

Mark, who focuses on the Andes region, developed a method of determining how much of a community’s water supply is glacier-fed by analyzing the hydrogen and oxygen isotopes in water samples. He recently took that experience to Nepal, where he collected water samples from the Himalayan glacier-fed Kosi River? as part of an expedition led by the Mountain Institute.

Based on his experience in the Rio Santa — where it was once assumed that 80 percent of water in the basin came from glacier melt — Mark said he expects to find that the impact of monsoon water is greatly underestimated in the Himalayas.

Jeff La Frenierre, a graduate student at Ohio State University, is studying Ecuador’s Chimborazo glacier, which forms the headwaters of three different watershed systems, serving as a water source for thousands of people. About 35 percent of the glacier coverage has disappeared since the 1970s.

La Frenierre first came to Ecuador as part of Engineers Without Borders to help build a water system, and soon started to ask what changes in the mountain’s glacier coverage would mean for the irrigation and drinking needs of the 200,000 people living downstream. Working with Mark and analyzing water streams, he said, is upending many of his assumptions.

Doomsday descriptions don’t fit
“The easy hypothesis is that it’s going to be a disaster here. I don’t know if that’s the case,” La Frenierre said. He agreed that overstatements about the impacts are rampant in the Himalayas as well, saying, “The idea that 1.4 billion people are going to be without water when the glaciers melt is just not the case. It’s a local problem; it’s a local question. There are places that are going to be more impacted than other places.”

Those aren’t messages that environmental activists will likely find easy to hear. Armstrong recalled giving a presentation in Kathmandu on his early findings to a less-than-appreciative audience.

“I didn’t agree with the doomsday predictions, and I didn’t have anything that was anywhere near spectacular,” Armstrong said. But, he added, “At the same time, it’s just basic Earth science, and we want to do a better job than we have been.”

The more modest numbers, they and other scientists stressed, don’t mean that glacier melt is unimportant to river basins. Rather, they said, they mean that the understanding of water systems throughout the Himalayan region must improve and water management decisions will need to be made at very local levels.

“We need to know at least where the water comes from,” Armstrong said. “How can we project into the future if we don’t know where the water comes from now?”

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

Wildfires Rage across Drought-Stricken Texas

Wildfires Rage across Drought-Stricken Texas: Scientific American Gallery.

 

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Texas, which has suffered extreme droughts in 2011, is now grappling with deadly, widespread wildfires. Two people were killed September 4 in a fire in Gladewater, Texas, and officials said September 6 that two more had died in  the massive Bastrop County fire near Austin. More than 1,000 homes have been destroyed in the past several days, according to the Texas Forest Service (TFS), and dozens of fires continue to burn across the Lone Star State.

NASA’s Earth-orbiting Aqua satellite captured this photograph of eastern Texas, Louisiana and the Gulf of Mexico on September 6. (State borders have been overlaid for reference.) In the past week the TFS has responded to 172 fires on 54,653 hectares; more than 1.4 million hectares—2 percent of the state’s land area—have burned this year.

The first half of the year was the driest on record in Texas. In June the U.S. Department of Agriculture designated 213 Texas counties as natural disaster areas; nearly all of the state is currently classified as drought level D4 (exceptional drought), the highest such listing on the National Drought Mitigation Center’s U.S. Drought Monitor. But the droughts and fires of 2011 may only be a preview of things to come; climate change is expected to raise temperatures and could also reduce rainfall in Texas, according to climate models.

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Simulation shows it’s possible to tow an iceberg to drought areas

Simulation shows it’s possible to tow an iceberg to drought areas.

Iceberg

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Image credit: Trevor Williams.

(PhysOrg.com) — Way back in the 70’s Georges Mougin, then an engineering graduate, had a big idea. He suggested that icebergs floating around in the North Atlantic could be tethered and dragged south to places that were experiencing a severe drought, such as the Sahel of West Africa. Mougin received some backing funds from a Saudi prince but most “experts” at the time scoffed at his idea and the whole scheme was eventually shelved.

