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  • So one of the most important solutions

  • to the global challenge posed by climate change

  • lies right under our foot every day.

  • It's soil.

  • Soil's just the thin veil that covers the surface of land,

  • but it has the power to shape our planet's destiny.

  • See, a six-foot or so of soil,

  • loose soil material that covers the earth's surface,

  • represents the difference between life and lifelessness in the earth system,

  • and it can also help us combat climate change

  • if we can only stop treating it like dirt.

  • (Laughter)

  • Climate change is happening,

  • the earth's atmosphere is warming,

  • because of the increasing amount of greenhouse gases

  • we keep releasing into the atmosphere.

  • You all know that.

  • But what I assume you might not have heard

  • is that one of the most important things our human society could do

  • to address climate change

  • lies right there in the soil.

  • I'm a soil scientist who has been studying soil since I was 18,

  • because I'm interested in unlocking the secrets of soil

  • and helping people understand this really important climate change solution.

  • So here are the facts about climate.

  • The concentration of carbon dioxide in the earth's atmosphere

  • has increased by 40 percent

  • just in the last 150 years or so.

  • Human actions are now releasing 9.4 billion metric tons of carbon

  • into the atmosphere,

  • from activities such as burning fossil fuels

  • and intensive agricultural practices,

  • and other ways we change the way we use land,

  • including deforestation.

  • But the concentration of carbon dioxide that stays in the atmosphere

  • is only increasing by about half of that,

  • and that's because half of the carbon we keep releasing into the atmosphere

  • is currently being taken up by land and the seas

  • through a process we know as carbon sequestration.

  • So in essence, whatever consequence you think we're facing

  • from climate change right now,

  • we're only experiencing the consequence of 50 percent of our pollution,

  • because the natural ecosystems are bailing us out.

  • But don't get too comfortable,

  • because we have two major things working against us right now.

  • One: unless we do something big,

  • and then fast,

  • emissions will continue to rise.

  • And second: the ability of these natural ecosystems

  • to take up carbon dioxide from the atmosphere

  • and sequester it in the natural habitats

  • is currently getting compromised,

  • as they're experiencing serious degradation because of human actions.

  • So it's not entirely clear

  • that we will continue to get bailed out by these natural ecosystems

  • if we continue on this business-as-usual path that we've been.

  • Here's where the soil comes in:

  • there is about three thousand billion metric tons of carbon in the soil.

  • That's roughly about 315 times the amount of carbon

  • that we release into the atmosphere currently.

  • And there's twice more carbon in soil than there is in vegetation and air.

  • Think about that for a second.

  • There's more carbon in soil

  • than there is in all of the world's vegetation,

  • including the lush tropical rainforests and the giant sequoias,

  • the expansive grasslands,

  • all of the cultivated systems,

  • and every kind of flora you can imagine on the face of the earth,

  • plus all the carbon that's currently up in the atmosphere, combined,

  • and then twice over.

  • Hence, a very small change in the amount of carbon stored in soil

  • can make a big difference in maintenance of the earth's atmosphere.

  • But soil's not just simply a storage box for carbon, though.

  • It operates more like a bank account,

  • and the amount of carbon that's in soil at any given time

  • is a function of the amount of carbon coming in and out of the soil.

  • Carbon comes into the soil through the process of photosynthesis,

  • when green plants take carbon dioxide from the atmosphere

  • and use it to make their bodies,

  • and upon death, their bodies enter the soil.

  • And carbon leaves the soil

  • and goes right back up into the atmosphere

  • when the bodies of those formerly living organisms

  • decay in soil by the activity of microbes.

  • See, decomposition releases carbon dioxide into the atmosphere,

  • as well as other greenhouse gases such as methane and nitrous oxide,

  • but it also releases all the nutrients we all need to survive.

  • One of the things that makes soil such a fundamental component

  • of any climate change mitigation strategy

  • is because it represents a long-term storage of carbon.

  • Carbon that would have lasted maybe a year or two

  • in decaying residue if it was left on the surface

  • can stay in soil for hundreds of years, even thousands and more.

  • Soil biogeochemists like me

  • study exactly how the soil system makes this possible,

  • by locking away the carbon in physical association with minerals,

  • inside aggregates of soil minerals,

  • and formation of strong chemical bonds

  • that bind the carbon to the surfaces of the minerals.

  • See when carbon is entrapped in soil,

  • in these kinds of associations with soil minerals,

  • even the wiliest of the microbes can't easily degrade it.

  • And carbon that's not degrading fast

  • is carbon that's not going back into the atmosphere as greenhouse gases.

  • But the benefit of carbon sequestration

  • is not just limited to climate change mitigation.

  • Soil that stores large amounts of carbon is healthy, fertile, soft.

  • It's malleable. It's workable.

  • It makes it like a sponge.

  • It can hold on to a lot of water and nutrients.

  • Healthy and fertile soils like this

  • support the most dynamic, abundant and diverse habitat for living things

  • that we know of anywhere on the earth system.

