Wednesday, July 30, 2014

Climate Change:  Soil Respiration Releases Carbon

Soil respiration chamber - This respiration chamber monitors the rate of carbon release from soils in a forest ecosystem. (Credit: Oregon State University) Click to enlarge.
The planet's soil releases about 60 billion tons of carbon into the atmosphere each year, which is far more than that released by burning fossil fuels.  This happens through a process called soil respiration. This enormous release of carbon is balanced by carbon coming into the soil system from falling leaves and other plant matter, as well as by the underground activities of plant roots.

Short-term warming studies have documented that rising temperatures increase the rate of soil respiration.  As a result, scientists have worried that global warming would accelerate the decomposition of carbon in the soil, and decrease the amount of carbon stored there.  If true, this would release even more carbon dioxide into the atmosphere, where it would accelerate global warming.

New work by a team of scientists including Carnegie's Greg Asner and Christian Giardina of the U.S. Forest Service used an expansive whole-ecosystem study, the first of its kind, on tropical montane wet forests in Hawaii to sort through the many processes that control soil carbon stocks with changing temperature.  Their work is published in Nature Climate Change.

The team revealed that higher temperatures increased the amount of leaf litter falling onto the soil, as well as other underground sources of carbon such as roots.  Surprisingly, long-term warming had little effect on the overall storage of carbon in the tropical forest soil or the rate at which that carbon is processed into carbon dioxide.

Climate Change:  Soil Respiration Releases Carbon

Monday, July 28, 2014

What's Eating America:  Corn is one of the plant kingdom's biggest successes.  That's not necessarily good for the United States. - by Michael Pollan

Green corn field (Credit: Shutterstock) Click to enlarge.
F1 hybrid corn is the greediest of plants, consuming more fertilizer than any other crop. Though F1 hybrids were introduced in the 1930s, it wasn't until they made the acquaintance of chemical fertilizers in the 1950s that corn yields exploded.  The discovery of synthetic nitrogen changed everything—not just for the corn plant and the farm, not just for the food system, but also for the way life on earth is conducted.

All life depends on nitrogen; it is the building block from which nature assembles amino acids, proteins and nucleic acid; the genetic information that orders and perpetuates life is written in nitrogen ink.  But the supply of usable nitrogen on earth is limited.  Although earth's atmosphere is about 80 percent nitrogen, all those atoms are tightly paired, nonreactive and therefore useless; the 19th-century chemist Justus von Liebig spoke of atmospheric nitrogen's "indifference to all other substances."  To be of any value to plants and animals, these self-involved nitrogen atoms must be split and then joined to atoms of hydrogen.

Chemists call this process of taking atoms from the atmosphere and combining them into molecules useful to living things "fixing" that element.  Until a German Jewish chemist named Fritz Haber figured out how to turn this trick in 1909, all the usable nitrogen on earth had at one time been fixed by soil bacteria living on the roots of leguminous plants (such as peas or alfalfa or locust trees) or, less commonly, by the shock of electrical lightning, which can break nitrogen bonds in the air, releasing a light rain of fertility.

What's Eating America:  Corn is one of the plant kingdom's biggest successes.  That's not necessarily good for the United States - by Michael Pollan

Wednesday, July 23, 2014

U.S. Midwestern Farmers Fighting Explosion of 'Superweeds'

Palmer Amaranth (Credit: Click to enlarge.
Farmers in important crop-growing states should consider the environmentally unfriendly practice of deeply tilling fields to fight a growing problem with invasive "superweeds" that resist herbicides and choke crop yields, agricultural experts said this week.

Resistance to glyphosate, the main ingredient in widely used Roundup herbicide, has reached the point that row crop farmers in the Midwest are struggling to contain an array of weeds, agronomists say.

Extreme controls are needed to fight herbicide-resistant weeds in some areas, University of Missouri weed scientist Kevin Bradley said in a report to farmers.  One particularly aggressive weed that can grow 1-2 inches a day is Palmer amaranth.

