TED2019
Asmeret Asefaw Berhe: A climate change solution that's right under our feet
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There's two times more carbon in the earth's soil than in all of its vegetation and the atmosphere -- combined. Biogeochemist Asmeret Asefaw Berhe dives into the science of soil and shares how we could use its awesome carbon-trapping power to offset climate change. "[Soil] 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," she says.
Asmeret Asefaw Berhe - Soil scientist
Asmeret Asefaw Berhe is a soil and global-change scientist and educator passionate about all things related to the science and beauty of soils. Full bio
Asmeret Asefaw Berhe is a soil and global-change scientist and educator passionate about all things related to the science and beauty of soils. Full bio
Double-click the English transcript below to play the video.
00:12
So one of the most important solutions
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to the global challenge
posed by climate change
posed by climate change
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lies right under our foot every day.
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It's soil.
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Soil's just the thin veil
that covers the surface of land,
that covers the surface of land,
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but it has the power to shape
our planet's destiny.
our planet's destiny.
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See, a six-foot or so of soil,
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loose soil material
that covers the earth's surface,
that covers the earth's surface,
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represents the difference between life
and lifelessness in the earth system,
and lifelessness in the earth system,
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and it can also help us
combat climate change
combat climate change
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if we can only stop treating it like dirt.
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(Laughter)
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Climate change is happening,
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the earth's atmosphere is warming,
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because of the increasing amount
of greenhouse gases
of greenhouse gases
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we keep releasing into the atmosphere.
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You all know that.
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But what I assume you might not have heard
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is that one of the most important things
our human society could do
our human society could do
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to address climate change
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lies right there in the soil.
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I'm a soil scientist who has been
studying soil since I was 18,
studying soil since I was 18,
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because I'm interested in unlocking
the secrets of soil
the secrets of soil
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and helping people understand this
really important climate change solution.
really important climate change solution.
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So here are the facts about climate.
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The concentration of carbon dioxide
in the earth's atmosphere
in the earth's atmosphere
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has increased by 40 percent
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just in the last 150 years or so.
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Human actions are now releasing
9.4 billion metric tons of carbon
9.4 billion metric tons of carbon
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into the atmosphere,
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from activities
such as burning fossil fuels
such as burning fossil fuels
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and intensive agricultural practices,
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and other ways we change
the way we use land,
the way we use land,
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including deforestation.
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But the concentration of carbon dioxide
that stays in the atmosphere
that stays in the atmosphere
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is only increasing by about half of that,
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and that's because half of the carbon
we keep releasing into the atmosphere
we keep releasing into the atmosphere
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is currently being taken up
by land and the seas
by land and the seas
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through a process we know
as carbon sequestration.
as carbon sequestration.
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So in essence, whatever consequence
you think we're facing
you think we're facing
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from climate change right now,
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we're only experiencing the consequence
of 50 percent of our pollution,
of 50 percent of our pollution,
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because the natural ecosystems
are bailing us out.
are bailing us out.
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But don't get too comfortable,
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because we have two major things
working against us right now.
working against us right now.
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One: unless we do something big,
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and then fast,
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emissions will continue to rise.
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And second: the ability
of these natural ecosystems
of these natural ecosystems
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to take up carbon dioxide
from the atmosphere
from the atmosphere
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and sequester it in the natural habitats
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is currently getting compromised,
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as they're experiencing serious
degradation because of human actions.
degradation because of human actions.
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So it's not entirely clear
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that we will continue to get bailed out
by these natural ecosystems
by these natural ecosystems
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if we continue on this
business-as-usual path that we've been.
business-as-usual path that we've been.
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Here's where the soil comes in:
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there is about three thousand billion
metric tons of carbon in the soil.
metric tons of carbon in the soil.
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That's roughly about 315 times
the amount of carbon
the amount of carbon
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that we release
into the atmosphere currently.
into the atmosphere currently.
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And there's twice more carbon in soil
than there is in vegetation and air.
than there is in vegetation and air.
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Think about that for a second.
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There's more carbon in soil
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than there is in all
of the world's vegetation,
of the world's vegetation,
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including the lush tropical rainforests
and the giant sequoias,
and the giant sequoias,
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the expansive grasslands,
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all of the cultivated systems,
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and every kind of flora you can imagine
on the face of the earth,
on the face of the earth,
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plus all the carbon that's currently
up in the atmosphere, combined,
up in the atmosphere, combined,
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and then twice over.
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Hence, a very small change
in the amount of carbon stored in soil
in the amount of carbon stored in soil
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can make a big difference
in maintenance of the earth's atmosphere.
in maintenance of the earth's atmosphere.
