This video is supported by Wren, a website with a monthly subscription   that helps fund projects to combat the climate crisis.

Click the link in the description  to learn more about making  a monthly contribution that supports  projects like rainforest protection programs. [♪ INTRO] Planet Earth is losing its roots. Plant ecosystems are so large and complex  that their roots are effectively global.   They shape the planet and hold  it in place against change.

And when we grow plants for  agriculture, we change root systems. Which means that in the  unavoidable act of growing food,  we’re losing a tool that helps us resist  the effects of the climate crisis. So here’s how we’re killing our  roots, and what we can do about it.

Deep roots stabilize the soil around them,  protecting sloped areas  from landslides and erosion. And they can also break up bedrock. All of these things make roots  foundational to forest ecosystems,  allowing other plants to grow.

In fact, trees completely changed  the planet forever when they showed   up around 400 million years  ago in the Devonian period. Not only do they keep plants fed and watered,   they can also make it easier for water  and nutrients to stay in the soil. Roots store water in them for drier days, and  heavily rooted soils also stay damp longer,   making these systems much more  resilient to drought conditions.

Since the climate crisis is only  going to increase the frequency   and intensity of droughts, roots are an  important bulwark against their effects. Roots can also contribute to  reducing climate change as a whole,  by taking carbon out of the  atmosphere and storing it in the soil. The carbon that plants use to  make sugar in photosynthesis   comes straight from the air in the form of CO2.

And much of that gets incorporated  into the plant’s biomass. And in plants with fairly extensive root systems,   much of that biomass is underground, where  it isn’t in contact with the atmosphere. When the plant dies and  microbes help it decompose,  some of that carbon stays trapped in the soil.

So when root systems are extensive,  carbon dioxide goes in one  way and doesn’t come back out. The carbon locked up in soils  is called soil organic carbon,  and roots are the primary  contributor to soil carbon storage, meaning that strong root systems can  directly help us fight climate change. So, roots store carbon, and they protect  soils from the effects of drought.

Roots are great. Thanks, roots! But, unfortunately, like everything  else, roots are changing.

Not all roots are created equal. Some plants, like trees and other woody plants, have deep and extensive root systems, while other plants, like the  crops that we grow to eat,  tend to have a shallower root system. And because we’ve converted so  much forest land into farmland,  we’ve changed the distribution  of plants across the globe, basically making it so that the  proportion of shallow-rooted crop plants is much higher than it otherwise would be.

On the other hand, there’s a  phenomenon called woody encroachment, which is where woody plants are spreading into  areas that never used to be able to support them. Mostly, this is happening at high latitudes,   where climate change is warming areas that  were previously too cold to support forests. And woody encroachment does  balance the scales somewhat,  bringing some deeper-rooted  plants back into the equation.

But in a 2022 study that used  models to predict global root depth, researchers showed that even with  woody encroachment happening,  Earth’s roots are getting  shallower across the globe. That’s because only a small portion of the Earth’s   surface is experiencing woody encroachment,  while agricultural land expands every day. In fact, the study showed that Earth has   likely lost 11.6 trillion cubic  meters of rooted volume already, which means the average root depth  globally has gotten about 8 cm shorter.

That’s a loss of 5% of Earth’s total root volume! Now, because this discovery is still so new,   it’s hard to say exactly what  the effect of that might be. But the amount of water soils can  store is a function of root depth,   and soils already don’t contain a lot of water.

This trend is likely to continue  in the next hundred years,  regardless of how the climate crisis plays out. Researchers who study the climate  crisis use models that make   different assumptions about what humans will do. Some models assume we’ll do nothing,   while others assume we’ll try harder.

But under  all of those scenarios, roots are in trouble. Under a scenario where we increase  our dependency on fossil fuels, models predict that the Earth could lose up to  32.4 trillion cubic meters of rooted soil by 2100. Which is almost three times  more than we’ve lost already,  and equates to 23 centimeters of  root depth all over the world.

And I wish I could tell you that was  the worst-case scenario, but…it is not. When researchers looked at the  model for what would happen to   roots if we drastically reduced emissions, in one of the most optimistic scenarios, they  found that root depths decrease even more,   by up to 43.5 trillion cubic  meters or 30 centimeters globally. And that’s because root depth is more connected  to land-use change than it is to climate change.

And if the climate crisis doesn’t  wreck land that's available for agriculture,   it’s projected in some regions  that more farmers will move in. Most of that root loss comes from shrublands  in North Africa, the Middle East, Asia,   and Australia, which are expected to  transition to grassland or farmland. What that means is that even though we need to  limit emissions, we can’t get tunnel vision.

We have to look at what it will take to preserve  the things that are working… like root systems. Otherwise a large portion of the soil won’t  be available for water or carbon storage,   which could lead to the soils becoming  poorer or less fertile in the future. And we’re still working on  ways to address the problem.

Reducing the amount of land being used  for agriculture can help reverse these trends.  But we can’t exactly  ask people to stop eating. However, we can reduce the amount of crops  that aren’t directly used to feed people. A lot of crops are used to feed livestock,   rather than humans, so reducing meat  consumption could definitely help.

That’s because energy is lost as  you move up in the food chain. An animal can eat more crops in its lifetime   than the energy that you would  get out of eating the animal. So energy-wise, it’s more efficient to eat the  crops directly than to eat the animal itself.

This especially matters for red meat like beef,   because it takes a lot more crops to feed a  cow than it does, say, a chicken or a turkey. Since beef farming is also carbon-intensive,  it really is a common-sense choice. And reforestation helps to restore roots as well.  Trees have deep roots, which you’d know if  you’ve ever tried to pull out an old stump, and policy changes that reduce  deforestation and plant more trees   could help balance root loss from agriculture.

As a bonus, both of these steps  also help with climate change. We're still learning about all  the ways that we affect the planet. But thankfully, many of these  problems are linked to each other,   so by working on one problem, we help solve  others, leading to a more sustainable world.

And keeping our Earth firmly rooted. Thank you for watching this SciShow video,  and thank you to Wren for supporting it! Wren is a website that helps combat the  climate crisis by funding projects from   preventing wildfires in California to providing  clean cooking fuel for refugees in Uganda.

For people who want to help our  planet but don’t know where to start,   Wren is an onramp to climate action. Wren curates climate fighting  initiatives that have the power  to make real change. So all you have  to do is choose your favorite one.

And this month, they added new partners in  the fight against our global climate crisis! Wren is now destroying harmful  refrigerants to save our ozone layer. Remember a few years ago everyone was  talking about chlorofluorocarbons getting   released into our atmosphere?

Well  Wren is doing something about that. You can join them by signing up to  make a monthly contribution at wren.co. And the first 100 SciShow viewers  who sign up with the link in the description will get the first month of  their subscription covered by Wren for free. [♪ OUTRO]