Terrific Trees: A SciShow #TeamTrees Compilation


Hey everybody, got a special video for
you today. I, you may not know this, love trees they’re tall and they’re skinny
just like me and they do so much for us from making oxygen so we can breathe to
cooling urban environments with their shade the literally holding the ground
together to prevent erosion so when we here at scishow heard that Mr Beast and
Mark Rober were assembling a team of tree lovers to help them plant 20
million trees by the end of 2019 we were all in everybody on the scishow
team agreed we are #TeamTrees and we want you to join us. For every
dollar you donate at teamtrees.org the Arbor Day Foundation will plant a tree
the goal is to get to 20 million by December 31st and we’ve put together
this compilation of our favorite tree episodes to inspire you to donate. So
kick back enjoy the show and be sure to head to teamtrees.org afterwards to
help us plant trees. [ ♪INTRO ] First up we’re going to talk about what
is arguably the most delicious tree out there: avocado trees. Don’t eat the tree
part, though, but who doesn’t love their tasty green fruit mashed and spread on a
piece of toast? But it turns out it is a bit of a miracle that avocados are still
around we very nearly lived in a world without them. Here’s Michael to explain their almost tragic fate. whether it’s sliced on top of a salad tucked into California sushi roll or
mashes guacamole in a burrito people seem to love avocados in fact people in
the United States munched through 4 billion of them in 2014 alone they taste
great they’re good for you but one of the most amazing things about avocados
is that they still exist see they had a special relationship with huge beasts
that lumbered around Central America tens of thousands of years ago and when
these animals went extinct avocados could easily have gone down with them
but luckily for us they were saved by some prehistoric farmers the word
avocado comes from the Aztecs specifically the Nahuatl word avocado
which means testicle I mean you can kind of see where they got the name it
probably has something to do with the you know the shape and texture of
avocados the way they hang from trees anyway before they became popular in the
rest of the world they were cultivated in Mesoamerica for thousands of years
avocados are a fruit basically swollen plant ovaries but nutritionally they’re
very different from other fruits you’d find in the supermarket first like
apples and oranges are composed mostly of water and sugar and in general fruit
is probably better for you than say a bag of sweets or a sugary drink because
it contains fiber which slows down the sugar absorption and makes you feel
fuller faster by comparison avocados have much less sugar but more protein in
fat that gives them that smooth creamy texture but it also puts them on the
calorific side for a fruit anyway they also contain high levels of potassium
and folate nutrients as well as vitamins c e and k and technically avocados are
berries like grapes and blueberries rather than holding lots of little seeds
the avocado goes all-in on one big seed that massive ball at the core of each
fruit and avocados with their huge seeds evolved alongside equally huge guts tens
of thousands of years ago during the Pleistocene epoch a menagerie of mega
fauna or giant animals roamed the Americas while woolly mammoths chilled
out in the North ground sloths weighing three tonnes and armadillos the size of
cars lived in the warm equatorial forest sneeze giant sloths and armadillos a lot
of avocados their digestive systems would break down the tough skin and
absorb the high-energy pulp then the indigestible seed which contains bitter
toxins that kept the animal from chewing it up passed right out the other end the
animals got a tasty meal and the avocado trees got to scatter their offspring
throughout the Mesoamerican forests plus the seeds got some nice
warm fertilizer to give them a nutritious boost and with these mega
fauna around to eat the fruit avocado trees could keep growing berries with
increasingly massive seeds a bigger the seed the more nutrients could be stored
inside as a starter kit for the baby tree this is especially useful in dense
tropical forests where canopies of older trees block out much of the light for
the saplings below so instead of depending entirely on sunlight for
energy the avocado seedlings could supplement photosynthesis with the
nutrients in their seed to survive this happy evolutionary match didn’t last
though eventually the megafauna suffered a mass extinction around ten to thirteen
thousand years ago we don’t know exactly why but scientists think the warming
climate at the end of the last ice age was partly responsible though it was
also suspiciously close to the time humans began spreading across the
Americas no doubt enjoying lots of giant mammal meat along the way this meadow
vacarro’s were in trouble without their large gutted evolutionary partners the
trees stopped thriving the fruit fell to the ground and the seeds mostly just
became food for mold but more hungry creatures were nearby the new human
arrivals love the avocados flesh as much as the ground sloths did they also had
the tools to eat them and the brains to figure out how to grow them avocados
were all set for domestication the avocados we eat today are probably a
little different than the ones that grew tens of thousands of years ago
for example thanks to artificial selection they probably have more pulp
than their ancestors but they’ve kept their huge seeds ready and waiting for
the guts of long-dead beasts so we’re lucky that thousands of years
