Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hello People, Goodbye Soil

08.01.2015

New study in Geology shows humans erode soil 100 times faster than nature

A new study shows that removing native forest and starting intensive agriculture can accelerate erosion so dramatically that in a few decades as much soil is lost as would naturally occur over thousands of years.


Paul Bierman, UVM

These are floodwaters laden with suspended sediment during the peak discharge of Hurricane Isabel flood on the Potomac River at Great Falls, Virginia, September 2003. Over 160,000 cubic feet per second of runoff, carrying sediment eroded from Piedmont riverbanks and farm fields upstream, submerged the falls. Floods of this magnitude recur about once a decade at Great Falls. New research by scientists at the University of Vermont and Imperial College, London, published in the February 2015 issue of the journal Geology, show that eroded soil, carried in rivers like this one, accelerated dramatically in the wake of European forest-clearing and intensive agriculture in North America.

Had you stood on the banks of the Roanoke, Savannah, or Chattahoochee Rivers a hundred years ago, you’d have seen a lot more clay soil washing down to the sea than before European settlers began clearing trees and farming there in the 1700s. Around the world, it is well known that deforestation and agriculture increases erosion above its natural rate.

But accurately measuring the natural rate of erosion for a landscape—and, therefore, how much human land use has accelerated this rate—has been a devilishly hard task for geologists. And that makes environmental decision-making—such as setting allowable amounts of sediment in fish habitat and land use regulation—also difficult.

Now research on these three rivers, and seven other large river basins in the US Southeast, has, for the first time, precisely quantified this background rate of erosion. The scientists made a startling discovery: rates of hillslope erosion before European settlement were about an inch every 2500 years, while during the period of peak land disturbance in the late 1800s and early 1900s, rates spiked to an inch every 25 years.

“That’s more than a hundred-fold increase,” says Paul Bierman, a geologist at the University of Vermont who co-led the new study with his former graduate student and lead author Luke Reusser, and geologist Dylan Rood at Imperial College, London. “Soils fall apart when we remove vegetation,” Bierman says, “and then the land erodes quickly.”

Their study was presented online on January 7, 2015, in the February issue of the journal Geology. Their work was supported by the National Science Foundation.

Precious resource
“Our study shows exactly how huge an effect European colonization and agriculture had on the landscape of North America,” says Dylan Rood, “humans scraped off the soil more than 100 times faster than other natural processes!”

Along the southern Piedmont from Virginia to Alabama—that stretch of rolling terrain between the Appalachian Mountains and the coastal plain of the Atlantic Ocean—clay soils built up for many millennia. Then, in just a few decades of intensive logging, and cotton and tobacco production, as much soil eroded as would have happened in a pre-human landscape over thousands of years, the scientists note. “The Earth doesn't create that precious soil for crops fast enough to replenish what the humans took off,” Rood says. “ It’s a pattern that is unsustainable if continued.”

The scientist collected twenty-four sediment samples from these rivers—and then applied an innovative technique to make their measurements. From quartz in the sediment, Bierman and his team at the University of Vermont's Cosmogenic Nuclide Laboratory extracted a rare form of the element beryllium, an isotope called beryllium-10. Formed by cosmic rays, the isotope builds up in the top few feet of the soil.

The slower the rate of erosion, the longer soil is exposed at Earth’s surface, the more beryllium-10 it accumulates. Using an accelerator mass spectrometer at the Lawrence Livermore National Laboratory, the geologists measured how much beryllium-10 was in their samples—giving them a kind of clock to measure erosion over long time spans.

These modern river sediments revealed rates of soil loss over tens of thousands of years. This allowed the team to compare these background rates to post-settlement rates of both upland erosion and downriver sediment yield that have been well documented since the early 1900s across this Piedmont region.

While the scientists concluded that upland erosion was accelerated by a hundred-fold, the amount of sediment at the outlets of these rivers was increased only about five to ten times above pre-settlement levels, meaning that the rivers were only transporting about 6% of the eroded soil. This shows that most of the material eroded over the last two centuries still remains as “legacy sediment,” the scientists write, piled up at the base of hillslopes and along valley bottoms.

“There's a huge human thumbprint on the landscape, which makes it hard to see what nature would do on its own,” Bierman says, “but the beauty of beryllium-10 is that it allows us to see through the human fingerprint to see what's underneath it, what came before.”

“This study help us understand how nature runs the planet,” he says, “compared to how we run the planet.”

Soil conservation
And this knowledge, in turn, can “help to inform land use planning,” Bierman says. “We can set regulatory goals based on objective data about how the landscape used to work.” Often, it is difficult to know whether conservation strategies—for example, regulations about TMDL’s (total maximum daily loads) of sediment—are well fitted to the geology and biology of a region. “In other words, an important unsolved mystery is: "How do the rates of human removal compare to ‘natural’ rates, and how sustainable are the human rates?" Rood asks.

While this new study shows that erosion rates were unsustainable in the recent past, “it also provides a goal for the future,” Rood says. “We can use the beryllium-10 erosion rates as a target for successful resource conservation strategies; they can be used to develop smart environmental policies and regulations that will protect threatened soil and water resources for generations to come.”

Contact Information
Joshua Brown
Senior Communications Officer
joshua.e.brown@uvm.edu
Phone: 802-656-3039

Joshua Brown | newswise
Further information:
http://www.uvm.edu/

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>