He said farmers facing extreme out-of-control weeds should try deep tillage, a practice that removes weeds but can also lead to soil erosion and other environmental concerns.

Farmers moved away from heavy tillage of the land decades ago, and the more sustainable 'no-till' farming has become the norm.  But it relies on heavy use of herbicides like glyphosate, and the U.S. Department of Agriculture says 70 million acres of U.S. farmland had glyphosate resistant weeds in 2013.

U.S. Midwestern Farmers Fighting Explosion of 'Superweeds'

Friday, July 18, 2014

How Existing Cropland Could Feed Billions More

Hoang Su Phi terraced fields, Ha Giang province, Vietnam. (Credit: © hoangtran / Fotolia) Click to enlarge.
Feeding a growing human population without increasing stresses on Earth's strained land and water resources may seem like an impossible challenge.  But according to a new report by researchers at the University of Minnesota's Institute on the Environment, focusing efforts to improve food systems on a few specific regions, crops and actions could make it possible to both meet the basic needs of 3 billion more people and decrease agriculture's environmental footprint.

The report, published Thursday in Science, focuses on 17 key crops that produce 86 percent of the world's crop calories and account for most irrigation and fertilizer consumption on a global scale.  It proposes a set of key actions in three broad areas that that have the greatest potential for reducing the adverse environmental impacts of agriculture and boosting our ability meet global food needs.  For each, it identifies specific "leverage points" where nongovernmental organizations, foundations, governments, businesses and citizens can target food-security efforts for the greatest impact.  The biggest opportunities cluster in six countries -- China, India, U.S., Brazil, Indonesia and Pakistan -- along with Europe.

How Existing Cropland Could Feed Billions More

Thursday, July 17, 2014

'Peak Soil' Threatens Future Global Food Security

Picture from the 2009 drought in China that left 3.7 million people without access to water. (Credit: Click to enlarge.
The challenge of ensuring future food security as populations grow and diets change has its roots in soil, but the increasing degradation of the earth's thin skin is threatening to push up food prices and increase deforestation.

While the worries about peaking oil production have been eased by fresh sources released by hydraulic fracturing, concern about the depletion of the vital resource of soil is moving center stage.

John Crawford, Director of the Sustainable Systems Program in Rothamsted Research in England said:
We know far more about the amount of oil there is globally and how long those stocks will last than we know about how much soil there is.

Under business as usual, the current soils that are in agricultural production will yield about 30 percent less than they would do otherwise by around 2050.
Surging food consumption has led to more intensive production, overgrazing and deforestation, all of which can strip soil of vital nutrients and beneficial micro-organisms, reduce its ability to hold water and make it more vulnerable to erosion.

Such factors, exacerbated by climate change, can ultimately lead to desertification, which in parts of China is partly blamed for the yellow dust storms that can cause hazardous pollution in Asia, sometimes even severe enough to cross the Pacific Ocean and reduce visibility in the western United States.

Arable land in areas varying from the United States and Sub-Saharan Africa, to the Middle East and Northern China has already been lost due to soil degradation.

The United Nations' Food and Agriculture Organization (FAO) has estimated that 25 percent of agricultural land is highly degraded, while a further 8 percent is moderately degraded.

'Peak Soil' Threatens Future Global Food Security

Monday, July 14, 2014

The Soil Pollution Crisis in China: Cleanup Presents Daunting Challenge

A chemical factory beside a rice paddy in Yixing in Jiangsu Province, where industrial pollution has contaminated soil and food crops. (Credit: Mark Ralston/AFP/Getty Images) Click to enlarge.
Recent research findings have brought some rays of hope to China’s beleaguered soil.  The Foshan Jinkuizi Plant Nutrition Company claims to have developed a soil remediation technology specifically designed for China’s heavy-metal polluted soil:  a microorganism that can change the ionic state of heavy metals in the soil, deactivating the pollutants so they do not harm crops.  The company claims that the method is cheap, convenient, easy to use, does not produce any secondary pollution, and is already in commercial production and use.