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But soil's not just simply
a storage box for carbon, though.
a storage box for carbon, though.
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It operates more like a bank account,
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and the amount of carbon
that's in soil at any given time
that's in soil at any given time
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is a function of the amount of carbon
coming in and out of the soil.
coming in and out of the soil.
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Carbon comes into the soil
through the process of photosynthesis,
through the process of photosynthesis,
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when green plants take carbon dioxide
from the atmosphere
from the atmosphere
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and use it to make their bodies,
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and upon death,
their bodies enter the soil.
their bodies enter the soil.
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And carbon leaves the soil
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and goes right back up into the atmosphere
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when the bodies of those
formerly living organisms
formerly living organisms
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decay in soil by the activity of microbes.
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See, decomposition releases
carbon dioxide into the atmosphere,
carbon dioxide into the atmosphere,
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as well as other greenhouse gases
such as methane and nitrous oxide,
such as methane and nitrous oxide,
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but it also releases all the nutrients
we all need to survive.
we all need to survive.
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One of the things that makes soil
such a fundamental component
such a fundamental component
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of any climate change mitigation strategy
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is because it represents
a long-term storage of carbon.
a long-term storage of carbon.
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Carbon that would have lasted
maybe a year or two
maybe a year or two
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in decaying residue
if it was left on the surface
if it was left on the surface
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can stay in soil for hundreds of years,
even thousands and more.
even thousands and more.
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Soil biogeochemists like me
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study exactly how the soil system
makes this possible,
makes this possible,
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by locking away the carbon
in physical association with minerals,
in physical association with minerals,
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inside aggregates of soil minerals,
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and formation of strong chemical bonds
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that bind the carbon
to the surfaces of the minerals.
to the surfaces of the minerals.
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See when carbon is entrapped in soil,
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in these kinds of associations
with soil minerals,
with soil minerals,
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even the wiliest of the microbes
can't easily degrade it.
can't easily degrade it.
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And carbon that's not degrading fast
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is carbon that's not going back
into the atmosphere as greenhouse gases.
into the atmosphere as greenhouse gases.
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But the benefit of carbon sequestration
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is not just limited
to climate change mitigation.
to climate change mitigation.
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Soil that stores large amounts of carbon
is healthy, fertile, soft.
is healthy, fertile, soft.
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It's malleable. It's workable.
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It makes it like a sponge.
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It can hold on to
a lot of water and nutrients.
a lot of water and nutrients.
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Healthy and fertile soils like this
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support the most dynamic, abundant
and diverse habitat for living things
and diverse habitat for living things
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that we know of anywhere
on the earth system.
on the earth system.
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It makes life possible for everything
from the tiniest of the microbes,
from the tiniest of the microbes,
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such as bacteria and fungi,
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all the way to higher plants,
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and fulfills the food, feed
and fiber needs for all animals,
and fiber needs for all animals,
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including you and I.
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So at this point, you would assume
that we should be treating soil
that we should be treating soil
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like the precious resource that it is.
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Unfortunately, that's not the case.
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Soils around the world are experiencing
unprecedented rates of degradation
unprecedented rates of degradation
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through a variety of human actions
that include deforestation,
that include deforestation,
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intensive agricultural production systems,
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overgrazing,
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excessive application
of agricultural chemicals,
of agricultural chemicals,
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erosion and similar things.
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Half of the world's soils
are currently considered degraded.
are currently considered degraded.
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Soil degradation is bad for many reasons,
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but let me just tell you a couple.
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One: degraded soils have diminished
potential to support plant productivity.
potential to support plant productivity.
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And hence, by degrading soil,
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we're compromising our own abilities
to provide the food and other resources
to provide the food and other resources
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that we need for us
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and every member of living things
on the face of the earth.
on the face of the earth.
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And second:
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soil use and degradation,
just in the last 200 years or so,
just in the last 200 years or so,
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has released 12 times more carbon
into the atmosphere
into the atmosphere
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compared to the rate at
which we're releasing carbon
which we're releasing carbon
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into the atmosphere right now.
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I'm afraid there's even more bad news.
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This is a story of soils
at high latitudes.
at high latitudes.
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Peatlands in polar environments
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store about a third
of the global soil carbon reserves.
of the global soil carbon reserves.
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These peatlands have
a permanently frozen ground underneath,
a permanently frozen ground underneath,
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the permafrost,
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and the carbon was able to build up
in these soils over long periods of time
in these soils over long periods of time
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because even though plants are able
to photosynthesize during the short,
to photosynthesize during the short,
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warm summer months,
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the environment quickly
turns cold and dark,
turns cold and dark,
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and then microbes are not able
to efficiently break down the residue.
to efficiently break down the residue.
