Hi. It’s Mr. Andersen and this environmental science video 10. It is on natural ecosystem
change. In this picture these researchers are holding ice cores that they collected
at Vostok station in Antartica. We can take those ice cores, melt them in the lab and
it releases this ancient atmosphere. So we could look at, for example, how carbon dioxide
levels have changed over the last 450,000 years. Now that corresponds with temperature
changes. So we have had periods of time where it is warmer and what are called ice ages
where it is much colder. Now the ice ages actually correspond with high dust concentrations
in the ice core because during ice ages we also have these massive deserts on our planet.
Wind increases and that sediment is trapped in the glaciers. And so the climate has changed
and that has affected ecosystems on our planet. But what is affecting the climate? It is where
the earth is in relation to the sun. And so as we have had changes in solar output that
has affected our climate. As we have had slight changes in our orbit or volcanoes or plate
tectonics, all of those things have affected our climate and therefore are affecting the
ecosystems. Not only the life but also the land. At the worst level it can cause what
are called mass extinctions on our planet where a number of species simply go away.
Lots of times that is followed by adaptive radiation where different species come back.
But for the most part what happens is species have to respond. So species will move back
and forth as the climate changes. Now it also affects the abiotic factors. So the land on
our planet. And so what happens after the land is destroyed or changed is we have succession
as life moves back into that area. It can be either primary or secondary. In primary
succession the soil and the community is gone. In secondary the soil and the community actually
remain. And so what is affecting our climate? It is where the earth is in relation to the
sun. And scientists have noted that the sun changes over time. So we have these sun spot,
eleven year sun spot cycles. But we have these larger changes in the output of the sun over
thousands of years. We also find precession in the earth. As it spins it also starts to
wobble over thousands of years. And that causes changes in our climate. The pole starts to
point in different directions so we get varying amounts of light. And then we are also finding
that there is precession in the orbit itself. As it moves around over thousands of years
we have changes in the amount of energy that we are getting from the sun. So all of these
correspond to changes in energy from the sun. So if we look at how these models match up
with the data that we are collecting in ice cores we can see this cycling of our climate
over time. We are going to have these ice ages. And if we look down at the northern
hemisphere this is what it would be like during the worst ice age. That whole area that is
gray would be covered in ices. That means most of Canada, Great Britain, all of Scandinavia
would be covered. It would move down into the US as well. Massive ice sheets. And then
we would have times where there is not much ice at all. Just this dark area where Greenland
is and then along the coast right here. Another things that can affect climate is going to
be volcanoes. And so for example in 1991, in the Philippines Mount Pinatubo exploded.
That increases the amount of sulfur dioxide in the atmosphere and it cools the planet
so the planet cooled over the next three years just due to this one eruption. And then we
can have plate tectonics that are affecting the amount of energy that we get as well.
So a simple example, South America slid into North America and Panama was formed. What
happened? There used to be a current that moved through here and that changed the whole
current. And so that is going to affect the climate. Or at the largest level Pangea was
all of the continents coming together. We had massive deserts forming in the middle.
And that is going to change species on our planet. It lead to some of the worst mass
extinctions on our planet. Where a large percent of life actually went away. Now this changed
eventually as they broke apart, we had an adaptive radiation and all of these dinosaur
species showed up. What happened to them? We had a giant asteroid impact. Mass extinction.
And that led to adaptive radiation of the mammals. And some people are saying we are
headed into a sixth mass extinction. And so this is the worst way that climate can affect
species. Now as the climate changes animals can move. And so polar bears are going to
be impacted. This is a distribution of prime polar bear habitat. And you can see it is
being impacted all the way around the pole. Now if polar bears do not go extinct, what
are they going to do? They are going to move into new areas. And they are going to exploit
new niches. Plants will do the same thing. And so as the planet has gotten warmer and
warmer and warmer, this is a distribution of prairie birch, spruce and pine trees over
the last 21,000 years. And so watch what happens to their distribution. So now we are looking
at 12,000 years ago. And now 6,000 years ago. And now present day distribution. So you can
see that as the ice retreated the plants moved into that area. Now they are not like polar
bears. They cannot walk, and so this is a slow transition. But the movement of seeds,
the movement of pollen moves them into that area. Now as the ice moves away what is left?
It is just going to be bare rock. And so how do we go from bare rock to life? That process
is called succession. An so what happens, we have some weathering. We have some pioneer
species that start to move in. And then we have some grasses. Then we start to have some
forbes and some bushes move in. You can see the soil is starting to increase. Then we
have small trees. And then we have larger trees that start to move into that area. And
so it takes hundreds if not thousands of years for this to occur. But you can see it taking
place right here. This is a lava flow. And over time soil is going to start to form and
then life is going to move back into that area. This is primary succession because all
that is left is the rock. We can also have secondary succession. So this is a forest
one year after a forest fire came through. And so you can see that some of the life is
starting to come back. Let me show you what it looks like a year later. Way more of that
life has come back. And that is because the soil is still there and a lot of the seeds
are still there and it is a natural way that this forest can rebuild itself. And so did
you learn the following. Could you pause the video now and fill in the blanks? So again
climate is affected by the sun’s output, the orbit, volcanism and then plate tectonics.
That changes the ecosystems, both land and life. Extinctions, mass extinctions eventually
leads to adaptive radiation. And on the land we can have succession, either primary or
secondary. And I hope that was helpful.