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Extinctions in Near Time: Biodiversity Loss Since the Pleistocene
A compilation of student podcast episodes developed at Stanford University
Introduction: Extinctions in Near Time
December 14, 2011 01:10 PM PST
Welcome to our podcast: Extinctions in Near Time-Biodiversity Loss Since the Pleistocene. Hello, my name is Liz Hadly and I am a professor of Biology at Stanford University. What you are about to hear is a series of episodes featuring nine freshman and one sophomore about the causes and consequences of extinction. None of these students had ever produced a podcast like this before, and each episode is a product of their own work. We hope you enjoy listening to these episodes as much as we enjoyed making them.
Thanks to the Stanford Introductory Seminar Program for supporting this project, and to Liz Neeley for her ‘Podcasting 101’ guidance.Contents
December 15, 2011 05:50 PM PST
Short intros for each episode
Photo: Creative Commons: Matt-80Animal magnetism and conservation by Jack Werner
December 15, 2011 05:51 PM PST
With me is my good friend, Not me.
In fact, a study estimated that 54% of all wildlife funding in the United States is devoted to just 1.8% of America’s endangered species.
Gorillas hold their babies like we do. Chimps use elaborate tools. Elephants mourn their dead. All these actions resonate with us.
First, they’ve guessed that people are much more likely to give money to conserve the Panda than, say, the south China Sika deer, which lives in the same area.
By that alone, they’re able to conserve more species.
But the really cool thing is that these charismatic animals are sometimes keystone species, and saving them can often help preserve all animals in their ecosystem. The logic is that if animals at the top are thriving, everything below them in the foodchain must be doing ok.
Many targeted charismatic species have huge ranges, like the Siberian tiger. Saving this tiger means making sure it has room to roam, and this helps all the animals in the forest.
Another example is the spotted owl. These owls need old growth forests to survive, so protecting the owls means saving the trees they nest in from logging.
Photo: Creative Commons by J Patrick FischerAre Worms Worthy of Conserving? by Jack Werner
December 15, 2011 05:52 PM PST
Me: In the last episode, we talked about efforts to save charismatic animals from extinction. In this episode, we ask a very different question: is it ever ok to MAKE an animal go extinct?
Not me: Of course not. It's immoral to just wipe a living creature off the face of the earth.
Me: Well, let me tell you about an animal I - and the U.N. - think should be made extinct: the guinea worm.
Guinea worms are these tiny little worms found in Asia and Africa.
Not me: Nothing wrong with worms.
Me: This worm is a parasite. People drink dirty water containing the worm's larvae, and these larvae burrow into their host's stomach and intestines.
Photo from Wikipedia
Me: I’ll tell you. After growing for about a year, the worm migrates to your feet, causing excruciating pain as it slithers through your leg. Then…a blister forms. Slowly, a worm three feet long and as thick as a spaghetti noodle crawls through your ruptured blister. The process often takes days, but the worst part about it is the horrible burning sensation you feel while the worm tunnels out of your body. Because it feels like your leg is on fire, you put your leg in water…at which point the worm releases her eggs, and the cycle starts all over again.
Not me: KILL IT
Me: Not so fast. These worms have brains and heartbeats and little worm children.
Not me: KILL IT
Me: Well, I do believe the guinea worm should be destroyed, but it helps to use something other than emotion in these decisions.
There are generally two ways the value of a species is measured: instrumental value and intrinsic value.
Instrumental value is the value of an animal as a means to an end. For example, bees pollinate about 2 billions dollars worth of crops in California each year.
Intrinsic value is a little trickier to understand. Basically, it's the value an animal has in and of itself. There is some debate on what makes an animal have intrinsic value, but many ethicists think characteristics like self-awareness, a conception of existing over time, and holding preferences for the future are key.
Not Me: So how does the worm stack up?
Me: Well, it has negative instrumental value - it causes excruciating pain to people and doesn't seem to have any benefit. And its intrinsic value is pretty low - as such a simple animal, it is unlikely to fulfill many of the requirements of intrinsic value.
Not me: So it's okay to get rid of it?
