How Animals Are Evolving Because of Climate Change

Squids are shrinking, [playful music]

birds are migrating,

lizards are getting blown away by hurricanes.

The signs are everywhere.

Animals are changing because of climate change.

But few people expected it to happen so fast.

[Voiceover] We asked biologists Thor Hanson

to walk us through three animal adaptation experiments.

We know that climate change is making hurricanes stronger

and one of the best examples comes to us

from the Turks and Caicos Islands in the Caribbean

where a small anole lizard, [playful music]

a distant relative of the iguana,

is facing increasing challenges due to hurricanes.

[Colin] It's a female Anolis scriptus on Pine Key.

[Voiceover] Soon after field biologist, Collin Donihue,

went to the Turks and Caicos in 2017

to study and take measurements of the lizards,

back-to-back hurricanes Irma

and Maria devastated the islands,

creating the perfect laboratory for him

to study natural selection

in response to climate change [playful music]

in real time.

It wasn't just one hurricane,

it was two strong hurricanes.

Had any lizards survived those hurricanes?

And if so, was the post-hurricane population different

from the one he had just measured?

When he remeasured all those lizards out in the wild,

he found that the survivors

of the hurricanes were different.

They all had larger toe pads

and they also had shorter back legs

when compared to the population he'd measured beforehand.

So the lizards that had small toe pads

and large, long back legs perished during that wind event.

[Voiceover] So to prove that the lizards

with the shorter back legs and larger toe pads

were more fit to survive during a hurricane,

Donihue tested how lizards reacted

to winds by aiming this leaf blower at them.

He needed to see how the lizards behaved

during hurricane force winds.

And since you can't [playful music]

be out there taking notes on lizards

during a real hurricane,

he decided to recreate one with the leaf blower

on the porch of his hotel room.

He put a dowel that was similar to the size of the sticks

that a lizard would hold onto in the wild.

So there's little lizard placed upon the dowel

with the leaf blower on hurricane force winds,

legs slipping free, flying in the wind.

As the wind speed increased,

you can see the lizards back legs flying free

and its whole body flying like a flag in the wind

and it's gone.

And I should say that no lizards were harmed

in the experiment itself.

He had a soft net [playful music]

that caught all the lizards

and they were also returned to the wild safely later.

Then he understood that when the lizard

is flapping like a flag in the wind,

shorter back legs reduce the drag

and it can hold on for a few seconds longer

and that might be the difference between survival and death.

What Colin realized

was that he had measured evolution in action,

survival of the fittest.

Natural selection playing out, not over thousands of years,

but in the course of a single field season.

And then he looked at the same question

from a wider viewpoint across the whole Caribbean.

Wherever strong hurricanes are more frequent,

we see the same features in the anole lizards.

The bigger toe pads, the stronger front legs,

and the shorter back legs.

[Voiceover] About 2,500 miles away,

a series of marine heat waves swept

through the Gulf of California,

warming the surface temperature of the water

and impacting various species,

including the Humboldt squid. [energetic music]

Humboldt squid are also known as jumbo squid

because they grow so large.

They can be 3, 4, 5, even 6 feet in length.

Fishers in the Gulf of California

were the first people to notice that something had changed

when they stopped catching the Humboldt squid.

When the scientists arrived to study this situation,

they found that in fact,

the Humboldt squid were still there,

and in some places more plentiful than before.

What had changed was their lifestyle and their body.

These were not immature or juvenile squid,

they were Humboldt squid at full size reproducing

and carrying out their lives in half the time they used to.

[Voiceover] Dr. William Gilly and his team

measured the squid they caught

and found a reduction of 50% or more

in their body size in response

to the stress of the higher water temperatures.

This adaptation is known as plasticity.

Plasticity is widely distributed in nature.

Some species have a lot of it, like the Humboldt squid,

some species have very little.

Plasticity is already built

into the genome of a species, it's already there.

[Voiceover] One example of plasticity occurs

when we travel to high altitudes, our body adapts

to the low density of the air and less oxygen

by making more red blood cells to compensate.

When we return to sea level, our body feels more energized.

So can the fact that the Humboldt squid thrived

in higher numbers in its new fun size

be considered a win for the species?

Climate change biologists are reluctant

to identify winners and losers in this great struggle

for survival, but certainly species

that have a plastic response the way those squid do

have a great advantage over species with limited plasticity.

From the warm waters of Mexico,

we traveled to the frigid north

to study another example of plasticity,

behavioral plasticity,

in the feeding patterns of this Arctic bird.

I think we're all familiar

with that iconic [playful music]

climate change image of the polar bear

stranded on a shrinking iceberg,

but if you could look beyond the bear

to the edge of the ice,

you might catch a glimpse of a tiny seabird

called the little auk or dovekie.

Dovekies feed along the edge of the ice flows

where there are a lot of plankton

and that has been their strategy for thousands of years.

It worked just fine until the ice flows began to shrink

and retreat farther and farther from the islands

where the dovekies breed.

And you can imagine

as that ice gets farther and farther away,

the dovekies have longer and longer to travel

to reach a place where they can get food

for their offspring.

And they have long been predicted

to be an early casualty of climate change.

[Voiceover] French scientist, David Grimley,

and his team placed transmitters on the birds

and wondered how long they would need to fly

to their usual plankton meal

which was now far away at the edge of the retreating ice.

So when they gathered around

to collect the first batch of data from their transmitters,

they were astounded because instead of flying an hour,

the dovekies had been in the air for less than four minutes.

David and his team realized that the dovekies

had found a new food source right on their very doorstep.

At the mouth of the fjord

where the milky blue meltwater from island glaciers

was slamming into the dark cold currents of the Arctic Ocean

and creating this place of plenty

for the dovekies to feed upon the stunned plankton.

[Voiceover] The dovekies continue to thrive

by being flexible enough as a species

to switch up their traditional feeding patterns

and adapt quickly to a changing environment.

The new dovekie behavior is not a permanent solution

to climate change.

The glaciers on those islands will melt away and disappear,

but it buys the dovekies time to find other ways

to adapt to a warmer world.

[playful music]

Plants and animals all over the world,

adapting their behaviors,

sometimes changing their bodies,

sometimes even evolving in response to climate change.

Not all species will have the ability

to adapt quickly enough to climate change.

The mouse-like Bramble Cay melomys

in Australia recently became the first mammal species

confirmed as a climate change casualty

when all of its known habitat was flooded by sea level rise.

So studying climate change biology

does not make scientists worry less about the crisis,

but it can help them to worry smart.

Learning which species are more resilient

and which are most at risk

so that we can allocate scarce resources

in terms of research and conservation

and policy to the species that need our help the most.

We can take inspiration from plants and animals

in terms of our own response to the crisis.

After all, if a tiny lizard can evolve

in response to climate change,

then it stands to reason we can change some of the behaviors

that are bringing it about.