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  • {♫Intro♫}

  • It's not a secret that we haven't been the greatest at taking care of the planet

  • we live and depend on.

  • But thankfully, there are countless conservation efforts happening all over the world to try

  • and undo some of that damage.

  • Because, y'know, better late than never.

  • When a species' population is in decline, we can try to find measures to slowand

  • hopefully, reversewhatever is going on.

  • But sometimes, a population has declined so dramatically that they require serious human

  • intervention to ensure they don't disappear forever.

  • That's when a species can become conservation-reliant.

  • This means they're in need of consistent, species-specific management in order to survive.

  • What exactly that looks like can vary… a lot.

  • Sometimes, it means directly protecting a species from whatever is threatening its survival,

  • like invasive predators or a toxin in their habitat.

  • Other times, it means that a species can only survive in human-run breeding programs and

  • may never be able to live in the wild again.

  • The reasons a species becomes conservation-reliant are often our fault, but at least we're

  • stepping up to care for them.

  • So, here are six ways a species can become conservation-reliant, and some of the strategies

  • we're using to keep those species alive.

  • Sometimes, when a compound is introduced to the environment, it has a dramatic and often

  • completely unintended effect.

  • Take the story of the California condor.

  • These condors are iconic scavengers and are the largest wild birds in North America.

  • But they've also become severely endangered due to lead poisoning.

  • This happens as condors ingest ammunition fragments in the carcasses they feed on, and

  • it's a major problem.

  • At one time, the total condor population was as low as 22 individuals!

  • Thankfully, in the 1980s, people did start captive breeding programs to boost those numbers,

  • and today, all 400 or so living condors are descended from those birds.

  • But their story isn't over.

  • Even after all these years of aggressive management, their population is still completely dependent

  • on the repeated release of captive-bred condors.

  • Part of that is because these birds reproduce very slowly.

  • They only lay an egg every 1-2 years, so infertile ones can have a significant impact.

  • To help with this and keep wild pairs nesting successfully, biologists have put their rock-climbing

  • skills to work, visiting condor nests on cliff faces to swap out any infertile eggs with

  • fertile ones from captive-bred birds.

  • The bigger problem, though, is that these animals are still being poisoned.

  • Wild birds have to be screened for lead poisoning each year, and then treated if there's enough

  • lead in their bloodstream.

  • Which requires a lot of time and energy.

  • Scientists are hoping this won't have to go on forever, though.

  • Their goal is to establish self-sustaining wild populations in the future, and to use

  • education programs to reduce the risk of lead poisoning.

  • The world is becoming a more interconnected place all the time.

  • And while that's great for a lot of reasons, it also means things like disease spread much

  • more easily.

  • There's a long list of species that have become conservation-reliant because new diseases

  • were introduced to their environment.

  • And one of them is the Panamanian golden frog.

  • This frog is Panama's national animal, and it packs a toxic punch so powerful that one

  • individual contains enough toxin to kill 1200 mice.

  • It was once found near forest streams along the slopes of Panama, but the spread of the

  • fungal disease chytridiomycosis has now wiped out the entire wild population.

  • The chytrid fungus is a serious killer.

  • It causes microscopic changes in amphibians' skin so that it becomes really thick.

  • And since amphibians absorb water and salts through their skinand sometimes even

  • breathe through itthis typically causes heart failure or suffocation.

  • In 2018, research published in the journal Science revealed that the deadly strain of

  • this fungus originated in East Asia, and likely spread to Panama through the global amphibian

  • trade.

  • So, yeah, this one is probably our fault, too.

  • As far as we know, these frogs now only exist in managed breeding facilities and zoos, but

  • researchers have been working on ways to protect future frogs if they're ever reintroduced

  • to the wild.

  • Their work is incredibly complex, and

  • they've investigated beneficial bacteria, probiotics with antifungal properties, and

  • gene expression in captive-bred populations.

  • They're even perfecting techniques to extract and freeze the frogs' sperm, to hopefully

  • add some genetic diversity into their gene pool.

  • Although the future is very uncertain for the Panamanian golden frog, this research

  • could greatly benefit other amphibian species, too.

  • Because it's not just the golden frog that's in such dire straits.

  • This fungus is known to infect hundreds of frog and salamander species across the globe,

  • and with so many of the world's amphibians are already threatened with extinction, protecting

  • them from the chytrid fungus is critical to their survival.

  • Many of these species are supported by a group called the Amphibian Ark, which supports amphibian-care

  • efforts around the world.

  • But ultimately, that's a lot of species to take care of.

  • So the sooner we can get them back to the wild, the better.

  • Sometimes, multiple factors are at play in a species' decline, and their conservation-reliance

  • hinges on more than one threat.

  • That's the case with one of the world's most famous shelled animals: the Galápagos

  • tortoises.

  • First, these gentle giants were dramatically overharvested in the 17- and 1800s, mostly

  • for food or oil.

  • So at least one species was already extinct before conservation efforts were even considered.

  • Then, even after we stopped eating the tortoises, the threats didn't go away, because they

  • still had to deal with a bunch of invasive species.