ago some farmers decided to plant a bunch of avocado trees and hey I bet
that thousands of years from now our descendants will be pretty happy if we
plant a whole bunch of trees too so don’t forget to go to team trees org
after this episode to help us plant 20 million trees and speaking of planting
trees avocados aren’t the only tree whose fate is in our hands the American
chestnut is also struggling to survive our modern world though that’s because
of a deadly fungus not the lack of seed spreaders time for Olivia to explain picture a forest full of gigantic trees
soaring 30 meters into the sky with 5 meter wide trunks you probably
envisioned something like the giant sequoias and redwoods that grow on the
western coast of the United States but a little over a century ago the east coast
of America was also home to giant trees so somewhat smaller than their Western
counterparts American chestnuts were huge and they were all over the eastern
US at the dawn of the 20th century then within a few decades
they were almost extinct the culprit a fungus that strangled the trees from
within brought by accident from Asia since their demise scientists have been
trying to figure out if there’s a way to bring the American chestnut back and
thanks to technological advances they may finally have a solution if they can
convince the government to let them plant genetically modified trees to
understand what happened to the American chestnut we have to go back in time to
the end of the 19th century back then American chestnut trees were known as
the Sequoias of the east because they had huge trunks and were tall like the
West Coast Giants and they were all over in 1900 around 1/4 of the hardwood trees
east of the Mississippi were American chestnuts in some places they made up as
much as 40% of the forests but by the 1940s they were all but gone the first
signs of trouble were seen in the Bronx Zoo in 1904 when Soares called cankers
were discovered on a stand of dying trees scientists soon realized that the
disease was widespread and by 1912 botanists had managed to identify both
the fungus responsible and it’s point of origin the chestnut blight fungus gets
under the trees bark by hitching a ride on insects the fungus then attacks and
feeds off of the trees water transmitting cambium tissues essentially
choking the tree the blight fungus probably arrived in New England in the
1870s when Japanese chestnut trees became popular ornamental plants the
imports are resistant to the blade so it’s likely they carried it to America
where the chestnut trees were totally susceptible and by the 1940s it’s
estimated that nearly 4 billion trees had died but they didn’t go extinct
entirely a few scattered populations still exist mostly trees that people
planted outside of their original range there are also smaller specimens along
the east coast that were isolated enough from their kin to avoid infection and it
turns out that like the Dread Pirate Roberts even the dead trees are only
most we did while the blade destroyed their trunks their root systems remained
and even decades later these living stumps occasionally eke out a chute of
new growth but it’s usually in vain because the blight is still around
although it isn’t doing much damage to them it’s still lurking in oaks that
took over after the chestnuts were wiped out so before any chestnut shoots can
reach a reproductive maturity they catch the blight but where there’s growth
there’s hope so scientists have been trying to figure out a way to bring
American chestnuts back to their former glory since the 1980s forestry
specialists and geneticists have tried all sorts of things to make blight
resistant trees they attempted a technique called back crossing for
example we’re surviving specimens and their offspring were carefully bred
together to select for natural resistance genes but while this method
seems to work for European chestnuts it hasn’t worked as well with the American
ones probably because the European ones were more resistant to begin with
researchers have also tried hybridizing American chestnuts with blight resistant
Chinese chestnuts but so far they haven’t been able to get the resistance
traits to reliably pass down from generation to generation but one method
that does seem to work is genetically modifying the trees it turns out that we
trust a fungal disease of wheat has a similar mechanism of infection to
chestnut blight both use a compound called oxalic acid to soften up
important structural tissues while also attacking their host cambium by
stimulating the growth of calcium oxalate crystals blocking the flow of
nutrients resistant forms of wheat produce an enzyme called oxalate oxidase
which breaks down the acid thereby blocking the dispersal of the disease
and preventing the growth of those crystals scientists have introduced this
wheat gene into American chestnuts and in 2014 they revealed that they produced
a 100% resistant tree that passed that trait onto its offspring success but the
trees haven’t been planted yet the researchers have conducted some
preliminary studies to show the trees don’t cause any unexpected harm to the
organisms that live in the environments that they once inhabited and then they
requested permission from the US Department of Agriculture to release the
transgenic trees into the wild but they’re still waiting for the green
light and that could take a while if it’s ever granted at all aside from the
general anxiety that accompanies the development of any GM
some ecologists worry that a return of the American chestnut would disrupt a
