Why Soil Rocks

Editor's note: 2015 is the UN-designated International Year of Soils. In celebration of soil, OSTP’s Associate Director for Science Jo Handelsman – microbiologist and soil enthusiast – will be taking to the OSTP blog throughout this year to share stories of the science behind this critical resource and how it continues to shape our economy and society in ways big and small.

2015 is the UN-designated International Year of Soils – one of the world's most important resources that will help determine the collective future for inhabitants of the Earth. Here we join the celebration of the services provided by this critical resource and set out to prove once and for all that soil does, indeed, rock.

Soil is the living, breathing skin of the Earth¹. It takes millennia to create and just a few short years to deplete. In every sense, it is essential to human existence – it provides nutrients essential to crop and animal production; it nourishes plant-life that provides shelter and habitat; it yields potent drugs that promote human health; and so much more.

Many earlier societies recognized this quite directly, often to the point of revering or worshipping the soil. In more recent history, Americans and their Presidents have also paid great tributes to soil. Franklin Delano Roosevelt one said:  “A nation that destroys its soils destroys itself.” And Thomas Jefferson remarked:  “While the farmer holds the title to the land, it belongs to all the people because civilization itself rests upon the soil.”

But, amidst the industrial age and urbanization, the rich tradition of honoring soil has eroded. There is perhaps no greater illustration of this trend than the popular reference to soil as “dirt.”

This alias obscures the complex, life-giving properties of soil – from which the forests and all other plants on Earth take nourishment and upon which so much of our existence depends.

Soil is a complex system of minerals derived from bedrock and organic components from animal, plant, and microbial activity. The organic and geologic aspects of soil are in dynamic interaction – with minerals shaping microbial life, and microbial activity changing minerals. The physical and biological features of most soils have been shaped by millennia of natural events and decades or centuries of human intervention.

In addition to being an elemental resource, soil is one that is shared – across communities, international borders, and even continents. Billions of tons of the Sahara Desert, for instance, move to the American continent every year by way of wind, enriching the natural resources of the Western Hemisphere. Less directly, soil also travels through the food we exchange.

Today, soil in many regions is challenged by practices that can lead to erosion. Iowa topsoil, for example – which is believed to be the deepest and most fertile on Earth – is eroding at twice the rate that it is being replenished. Fully one third of all soils on Earth are in a state of degradation, and it can take up to 1,000 years for just 1 cm of soil to form. Soil, therefore, needs and deserves not just attention, but also stewardship. 

Soil plays an important role in nutrient cycles that are important beyond those that affect plant productivity. Many frozen alpine and tundra soils, for instance, contain substantial populations of microorganisms that produce methane – a potent greenhouse gas. In some cases, with as little as a one-degree increase in temperature, these organisms will begin to thaw, kicking their methane-producing metabolisms into high gear. Scientists are only beginning to catalogue the vast numbers of these microorganisms and whether (and how much) the methane they produce could contribute climate change.

The microorganisms living in soil are the most diverse community on Earth, estimated to contain at least 10,000 species per gram (per gram!). We are truly indebted to these soil microbes, as most of them are our biochemical allies—providing soil with the capacity to detoxify and recycle many kinds of chemicals.

One unexpected property of soil microbial communities, for example, is their ability to degrade synthetic compounds – those created by humans – even though the microorganisms have never seen these compounds before. For example, almost all gas stations in the United States keep their gasoline storage tanks underground. Sometimes, potentially harmful gasoline leaks out of the tanks. When this occurs, a network of bacteria in the soil spring into action to degrade the many harmful chemicals in gasoline before they reach our groundwater. Contaminants like gasoline, pesticides, and heavy metals regularly seep into the ground and often are stopped in their tracks by microorganisms living in the soil that can degrade and neutralize these hazards. At the same time, inorganic portions of soil contain minerals that immobilize hazardous chemicals that would otherwise contaminate our water. Soil is Nature's best filter.

Still, one of the most dramatic discoveries in the ground in the 20^th century was the abundance of antibiotic-producing bacteria residing in soils worldwide. About 75% of the antibiotics in clinical use today are derived from soil organisms, and many more are undoubtedly waiting to be discovered. Human chemists have never come close to matching the relentless creativity of soil bacteria.

Earlier this year, scientists at Northeastern University reported a new method to access more than the just 1% of soil bacteria that can be captured today in standard laboratory cultures. Their method led to discovery of a new antibiotic whose activity is due to an entirely new mode of action; the same method promises to provide many more drugs in the future.

Throughout this year of soil celebration, we will explore some of these topics in more detail here on the OSTP blog. Please stay tuned right here and don’t forget, RESPECT YOUR SOIL!

¹Logan, William Bryant, 2007. "Dirt: The Ecstatic Skin of the Earth".

Dr. Jo Handelsman is Associate Director for Science at the White House Office of Science & Technology Policy.