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7 Times Invasive Species Actually Helped - Video học tiếng Anh
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7 Times Invasive Species Actually Helped
7 Times Invasive Species Actually Helped
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0:00
There are plenty of horror stories about invasive species.
0:03
Like wild hogs tearing up crops or zebra mussels damaging lakeshore infrastructure.
0:07
But every once in a while, invasive species have actually been known to do some good.
0:10
Invasive species, or alien taxa, are critters that thrive in places they didn’t originate in.
0:16
They can disrupt a habitat’s natural balance by displacing or outcompeting native species.
0:20
And in the United States alone, these disruptions cost roughly 21 billion dollars a year.
0:25
So it might seem like these species are always pests that we’d like to eliminate.
0:29
But as it turns out, some of them are more beneficial than we initially thought.
0:33
Like these seven invasive species that have actually kinda helped.
0:37
[♪ INTRO]
0:40
Green anoles are quick little lizards that you can find all over Florida.
0:44
They’re native there, but these days, you’re more likely to spot their cousins, brown anoles.
0:48
Brown anoles came from places like Cuba,
0:50
the Bahamas, and the Cayman Islands, and they’re invasive in Florida.
0:53
While they aren’t super destructive, they do compete with the green guys.
0:57
Wherever brown anoles move in, the green anole population gets pushed out.
1:00
Despite this concern, brown anoles have been pretty helpful to us.
1:04
Because it turns out that local mosquitoes have a taste for them.
1:07
And when mosquitoes are busy feasting on lizards, that means they’re not bugging
1:11
residents, tourists, and other species affected by mosquito-borne viruses.
1:15
As an Florida man myself, I definitely find this helpful.
1:18
But lately, there’s another bully on the playground that’s been causing a ruckus.
1:21
It’s a burlier, more aggressive, and equally invasive lizard called the Peter’s rock agama,
1:26
and they’re starting to outcompete brown anoles.
1:28
You might not immediately notice the difference if the Peter’s rock agama replaced brown anoles.
1:32
But mosquitoes don’t bite the Peter’s rock agama as often.
1:36
So with fewer brown anoles to snack on, mosquitoes will have to move back to other victims.
1:42
We don’t yet know how this invasive lizard
1:44
showdown will affect the spread of diseases like West Nile virus.
1:47
The research is still ongoing, so we still can’t quite determine whether
1:50
brown anoles are a net positive to the overall Florida ecosystem.
1:54
But this next invader does seem to be certifiably useful…
1:58
In this case, it’s a grass that had an unexpected benefit for the Botteri’s
2:02
sparrow, an unassuming little brown bird that has historically lived in southern Texas and Arizona.
2:07
But for a period in the late 1800s, the Botteri’s sparrow was driven out of Arizona.
2:12
The tall native grasses where the sparrows nest had been overgrazed by cattle.
2:16
To replace the disappearing native grasses, lovegrasses were introduced as cattle feed.
2:21
Unfortunately the cattle didn’t love the lovegrasses, so they kept eating the small
2:26
amounts of native grass that remained, allowing the lovegrasses to spread faster than expected.
2:31
But, helpfully for the Botteri’s sparrows,
2:33
these non-native lovegrasses put up “vacancy” signs as they quickly swept across Arizona.
2:39
When the sparrows finally returned to Arizona in the 1960s,
2:43
they were spotted nesting in the invasive lovegrasses!
2:45
Researchers initially worried the alien grasses might be an “ecological trap”.
2:50
In other words, although the sparrow feels safe using the habitat,
2:54
it might not offer as much cover from predators or facilitate healthy breeding.
2:58
But they found that birds nesting in non-native grasses reproduced
3:01
at the same rates as birds nesting in native ones.
3:04
So even though the native habitat will always be the best home for the Botteri’s sparrow,
3:08
lovegrasses seem to be an acceptable alternative, given the state of the grass-housing market.
3:13
While these grasses were a highly visible invader with big impact,
3:16
tiny critters can pack a powerful punch, too.
3:19
Such as the microbial invaders in the Caribbean that are helping out corals.
3:23
This probably isn’t breaking news to you,
3:25
but coral reefs are threatened by rising temperatures and changing ocean chemistry.
3:29
Their life is a little complicated, because they rely on symbionts, tiny microbial partners.