Me: Yes, and people have been trying. In 1986, there were 3 and a half million cases of guinea worm disease. In 2010, there were less than two thousand.
However, the decision to make an animal go extinct cannot be taken lightly. Just because an animal grosses us out does not mean it's alright to kill it. And many animals have hidden instrumental values. Next episode we'll talk about two more creatures, the disgusting leech and the lethal cigarette snail.
Both of these animals, it turns out, have fantastic benefits for humans.
But that's all the time we have for today. Thanks for listening.
Photo: PD-USGOV.Megafaunal Loss by Mark Valentine
December 15, 2011 05:52 PM PST
Hello again. Like I said before, I’m Mark Valentine and I’m going to be talking about Megafaunal Extinction and how it affects present and future biodiversity. Before I begin, you probably are going to want to know what exactly Megafauna are. Megafauna are HUGE animals. This would certainly include animals like elephants and giraffes, but also lions, tigers and bears. All these animals, however, are relatively well known and still exist in the world today. What many people don’t know is that there were many incredible Megafauna that existed a few thousand years ago that are now extinct. Around 50,000 years ago, at the end of the last Ice Age, Megafauna worldwide underwent massive and widespread extinctions . Before then, there were all kinds of amazing and enormous animals worldwide: In Eurasia, there were wooly mammoths and saber tooth cats, which you’ve probably heard of, but in North America there were beavers the size of small cars and 9 foot tall Bison with horns that spanned over 6 feet , in South America there were 5 foot tall armadillos and Giant Ground Sloths the size of elephants , and in Australia there were wombats the size of Hippopotamuses . All these animals have two things in common: One, that they are absolutely massive, and two, that they have all contributed to the historical phenomenon that Megafauna are more likely to go extinct than smaller animals . So what caused these extinctions? There are two causes. We know that human hunting lead to the extinction of many Megafaunal species, like Steller’s Sea Cow, which was basically a 30 feet long , 20,000 pound manatee . Another major cause of these extinctions was climate change. A recent study showed that climate change had significant effect on many species, and actually may have been the cause of extinction for wooly rhinos, giant bison, and other Megafauna . So what does this mean for present and future biodiversity? It’s not good. The same two factors—humans and climate—are again playing a role in Megafaunal extinctions. As humans increase in population and expand outwards, more and more animals are being threatened, and since Megafauna need more living space than other animals they are more affected. Animals including pandas and tigers are already endangered because of this. We’re also experiencing global climate shifts due to global warming, which is already causing a decline in Megafauna like the polar bear . The continued global trend of a loss of large animals is clearly leading towards one result: a world overrun with the smallest kinds of animals which can live alongside humans, or in other words, a world overrun with rodents . But this does not have to happen. If we as humans can dramatically change the way we live to reduce climate change and preserve wildlife, we can maintain biodiversity, especially among Megafauna, for much longer. The only question is, can we change? ```
December 15, 2011 05:53 PM PST
Why has the Pacific Island of Guam gone from sounding…like this...to a little more like this...
Hello again everyone!
OOOOOK, that's enough from you.
The Brown Tree Snake’s home is Papua New Guinea and Northern and Eastern Coastal Australia. However, it has found new home. Research estimates that around the late 1940s, the Brown Tree snake was inadvertently transported in a cargo ship to the Island of Guam where it quickly found an abun dance of defenseless prey. The Brown Tree Snake targeted nearly every animal on Guam, including Guam’s 13 native forest birds. Of those 13 bird species, only 3 species of birds have survived. The lone bird you hear now is the Mariana crow. The last female crow on Guam died earlier this year, and there are only two male crows left.
We can’t let this silence spread across the Pacific to other islands. We, the public, must express our concerns about our beloved islands across the Pacific to let Governments know that we strongly support policies that control Brown Tree Snake populations, and prevent the Brown Tree Snake from being inadvertently transported once again.
So far, trapping snakes has been the most successful way to protect what birds remain. Proposed ideas like introducing predators to eat the Brown Tree Snakes hold little value since there are no other predators on Guam to eat those predators in turn. For example, if a predator like the mongoose were brought to Guam to eat the snakes, then Guam would just have a mongoose problem in place of its snake problem.