Cut to 2009 and French software firm Dassault Systemes, who thought maybe Mougin was on to something after all and contacted him to suggest modeling the whole idea on a computer. After applying 15 engineers to the problem, the team concluded that towing an from the waters around Newfoundland to the Canary Islands off the northwest coast of Africa, could be done, and would take under five months, though it would cost nearly ten million dollars.

In the simulation, as in a real world attempt, the selected iceberg would first be fitted with an insulating skirt to stave off melting; it would then be connected to a tugboat (and a kite sail) that would travel at about one knot (assuming assistance from ocean currents). In the simulated test, the iceberg arrived intact having lost only 38 percent of its seven ton mass.

A real world project would of course require hauling a much bigger berg; experts estimate a 30 million ton iceberg could provide fresh water for half a million people for up to a year. There would also be the problem of transporting the water from the berg in the ocean to the drought stricken people. The extraordinary costs for such a project would, it is assumed, come from the price tag for the skirt, five months of diesel fuel for the tugboat, the man hours involved and then finally, distribution of the fresh water at the destination.

Scientists estimate that some 40,000 icebergs break away from the polar ice caps each year, though only a fraction of them would be large enough to be worth the time and expense of dragging them to a place experiencing a drought, such as the devastating one currently going on in the Horn of Africa.

Mougin, newly reinvigorated by the results of the recent study, at age 86, is now trying to raise money for a real-world test of the idea.

Peanut butter to the rescue in Somalia famine?

Peanut butter to the rescue in Somalia famine? – health – 26 July 2011 – New Scientist.

The Plumpy’Nut is coming. But will it arrive in time to save 3.5 million people who the Somali foreign minister says may starve to death?

Today the UN World Food Programme has airlifted 14 tonnes of the highly enriched “therapeutic” peanut butter to Mogadishu, the Somali capital, for immediate distribution to the 40,000 refugees who have gathered there to escape the triple crisis of drought-aggravated famine, war and escalating food prices.

Since it was recommended by the World Health Organization in 2007 as the emergency food of choice for malnourished infants, Plumpy’Nut, manufactured by French company Nutriset, has become a staple of international famine relief. Children can eat it straight from the packet instead of having to be fed intravenously. Based on peanut butter, it contains sugar, vegetable fat, and skimmed milk powder enriched with vitamins and minerals.

Now it’s at the heart of a twin-track plan agreed in Rome, Italy, today by the UN to address the famine crisis affecting 12 million people in the Horn of Africa.

Proven best

Stéphane Doyon, a nutrition expert for the charity Médecins Sans Frontières, says that sending ready-to-eat therapeutic foods like Plumpy’Nut is the best strategy to combat malnutrition in children rapidly. “It’s proven to work best against severe malnutrition, especially in situations where you don’t have the flexibility to individualise interventions,” he says. “Based on clinical science and evidence, they contain the right blend of macro and micronutrients needed to rehabilitate children from severe malnutrition.”

The crisis is particularly affecting Somalia itself and neighbouring Kenya and Ethiopia, where refugees from Somalia are arriving at a rate of 1500 to 2000 per day, according to the UNHCR refugee agency. The UN today agreed that the long-term solution is to invest in the future of farming in the region, but the other, much more urgent priority is to save those close to death through starvation.

“It’s vital we reach those at the epicentre of the famine with food assistance, especially the highly fortified nutritious products that are so important for vulnerable children,” WFP’s executive director Josette Sheeran said in a statement in Rome.

Famine ravages East Africa

Famine continues to ravage East Africa – Features – Al Jazeera English.

In Somalia, where civil war has ravaged the country, where conflict continues to claim victims, a new hardship is being visited on the innocent.

Thirty years ago the world rallied to help the famine victims of Ethiopia and across the Horn of Africa, and vowed never again.

Now, after the worst drought in the region in 60 years, thousands are dead, thousands dying and more than 11 million people are at risk.

The drought was officially declared last week by the United Nations, and the international community is now trying to co-ordinate an action plan.