3:33
In the corals’ case, they’re algae that live in the coral
3:36
and make food for it by photosynthesizing.
3:39
Like a little live-in grocery store.
3:40
One species of symbiont, Symbiodinium trenchii,
3:43
has been spreading from the Indo-Pacific to the Caribbean.
3:46
S. trenchii isn’t like other microbes.
3:48
It’s better at photosynthesizing under stressful conditions than
3:51
the local Caribbean algae are, so it can tolerate higher temperatures.
3:55
As a result, coral colonies infiltrated by S. trenchii also do better when things get toasty.
4:00
It definitely sounds great that S. trenchii helps corals withstand higher temperatures,
4:04
but there could be hidden costs tagging along.
4:07
For example, in some colonies,
4:08
this invasive symbiont seems to change how fast corals form their hard exoskeletons.
4:14
So we’ll keep an eye on that for a bit before declaring S. trenchii as a coral hero.
4:18
And it turns out that corals and crocodiles have something in common,
4:22
because crocs also got a little help from an invader…
4:25
But before we tell you who, we need a little help from this sponsor.
4:29
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5:05
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5:21
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5:26
Australia’s feral pigs are the descendents of 19th century domestic
5:29
pigs that were convicted of crimes and then shipped off to Australia.
5:33
Just kidding, the pigs weren’t criminals,
5:34
they were just brought to Australia as a food source for colonists.
5:37
Today, there are about 23 million feral pigs in Australia.
5:41
Feral pigs cause all kinds of environmental havoc,
5:44
from disturbing vegetation to spreading weeds to wholescale habitat destruction.
5:48
But not everyone has a beef with Australia’s feral pigs.
5:52
Crocodiles find them quite useful!
5:54
Until the 1970s, crocodile hunting was unregulated in this part of the world,
5:58
and the croc population dwindled to just a few thousand animals.
6:02
When the government realized how much danger they were in, crocodiles were given protected status.
6:06
That surely helped.
6:07
But researchers think they got an assist from those invasive pigs.
6:10
In 2022, scientists compared samples of modern crocodile bones to those
6:15
of animals killed between 1968 and 1986.
6:18
They found that the older crocodile bones contained more specific isotopes of carbon
6:23
and nitrogen than the bones of modern saltwater crocodiles.
6:26
Higher abundance of those carbon and nitrogen isotopes is associated with a fish-forward diet,
6:31
because seafood like catfish and barramundi have more of those isotopes.
6:36
Aquatic wildlife was the traditional fare of crocodiles in the past.
6:40
But the decreased amounts of those carbon and nitrogen isotopes in the modern crocs suggests that,
6:45
in the post-hunting era, crocs are relying more on terrestrial prey.
6:49
The invasive pigs probably account for a big chunk of that land-based buffet, because they’re pretty
6:54
easy pickings: they’re plentiful, nutritious, and often wallow in mud near croc territory.
6:59
This suggests the pigs have contributed to the crocs’ resurgence Down Under!
7:03
Speaking of Australia, our next invader is a native Aussie.
7:06
The eucalyptus tree first arrived in California during the gold rush,
7:09
and quickly became a local landscaping darling.
7:12
Today, it’s seen for what it is: invasive.
7:14
Large eucalyptus groves can affect a microclimate’s temperature,
7:17
humidity, shading, and soil characteristics.
7:19
But the eucalyptus tree is also offering a big helping hand to California’s butterflies.
7:24
In California, 34% of native butterflies use
7:27
non-native plants for food or as a place to lay eggs.
7:30
Butterflies aren’t doing so well lately because of widespread habitat loss.
7:34
So any help they can get is welcome.
7:35
One of California’s most iconic butterflies,
7:38
the Monarch butterfly, is also one of the most vulnerable.
7:40
The population of monarchs that migrate up and
7:43
down the west coast has declined by roughly 95 percent since the 1980s.
7:47
Scientists put this population’s chance of
7:49
extinction before the year 2080 at roughly 99 percent.
7:53
That is pretty bleak.
7:54
One of the major reasons for that decline is loss of suitable habitat.
7:58
These western monarchs usually spend the winter on the coast of California.
8:01
They migrate during the day, but roost in trees overnight.