With that in mind, the greatest thing that Guam and other pacific islands can do (and have done) is invest in Brown Tree Snake prevention. Prevention measures are easy to enact--- Simple measures that include inspecting ship cargo, and any kind of shipment in and out of Pacific islands.
Everything aside though, we need to step back and realize that we can’t see the Brown Tree Snake as an evil animal. It is our fault, not the fault of the Brown Tree Snake, that Guam’s birds have become extinct. The animals of Guam, and the Brown Tree Snake played according to the rules--- they have all been living to the best of their abilities in their environments. And just because the Brown Tree Snake can do its job incredibly well, we can’t fault this skilled hunter for success.
You are the future, and now that you know how our simple, human mistakes impact the natural world, I invite you to remain conscious of human interaction with living and non-living environments. Collectively, it is an educated and conscious human population that will tend towards harmony with nature. Thank you for listening.
Photo: By USNPSLittle Brown Bats & White Nose Fungus by Nora Tjossem
December 14, 2011 01:36 PM PST
Did you hear that?
But go outside right now if you want to, because it’s possible that within the next sixteen years, you won’t be hearing more than a recording. The little brown bats of North America are fighting a losing battle against an enemy we call...
How does a fungus take out three out of every four bats?
Picture this: It’s late October. You’re a bat, hanging upside down in preparation for winter. This means you’ve eaten your fill of summer insects, you’ve huddled together with your family members, and you’re ready to shut down for the long, cold Northeastern winter ahead. You enter what’s called “torpor” - your body temperature decreases, you are using less energy and fewer resources, and you wake up sleepily every few weeks to replenish.
However, your body is now incredibly vulnerable. This is when the fungus strikes, eroding the exposed skin on your ears and wing membranes. You have what is known as White-Nose Syndrome.
What does this mean?
Little brown bats are the most common of bats in North America, but they are now facing a threat that could lead to their eradication in the Northeast in under two decades. This means that the children of my generation’s college students may never get to see a little brown bat in New England. Also, insect populations could vastly increase. An individual bat eats about 3 to 7 grams of insects per night - that’s about the amount of ground coffee required for your 8 oz morning cup. Think of that many mosquitoes instead!
Social animals, such as bats, elephants, dolphins, and humans, are especially prone to rapid-spreading disease. It’s easy to be content with the current status of bat populations, but if we don’t pay attention and focus our research efforts now, a disease that first appeared only five years ago could lead to the eradication of our friend the little brown bat.
December 14, 2011 03:39 PM PST
The Relationship Between Maize and Teosinte
You probably already know that maize, or corn, is one of the most culturally and commercially important crops in the world, with hundreds of applications in areas from agriculture to energy. But what you may not know is that teosinte, one of corn’s closest genetic relatives, is currently under threat of extinction. Then again, so are a lot of other plants—why is teosinte worth worrying about? My name is Dylan Sweetwood, and I’m going to talk about the relationship between maize and teosinte and why this relationship is important to preserve.
Humans have grown maize for thousands of years—so long, in fact, that it can no longer reproduce without human cultivation. This long history has resulted in a genetic bottleneck, which means that all modern varieties of corn are genetically indistinguishable. Traditionally, this was considered advantageous, but now scientists believe that genetic diversity is beneficial for crop persistence. Corn’s limited genetic toolkit makes it more susceptible to natural disasters like drought and climate change, which is a big problem for farmers.
Fortunately for the agricultural industry, teosinte, which is usually found growing on the edge of cornfields, hybridizes well with its domestic relative. Hybridization is when two related species swap genes, resulting in a genetic mixture. Maize and teosinte have hybridized naturally for millennia; by hybridizing the two selectively, it would be possible to breed new varieties of maize whose gene pools are diversified and strengthened by teosinte. These genes may offer resistance to natural stressors and sometimes even increase crop yield—something farmers would definitely be happy about.
