Carbon from soil & trees: curse or cure?—Interview w/Thomas Crowther—Radio Ecoshock 2019-03-06

There is far more carbon stored in the soil of planet Earth than in its atmosphere. If soil organisms release that carbon as carbon dioxide, faster as the climate warms, we may not be able to stop it.

Or can we? Visionary scientist Thomas Crowther from ETH Zurich speaks on carbon, global warming, the Arctic, and a plan to plant a trillion trees to help stabilize the climate. Yes we can—and the kids have already started.

Our guest Dr. Thomas Crowther is an assistant professor of Global Ecosystem Ecology at ETH Zurich. He directs the Crowther Lab. Thomas is also a Marie Curie Fellow at the Netherlands Institute of Ecology. Our last interview on Radio Ecoshock was in December 2016, and he’s been busy since then. If you care about life, this is a must-listen guest.

Show by Radio Ecoshock, reposted under CC License. Episode details at

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At the 2019 Annual meeting of the American Academy for the Advancement of Science in Washington this February, Thomas presented a chart showing WHERE carbon is buried under the soil. The biggest depository of carbon in the soil is a surprise. There more carbon held in the Arctic, than in plant-rich places like the Tropics.

Yes growth in tropical rainforests is lush, with massive amounts of carbon held in plants. But warmer temperatures and adequate water in the soil means bacteria is rich, and the tropical soil is actually poor in carbon. By contrast, there is less plant production each year in the Arctic, but in the cold or even frozen soil, very little plant residue is processed in the soil. That carbon builds up over thousands of years, becoming a huge storehouse—unless the soil is warmed, as it is now.

Increasing carbon loss from the Arctic adds to the greenhouse effect, thus creating a positive feedback loop heating the planet even more. Crowther’s team research found warming of the world’s Arctic and sub-Arctic regions is causing the release of soil carbon, and that could accelerate climate change by 17 percent by 2050.

The first global map of life under the soil has been developed by the Crowther Lab. He also tells us about the Global Soil Biodiversity Initiative.

Check out the article “Losses of soil carbon under global warming might equal US emissions” November 30, 2016, Yale University.

In another interview, Crowther says: “there are probably more animals in the Arctic than the Tropics”. That is mind-blowing. He is counting as animals tiny creatures like nematode worms in the soil.

Our second adventure into Crowther’s projects starts by asking how many trees there are on Earth. Until he tackled this, getting that number seemed impossible. His techniques involved calling in records from foresters all over the world, plus satellite data and other information (including soil productivity)—to model out the total. He found previous estimates were way too low. There are about 3.04 trillion trees on Earth! Trees on Earth may be comparable in number to stars in our galaxy.

The better news is: he finds we could grow another 1.2 trillion new trees. These could be planted without having to give up croplands or city space to do it. The United Nations has a program aiming to plant a trillion trees. If that is successful, those trees could capture enough carbon to reduce our exposure to extreme climate change. Tree planting cannot totally save us, but it can play a huge role. It is hard to imagine any other way to capture enough carbon to matter.

To find out more, look up the Plant for the Planet Initiative and their Trillion Tree Campaign.

Beyond the global soil data we talked about, The Crowther lab is launching a second giant pool of data for use by the international community. It is called “the Global Forest Biodiversity Initiative“.

When I watch a couple of Crowther’s YouTube video presentations, I’m stunned by the brand new maps of where things grow on our planet, or life we’ve never seen, hidden underground. We expect experts to use GIS—Geographic Information Systems—to communicate complex results. But now scientists can also use those maps as tools of discovery, to find new things.

Thomas Crowther coauthored the 2016 paper “Quantifying global soil carbon losses in response to warming”. The key conclusion says scientists have found “empirical support” that rising temperature can stimulate carbon loss from the soil that “could accelerate planetary warming over the twenty-first century.”

This large feedback has been left out of the large-scale models that create projections of warming. That means experts advising governments, and the Intergovernmental Panel on Climate Change, have lower estimates of developing global warming than reality.

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