News / Science & Technology

Dust From Farming May Affect Rainfall

Dust storm in the Sahara (Parc National du Banc d'Arguin)
Dust storm in the Sahara (Parc National du Banc d'Arguin)

Multimedia

Audio

New research suggests agriculture has greatly increased the amount of dust blowing off of West Africa, the world's largest source of atmospheric dust, and may have been one factor driving the decrease in rainfall in the region over the past several centuries.

Dust is more than a housekeeping nuisance. To climate scientists, dust is a force of nature. It's the most abundant particle in the atmosphere, and it reflects sunlight and heat.

Africa's Sahel region
Africa's Sahel region

The world's largest source of dust is the Sahara and Sahel region of West Africa. And its influence on the environment is surprisingly wide-ranging, according to Stefan Mulitza, a marine geologist at the University of Bremen in Germany.

"It probably interacts with cloud formation; people think that it has an influence on the quantity of precipitation; hurricane activity through the cooling of the sea surface is probably affected; and last but not least, the quality of the air we breathe" is also affected by dust, Mulitza says. Dust from severe West African dust storms can blow all the way across the Atlantic Ocean to the U.S. state of Florida.

3,000 years of dust

But it's been hard for scientists to unravel what impact human activity has had on dust production in West Africa, in part because good data from satellites and ground stations has only been available for the last few decades.

Saharan dust blowing off Northwest Africa to the Atlantic Ocean
Saharan dust blowing off Northwest Africa to the Atlantic Ocean

In a new study in the journal Nature, Mulitza and his colleagues studied ocean sediments off the coast of Senegal and Mauritania. They constructed a record of West African dust production stretching back more than three thousand years.

For nearly that entire period, dust generation followed a predictable pattern: more dust in drier years, less in wetter ones. But then, beginning in the 19th century, something surprising happened: dust production increased dramatically.

Mulitza says that increase in dust coincides with a major economic change in the Sahel region.

"In the 19th century groundnuts were introduced into Senegal, just as one example," he says. "And there was a very widespread commercial agriculture to fuel the groundnut oil industry."

Unintended consequences

Farmers in the Sahel cleared forests to produce groundnuts and other cash crops. He says that disrupted the sandy soil and led to a sharp rise in the amount of dust blowing off the Sahel.

Mauritanian landscape. The photo was taken on a field trip to Mauritania led by Jan-Berend Stuut in November 2009.
Mauritanian landscape. The photo was taken on a field trip to Mauritania led by Jan-Berend Stuut in November 2009.

And that dust may have been one factor behind the drier climate in the region over the past few centuries. Although the effects of dust on climate are complex and not fully understood, it may cool surface temperatures, which can shift precipitation patterns away from the region.

Atmospheric scientist Charlie Zender at the University of California at Irvine says this is the first study to link farming with increased dust generation in the world's largest source of dust. And he says there may be lessons for farmers elsewhere in the world.

"In those regions where rainfall isn't plentiful and abundant, this study suggests that using those surfaces for agriculture, using that land, will lead to these types of unintended consequences, whether that's in Africa or not," he says.

Cooling dust

Cornell University climate researcher Natalie Mahowald says if future studies confirm Mulitza's findings, it could have larger implications for climate change research.

"It would mean that there has been a cooling from dust over the 20th century that we haven't really been thinking about previously," she says. "And this cooling could be hiding some of the increase or the warming that should be happening from carbon dioxide."

Mahowald says that could mean the Earth is more sensitive to the warming effects of carbon dioxide than previously thought.

Mulitza says his findings may not be all bad news. He notes that increased dust over the tropical Atlantic may have lowered ocean surface temperatures, which may have reduced hurricane activity. "The climate system is coupled," he says. "And if you change something in the tropics, and you change something in the African dust source, it has global consequences" – although, he says, more research will be needed to quantify exactly what those consequences are.

You May Like

Lebanese Media Unite to Support Palestinians in Gaza

Joint newscast billed as Arab world’s first unified news bulletin in support of Hamas-controlled Gaza Strip More

Photogallery Australian PM Alleges ‘Coverup’ at MH17 Crash Site

Meanwhile, Russia's ambassador to Malaysia denies plane's black boxes were opened before they were handed over to Malaysian officials More

Despite Advances in AIDS Treatment, Stigma Lingers

Leading immunologist tells VOA that stigma is often what prevents those infected with disease from seeking treatment More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
IAEA: Iran Turns its Enriched Uranium Into Less Harmful Formi
X
July 22, 2014 10:26 AM
Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.
Video

Video IAEA: Iran Turns its Enriched Uranium Into Less Harmful Form

Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.
Video

Video Relic of Saint Draws Catholics Worried About Immigration Issue

A Roman Catholic saint who is a figure of devotion for those crossing the border into the United States is attracting believers concerned about the plight of undocumented immigrants. Mike O'Sullivan reports from Los Angeles, where a relic of Saint Toribio has drawn thousands to local churches.
Video

Video Ukraine Rebels Surrender MH17 Black Boxes

After days of negotiations, a senior separatist leader handed over two black boxes from an airliner downed over eastern Ukraine to Malaysian experts early Tuesday. While on Monday, the U.N. Security Council unanimously demanded that armed groups controlling the crash site allow safe and unrestricted access to the wreckage.
Video

Video In Cambodia, HIV Diagnosis Brings Deadly Shame

Although HIV/AIDS is now a treatable condition, a positive diagnosis is still a life altering experience. In Cambodia, people living with HIV are often disowned by friends, family and the community. This humiliation can be unbearable. We bring you one Cambodian woman’s struggle to overcome a life tragedy and her own HIV positive diagnosis.
Video

Video Nature of Space Exploration Enters New Age

Forty-five years ago this month, the first humans walked on the moon. It was during an era of the space race between the United States and the Soviet Union. World politics have changed since then and -- as Elizabeth Lee reports -- so has the nature of space exploration.
Video

Video Chicago’s Argonne Lab Developing Battery of the Future

In 2012, the U.S. Department of Energy’s Office of Science awarded a $120 million grant to a new technology center focused on battery development - headquartered at Argonne National Laboratory in suburban Chicago, Illinois. As VOA’s Kane Farabaugh reports, there scientists are making the next technological breakthroughs in energy storage.
Video

Video In NW Pakistan, Army Offensive Causes Massive Number of Displaced

Pakistan’s army offensive in North Waziristan has resulted in the large-scale displacement of the local population. VOA's Ayaz Gul reports from northwest Pakistan where authorities say around 80 percent of the estimated 1 million internally displaced persons [IDPs] have settled in Bannu district, while much of the remaining 20 percent are scattered in nearby cities.
Video

Video Kurdish Peshmerga Force Secures Kirkuk, Its Oil

The Kurdistan regional government has sent its Peshmerga troops into the adjacent province of Kirkuk to drive out insurgents, and to secure the area's rich oil fields. By doing this, the regional government has added a fourth province to the three it officially controls. The oil also provides revenue that could make an independent Kurdistan economically strong. VOA’s Jeffrey Young went out with the Peshmerga and filed this report.
Video

Video Malaysia Reeling: Second Air Disaster in Four Months

Malaysia is reeling from the second air disaster in four months involving the country’s flag carrier. Flight 340 vanished in March and despite an extensive search, no debris has been found. And on Thursday, Flight 17, likely hit by a surface-to-air missile, came apart over eastern Ukraine. The two incidents together have left more than 500 people dead. VOA Correspondent Steve Herman reports from Kuala Lumpur.

AppleAndroid