Unfortunately, natural hybridization is risky. Because maize and teosinte have been hybridizing for so long, their hybrids usually have high fertility rates; farmers often consider these hybrids weeds and they exterminate them, which stops teosinte genes from being passed on to future generations of crop corn. As you might guess, infestation of maize-teosinte hybrids in and around cornfields is actually threatening teosinte because it dilutes the wild type. Teosinte also has a very narrow geographical range, limited to small populations in Central America; because of this, teosinte is more vulnerable in the face of environmental changes and invasive species. The small range of teosinte combined with genetic swamping has pushed this wild species to the brink of extinction.
Today, the teosinte population is less than half of what it was fifty years ago. Controlled hybridization of maize and teosinte could have a lot benefits, like increased hardiness and favorable crop yields. The same holds true of many common crops and their wild crop relatives, but considering how important corn is to humans—and anticipating how much more vital it will be in the future—teosinte preservation is an issue that requires immediate action. Thank you.
Wilkes, H. G. 1972. Maize and Its Wild Relatives. Science 177: 1071-077.Where did the Dingo go? By Lauren Sweet
December 15, 2011 05:54 PM PST
Hi I’m Lauren and your listening to “Where did the Dingo Go?”
Thanks for listening
December 14, 2011 03:31 PM PST
Bartholomew: Hey guys. So last week I took my family to the zoo where we watched a show about orangutans. I was a little upset to hear that they’re declining in numbers. Anyway, last night I met up with Nicole Ruiz, a Stanford student interested in orangutan conservation, and she let me in on the little things that make orangutans so special. Tune in to find out what I learned!
B: Hi Nicole, thanks for taking the time out to speak with me. So what can you tell me about orangutans? What makes them so special?
N: So I’d like to begin by giving you a little background of where they live. Wild orangs are located on either the island of Sumatra or Borneo. Sumatran orangutans are more critically endangered, though. They have a population of about 7000. Bornean orangutans have a population of about 50000. I don’t know if you know this, but orangutans are one of the great apes. This includes chimps, gorillas, bonobos, humans, and, of course, orangutans.
B: Wait--so are you telling me these animals are close relatives of humans?
N: Yeah it’s pretty amazing! Did you know that orangutans actually share approximately 97% of their DNA with us? Scientists first sequenced orangutan’s genome with a female Sumatran orang named Suzie.
B: No, I didn’t know that, but that’s amazing! I noticed how calm and quiet they were in the zoo, not at all like the chimps.
N: Great observation! Orangutans are extremely gentle and shy. They’re probably the gentlest great apes. Studies have shown that baby orangs have an exceptionally close attachment to their mothers. She spends 8 years non-stop teaching her offspring how to survive. So then after those 8 years, they’ll separate and start living in solidarity. I personally think that this special attachment makes orangutans unique and awesome.
B: Their offspring must learn a lot from their moms if they’re with them for 8 years, right?
N: They learn so much from their mothers, especially through cultural behaviors that are passed down from generation to generation. Different orangs have different family traditions! This, in turn, creates different orangutan behavior and culture. If there are two orangutans that live on opposite sides of Borneo, they won’t have the same set of behaviors. This is just due to the way they’re brought up. This is the old nature vs. nuture story, just as in us humans!
B: I never knew that animals acted so similarly to humans.
N: Also remember that orangutans are important for more than just being similar to humans. Another unique feature is the color of their hair. You may have noticed that they’re red and orange. Other great apes are black and brown in color. They don’t have that nice color that orangutans have. But aside from their color, orangutans are important members of the tropical forests they are found in. They help in forest regeneration. Since most of their diet consists of fruit, they end up spreading the fruits’ seeds via their feces. This actually helps grow more plants in their environment.
B: Well who knew that spreading feces could actually result in a very positive outcome! Well, when I learn about these animals I want to know what is making them threatened.
N: Two major problems that are affecting orangs are deforestation and illegal poaching. The more the forests are destroyed, the fewer orangs that can exist. There are groups, such as the Centre for Orangutan Protection, that are trying to stop deforestation. There definitely are laws in place to stop illegal capture or killing of orangs, but they are tough to enforce without adequate funding for patrols.
