Name: How African Dust Feeds Florida's Crops
Uploaded: 2021-05-19T02:54:49.000Z
Duration: 5 min 47 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

基礎受動態

When you eat a tomato from Florida, chances are it was grown in African soil.

転換語

But not because someone shipped the dirt over there or anything.

Every year, tons of dust from the Sahara desert is kicked up by dust storms, blasted high

into the sky, and whisked across the Atlantic Ocean on wind currents.

In fact, our oceans and continents are all linked into this weird, global dust ecosystem.

Whether it's going from Australia to New Zealand or from Asia to Oregon, the current

estimate, worldwide, is that 3 billion tons of dust move through the atmosphere every

It comes with some powerful, and surprising, global effects, not all of which are good.

But one way or another, this dust is definitely changing our world.

Scientists can track how the dust moves using satellite images or by analyzing soil samples.

The dust in certain regions tends to contain specific kinds or amounts of elements, and

So by measuring where those fingerprints turn up, the researchers can see how the dust has

Scientists estimate that more than 30% of the soil in Barbados comes from Africa.

And the stuff in the Bahamas and the Florida Keys?

Besides being weird to think about, the dust is also really important.

In fact, without African dust, the vegetation on some Caribbean islands wouldn't be nearly

See, those islands, along with parts of Florida, are mostly built of crusty coral.

When that coral breaks down, it leaves a pile of broken-up calcium — which, on its own,

But blast over some African dust and voila.

You've suddenly got nutrients in your soil, like magnesium, phosphorous, and potassium,

Dust nourishes soil all over the world, too, including in the Amazon rainforest and northern

So, on your next tropical vacation, you can thank dust for the scenery.

Now, all that might sound great — and it is.

But long-distance dust can also bring less welcome visitors, too, like pesticides and

For example, mercury made in China gets mixed in with the dust and blows east across the

Scientists have detected it in rivers and from the top of roughly 3 kilometer high at

They know it's from China because it has a specific chemical profile, but also because

the mercury only wafts in when the wind blows from the west.

So it's almost certainly coming from Chinese coal-fired power plants.

Mercury has plenty of ill effects on humans and ecosystems, including birth defects and

reproductive problems, so accumulating more of it in the water or soil isn't exactly

I mean, it's not great anywhere in the world, but it's harder to manage when it's blowing

Even without mercury, long-distance dust is also linked to problems with asthma and other

That's because the particles that travel around the world tend to be especially fine

The dust can pick up some other hitchhikers, too, including live locusts and, most surprisingly,

Until around 2000, scientists figured that intense ultraviolet radiation from the sun

would kill anything alive on its way across the ocean.

In a 2002 study from the journal American Scientist, researchers used petri dishes to

collect air samples in the Caribbean on an especially dusty day, and soon, microbes grew

Microbes aren't always bad, but altogether, about 20% of the ones found in international

dust have been linked to plant and animal diseases.

One microbe from Africa seems to be strongly linked to a disease killing fan coral in the

Another is the same disease that causes diseases in Florida's carrots.

Even occasional human pathogens -- like ones linked to urinary tract or respiratory infections

The scientists think that the microbes that survive the journey either have dark pigment,

which could act like sunscreen, or float near the bottom of the dust clouds where radiation

Enough attention is paid to these flying microbes that there's even a name for this field

Now, flying dust might have a big impact on ecology, but its influence isn't just linked

The dust can also interact with Earth's weather — like how African dust weakens

As the dust flies through the air, it can darken the clouds.

That reduces how much of the sun's heat reaches the Atlantic, and keeps the ocean

That, in turn, suppresses hurricane formation, since warm ocean temperatures fuel the monster

This actually happened in 2006, when thick African dust caused the north Atlantic to

That year, only five hurricanes formed in the Atlantic compared to the 15 the year before

So, from fewer hurricanes to flying microbes, the global dust ecosystem is kind of a mixed

But one way or another, it's definitely cool.

Scientists are still working out what this vast, global migration of dust really means

— like what it carries, and how, for better or worse, it's altering our world.

And with more tracking and more experiments, hopefully we'll find even more of those

Thanks for watching this episode of SciShow!

Besides causing problems on Earth, dust can cause even more trouble in space — and in