century-old ecosystem that’s developed without it on
the other hand if successfully put in action this method could also work for
restoring other wild tree populations beleaguered by fungal invasives like elm
trees I guess only time will tell if the Sequoia of the east will once again
stand tall it’s really sad that billions of
chestnuts just died so suddenly even today we’re losing trees at an alarming
rate which is why it’s more important than ever to plant more and you can help
us do that if you go to team trees org after this episode it would be a shame
if we didn’t have all the wonderful weird trees we have today like for
example the ones in Europe’s dancing forests oh look it’s a younger version
of me here with the deets on those the dancing forest of Kaliningrad is
exactly the kind of place where you’d expect to find a werewolf creeping
through the mist located in a place called the caronian spit off the Baltic
Sea on the border of Russia and Lithuania the strange forest is known to
locals by a jollier name the drunken forest because well the stand of pine
trees looks more than a little schnockered as they twist and curves
stretching upward and contorted loops to find their way to the sky and here’s the
thing no one knows why these trees look like they’re grinding to Marvin Gaye of
course theories abound some suggesting unstable soils the cause or beetle
damage or even nuclear radiation local legends say that crawling through one of
these tree loops in the right direction will earn you an extra year of life a
more popular non-magical theory suggests spousal winds were the original shaping
force and there is a precedent for that if you’ve ever hiked into an Alpine zone
forests you’ve probably seen patches of stunted twisted supercooled mini trees
called Krumholtz they get so thoroughly clobbered by a harsh cold winds that
they end up growing more horizontal than vertical but some people think that the
trees in the dancing forest have been trained to grow that way humans have
long been manipulating trees for commercial or aesthetic purposes in mr.
Miyagi and his bonsais he was all about tree shaping humans can train a young
tree to grow in unconventional ways by laying a heavy object on its skinny
trunk sometimes for years the tree just like the house plant in your windowsill
wants to grow toward the Sun really bad and no weight is going to stop it from
reaching the light a process called phototropism and whether plants are made
to bend intentionally or not the effects of phototropism can change the character
of its tissues in trees the wood that forms under the pressure of weight is
called reaction wood or in conifers compression wood it’s created when the
layer of tissue beneath the bark called the cambium thickens below the source of
the pressure to support the horizontal weight of the tree in time the funny
shape of the bend becomes permanent and it leaves behind a record of oval or
oblong instead of more circular rings in the case of the dancing of forests local
historians have no recollection of any human manipulation to create this effect
but there is another forest in Northwest Poland called the crooked forest made of
about 400 pine trees that all have uniform 90-degree bends at
base of their trunks the trees are all the same age and they all bend north
because of this uniformity many people believe that this forest was manipulated
by humans perhaps to grow uniquely shaped wood for oxen yokes ship hulls or
for furniture making that particular theory maintains that the trees were
shaped before 1930 but were abandoned before they could be harvested with the
outbreak of World War two but ultimately even the cause of the crooked forests
odd tree shapes remains a mystery and they could also be attributed to some
powerful force like strong winds heavy snow and ice pack or even the result of
one of my favourite theories being run over by Nazi tanks as young trees during
the war you know all this reminds us that while scientific explanations of
natural phenomena are usually pretty cool and often necessary sometimes it’s
maybe a little bit cooler for it just to be a mystery
oh those twisty trees are very cool you know what else would be cool if team
trees successfully plants 20 million trees in the next two months you know
you want to be a part of that and you can be if you go to team trees org to
donate and speaking of cool things it’s fall here in the northern hemisphere
which means the temperature is falling and leafy trees are painting the
landscape with beautiful yellows oranges and reds if you’ve ever wondered why
that happens we’ll wonder no more Michaels got the skinny on autumn leaves
the changing leaves of autumn are really awesome to look at but they’re also a
really striking example of nature taking extreme measures to protect itself
you’re probably familiar with photosynthesis it’s the process plants
use to turn carbon dioxide water and light energy into sugars and oxygen and
you probably also know that photosynthesis depends on a pigment a
colored compound called chlorophyll but you may not realize that plants contain
lots of other pigments as well some of the most important are the carotenoids
yellow orange and brown pigments they give color to things like corn carrots
pumpkins and sweet potatoes and the anthocyanins which give red and purple
color to cherries berries pomegranates and red apples to name a few all of
these pigments play an important role in the plant’s functions but there’s
usually far more chlorophyll in a plant than anything else because
photosynthesis is a plant’s number-one job however many trees are less active