B: That’s terrible, but all this makes me want to learn more and to take action. Thanks so much for talking with me today, Nicole.
Campbell-Smith G, Campbell-Smith M, Singleton I, Linkie M (2011) Apes in Space: Saving an Imperilled Orangutan Population in Sumatra. PLoS ONE 6(2): e17210. doi:10.1371/journal.pone.0017210
Changes in Orangutan Caloric Intake, Energy Balance, and Ketones in Response to Fluctuating Fruit Availability Cheryl D. Knott Received June 3, 1997; revised February 25, 1998; accepted April 6, 1998
Chen, C.-C., Pei, K.-C., Yang, C.-M., Kuo, M.-D., Wong, S.-T., Kuo, S.-C. and Lin, F.-G. (2011), A possible case of hantavirus infection in a Borneo orangutan and its conservation implication. Journal of Medical Primatology, 40: 2–5. doi: 10.1111/j.1600-0684.2010.00442.x
Meijaard E, Welsh A, Ancrenaz M, Wich S, Nijman V, et al. (2010) Declining Orangutan Encounter Rates from Wallace to the Present Suggest the Species Was Once More Abundant. PLoS ONE 5(8): e12042. doi:10.1371/journal.pone.0012042
"Orangutan." Honolulu Zoo. N.p., n.d. Web. 1 Dec 2011. <http://www.honoluluzoo.org/orangutan.htm>
PERKINS, L. (1998), Conservation and management of orang-utans Pongo pygmaeus ssp. International Zoo Yearbook, 36: 109–112. doi: 10.1111/j.1748-1090.1998.tb02891.x
Serge A. Wich, Erik Meijaard, Andrew J. Marshall, Simon Husson, Marc Ancrenaz, Robert C. Lacy, Carel P. van Schaik, Jito Sugardjito, Togu Simorangkir, Kathy Traylor-Holzer, Matt Doughty, Jatna Supriatna, Rona Dennis, Melvin Gumal, Cheryl D. Knott and Ian Singleton (2008). Distribution and conservation status of the orang-utan ( Pongo spp.) on Borneo and Sumatra: how many remain?. Oryx, 42 , pp 329-339 doi:10.1017/S003060530800197X
Sumatran Orangutan Society. N.p., n.d. Web. 1 Dec 2011. <http://www.orangutans-sos.org/orangutans/crisis>Juan Fernandez Island and the Endemic Firecrown Hummingbird by Michael Peñuelas
December 15, 2011 05:55 PM PST
On an island called Isla Juan Fernandez in the Pacific Ocean there lives a hummingbird that I’ll tell you a bit about today called the Juan Fernandez Firecrown. It is a strikingly beautiful little thing, and it lives only on this one island (Hodum). Today it is threatened for a whole host of reasons, all caused in some way by humans, and exacerbated by the remoteness and size of the island on which it lives.
Isla Juan Fernandez is an island 400 miles off the coast of Chile (Terrestrial Eco…). It has been 400 miles away from the mainland and therefore any contact with other ecosystems, for 4 million years (Anderson pp1). In that time, the biota, meaning the total complement of animals and plants, that initially settled the island has evolved on its own, independent from outside interference, and formed a totally endemic, native ecosystem (Anderson pp1).
Later on as humans began to arrive, which didn’t happen until this century, they brought things with them. Things like invasive plant and animal species, things like fires, things like agriculture or a need for building materials. Humans tend to bring these things as unintended baggage wherever they go.
In Chile there are 296 species of breeding birds,11 of which, only 11, are endemic to (or found only in) Chile, and 5 of those 11 are restricted to Juan Fernandez Island alone (Terrestrial Eco…). Does that give you a good idea of how impressive and valuable the endemic biodiversity of this one island is? Almost half of the species of breeding birds endemic to Chile, a large country housing every sort of ecosystem within its borders, ranging from snow-capped mountains to expansive deserts to wave-battered coasts and dense rainforests, are from this island.
