Extinctions in Near Time: Biodiversity Loss Since the Pleistocene
Liz Hadly
12 episodes
6 months ago
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?
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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?
Juan Fernandez Island and the Endemic Firecrown Hummingbird by Michael Peñuelas
Extinctions in Near Time: Biodiversity Loss Since the Pleistocene
4 minutes
13 years ago
Juan Fernandez Island and the Endemic Firecrown Hummingbird by Michael Peñuelas
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 s(continued)
Extinctions in Near Time: Biodiversity Loss Since the Pleistocene
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?