in the winter because they grow at northern and southern latitudes that get
less sunlight during those months these trees are called
deciduous from the Latin word that means to fall off since deciduous trees don’t
do much photosynthesis in the winter it doesn’t really make sense to spend
of energy maintaining big green leaves so when the days get shorter and the
temperature gets cooler they send less of their limited resources to the leaves
and start using what water and nutrients they have to keep the rest of the tree
alive the chlorophyll in the leaves breaks down and the green color
gradually goes away and when that happens the other pigments which were
there all the time are better able to show off their colors before the leaves
die entirely and fall off the tree so the leaves aren’t actually changing
pigments they’re just losing their strong green pigment to reveal the other
colors in the tissue after the tree stops supply of food and water to the
leaves all that’s left is for the tree to cut them off the tree forms a special
layer of weakly bound cells near the base of the Leafs stock then another
layer of cells at the very bottom of the stalk expands to push the leaf away
eventually the leaf can be knocked off easily even by a light wind and then
it’s your job to rake them up it’s pretty weird when you think about it
that deciduous trees just discard huge chunks of themselves every year to make
it through to spring it’s just like oh I don’t need these hands anymore I’ll grow
new ones in a few months so here’s a really young me to talk about the oldest
trees in the world well when you started talking about the oldest or biggest or
almost any other superlative in nature you’re unlikely to find a cut and dry
answer there are in fact two contenders for oldest tree and it depends on how
you define the term the oldest known individual tree was discovered in 2012
in the white mountains of east central California a great northern Bristlecone
pine that’s 5060 three years old that’s older than the pyramids here’s a photo
of a similar Bristlecone pine now it doesn’t look exactly alive and that may
be part of its secret to success the high cold arid climate of the White
Mountains turns out to be the perfect environment for fostering these ancient
trees strangely the higher you go in those mountains the older the trees get
and several studies have suggested that the longevity of pines there is directly
related to how bad the growing conditions are not only is the average
rainfall in the White Mountains less than 30 centimeters per year but most of
the trees are growing on dolomite a type of limestone in highly alkaline soil
with very few nutrients but over time bristlecones have adapted to this
alkalinity unlike other trees which has left them
to grow without much if any competition whistle guns also don’t expend a lot of
energy on their growth in a good year the trees girth will increase by about
0.25 millimeters so instead they can make the most of their meager resources
as a result bristlecones tend to have a pretty high proportion of dead to live
wood but this has its advantages to reducing respiration and water loss and
it also helps that there aren’t many other trees around which makes it less
likely that they’ll fall victim to a forest fire over the millennia
researchers are able to determine these trees precise age thanks to a process
called cross dating which involves taking core samples from both living and
dead trees and then matching up the patterns of their rings to come back
with a timeline that goes back thousands of years for our second contender we’re
going to Fish Lake National Forest in south-central Utah here it lives a
clonal colony of quaking aspen that may very well be the oldest living thing on
earth it’s been named Pando and every tree or stem as they’re called in the
half square kilometer colony is genetically identical although no
individual tree in the colony is older than 200 years they’re all connected by
a single root system that’s at least 80 thousand years old and possibly much
older at over 6,000 metric tonnes it also holds the distinction of being the
heaviest known living organism on earth so how did bando get so old clonal
colonies like panda can reproduce either by flowering and producing seeds or by
producing a clone of themselves in this case cloning just means extending the
enormous network of roots enforcing a new stem up through the ground because
the heart of Pando is so far beneath the ground it can’t be killed by a forest
fire recent studies have found that Pando hasn’t reproduced sexually in more
than 10,000 years that’s quite a dry spell and not that surprising given its
age that just means that it’s up to the root system to continue producing clones
and letting the forest fires burn to keep invading conifers at bay so thanks
for the evolutionary tips world’s oldest trees I’ll be sure to keep them in mind
when I turned 5000 years old and want to go for another five thousand
80,000 years just imagine what Pando has witnessed in its lifetime it must feel
like every new clone tree grows into a totally different world and it’s not
just Pando of course lots of trees can live for centuries if not millennia
trees planted today could last long after you and I are gone they’ll be
witness to the future we’re creating with the choices we make so let’s make
good choices for them and for us by planting trees we can make the world a
better place in all sorts of ways so I hope you’ll join us you can be part of
team trees by donating at team trees org every dollar donated plants a tree
thanks to the Arbor Day Foundation you