Tue, Oct 10, 2017 - Page 9 News List

There is a climate bomb under your feet

As the top 3 meters of earth stores more carbon than the entire atmosphere and plants combined, taking care of the planet’s soil is critical for stabilizing atmospheric carbon dioxide concentrations

By Eric Roston  /  Bloomberg

Illustration: Yusha

Long before most people ever heard of climate change, scientists divided a patch of Harvard University-owned forest in central Massachusetts into 18 identical 6m by 6m squares. A canopy of red maple and black oak trees hangs there, looming above the same stony soil tilled by colonial farmers. Rich in organic material, it was exactly what the researchers were looking for.

They broke the land up into six blocks of three squares each. In every block, one square was left alone, one was threaded with heating cables that elevated its temperature 5°C above the surrounding area. The third square was threaded with cables, but never turned on, as a control.

That was 26 years ago.

The purpose was to measure how carbon-dioxide might escape from the Earth as the atmosphere warms. What they found, published this month in the journal Science, might mean the accelerating catastrophe of global warming has been fueled in part by warm dirt.

As the Earth heats up, microbes in the soil accelerate the breakdown of organic materials and move on to others that might have once been ignored, each time releasing carbon dioxide into the atmosphere.

Extrapolating from their forest study, the researchers estimate that over this century the warming induced from global soil loss, at the rate they monitored, would be “equivalent to the past two decades of carbon emissions from fossil fuel burning and is comparable in magnitude to the cumulative carbon losses to the atmosphere due to human-driven land use change during the past two centuries.”

Taking care of the planet’s soil is “critical for stabilizing atmospheric CO2 [carbon dioxide] concentrations,” the report said.

However, the good news is that the research community is now fully on the case. Over the past week, at least four high-profile papers largely funded by the US government have contributed new evidence, observations and insight into the role of soil and forests in the global carbon cycle — the flow of material in and out of land, air, life and sea that is currently broken and getting worse.

From a technical perspective what they are talking about here is plain old dirt. Ground. Loam. Land. Trees and leaves.

From a practical perspective, it is something different entirely. Soil is also cotton, corn, soybean, wheat, oranges, cattle, and the rest of humanity’s food and fiber.

When it is healthy, it grows almost everything we need. It absorbs and retains moisture that might otherwise flood valleys where people live. It also absorbs and retains carbon that might otherwise be heating up the atmosphere.

The atmosphere gets all the attention in climate change, mostly because that is where the warming happens. Even the oceans draw more concern than soil, especially when their warming temperature helps fuel massive storms and floods that kill humans and destroy communities, but the seas should not be ignored: They hold 60 times more carbon than the atmosphere and absorb more than 90 percent of the heat industrial pollution generates.

The soil, though, has been largely ignored until lately.

It is something that is both hugely influential on global warming and something humanity has a good deal of control over.

The top 3m or so of earth stores more carbon than the entire atmosphere and plants combined. Taking care of the planet’s soil is “critical for stabilizing atmospheric CO2 concentrations,” according to a synthesis by Stanford University’s Robert Jackson and five colleagues, published in the Annual Review of Ecology, Evolution and Systematics.

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