The Lowdown on Topsoil: It's Disappearing
The planet is getting skinned.
Call it the thin brown line. Dirt. On average, the planet is covered with little more than 3 feet of topsoil -- the shallow skin of nutrient-rich matter that sustains most of our food and appears to play a critical role in supporting life on Earth.
"We're losing more and more of it every day," said David Montgomery, a geologist at the University of Washington. "The estimate is that we are now losing about 1 percent of our topsoil every year to erosion, most of this caused by agriculture."
"It's just crazy," fumed John Aeschliman, a fifth-generation farmer who grows wheat and other grains on the Palouse near the tiny town of Almota, just west of Pullman.
"We're tearing up the soil and watching tons of it wash away every year," Aeschliman said. He's one of a growing number of farmers trying to persuade others to adopt "no-till" methods, which involve not tilling the land between plantings, leaving crop stubble to reduce erosion and planting new seeds between the stubble rows.
Montgomery has written a popular book, "Dirt," to call public attention to what he believes is a neglected environmental catastrophe. A geomorphologist who studies how landscapes form, Montgomery describes modern agricultural practices as "soil mining" to emphasize that we are rapidly outstripping the Earth's natural rate of restoring topsoil.
"Globally, it's clear we are eroding soils at a rate much faster than they can form," said John Reganold, a soils scientist at Washington State University. "It's hard to get people to pay much attention to this because, frankly, most of us take soil for granted."
The National Academy of Sciences has determined that cropland in the U.S. is being eroded at least 10 times faster than the time it takes for lost soil to be replaced.
The United Nations has warned of worldwide soil degradation -- especially in sub-Saharan Africa, where soil loss has contributed to the rapidly increasing number of malnourished people.
Healthy topsoil is a biological matrix, a housing complex for an incredibly diverse community of organisms -- billions of beneficial microbes per handful, nitrogen-fixing fungi, nutrients and earthworms whose digestive tracts transform the fine grains of sterile rock and plant detritus into the fertile excrement that gave rise to the word itself ("drit," in Old Norse).
As such, true living topsoil cannot be made overnight, Montgomery emphasized. Topsoil grows back at a rate of an inch or two over hundreds of years. Very slowly.
"Globally, it's pretty clear we're running out of dirt," Montgomery said.
Ron Myhrum, state soil scientist with the U.S. Department of Agriculture's office in Spokane, agreed that global soil loss is a huge problem. But Myhrum said erosion rates in the Northwest region have improved recently because of better conservation farming practices, including federal payments to farmers to leave some natural ground cover in highly erodible areas.
"We don't have the kind of dust storms here we used to have," Myhrum said. "What's more alarming to me than erosion is conversion of farmland to urban use."
That is indeed another way to lose soil -- paving it over. Judy Herring, manager of King County's farmland preservation program, said the county has lost 60 percent of its farmland since the 1960s. In 1979, Herring said, voters approved a bond program that buys back farmland to protect it from development (and has done this for 13,200 acres so far).
But while some land is lost to development, pollution or changing weather patterns, Montgomery, Reganold and others say global soil loss is a crisis mostly rooted in agriculture.
"Erosion rates have improved here, but that doesn't mean they're good," Reganold said. Topsoil clearly is still being stripped off faster than it can be regenerated, he said.
Aeschliman, the Palouse farmer, a stocky and energetic man who doesn't seem to notice that he's in his 60s, stood on a dirt road looking at the difference between his land and that of a neighbor. Because most neighbors are relatives, he did not provide any names here.
"Just look at that!" he bellowed, pointing to a series of water-carved cracks and gouges running down a recently tilled field of wheat. Every year, he said, these fields are tilled and the rains come, washing the soil down into the road so deep the county routinely has to dig it out. The rest of the soil runs off to the Snake River and, eventually, to the Pacific.
"Here, look at this stuff," Aeschliman said as he held up a handful of the fine brown silt that had eroded off his neighbor's (cousin's) hillside. "Now, look over here."
He walked across the road to his no-till wheat field. Unlike the rolling hills of loose dirt on the tilled field, Aeschliman's field looks more like a shag rug, with its rows of dead wheat stubble. He reached down into the dirt and pulled out a coarsely textured, much darker clump of dirt, roots and debris.
"This soil is full of worms, bacteria and all sorts of life," Aeschliman said. "And it stays put. That stuff over there (waving his thick hand back behind him) is just powder, brown dust. It's dead. There's no worms, no life in it."
Thirty years ago, Aeschliman was one of the first in the Palouse to grow his grains using no-till farming methods. He's an ardent no-till proselytizer today, but he didn't abandon tilling the fields based on some organic epiphany or desire to save the world.
"I just got tired of all the mud," Aeschliman said. The family home, built in the 1880s, sits at the base of a long drainage off the rolling wheat fields. Every spring, with the tilling and the rain, his home would be a foot deep in muddy runoff.
No-till farming could do a lot to reduce topsoil erosion, Reganold said, but it's not without its downsides. Switching to no-till farming requires heavy upfront investment and learning new techniques, he said, and also tends to depend more on herbicides because the weeds are no longer controllable by plowing them into the soil.
Organic farming methods also can reduce soil loss, Reganold said. He cited his own research, which has shown a marked increase in soil health, water retention and regrowth when organic methods are used rather than the traditional methods.
A regional association of farmers and other proponents of no-till agriculture, also known as direct-seed farming, is holding its annual meeting in Kennewick next week. Aeschliman is one of the founders of the organization, the Pacific Northwest Direct Seed Association, and is happy to see that no-till farming is growing in popularity.
"It's both good for the soil and good for your pocketbook," he said.
P-I reporter Tom Paulson can be reached at 206-448-8318 or email@example.com.
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