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So the soil carbon bank
in these polar environments
in these polar environments
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built up over hundreds
of thousands of years.
of thousands of years.
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But right now, with atmospheric warming,
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the permafrost is thawing and draining.
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And when permafrost thaws and drains,
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it makes it possible
for microbes to come in
for microbes to come in
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and rather quickly
decompose all this carbon,
decompose all this carbon,
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with the potential to release hundreds
of billions of metric tons of carbon
of billions of metric tons of carbon
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into the atmosphere
in the form of greenhouse gases.
in the form of greenhouse gases.
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And this release of additional
greenhouse gases into the atmosphere
greenhouse gases into the atmosphere
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will only contribute to further warming
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that makes this predicament even worse,
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as it starts a self-reinforcing
positive feedback loop
positive feedback loop
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that could go on and on and on,
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dramatically changing our climate future.
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Fortunately, I can also tell you
that there is a solution
that there is a solution
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for these two wicked problems
of soil degradation and climate change.
of soil degradation and climate change.
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Just like we created these problems,
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we do know the solution,
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and the solution lies
in simultaneously working
in simultaneously working
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to address these two things together,
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through what we call
climate-smart land management practices.
climate-smart land management practices.
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What do I mean here?
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I mean managing land
in a way that's smart
in a way that's smart
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about maximizing
how much carbon we store in soil.
how much carbon we store in soil.
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And we can accomplish this
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by putting in place
deep-rooted perennial plants,
deep-rooted perennial plants,
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putting back forests whenever possible,
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reducing tillage and other disturbances
from agricultural practices,
from agricultural practices,
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including optimizing the use
of agricultural chemicals and grazing
of agricultural chemicals and grazing
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and even adding carbon to soil,
whenever possible,
whenever possible,
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from recycled resources
such as compost and even human waste.
such as compost and even human waste.
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This kind of land stewardship
is not a radical idea.
is not a radical idea.
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It's what made it possible
for fertile soils
for fertile soils
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to be able to support human civilizations
since time immemorial.
since time immemorial.
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In fact, some are doing it just right now.
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There's a global effort underway
to accomplish exactly this goal.
to accomplish exactly this goal.
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This effort that started in France
is known as the "4 per 1000" effort,
is known as the "4 per 1000" effort,
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and it sets an aspirational goal
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to increase the amount of carbon
stored in soil by 0.4 percent annually,
stored in soil by 0.4 percent annually,
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using the same kind of climate-smart
land management practices
land management practices
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I mentioned earlier.
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And if this effort's fully successful,
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it can offset a third
of the global emissions
of the global emissions
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of fossil-fuel-derived carbon
into the atmosphere.
into the atmosphere.
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But even if this effort
is not fully successful,
is not fully successful,
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but we just start heading
in that direction,
in that direction,
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we still end up with soils
that are healthier, more fertile,
that are healthier, more fertile,
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are able to produce all the food
and resources that we need
and resources that we need
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for human populations and more,
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and also soils that are better capable
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of sequestering carbon dioxide
from the atmosphere
from the atmosphere
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and helping with
climate change mitigation.
climate change mitigation.
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I'm pretty sure that's what politicians
call a win-win solution.
call a win-win solution.
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And we all can have a role to play here.
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We can start by treating the soil
with the respect that it deserves:
with the respect that it deserves:
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respect for its ability
as the basis of all life on earth,
as the basis of all life on earth,
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respect for its ability to serve
as a carbon bank
as a carbon bank
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and respect for its ability
to control our climate.
to control our climate.
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And if we do so,
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we can then simultaneously address
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two of the most pressing
global challenges of our time:
global challenges of our time:
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climate change and soil degradation.
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And in the process, we would be able
to provide food and nutritional security
to provide food and nutritional security
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to our growing human family.
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Thank you.
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(Applause)
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ABOUT THE SPEAKER
Asmeret Asefaw Berhe - Soil scientistAsmeret Asefaw Berhe is a soil and global-change scientist and educator passionate about all things related to the science and beauty of soils.
Why you should listen
As Asmeret Asefaw Berhe tells it: "My research investigates: 1) how the soil system controls the earth's climate, in particular how otherwise thermodynamically unstable organic compounds can remain in soil for up to millennia, and 2) the dynamic two-way relationship between human communities and the soil system that we depend on for our food and nutritional security, and the socio-political implications of land degradation.
"I have a strong commitment towards education, outreach and mentoring. I am driven to ensure that scientific education and careers are equally accessible to people from all walks of life, and that academic workplaces are free from bias and harassment."
Asmeret Asefaw Berhe | Speaker | TED.com