[music playing] The world's tallest tree reaches 380 feet into the sky.

One giant Sequoia is made of enough wood to fill a 747.

One Baobab tree in South Africa is so wide that they put a pub inside of it.

These enormous trees might be rooted in the ground, but almost all of their physical mass grows out of the air.

A tree's dry weight, all the leaves, branches, and trunks, xylem, and phloem, and chloroplasts are all built from carbon dioxide.

Even the water they hold was once water vapor that fell as rain.

Trees eat air and turn into more tree.

[singing] Planting trees might be a way to combat climate change, an easy way of sucking excess carbon out of the air.

If every person alive planted one that would be more than 7 billion new trees.

But is that a lot or not?

How many trees are there on Earth?

Figuring out how many trees there are on earth sounds like a simple question.

But it's surprisingly difficult to answer.

I mean we can't exactly go out and count them all.

1,725, 1,027--- Dang it.

But it's an answer to that scientists need to know.

Not only are trees an important part of the carbon and water cycle, 80% of terrestrial species call them home, as do 300 million people.

1.6 billion people rely on forests for their livelihood.

They control erosion, filter groundwater, and provide raw materials for everything from paper, to log cabins, even Ikea furniture.

Trees are terrific.

Until this year our best estimate for Earth's tree population was around 400 billion, or about 60 trees for every person.

But this was based on satellite imagery estimates, which is kind of like trying to count the hairs on someone's head from on top of a skyscraper.

In 2015 scientists gathered half a million measurements of tree density on the ground from every continent on Earth besides Antarctica-- spoiler, not known for their trees down there-- to create a global map of forest trees stretching across jungles, deserts, grasslands, tundra, everything.

This new estimate puts the number of trees on earth at-- get this-- 3 trillion.

That's un-be-leaf-able.

That's almost 10 times higher than previous estimates, more than 420 trees for every human.

Now a whopping 43% of those trees are in tropical and subtropical regions the most biologically diverse ecosystems on land.

But they're also among the most threatened.

Tens of thousands of years ago before humans conquered Earth our planet had twice as many trees.

Today deforestation to make way for agriculture, mining, and urbanization continues to erase trees from the map.

17% Of the Amazon has disappeared in the past 50 years.

Sumatra has lost 85% of its forest.

Nobody cares for the woods anymore.

All in all, we're losing about 48 football fields of forest every minute, 15 billion trees per year.

Fewer trees can also lead to less rain.

Trees, like all plants, lose water through pores in their leaves in order to cool off and to move nutrients upward from the roots and trunk.

As a result forests create massive clouds of water vapor that condense and fall back down as rain.

It's a nice cycle of water in water out.

But cut down the forests and droughts and fires may take that rain's place.

Scientists think maybe 15% of all greenhouse gas emissions have come from deforestation.

To put it simply, where there's more trees there's less carbon in the air.

Plus it looks nice.

And there's more shade.

There's more places to put hammocks, and rope swings, and tree houses.

It's a win-win-win-win-win.

So there you have it, Earth's tree population counted one twig at a time.

With 3 trillion trees on earth planning a few billion more might seem like small potatoes, but even one tree can be quite the seed for tomorrow.

Stay curious.