8:04
They specifically need trees with thick canopies that maintain a comfortable temperature.
8:08
Many of the large, native trees that fit that bill have been removed by logging and development.
8:13
So western monarch butterflies have shifted to roosting mostly in eucalyptus trees.
8:18
They provide safety and nectar for the butterflies,
8:20
giving them a better shot at survival.
8:22
So I guess those silver-lined leaves have an ecological silver-lining, too.
8:27
And we have another example for you of invasive trees providing refuge for vulnerable species.
8:32
This next tree may help protect a native snail from a dangerous predator.
8:36
The common Norway rat is probably the one you’re most familiar with.
8:39
But the black rat is a different species, native to India.
8:42
In most places, they’ve been largely out-competed by the Norway rat,
8:47
but black rats are still found on most continents and are considered invasive.
8:51
Japan in particular has a problem with black rats.
8:54
They wreak way more havoc than the typical ratty
8:56
shenanigans you’d expect in attics and back alleys.
8:59
Black rats also threaten native species,
9:01
including one of its favorite snacks: the Japanese land snail.
9:04
This is where our invasive tree steps in.
9:07
The drooping sheoak is also native to Australia, just like eucalyptus.
9:11
But now it’s found on Anijima, an uninhabited island in Japan’s Ogasawara Archipelago.
9:16
These trees’ destructive power is their ability to form a homogenous, nearly impenetrable forest.
9:22
They grow fast, lay down a thick network of roots, and drop a lot of litter on the forest floor,
9:27
which basically makes it impossible for native plants to grow there.
9:30
But that hostility to native plants also makes
9:33
them an excellent hiding spot for those land snails.
9:36
In fact, land snails dodge rats better in the sheoak forests than in native vegetation.
9:42
Researchers think they might be hiding from the
9:43
black rats in the litter that collects under these trees.
9:46
Because when conservationists removed the trees,
9:49
they also found that the snail population declined.
9:52
So it seems like the sheoaks are giving our snail friends some much needed shelter.
9:56
Although there are still a lot of reasons to remove the sheoaks, researchers advocate for
10:00
addressing the black rat population first, to give the land snails a better chance of surviving.
10:05
And to wrap things up, we’re headed back to Florida, you can’t escape.This time
10:08
we’re talking about their huge problem with Burmese pythons.
10:12
These constrictors are native to southeast Asia, but were imported to Florida by the pet trade.
10:17
At some point, a few escaped captivity or were deliberately released,
10:20
and they found that Florida’s habitats suit them just fine.
10:24
Today, officials say the Florida Everglades
10:26
are likely home to “tens of thousands” of Burmese pythons.
10:30
They are not friendly neighbors.
10:32
Burmese pythons have been feeding on native species.
10:35
For some species, their population has declined as much as 95% since the pythons moved in.
10:40
But the snakes have actually been helpful in one small way: they eat raccoons.
10:44
Even though raccoons are native Floridians, it’s kind of helpful
10:47
to have fewer of them because raccoons eat the eggs of freshwater turtles.
10:52
One research study found that python-infested areas also had
10:55
much lower rates of predation on artificial turtle nests, compared to areas without pythons.
11:00
And they’re pretty sure that’s because pythons had eaten many
11:03
of the animals that do the turtle nest predation.
11:06
Even though the pythons are indirectly helping turtles and other egg-laying
11:09
species, it doesn’t negate the other serious problems they cause.
11:14
As you might have guessed, when it comes to nature, there are no clear cut villains or heroes.
11:18
And although in many cases invasive species have earned their bad reputation,
11:22
we can’t always assume that all invasives are all bad all of the time.
11:26
In fact, some scientists are trying to quantify both the negative and
11:30
positive impacts of alien taxa using hypothetical scenarios based on real data.
11:35
This would let them categorize alien taxa’s potential benefits from minimal to massive,
11:40
and allow conservationists to weigh the pros and cons of evicting any invasives.
11:44
As is often the case, the full picture is complex.
11:47
Scientists have learned that while eradicating invasive species is usually
11:51
necessary to protect native species, it should be approached with caution,
11:54
and only after considering all of the invasive species’ helpful impacts, too.
11:58
Because sometimes you can find a friend in the most unexpected places.
12:03
[♪ OUTRO]
