Since life appeared on Earth, each kind of creature has had just a certain amount
of time before its kind disappeared forever, and new creatures took
its place. Temporary
environmental changes like those from hurricanes, ice storms, or
fires may kill lots of organisms, but they don't usually put a whole kind
of living thing in much danger of disappearing. But effects
of events like ice ages, volcanic
eruptions, or meteor collisions can last thousands of
years. When that happens, life is at risk.
Some scientists think dinosaurs disappear because a meteor collision
changed the environment for a long time, and dinosaurs couldn't
adapt to survive it. In the past few 1000
years, people have changed the environment in big ways and for
the long term, our homes, ranches, farms,
and cities take up space. We pollute,
hunt, overfish, destroy habitat,
introduce exotic species. All this takes away from living
things in the wild and from their habitats.
Living things that couldn't adapt to a change and no longer
exist anywhere on earth are said to be extinct.
Since people began changing the environment, organisms have gone
extinct faster and faster. Right now, 1000
times faster than at any time in the last 65 million years.
If we keep it up, we may soon see 1100 extinctions a
day.
Kinds of organisms that aren't extinct but whose populations are
dangerously low are at risk of becoming extinct or
endangered. Creatures become
endangered for lots of different reasons. The naday goose of Hawaii
is endangered partly because of the mongoose. The mongoose was
introduced to control rats in the sugar cane fields. As
it turned out, the rats slept all day while the mongoose hunted.
So instead of eating rats, the mongoose turned to the eggs of the na na
goose. Now fewer than 100 na na geese are left in Hawaii.
Both natural and human danger threaten the West Indian manatee.
Manatees are mammals that live in the warm waters of Florida and Georgia
and migrate north in the summer. If they are a little late migrating
back to warm water, they could die.
Many are injured by boats or are caught in nets. About
150 of the remaining 2000 die every
year since they only have one calf every 2 to 5 years.
Their numbers are dropping fast.
Some animals are endangered because something they need in their habitat
is disappearing. Carterbo butterfly caterpillars
eat only wild lupin, a plant that grows in sandy pine and
oak barrens where there are occasional forest fires. The fires
burn back shrubs and plants which shade out the lupin.
Unfortunately, humans put out the fires and kill the lupin with
pesticides. After 20 years of this, just 1 out of
every 100 carner blooms are left.
With so much development and growth concentrated on the coasts of
North America, it's really important to look out for living things that are
at risk.
Hey Dave, isn't that a wood turtle? Yeah, that is a wood turtle. Do you think you can catch it?
So why are these species of species at risk? Well, wood turtles have a
lot of different problems. One problem is actually something that wood
turtles have lived with for a long time, and that's just the fact that there's not a lot of this kind of
habitat around so they're really limited to that area uh
that creates a problem though when people impact those wetlands that they need
so when the wetlands disappear, of course they lose their habitat. uh, another reason
is like a lot of turtles, wood turtles will cross roads, and when they
cross roads their shells are hard. But they certainly can't
support the weight of a car and so they get killed that way and actually a
third way is that too many of them have been over collected for the pet
trade, so people have purchased them and brought them home and
unfortunately a lot of those turtles either die or they never make it back into
the wild so that's been a problem as well.
People sometimes can help animals out too. There's one animal that was hurt by
people and then brought back from the verge of extinction and that's the peregrine
falcon.
By 1964, peregrine falcons had completely disappeared from the
eastern part of the United States. Their population decline was caused by
DDT, a pesticide farmers and gardeners used to kill insects.
Peregrine falcons ate prey tainted with the pesticide. Over time,
DDT built up in their bodies and caused them to lay eggs with very thin
shells. The thin shells were easily crushed by adults during
incubation. Bald eagles and other bird species also
experience population declines because of DDT and other pollutants.
DDT was banned for use as a pesticide in the United States in
1972. At that point, there were only 40 breeding
pairs of peregrine falcons in the west and no breeding pairs in the east.
People started programs to reintroduce the peregrine falcon to its habitat.
Peregrine falcons were bred in captivity and then released into the wild.
Since 1974, more than 6000 falcons have been released,
and today the peregrine falcon population is growing.
