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[MUSIC]
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"This episode is supported by Prudential"
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Here in Tambopata Peru, EO Wilson once found
more species of ant in a single tree than
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there are in all of the British Isles.
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Scientists have seen this pattern all over
the world.
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More species exist near the tropics.
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Why is that?
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[MUSIC]
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In one night here in the Peruvian rainforest,
I saw more insects in an hour than I've seen
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in my entire life, total.
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It's not just insects.
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Birds, mammals, plants… tropical rainforests
are some of the most biodiverse places on
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Earth.
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It's not just the abundance of it, it's how
many different species we find in a given
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area.
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But why is that?
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It might seem obvious, or even like a silly
question, but the more you think about it,
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the weirder it gets, because life has shown
it can succeed pretty much anywhere, from
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the top of the highest mountains to the bottom of the
ocean . But Earth's most biodiverse places
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are always regions like this, tropical
rainforests.
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One reason why is maps lie to us.
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Rectangular projections are distortions of
a sphere that make the poles look bigger and
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tropics look smaller than they really are.
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When in reality, the tropics contain about
40% of area on Earth.
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Unsurprisingly, larger areas usually have
more species.
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In less than half a square kilometer in the
Amazon, we can find as many tree species as
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we find in four million square kilometers
of temperate forest.
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Species here are at a higher density.
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There must be something special about tropical
ecosystems.
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Climate is one factor.
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When we look at plant fossils and where they
are found in different times in Earth’s
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natural climate history, tropical forests
are older than temperate forests, they've
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had more time to become rich.
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But while tropical regions avoided the last
ice age and don't have cold winters, it's
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not EASY to survive here.
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There are dry and wet seasons, there's competition
for resources, no matter what kind of organism
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you are, there's a lot of stuff that wants
to eat you.
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On average the tropics are warm and they get plenty of water.
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This part of the planet gets more average solar radiation throughout the year.
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Which means that plants and the animals they
support get more energy,
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they are more productive.
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But this still only explains why there's *more*
life, not why so many *different* kinds of
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life.
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If you've got a pie, more people can get a
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slice if you cut it up into a thousand tiny
ones vs just a few.
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We call these slices niches, the habitat and
conditions that one organism needs to flourish,
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and here in the rainforest, there's a lot of slices.
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Organisms that live at higher latitudes have
to be more adaptable,
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be able to handle lots of different conditions.
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One week it might be snowing.
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The next, flowers and fish are everywhere.
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Specialization is too risky, you’ve gotta
be adaptable.
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Life is more stable in the tropics.
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One thing I noticed here in Peru is the sun sets a lot earlier here this time of year
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than what I'm used to back at home.
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Here near the equator there's essentially the same number of hours in day and night no matter what month it is.
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Let's say you're a bird that eats insects, and maybe these bats over here
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You've got the same number of hours to do your feeding. The birds get the day shift, the bats get the night shift.
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You get to split that niche evenly. That wouldn't work at higher latitudes and more temperate climates.
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There's simply just too much change, too much disruption for these species to keep track of.
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And this might explain a reason why more species
coexist near the equator.
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The tropics are crowded, so the competition
for resources is extreme.
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That competition drives organisms to specialize,
like how we see ants or caterpillars that
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might be able to live on just one single type
of plant.
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But because climate and seasons are more stable,
that specialization isn’t as risky.
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More species, less area.
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These theories are really good at explaining
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why there's so many species in the rainforest
NOW, but we're still missing the beginning
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of our story, where those species came from.
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It's possible that evolution is actually working on overdrive here near the equator, speciation,
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the creation of new species by various natural
forces, actually happens FASTER near the equator.
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Each generation of living things gathers changes, mutations, some are good,
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some are bad, some are neither, but it isn't until
those changes are passed on to the next generation
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that natural selection and time
can do their thing .
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The reason that bacteria are so good at adapting
is because they reproduce quickly, they have more generations
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in less time.
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The same thing happens here in the rainforest. Plants and animals
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grow up faster, they can have more generations.
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This drives competition, this is what forces plants and animals to specialize
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in all of the amazing ways that we've seen.
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This theory, that evolution happens faster
near the equator, finally ties together the
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ideas of time, area, and energy to explain
the origin of biodiversity.
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There's an idea that says the tropics are
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so well suited to the creation of new species…that it's like an engine for biodiversity
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Another idea says the tropics are so rich
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and productive, and the climate's so stable,
that things don't go extinct as fast.
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More species are born here and species live
longer here, the tropics are both a cradle
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AND a museum.
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Scientists even think that over many many years, species from places like this
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go and seed biodiversity throughout the rest of the world.
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This is why it's so important to protect
the rainforest, to preserve life's cradle
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and museum.
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To keep it from being cut up, because more area
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means more species.
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To keep the climate from changing, to keep life here
stable and rich.
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Chemists know all the elements on the periodic
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table.
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Physicists probably know all the subatomic particles
that make up matter.
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But biology still hasn't answered one of
its most basic questions: how much life IS
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there?
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EO Wilson once wrote that "unlike the rest
of science, the study of biodiversity has
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a time limit".
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If species begin to go extinct faster
than we can describe them, the we might never
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know how much life Earth has to offer.
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And now that I've seen something like THIS, I don't want to see that happen.
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Stay curious.
