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Why do Some Species Thrive in Cities? - Video học tiếng Anh
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Why do Some Species Thrive in Cities?
Why do Some Species Thrive in Cities?
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Sous-titres (31)
0:01
Since the mid-1800’s, Adelaide’s mammal diversity has fallen by more than a quarter,
0:06
New York City has lost nearly half of its native plants, and at least 25 species of
0:10
butterflies have disappeared from Rome. Our concrete jungles can be hard on wildlife,
0:18
but there are plants and animals that survive – even thrive – in them.
0:23
Some lucky species happen to be naturally suited to cities. For instance, English ivy
0:28
and rock pigeons climb and roost on vertical structures like trees and cliffs anyway, so
0:34
brick walls and sky-high ledges are fine substitutes. And omnivorous raccoons thrive
0:40
on an endless buffet of everything from corn chips to cockroaches, helping them live ten
0:45
times more densely in cities than in woodland habitats . Natural flexibility can also help
0:50
animals cope with the stresses of metropolitan living: coyotes that colonize cities often
0:56
become more nocturnal to minimize their encounters with humans.
1:00
Most species can’t adopt an urban lifestyle so easily. But over several generations, genetic
1:06
change can help some populations evolve into city slickers.
1:10
New York City’s white-footed mice are one example: DNA sequencing suggests that these
1:15
urban dwellers' genes differ from their country cousins' in more than 30 significant ways.
1:21
We don't yet know exactly what effects these changes have, but we know they’ve shown
1:25
up in genes involved in fighting disease and processing toxins, traits that likely help
1:30
mice survive in crowded landscapes .
1:33
We usually think of evolution as a slow process, so evolving fast enough to keep up with urbanization
1:40
may seem like a tall order. But when a big challenge springs up suddenly , an uncommon
1:45
trait that helps individuals cope can become the genetic norm surprisingly fast - especially
1:51
in speedy breeders - because those without it may not get a chance to reproduce.
1:56
For example after factories dumped thousands of tons of toxic PCBs into the Hudson River
2:01
in the mid-twentieth century, it took just just six decades for 99 percent of the local
2:06
tomcod to evolve a protective mutation that blocks the toxin from entering their cells.
2:11
And in Montpelier, France, it’s taken fewer than 12 years for urban weeds to start producing
2:17
a larger proportion of heavy seeds, boosting their odds of settling in a patch of nearby
2:22
soil instead of crash-landing on concrete. As urban and rural populations diverge genetically
2:28
and geographically, there’s even a chance that some could split in two.
2:33
This doesn’t mean that cities are a boon for biodiversity , but they aren’t biological
2:38
dead zones either - they’re more like accidental laboratories where the limits of life’s