They gathered in Rome at the headquarters of the United Nation’s Farming and Agriculture Organisation (FAO), the representatives of 191 countries, of non-government organisations, of charities and aid groups.

They were told by the foreign minister of Somalia’s government in exile Mohamed Ibrahim: “The people of Somalia now face widespread famine for a wide array of reasons, extremely low rates of rainfall for the past two years, al-Shabab’s blockade of humanitarian and aid agencies access to the needy, the vulnerability of the Somali people and the continual chaos and instability throughout the region”.

Famine in a failed state

The problem of access has dominated much of the discussion. Somalia is a failed state. The rule of law is ignored and the Islamist fighters of al-Shabab control large parts of the country. They have in the past banned international aid agencies from working in the area with threats of extreme violence. In early July it said would accept groups it had blocked. But just last week, it again said it would stop groups it considered Western or ”Christian”. And so people continue to starve, blocked from the help that could save them.

The famine is biting in Somalia, but 11 million people in Ethiopia, Kenya, Djibouti and Eritrea are also struggling to find enough food to eat. The drought has destroyed crops, conflict has forced people to run from the areas where they live, and – crucially – where they farm. The drop in production has led to a spike in demand, sending food prices soaring beyond the reach of most ordinary families. Refugees are spilling out of Somalia, heading to refugee camps where they hope not for a better life, but simply for the chance of one.

Josette Sheeran is the head of the UN’s World Food Programme. She arrived at the conference on the overnight flight from East Africa, having toured the areas most affected.

She saw thousands of Somalis slowly making their way to the temporary camps which are now almost bursting with exhausted, emaciated people. “What we saw is children who are arriving so weak that many of them are in stage four malnutrition and have little chance – less than 40 per cent chance – of making it,” she told the delegates.  “We also heard from women who had to leave babies along the road and make the horrifying choice of saving the stronger for the weaker or those who had children die in their arms,” she added.

Sheeran, who has been credited with bringing a new dynamism to the World Food Programme, denied that the world had ignored warnings that a crisis was coming, only waking up when pictures of dead babies started to fill the TV  screens. “This drought is worse than the one in the 1980s, but fewer people are dying because of the programmes put in place, the early-warning systems and the resilience measures that have been introduced.  It’s still too many and we need to work to save lives.”

Kanayo Nwanze is an agricultural specialist who runs the UN’s International Fund for Agricultural Development. He welcomes the international intervention but believes Africa should be doing much more to help Africans: ”If Africa does not get its house in order and expects the world to help us out, we are dreaming”, said Nwanze. And he told me, “Tanzania, Kenya and Ghana are moving ahead with agriculture but less than ten countries have fulfilled the pledge they made in 2003 to set aside ten per cent of their budgets for agriculture”.

Nwanze pointed out that 30 years ago, Africa was a net exporter of many foods. “Now it imports.  And that is due to bad governance.”

The international community has pledged many millions to help with the immediate crisis, but Barbara Stocking of the charity Oxfam believes that short-term fixes don’t help the long-term problems.  Describing the famine as “shameful”, she said, “We have not had the investment in small producers across the world that was expected.  The money has simply not come through”. And she insisted that people must hold their governments to account when they promise money to help and then don’t follow through.

As one delegate told me: “People are dying in the drought in the Horn of Africa because the rains failed. The international community can’t afford to do the same.”

Valle Grande, New Mexico, reveals evidence of ancient megadrought

Valle Grande, New Mexico : Image of the Day.

Valle Grande, New Mexico

acquired May 25, 2011 download large image (5 MB, JPEG)
acquired May 25, 2011 download GeoTIFF file (41 MB, TIFF)

The American Southwest is prone to drought, and the summer of 2011 proved no exception, when a severe drought extended from Arizona to Florida. But a sediment core from New Mexico suggests that today’s droughts—even the 1930s Dust Bowl—are fleeting events compared to conditions of the ancient past. Hundreds of thousands of years ago, some droughts could persist for centuries. Researchers find one ancient period of warm, dry conditions especially intriguing because it was, in many ways, similar to conditions on Earth during the last 10,000 years.