  • Whether it's accidental or not, we humans have a bad habit of bringing species to places

  • they don't belong.

  • These invasives can displace native plants and animals, can outcompete them, or can alter

  • their new environments.

  • They can also become a predatory threat.

  • Or, in the case of the poor Galápagos tortoises, all of these things can be true.

  • For example, black rats were introduced to the Galápagos Islands in the late 1800s,

  • and they've been eating tortoise eggs and babies ever since.

  • Then, goats were brought there and dramatically changed the vegetation the tortoises depend

  • on.

  • Eventually, pigs were introduced and started feeding on nestlings and eggsand the

  • list just kept growing.

  • Today, the tortoises also have to deal with an invasive ant that attacks hatchlings, and

  • even invasive blackberries that prevent them from reaching food and breeding sites.

  • We really messed up those islands, friends.

  • As a result of all this, tortoise breeding programs are required to repopulate the islands,

  • and in some cases, they're the only way the animals can reach adulthood without getting

  • eaten.

  • So far, these programs have been successfulbut even better, we've also been able

  • to deal with some of those invasives.

  • By 2006, goats were eliminated from several of the islands, and black rats were eradicated

  • from Pinzón Island in 2012.

  • Then, two years later, wild-bred tortoise hatchlings were seen on the island for the

  • first time in a century!

  • That said, eradicating invasive predators from all islands may not be possible, especially

  • with the larger ones.

  • But there's still a lot of hope.

  • For the most part, we don't want other species to become reliant on us.

  • We want them to survive and thrive all by their bad selves.

  • But sometimes, the needs of a species don't overlap with what people want.

  • And while it's a hotly-debated topic, fire suppression is a key example of that.

  • Fires are a normal part of nature, and certain ecosystems rely on them to control forest

  • growth.

  • The problem is, those forests are often close to areas where people live, so they get suppressed

  • or otherwise prevented.

  • And the species that rely on them tend to sufferlike the Karner blue butterfly.

  • It was once found abundantly across 12 U.S. states and one Canadian province, but in the

  • last 15 years or so, the population has dropped by 99%.

  • That's because Karner blue caterpillars only feed on one type of plant: the wild lupine.

  • And to thrive, the lupine needs fire.

  • More specifically, it needs fires to open up forest canopies and allow sunlight to reach

  • the ground.

  • Otherwise, it will be out-competed by pines, oaks, and shrubby vegetation.

  • To get around this, scientists and land managers are working together to use intentional, smaller,

  • prescribed fires to mimic what the wild lupine needs, and to protect species like the Karner

  • blue butterfly.

  • Like other conservation methods, it's something that takes a lot of time and effort, but many

  • people argue it's the best option.

  • Finally, sometimes the loss of one species means the demise of another.

  • This was true for a cliff-dwelling plant species commonly known as alulaalthough it's

  • also called Cabbage on a Stick because, well, look at it.

  • This plant is endemic only to the Hawai'ian islands of Kaua'i and Ni'ihau.

  • And unfortunately, its pollinator likely disappeared before we were even sure what it was.

  • Based on the plant's flower shape, color, and size, we now think it was likely a kind

  • of long-tongued moth.

  • But regardless, it seems to be gone now.

  • This means that the alula can no longer breed in the wild on its own, so scientists had

  • to step in and help.

  • Of course, these plants do live on cliffs, so this was an extra special kind of rescue.

  • In the beginning, dedicated conservationists with mad skills had to rappel down steep cliffs

  • to manually transfer pollen between plants.

  • Just in case you thought biologists weren't hardcore.

  • Once the plants produced fruit, they were collected so that the seeds could be grown

  • and cared for in greenhouses.

  • The plants haven't been found on Ni'ihau since the 1940s, and although there was a

  • population in Kaua'i, storms wiped it out in the '80s and '90s.

  • Right now, there is only one known wild plant remaining.

  • That being said, conservation efforts made the plants quite popular in greenhouses and

  • nurseries around the world, so they're still out there.

  • And the hope is that, eventually, they can be planted in the wild again.

  • But without a pollinator, this species looks to be heavily conservation-dependent for the

  • foreseeable future.

  • Sadly, in many of these cases, the damage has already been done, and some of these species

  • may never thrive without human intervention.

  • But intensive conservation programs are preventing them from disappearing forever, and many researchers

  • are hopeful that they'll be able to get their species back into the wild.

  • Either way, one thing is for sure: One of the most important factors when it comes to

  • protecting the world's biodiversity is just understanding the impact we're having.

  • So as we keep learning and teaching each other, maybe we'll stop some future problems before

  • they start.

  • This episode of SciShow is brought to you by our patrons on Patreonso if you're

  • a patron, thank you!

  • We couldn't do all of this research and production stuff without your support, and

  • your generosity makes a huge difference.

  • If you want to help us keep making free online content like this, you can go to patreon.com/scishow.

  • {♫Outro♫}

{♫Intro♫}

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B1 中級

物種依賴人類生存的6種方式 (6 Ways Species Rely on Humans for Survival)

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    林宜悉 發佈於 2021 年 01 月 14 日
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