In another possible breakthrough, in April the Guangdong Geoanalysis Research Center announced a new product, Mont-SH6, which it says is a powerful absorber of toxic heavy metals such as cadmium, lead, mercury, copper, and zinc.  Liu Wenhua, chief engineer at the center, claims that the product can reduce soil cadmium levels by over 90 percent, and that materials and manufacturing costs are low: remediation of 1.48 acres of cadmium-contaminated rice fields with this technique costs about $4,800.  Mass production, according to Liu Wenhua, could bring this down to between $320 and $480.

The Soil Pollution Crisis in China:  Cleanup Presents Daunting Challenge

Friday, July 4, 2014

Thomas Jefferson:  ‘Intergenerational Equity’ and Topsoil Depletion

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The most succinct, systematic treatment of intergenerational principles left to us by the founders is that which was provided by Thomas Jefferson in his famous September 6, 1789 letter to James Madison. The letter was Jefferson’s final installment in a two year correspondence with Madison on the proposed Bill of Rights.  Given the importance of this letter as background material for the bill of rights, and its independent value as a brilliant statement of intergenerational equity principles, it serves as the natural starting point for a discussion of the founders’ views on specific intergenerational issues.

Jefferson begins his letter by asserting that:
The question [w]hether one generation of men has a right to bind another … is a question of such consequences as not only to merit decision, but place also among the fundamental principles of every government…. I set out on this ground, which I suppose to be self-evident, ‘that the earth belongs in usufruct to the living’ ….
Generational Sovereignty and the Land – The Earth as Tenancy-in-Common - Thomas Jefferson's Usufruct, part 1 (part 2 below)

The contemporary issue to which Jefferson’s arguments most literally apply is the problem of topsoil depletion.  As a planter in predominantly agrarian Virginia, who tended to view wealth as the direct or indirect product of the earth, it was natural for Jefferson to phrase his discussions of intergenerational relations — even intergenerational economic relations — in terms of soil:
Are [later generations] bound to acknowledge [a national debt created to satisfy short-term interests], to consider the preceding generation as having had a right to eat up the whole soil of their country, in the course of a life….? Every one will say no; that the soil is the gift of God to the living, as much as it had been to the deceased generation; and that the laws of nature impose no obligation on them to pay this debt.
Jefferson asserts that each generation has the right to inherit, undiminished, the same topsoil capital that its predecessors enjoyed.  Our society’s failure to recognize and defend this most basic principle of intergenerational fairness during the past century has resulted in topsoil depletion that has reached crisis proportions.  Soon we may have literally and irreparably “eaten up the whole soil of our country.”

Generational Sovereignty and the Land – The Earth as Tenancy-in-Common - Thomas Jefferson's Usufruct, part 2

Wednesday, July 2, 2014

Invasive Plants Can Release Soil Carbon, Accelerate Global Warming

Kudzu covered abandoned barn (Credit:
In a paper published in the scientific journal New Phytologist, plant ecologist Nishanth Tharayil and graduate student Mioko Tamura show that invasive plants can accelerate the greenhouse effect by releasing carbon stored in soil into the atmosphere.

Since soil stores more carbon than both the atmosphere and terrestrial vegetation combined, the repercussions for how we manage agricultural land and ecosystems to facilitate the storage of carbon could be dramatic.

In their study, Tamura and Tharayil examined the impact of encroachment of Japanese knotweed and kudzu, two of North America's most widespread invasive plants, on the soil carbon storage in native ecosystems.

"Our findings highlight the capacity of invasive plants to effect climate change by destabilizing the carbon pool in soil and shows that invasive plants can have profound influence on our understanding to manage land in a way that mitigates carbon emissions," Tharayil said.

Tharayil estimates that kudzu invasion results in the release of 4.8 metric tons of carbon annually, equal to the amount of carbon stored in 11.8 million acres of U.S. forest.

Invasive Plants Can Release Soil Carbon, Accelerate Global Warming