Clues about this ancient period are preserved in a dry lakebed in New Mexico named Valle Grande. On May 25, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of the lakebed. It is an unevenly shaped expanse of beige grassland situated inside the larger Valles Caldera.

Researchers extracted a 260-foot (80-meter) sediment core from this lakebed in 2004, and published their analysis in 2011. Ancient lake muds in the core document the region’s climate between 360,000 and 550,000 years ago. During that time, glaciers advanced over North America in recurring ice ages, and conditions warmed in interglacial periods. The core includes sediments from two warm interglacials.

One interglacial covered in the sediment core that particularly interested the research team is known as Marine Isotope Stage 11 (MIS 11), which occurred around 400,000 years ago. Our planet’s orbit around the Sun has varied over geologic time, but the 50,000-year period comprising MIS 11 experienced an orbital configuration similar to that of the last 10,000 years and, consequently, the amount of solar radiation reaching the Earth was similar.

During MIS 11, the researchers found, the climate of the American Southwest underwent a series of changes. As ice-age conditions gave way to warming, plant life thrived in a seasonally wet climate. But the warming continued, withering grasses and shrubs, and drying out lakes. Mud cracks in the sediment core illustrate the aridity. The drought documented by the sediment core lasted thousands of years—a megadrought.

The sediment core suggests that the megadrought occurring in MIS 11 not only began abruptly, but also ended abruptly, replaced by cooler, wetter conditions. As geologists explain, we live in an interglacial today; Earth’s most recent ice age ended only about 10,000 years ago. The similarity of the Earth’s orbital configuration between MIS 11 and now suggests that, as happened hundreds of thousands of years ago, the Southwest might eventually experience cool, wet conditions again. Such a transition could be derailed, however, by warming caused by increased concentrations of greenhouse gases.

  1. References

  2. Fawcett, P.J., Werne, J.P., Anderson, R.S., Heikoop, J.M., Brown, E.T., Berke, M.A., Smith, S.J., Goff, F., Donohoo-Hurley, L., Cisneros-Dozal, L.M., Schouten, S., Sinninghe Damste, J.S., Huang, Y., Toney, J., Fessenden, J., WoldeGabriel, G., Atudorei, V., Geissman, J.W., Allen, C.D. (2011). Extended megadroughts in the southwestern United States during Pleistocene interglacials. Nature, 470, 518–521.
  3. Rickman, J.E. (2011, February 28). Dry lake reveals evidence of southwestern “megadroughts.” Los Alamos National Laboratory. Accessed July 18, 2011.
  4. U.S. Drought Monitor. (2011, July 14). Conditions for July 12, 2011. (PDF file) University of Nebraska, Lincoln. Accessed July 16, 2011.
  5. University of California Museum of Paleontology. The Pleistocene. Accessed July 18, 2011.
  6. Williams, J. (2011). Climate change: Old droughts in New Mexico. Nature, 470, 473–474.

NASA image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 Team. Caption by Michon Scott.

Instrument: 
EO-1 – ALI

Global warming not to blame for 2011 droughts

Global warming not to blame for 2011 droughts – environment – 15 June 2011 – New Scientist.

ADD one more to the list: after the driest spring in more than 20 years, parts of eastern England are officially in a state of drought, according to the UK’s Department for Environment, Food and Rural Affairs. This comes hard on the heels of some of the worst droughts on record across the globe, from Texas to China.

While global warming is an obvious suspect, there’s no evidence that it is to blame. Though climate change models predict extended droughts and periods of intense rainfall for the end of the 21st century, they don’t explain the current droughts, says Martin Hoerling at the US National Oceanic and Atmospheric Administration. “A lot of these extreme conditions are natural variations of the climate. Extremes happen, heat waves happen, heavy rains happen,” he says.