  • It makes life possible for everything from the tiniest of the microbes,

  • such as bacteria and fungi,

  • all the way to higher plants,

  • and fulfills the food, feed and fiber needs for all animals,

  • including you and I.

  • So at this point, you would assume that we should be treating soil

  • like the precious resource that it is.

  • Unfortunately, that's not the case.

  • Soils around the world are experiencing unprecedented rates of degradation

  • through a variety of human actions that include deforestation,

  • intensive agricultural production systems,

  • overgrazing,

  • excessive application of agricultural chemicals,

  • erosion and similar things.

  • Half of the world's soils are currently considered degraded.

  • Soil degradation is bad for many reasons,

  • but let me just tell you a couple.

  • One: degraded soils have diminished potential to support plant productivity.

  • And hence, by degrading soil,

  • we're compromising our own abilities to provide the food and other resources

  • that we need for us

  • and every member of living things on the face of the earth.

  • And second:

  • soil use and degradation, just in the last 200 years or so,

  • has released 12 times more carbon into the atmosphere

  • compared to the rate at which we're releasing carbon

  • into the atmosphere right now.

  • I'm afraid there's even more bad news.

  • This is a story of soils at high latitudes.

  • Peatlands in polar environments

  • store about a third of the global soil carbon reserves.

  • These peatlands have a permanently frozen ground underneath,

  • the permafrost,

  • and the carbon was able to build up in these soils over long periods of time

  • because even though plants are able to photosynthesize during the short,

  • warm summer months,

  • the environment quickly turns cold and dark,

  • and then microbes are not able to efficiently break down the residue.

  • So the soil carbon bank in these polar environments

  • built up over hundreds of thousands of years.

  • But right now, with atmospheric warming,

  • the permafrost is thawing and draining.

  • And when permafrost thaws and drains,

  • it makes it possible for microbes to come in

  • and rather quickly decompose all this carbon,

  • with the potential to release hundreds of billions of metric tons of carbon

  • into the atmosphere in the form of greenhouse gases.

  • And this release of additional greenhouse gases into the atmosphere

  • will only contribute to further warming

  • that makes this predicament even worse,

  • as it starts a self-reinforcing positive feedback loop

  • that could go on and on and on,

  • dramatically changing our climate future.

  • Fortunately, I can also tell you that there is a solution

  • for these two wicked problems of soil degradation and climate change.

  • Just like we created these problems,

  • we do know the solution,

  • and the solution lies in simultaneously working

  • to address these two things together,

  • through what we call climate-smart land management practices.

  • What do I mean here?

  • I mean managing land in a way that's smart

  • about maximizing how much carbon we store in soil.

  • And we can accomplish this

  • by putting in place deep-rooted perennial plants,

  • putting back forests whenever possible,

  • reducing tillage and other disturbances from agricultural practices,

  • including optimizing the use of agricultural chemicals and grazing

  • and even adding carbon to soil, whenever possible,

  • from recycled resources such as compost and even human waste.

  • This kind of land stewardship is not a radical idea.

  • It's what made it possible for fertile soils

  • to be able to support human civilizations since time immemorial.

  • In fact, some are doing it just right now.

  • There's a global effort underway to accomplish exactly this goal.

  • This effort that started in France is known as the "4 per 1000" effort,

  • and it sets an aspirational goal

  • to increase the amount of carbon stored in soil by 0.4 percent annually,

  • using the same kind of climate-smart land management practices

  • I mentioned earlier.

  • And if this effort's fully successful,

  • it can offset a third of the global emissions

  • of fossil-fuel-derived carbon into the atmosphere.

  • But even if this effort is not fully successful,

  • but we just start heading in that direction,

  • we still end up with soils that are healthier, more fertile,

  • are able to produce all the food and resources that we need

  • for human populations and more,

  • and also soils that are better capable

  • of sequestering carbon dioxide from the atmosphere

  • and helping with climate change mitigation.

  • I'm pretty sure that's what politicians call a win-win solution.

  • And we all can have a role to play here.

  • We can start by treating the soil with the respect that it deserves:

  • respect for its ability as the basis of all life on earth,

  • respect for its ability to serve as a carbon bank

  • and respect for its ability to control our climate.

  • And if we do so,

  • we can then simultaneously address

  • two of the most pressing global challenges of our time:

  • climate change and soil degradation.

  • And in the process, we would be able to provide food and nutritional security

  • to our growing human family.

  • Thank you.

  • (Applause)

So one of the most important solutions

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TED】アスメレ・アセフォー・ベルヘ。足元にある気候変動の解決策 (足元にある気候変動の解決策|Asmeret Asefaw Berhe: ) (【TED】Asmeret Asefaw Berhe: A climate change solution that's right under our feet (A climate change solution that's right under our feet | Asmeret Asefaw Berhe:))

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    林宜悉 に公開 2021 年 01 月 14 日
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