Peregrines are found on every continent except Antarctica. They live
where there's open space and nest on cliffs or bluffs over water. Some have
adapted to urban environments and nest on tall city buildings and under
bridges. They don't build nests, but they may use the nests built by
other birds. Perriins can lay 23, or up to
6 eggs at a time. Females usually incubate the
eggs, and the males help care for the chicks. Adult
peregrine falcons are about the same size as crows. They have long pointed
wings and mustache-like markings on the sides of their face. Males and
females look alike, but the females are a little larger. They're good
hunters and may be the fastest animals on Earth diving from the sky
at speeds of over 100 miles an hour. Perregrine falcons
usually strike their prey with a closed talent and knock it to the ground.
The prey is most often small birds like doves and pigeons, but they've
also been known to catch larger birds like ducks and gulls.
Humans are still a threat to peregrine falcons. Development can hurt
the falcon's natural habitat. Rock climbers can disturb nesting
places, and pollution can still affect their food supply.
Humans almost drove the peregrine falcon into extinction in the US, but
worked to bring it back. Today populations are growing, but we
have to monitor the species to make sure it stays healthy.
Monitoring the health of different species can tell us a lot about the health of the environment.
Susie Von Otiggen of the US Fish and Wildlife Service is
monitoring the health of dwarf wedge mussels, and Sarah and
Docov are going to help her.
Wow, is this where they live? Yes, this is the Ashet River
and it's one of the better populations of the dwarf wedge mussels right here.
Why is this habitat good for mussels? OK, well, take a look. dwarf wedge
mussels live in free flowing running water, not in ponds or
lakes. You'll never find them there. And then look over here at the canopy, it provides
shade and if you had them in just plain sun, you get these temperature
extremes and also the water quality is pretty good here. So
you wanna go in? All right, let me explain one thing too what we're gonna do
an easy way to find out what species you have is not to look for the live ones because sometimes
they're hardest to look for the shells because a lot of animals eat these
mussels and what we're gonna do is collect all the shells we see, and I'm gonna give you a bag each.
And put them in the bag and then we'll go through and see if we find any dwarf wedge muscle.
Yeah You know what this
is dwarfs. I found a live dwarf we also. Congratulations.
Don't put them in the bag. 00 yeah, it's alive because that's right, it's
alive.
Can you remember how many species we've found now live and dead,
3 alive 3 species that are alive. That's right, and 44 that
are dead. We found the triangle floater. You just found that one. You just found that
one you just found that one. And then what's the one that's all over the
elliptia, right? And the 4th
species that we found to shells up but not live
is the squat, right. What we're gonna do
Dump all the shells out gently on the ground and then we're gonna try and separate them to all the different
species we have and let's put the dwarf wedge up here because they're the smallest,
right? And we'll try and count what we have of all the different species.
Waffle, right. Oh, you really got.
5678.
Good because these are not the same animal. They're different halves of different animals.
Why is it important to save all these mussels? Well, if you can see,
there are very few of the dwarf wedge here. There's a lot of the elliptios,
less of some of the squaw foot and still a pile of the triangle
floaters, which indicates to me that they're very rare and uncommon in this
river. The other thing with the dwarf wedge muscle, they're very
sensitive animals much more so than the elliptio which can live anywhere and it
indicates water quality if this starts to decline if we see less and
less over time, but nothing else has changed physically that we can see, then
we expect that the water quality is declining. What we do is we call. These bio
indicators so they're very important to tell us what's happening in our
environment so that's one reason and the other reason is once they're gone
they're gone that's it they're history and we can't bring them back so it's
a a moral and ethical reason that we can't afford to lose these
species because we can't recreate them.
What have we learned today?
Animals and plant species that can't easily adapt to
environmental changes can become endangered or even extinct.
Some environmental changes are caused by natural events like earthquakes and
volcanoes, but other environmental changes are man-made.
There are lots of things people can do to preserve natural habitats
and protect animal and plant species from extinction.
Now you know how danger.
Major funding for Nature Works was provided by American Honda
Foundation. Additional funding was provided by Alice Freeman
Mutchnick, Alice J Rene Charitable Trust, Cogswell
Benevolent Trust, the Finnita Fund, Greater
Piscataqua Community Foundation, Moreridge Family
Trust, the Natural Areas Wildlife Fund, Ross