By Linda Qiu, National
Geographic
PUBLISHED Sat Dec 06 04:03:00 EST 2014
PUBLISHED Sat Dec 06 04:03:00 EST 2014
An ancient Byzantine ruin outside
Aleppo, Syria, is a testament to the impact of soil erosion on a once
prosperous community. Misusing soil has led to the collapse of ancient
civilizations as well as conflicts in the modern world.
Photograph by Jim Richardson,
National Geographic
We walk on it every day. Get it
under our fingernails. Track it into the house. But do we really appreciate the
vital role soil plays—not just in the environment, but in human health?
The United Nations Food and
Agriculture Organization is giving soil its due. Friday, December 5, is World Soil Day, and 2015, the FAO has declared,
will be the
International Year of Soils.
"The minerals, the nutrients
that make up our muscles and bones almost entirely come from soil," says Jerry Glover, a National Geographic Emerging
Explorer and agroecologist at the U.S. Agency for International Development.
"This is, of course, very
critical because we're supposed to be increasing agricultural production to
feed and nourish some of the ten billion people, but it's at the same time that
our soils are the thinnest and most nutrient depleted."
Here are five things you should know
about soil.
1. Soil, like oil, is a finite
resource.
Poor farming practices deplete soil
nutrients faster than they are able to form, leading to loss of soil fertility
and degraded lands. Glover compares it to the concerns that surround oil
depletion.
"We still continue to harvest
more nutrients than we replace in soil," he says. If a country is
extracting oil, Glover points out, people worry about what will happen if the
oil runs out. But they don't seem to worry about what will happen if we run out
of soil. (Read "Our Good Earth" in National Geographic magazine.)
By 1991, an area bigger than the
United States and Canada combined was lost to soil erosion—and it shows no
signs of stopping. In fact, says Glover, native forests and vegetation are
being cleared and converted to agricultural land at a rate greater than any
other period in history. To restore soil in the United States to its
pre-Columbian levels would take about 200 years.
Cletus Reed, 80, and his grandson
Sam stand at a cross-section of exposed ground on their Iowa corn farm.
Photographer Jim Richardson created the cross-section to illustrate the
potential impact of erosion. The Reeds, who lost more than a foot of topsoil to
erosion, subsequently altered their farming practices.
Photograph by Jim Richardson,
National Geographic
2. Misusing soil can topple
civilizations.
Modern examples of the impact of
soil erosion are well-known: the Dust Bowl in the American and Canadian
prairies, the erosion of China's Loess Plateau, the famine in Africa's Sahel.
Ancient societies also reaped what they sowed when it came to their farming
practices.
"The Romans still plowed
themselves out of business, as did the Greeks, and Easter Islanders," says David Montgomery, who studies topography at the
University of Washington in Seattle and is the author of Dirt: The Erosion of Civilizations.
On the flip side, few societies have
actually taken care of their soil, he says. Inca terracing practices and
agroforestry on the Polynesian island of Tikopia are on the short list of
exceptions.
3. Good soil usage helps prevent
droughts.
During recent droughts in the
western U.S., farmers who used no-till practices—for example, not disturbing
the soil through plowing—produced healthier crops, according to Montgomery.
Soil conservation goes hand in hand with water conservation, he says; healthier
soils retain more water.
The impact of poor soil use,
meanwhile, goes beyond food production. Wind can carry thinned topsoil off
fields and onto large bodies of water. Through a process known as
eutrophication, the excess nutrients hasten plant growth and algae bloom,
sucking up oxygen in the water and killing fish and other marine fauna.
"In the Gulf of Mexico, dead
zones have developed during certain parts of the year," says Glover.
"These are often prime fishing areas and prime biodiversity areas, now
dead because of soil carried thousands of miles downstream."
4. High-tech makes a difference.
There has been improvement in soil
conservation in the United States since the introduction of no-till and
low-till farming, but reducing soil disturbance is not enough. The restoration
of soil health, experts say, will require new practices and old-fashioned
"soil husbandry."
Experts agree that healthy soil
requires a marriage of ecology and technology, such as planting perennial
strains of grain crops. Another approach: sophisticated farming systems that
integrate crop production with native vegetation and livestock—a system that
has successfully restored soils in northern Ethiopia, says Glover. (Related: "Why Tiny Microbes Mean Big Things for Farming.")
Date
trees line a terrace in the Loess Plateau region of China. Restoration projects
like this one mix forestry with agriculture to improve soil fertility.
Photograph by Jim Richardson, National Geographic
5.
Soil is alive.
Chemical
fertilizers, which replace three or four nutrients, are simply not enough to
replace the complex system that is soil. They're "not a full health
package," says Glover.
That's
because soil is crawling with microbes and bugs, which nourish the soil. They
help cycle nutrients in exchange for plant sugars. It's a symbiotic
relationship that is the root of life, but we don't fully understand it,
according to Montgomery.
"This
is brand-new science. Over the past 30 years, there's been a big shift in our understanding
of microbial connections and the community dynamics under the ground," he
says. "It's the hidden half of nature."
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