One of those species is the Juan Fernandez Firecrown, which I mentioned earlier. This hummingbird is critically endangered, and habitat and food limitations are two of the factors implicated in its decline (Hagen pp5). The endemic ecosystem in which it lives has itself been altered. In this specific example of the native hummingbird, a small bee has been recently introduced to the island. It was initially considered to be irrelevant to the ecosystem there because it didn’t seem to pose a competitive danger to the native insects and actually was thought to possibly be beneficial by pollinating the endemic plants (Anderson 10). The issue, then, began to arise when the bees began to do two things that were unanticipated. First, they began to outcompete the hummingbirds, which technically did fit with the scientists’ predictions, as the birds aren’t fellow insects, yet it still hurt the Firecrown’s population significantly. Second, these bees began to frequent the newly introduced invasive plants, instead of the native plant species.
What is so problematic about this is that the system as a whole is so incredibly complex that removing any one element in an attempt to remedy the system is virtually impossible without causing some other element to unravel the system yet further. What I mean by that is that removal, for example, of the bees would cause the hummingbirds’ population to rise again as they would no longer be competing for nectar. So too, however, would the populations of the invasive plants because they would have the new help of more hummingbirds. If you removed just the invasive species of plants, then, the bees would still outcompete the hummingbirds, and though the native plants would return en masse, the Firecrown might very well continue on its path to extinction.
This is why protecting Isla Juan Fernandez is so difficult. The island is home to a breath-taking array of plants and animals and provides a model for what a true, un-tarnished ecosystem would look like yet even this island is slowly, inexorably being corrupted. This island is in and of itself one of the most, if not the most, valuable existing model of an ecosystem comprised of endemic biodiversity on the planet. It is a small island. When you look at all of the scientists in the world interested in biodiversity, you would think that they would be able to save this small, incredibly valuable island rather easily. And they are trying. But saving, for example, the Juan Fernandez Firecrown, turns out to be far, far more complicated than it may first appear.
Anderson, Gregory J., Gabriel Bernardello, Tod F. Stuessy, and Daniel J. Crawford. "Breeding System and Pollination of Selected Plants Endemic to Juan Fernández Islands." American Journal of Botany. 2001.
Hagen, Erin N., Jonathan D. Bakker, and Robert I. Gara. "Aerial Arthropod Communities of Native and Invaded Forests, Robinson Crusoe Island, Chile." Environmental Entomology, Aug. 2010.
Hodum, Peter, and Erin Hagen. "Conservation of the Critically Endangered Juan Fernández Firecrown (Sephanoides Fernandensis)." Juan Fernandez Island Conservancy. Oikonos. Web. 28 Nov. 2011. .
"Terrestrial Ecoregions -- Juan Fernández Islands Temperate Forests (NT0401)." World Wildlife Fund. Web. 24 Oct. 2011. .
Photo: Creative Commons Héctor Gutiérrez GuzmánUrban Makeover Advice by Yari Greaney
December 15, 2011 05:56 PM PST
It seems so innocent. Pretty houses with manicured lawns, several little parks with small grassy fields bordered by metal fences, a few house sparrows hopping around the picnic tables. We’d call it a beautiful town. Unfortunately, this perception of beauty is deadly (Rosenzweig).
December 15, 2011 05:56 PM PST
Hi everyone, my name is Isabel Cardenas and I’ll be talking about the market for bear bile and what it means to farmed bears, wild bears, and North American bears.
Photo: wikipedia by Tambako
The transition 11,700 years ago from the Pleistocene glacial period into the Holocene interglacial witnessed the expansion of humans around the world, climatic warming and the demise of many large vertebrate species. Since that time extinctions have continued on land and in the sea, culminating with the biodiversity crisis we are experiencing today. We explored these prehistoric extinctions—Who? When? Where? and Why?—in order to learn more about our planet’s future. Students then translated their knowledge into a podcast for a general audience addressing the question: Why do we care when species face extinction?
I am a biology professor at Stanford University. I endeavor to understand how environmental change influences the distribution and abundance of animals on the planet....and I love to teach about the diversity of life in all its guises.
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