What if there were 1 trillion more trees? - Jean-François Bastin
Standing at almost 84 meters tall,
this is the largest known living tree
on the planet.
Nicknamed General Sherman,
this giant sequoia has sequestered
roughly 1,400 tons of atmospheric carbon
over its estimated 2,500 years on earth.
Very few trees can compete
with this carbon impact,
but today, humanity produces more
than 1,400 tons of carbon every minute.
To combat climate change,
we need to steeply reduce
fossil fuel emissions,
and draw down excess CO2
to restore our atmosphere’s balance
of greenhouse gases.
But what can trees do to help
in this fight?
And how do they sequester carbon
in the first place?
Like all plants, trees consume
atmospheric carbon
through a chemical reaction
called photosynthesis.
This process uses energy
from sunlight
to convert water and carbon dioxide
into oxygen
and energy-storing carbohydrates.
Plants then consume
these carbohydrates in a reverse process
called respiration,
converting them to energy
and releasing carbon
back into the atmosphere.
In trees, however, a large portion
of that carbon isn’t released,
and instead, is stored
as newly formed wood tissue.
During their lifetimes,
trees act as carbon vaults,
and they continue to draw down carbon
for as long as they grow.
However, when a tree dies
and decays,
some of its carbon will be released
back into the air.
A significant amount of CO2
is stored in the soil,
where it can remain
for thousands of years.
But eventually, that carbon
also seeps back into the atmosphere.
So if trees are going to help
fight a long-term problem
like climate change,
they need to survive to sequester
their carbon
for the longest period possible,
while also reproducing quickly.
Is there one type of tree
we could plant that meets these criteria?
Some fast growing, long-lived,
super sequestering species
we could scatter worldwide?
Not that we know of.
But even if such a tree existed,
it wouldn’t be a good
long-term solution.
Forests are complex networks
of living organisms,
and there’s no one species
that can thrive in every ecosystem.
The most sustainable trees to plant
are always native ones;
species that already play a role
in their local environment.
Preliminary research shows
that ecosystems
with a naturally occurring diversity
of trees have less competition
for resources and better resist
climate change.
This means we can’t just plant trees
to draw down carbon;
we need to restore depleted ecosystems.
There are numerous regions
that have been clear cut
or developed that are ripe for restoring.
In 2019, a study led
by Zurich’s Crowtherlab
analyzed satellite imagery
of the world’s existing tree cover.
By combining it with climate and soil data
and excluding areas necessary
for human use,
they determined Earth could support
nearly one billion hectares
of additional forest.
That’s roughly 1.2 trillion trees.
This staggering number surprised
the scientific community,
prompting additional research.
Scientists now cite a more conservative
but still remarkable figure.
By their revised estimates,
these restored ecosystems
could capture anywhere from 100 to 200
billion tons of carbon,
accounting for over one-sixth
of humanity’s carbon emissions.
More than half of the potential
forest canopy
for new restoration efforts
can be found in just six countries.
And the study can also provide insight
into existing restoration projects,
like The Bonn Challenge,
which aims to restore 350 million hectares
of forest by 2030.
But this is where it gets complicated.
Ecosystems are incredibly complex,
and it’s unclear whether they’re best
restored by human intervention.
It’s possible the right thing
to do for certain areas
is to simply leave them alone.
Additionally, some researchers
worry that restoring forests
on this scale may have unintended
consequences,
like producing natural bio-chemicals
at a pace that could actually
accelerate climate change.
And even if we succeed
in restoring these areas,
future generations would need
to protect them
from the natural and economic forces
that previously depleted them.
Taken together, these challenges
have damaged confidence
in restoration projects worldwide.
And the complexity
of rebuilding ecosystems
demonstrates how important
it is to protect our existing forests.
But hopefully, restoring
some of these depleted regions
will give us the data and conviction
necessary to combat climate change
on a larger scale.
If we get it right, maybe these modern
trees will have time to grow
into carbon carrying titans.