Drought across the southern US – and heavy rains across the north of the country – are a result of La Niña, says Michael Hayes, director of the National Drought Mitigation Center at the University of Nebraska-Lincoln. An extended holding pattern in the jet stream, the same type of “blocking event” that caused last summer’s heat wave in Russia, is responsible for this year’s European droughts, says Michael Blackburn of the University of Reading, UK.

As for the apparent convergence of droughts worldwide, Mark Saunders of University College London says current conditions aren’t that unusual. News media may simply be more tuned in to reporting extreme weather events.

African land grab could lead to future water conflicts

African land grab could lead to future water conflicts – environment – 26 May 2011 – New Scientist.

IS THIS the face of future water conflicts? China, India and Saudi Arabia have lately leased vast tracts of land in sub-Saharan Africa at knockdown prices. Their primary aim is to grow food abroad using the water that African countries don’t have the infrastructure to exploit. Doing so is cheaper and easier than using water resources back home. But it is a plan that could well backfire.

“There is no doubt that this is not just about land, this is about water,” says Philip Woodhouse of the University of Manchester, UK.

Take Saudi Arabia, for instance. Between 2004 and 2009, it leased 376,000 hectares of land in Sudan to grow wheat and rice. At the same time the country cut back on wheat production on home soil, which is irrigated with water from aquifers that are no longer replenished – a finite resource.

Meanwhile, firms from China and India have leased hundreds of thousands of hectares of farmland in Ethiopia. Both China and India have well-developed irrigation systems, but Woodhouse says their further development – moving water from the water-rich south to northern China, for instance – is likely to be more costly than leasing land in Africa, making the land-grab a tempting option.

But why bother leasing land instead of simply importing food? Such imports are equivalent to importing “virtual water”, since food production accounts for nearly 80 per cent of annual freshwater usage. A new study into how this virtual water moves around the world offers an explanation for the leasing strategy. Ignacio Rodriguez-Iturbe of Princeton University and Samir Suweis of the Swiss Federal Institute of Technology in Lausanne have built the first mathematical model of the global virtual water trade network, using the UN Food and Agricultural Organization’s data on trade in barley, corn, rice, soya beans, wheat, beef, pork, and poultry in 2000. They combined this with a fine-grained hydrological model (Geophysical Research Letters, DOI: 10.1029/2011GL046837).

The model shows that a small number of countries have a large number of connections to other countries, offering them a steady and cheap supply of virtual water even if some connections are compromised by drought or political upheaval. A much larger number of countries have very few connections and so are vulnerable to market forces.

Most importantly, the model shows that about 80 per cent of the water flows over only about 4 per cent of the links, which Rodriguez-Iturbe calls the “rich club phenomenon”. In total, the model shows that in 2000, there were 6033 links between 166 nations. Yet 5 per cent of worldwide water flow was channelled through just one link between two “rich club” members – the US and Japan.

The power of the rich club may yet increase. The model allows the team to forecast future scenarios – for example, how the network will change as droughts and spells of violent precipitation intensify due to climate change. Predictably, this will only intensify the monopoly, says Suweis. “The rich get richer.”

China and India are not currently major players in the virtual water network on a per capita basis, and as the network evolves they could find themselves increasingly vulnerable to market forces and end up paying more for the food they import. Leasing land elsewhere is an attempt to secure their food and water supply in a changing world. But it could be a short-sighted move.

Last year, Paolo D’Odorico of the University of Virginia at Charlottesville showed that a rise in the virtual water trade makes societies less resilient to severe droughts (Geophysical Research Letters, DOI: 10.1029/2010GL043167). “[It] causes a disconnect between societies and the water they use,” says D’Odorico. The net effect is that populations in nations that import water can grow without restraint since they are not limited by water scarcity at home.

Although this could be seen as a good thing, it will lead to greater exploitation of the world’s fresh water. The unused supplies in some areas that are crucial in case of major droughts in other areas will dry up. “In case of major droughts we [will] have less resources available to cope with the water crisis,” says D’Odorico.

In the end, then, the hunt for water that is driving emerging economies to rent African land to grow their crops could come back to haunt them.