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How African Dust Feeds Florida’s Crops


[♩ INTRO ] When you eat a tomato from Florida, chances
are it was grown in African soil. 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. It takes about a week. Then, it’s hello, Florida. 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 year. 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 they act kind of like a fingerprint. So by measuring where those fingerprints turn
up, the researchers can see how the dust has migrated and what its effects are. A lot of those effects involve ecology. Like for starters, dust builds soil. Lots of soil. Scientists estimate that more than 30% of
the soil in Barbados comes from Africa. And the stuff in the Bahamas and the Florida
Keys? Mostly African imports. 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 so lush. 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, isn’t that fertile. But blast over some African dust and voila. You’ve suddenly got nutrients in your soil,
like magnesium, phosphorous, and potassium, and things get a whole lot greener. Dust nourishes soil all over the world, too,
including in the Amazon rainforest and northern Hawaiian islands. 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 metals. For example, mercury made in China gets mixed
in with the dust and blows east across the Pacific. Scientists have detected it in rivers and
from the top of roughly 3 kilometer high at Mt. Bachelor in Oregon. 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 a great idea. I mean, it’s not great anywhere in the world,
but it’s harder to manage when it’s blowing all over the place. Even without mercury, long-distance dust is
also linked to problems with asthma and other respiratory diseases. That’s because the particles that travel
around the world tend to be especially fine and harmful to lungs. The dust can pick up some other hitchhikers,
too, including live locusts and, most surprisingly, microbes. Until around 2000, scientists figured that
intense ultraviolet radiation from the sun would kill anything alive on its way across
the ocean. But they were wrong. 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 in them. 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 Caribbean. 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 — can hitch a ride. 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 isn’t as intense. Enough attention is paid to these flying microbes
that there’s even a name for this field of research: aeromicrobiology. Now, flying dust might have a big impact on
ecology, but its influence isn’t just linked to soil or plant diseases. The dust can also interact with Earth’s
weather — like how African dust weakens hurricanes. Yeah. Hurricanes. 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 surface cooler. That, in turn, suppresses hurricane formation,
since warm ocean temperatures fuel the monster storms. So more dust equals fewer hurricanes. This actually happened in 2006, when thick
African dust caused the north Atlantic to cool a third more than usual. That year, only five hurricanes formed in
the Atlantic compared to the 15 the year before when there was less dust. So, from fewer hurricanes to flying microbes,
the global dust ecosystem is kind of a mixed bag. 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 weird effects soon. Thanks for watching this episode of SciShow! Besides causing problems on Earth, dust can
cause even more trouble in space — and in fact, it’s kind of an astronaut’s worst
enemy. You can learn all about it over at SciShow
Space. [♩ OUTRO ]

100 Comments

  1. Kitty Beans Author

    Coming this Summer…
    A new old classic horror film sure to shake you to the core…
    when an African dust storm carrying ordinary microbes…
    is exposed to unordinary radiation from space…
    meets a superordinary hurricane… you get…
    ATTACK OF THE MUTANT SENTIENT HURRICANE FROM SPAAAACE!
    No one is safe…
    not even the president,
    of the sewing and knitting club!
    Let alone of the United States.
    Batten down the hatches, because it's time for…
    ATTACK OF THE MUTANT SENTIENT HURRICANE FROM SPAAAaaaaceeee!

    Reply
  2. FarawayWayfarer Author

    I don’t remember much about it, but I remember in The Voyage of The Beagle it was mentioned dust (or spores?) raining on ships, coating them in a thin layer. I’d need to read it again to be more exact, but does anyone know what that was? This video reminded me of that.

    Reply
  3. Tharindu Kottegoda Author

    Just wondering, how come Africa can't be as productive as places like Florida or the Caribbean if their dust and soil is so fertile? Thank you

    Reply
  4. Andrew Church Author

    Ok, this presenter IS listenable. That (one of the) guy(s) who’s been around forever still the best. Even he has a very occasional dud, but without detail analysis hard to know if its due to bad performance, script or editing

    Reply
  5. Daniel Campbell Author

    Not that I'm a scientist or anything but; I wonder if we could purposely kick up enough dust to try and counteract global warming. The act of all that dust absorbing a portion of the sun's light might help bring us down a little bit. Just a random thought.

    Reply
  6. MIWAsan Author

    damn it. again a video with Olivia. probably something interesting, but sorry, can't watch it with her. she might be a nice person and all, but sorry to say: she's not somebody to put behind a camera. really a shame so many videos just not really watchable because its done with Olivia.

    don't want to bash an her personally, but she just isn't the type person one enjoys watching.

    Reply
  7. Julia Young Author

    Florida DEP maintains the air samplers used to measure particulate in the air. When the Saharan dust comes over the particulate count is enough to raise our air quality index (AQI) from the good range into the moderate range. The used filters, which are normally a greyish brown, change to a much lighter tan. I used to have pictures but I can't find them. Anyone who is curious should be able to get copies through a Sunshine law request.

    Reply
  8. Mike D Author

    So after all these centuries of dust landing in,for example,Oregon,where does it go from there?
    It just doesn't keep piling up there,or there would be 50,000 foot mountains all over it.
    It all has to cycle to somewhere else,somehow.

    Reply
  9. Life; The Tragic Comedy Author

    Sand is SiO2, so where do all the nutrients come from? Sure, Africa, but really, why are they in the sands of uninhabitability?

    Reply
  10. Daniel Dulu Author

    If you think that is all that is coming from China then your sorrowfully mistaken. Moving all that industry over might have solved the pollution regulations that were being imposed on American businesses but all you did was move the pollution over there that ends up being carried by the jet stream back to here and deposited on our food sources, something we were trying to avoid doing through clean air regulations.

    Reply
  11. Ken O Author

    Do we know the breakdown (percentages) of household dust, office dust, typical dust outdoors in cities/ in suburbs. And what percent of the dust is from over 20 miles away, and what percent is from space. (Of cause that last possibility leads to more questions.) Do our shedding skin cells make their way around the globe?

    Reply
  12. dizzious Author

    Years ago I heard about the effect this dust has on rainforests in South America. I hadn't heard anything about it since then so I was starting to doubt the accuracy of the idea. Thanks for confirming the existence of this cool thing for me, SciShow.

    Reply
  13. Turtle Von Nurtle Author

    "Most surprisingly microbes"? That seems like the least surprising, more surprising is a giant locust hitchhiking on a tiny piece of dust.

    Reply
  14. Trigger Happy Author

    Weird so global warming causes more desert and warmer oceans but the desert dust is helping to calm the storm a little sort to speak a little bit. It's a strange sickness. Like people kill most species on earth but we save a few here and there.

    Reply
  15. spirit Johnson Author

    He caused the East Wind to blow in the heavens and by his power he brought in the South Winds Psalms chapter 78 verse 26 all praise go to the most high.

    Reply

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