Lesson 6 - Change Over Time

[Vince] Hi, boys and girls. Welcome back to the Sandia Mountain Natural History Center. We're a little further up the trail today in in an area that's more forested than we've been in another at other times. I want to ask you guys a few questions. What have we been learning about? Yeah, we've been learning about ecosystems and what are ecosystems made of.

They have different parts, don't they? That's right. They have abiotic and biotic parts. We've also spent some time learning about some of the specific biotic parts like producers and consumers. Now, I have a question for you. Do ecosystems stay the same all the time or do they change? If you're thinking they change, you would be correct.

Ecosystems do not stay the same. They change. Now, the question is, how do they change? Well, they change through natural forces and natural mechanisms, things like fire, things like water, things like weather and climate, but we're also going to spend some time talking about rocks and fossils as well. Some changes occur really fast, within a matter of hours or even minutes sometimes.

Sometimes ecosystems or changes occur over long periods of time. Sometimes thousands or millions of years. Other changes happen over and over and over again. We call those changes cycles or seasonal cycles. So, now I have another question.

How do scientists know that ecosystems change? In other words, what do scientists do to figure out that the ecosystems are changing over time? If you're thinking about they figure it out when they make observations, you would be absolutely correct. Scientists make observations of things that they're looking at to try to understand what's occurring.

So today, we're going to start by making some observations and thinking through what kinds of changes occur in the ecosystem. We're going to focus on abiotic factors and how they help ecosystem change over time. I want to start with a colleague of mine. His name is Paul and he's going to talk to us about things like fire.

[Paul] So, a fire is a natural process. How do they start? Lot of people would say that they start by humans but there's a more natural way that they start. Lightning. Yes, so what happens is light a lightning storm will come over and if you notice all these trees, these ponderosa trees, the trees with the orange bark, they're the tallest trees in the forest.

So, when that storm comes over, would you want to be standing under one of these tall pine trees? Probably not. So, these tall ponderosas, they get struck by lightning and then, one of several things happens. Either the inside of the tree slowly smolders and as the storm passes, it slowly smolders until it reaches the outside and then embers fall into these needles on the ground.

Or the tree sparks right away and embers fall into these needles on the ground okay but that's how the fire starts alright. But then a lot of people will say well why would the ponderosas want to start a fire doesn't wood burn. That's right but these ponderosas have a specific way of surviving the fires. First of all that fire that they start is burning on the ground. Now we look at the tree.

How would that fire climb this tree? Are there any branches down low? Now we can see a few little stubs here and there. What happens is this is a self-pruning tree. So, as the tree grows, it sheds its lower branches and those are what we call ladder fuels. So, it's very hard for the fire to climb the tree. Other people will say, well, won't the bark burn? Well, it will burn but it's very paper like.

So, the bark catches on fire but then it flakes right off, floats to the ground and that's very hard then to catch the whole tree on fire. And then people will say, well, what about just the pure heat? This bark is about an inch thick. So, it's going to act as an insulator. So, what happens is the fire burns right past the ponderosa. It it burns off the bottom of the tree a little bit but the ponderosa survives the fire.

As a matter of fact, the more ponderosa go through fire, the stronger they are for the next fire. Their their crowns or their canopy, the green parts of the tree actually get pushed up each fire and their wood gets harder each time it survives a fire. So, Ponderosa actually needs lightning and wants fires. So now we're in the Bosque down by the Rio Grande River and different forces are are causing quick changes. Where before in the ponderosa we had fire. Now we're talking about floods.

Flooding is a very important part of the Rio Grande Bosque ecosystem. You might say aren't floods bad? Well in certain circumstances of course they're not good. But this ecosystem actually needs flooding. Because cottonwood trees, the predominant trees that we see around us, they rely on flooding to grow because without floods, we don't have mud and without mud, those seeds that you see sprinkling down in the spring, those seeds won't grow in dry soil.

They need moist and damp soil in order to grow. So, what a flood does is it comes through and it scour away a lot of these bushes and and the debris that's been left all winter and it creates space for these trees to grow. One of the problems that we're facing though is that we see that we have all tall cottonwood trees. That means the cottonwood trees are all older or mature. What do you think the problem with that is?

I know that's a tough question but there's no young cottonwoods and the reason for that is we haven't had flooding and the reason we haven't flooding is because we have changed the river to suit the needs of humans and what we've done is we've dammed the river several times up up river and we've also build dikes along the river. What this does is controls the flooding which makes it safer for people to live by the river but it eliminates flooding and when we eliminate flooding, we're changing the way the ecosystem works.

So now, all of our cottonwood trees are reaching the end of their life. Can you think of a way that you can save the cottonwoods?

[Steven] So, Paul was just talking to you about fire in the forest in an ecosystem as well as flooding in an ecosystem. One of those two things can cause something that created this that I'm standing in right here. I'm down low goes up high that way and it goes up high over that way. What do you think is going to cause some formation like this?

Fire or water? Yeah, most likely water is going to cause something like that. Now, we're going to be talking about weathering and erosion. So, here we are up close to some of the rock that really makes up the mountain. We can see it because all the dirt that covered it up, the soil and the other rock has gone away.

Now, what makes it go away? Well, it was one of those words that I just mentioned, erosion, that's right. So, erosion is when rock, bits of rock, soil, and we can also call this the dirt and stuff in the soil sediment. When that stuff gets moved, whether it's by water washing it away or gravity pulling it down or wind blowing a little bit of of dirt away, that's erosion.

Now, it has to get into small parts to be able to get moved because this rock right here, this rock's not going to move anywhere unless pieces of it break off. So, what causes that? Well, that's the other word I talked about. Weathering. So, what do you think makes weathering happen? Well, yeah. Obviously, the weather, right? Because it's in the word. So, every time it rains, it might dislodge, it might break away a little tiny piece or particle of rock.

If it rained and water went in the cracks of the rock and then it froze that night. Well, that water when it freezes is going to expand. It's going to push just like if you put a water bottle in a freezer and it gets bulgy, it pushes out like this and it makes the bottle messed up. Same thing happens. So, what do you think is going to happen to these pieces of rock when if when the water inside the cracks freeze? Yeah, the pieces of rock will break off and those cracks might get bigger.

Here's something else that will make the cracks expand and pieces of rock break away. This little tiny piñon tree. It's growing right out of the rock but can it really grow right at a solid rock? No. The seed fell and it landed in a yeah in one of these little cracks here and then it took root. As this tree really slowly grows and the roots in there grow larger. It's going to push the rock and open it up as well.

So plants can even cause some of the rocks to break up. Um now this stuff that's happening. The weathering and the erosion. Weathering happens super, super, super slow. Erosion, it usually happens pretty slow as well. So, weathering and erosion are a slow change to an ecosystem.

[Vince] Hello again, boys and girls. Paul and Steven have talked about weather in their discussions earlier and I'm wondering what the difference is between weather and climate. Well, weather is what's happening right now. Climate happens over years and years over a long period of time. You'll notice I'm standing by this piece of machinery here. What do you think it's measuring?

Is it measuring climate or weather? You be right if you said weather because this machine is measuring the temperature. It's probably about 70 degrees. It's also measuring the wind speed and the wind direction. It's measuring other things like humidity and pressure. So, weather is what happens on a day-to-day basis. Think about it this way. When you get ready to go outside of your home, you have to think about what to wear, don't you?

Well, weather the day-to-day weather indicates what we should wear from day to day today could be 70 tomorrow we could get a storm and it could be 35° and maybe we get a little snow. Climate on the other hand is something that happens over a very long period of time, decades, hundreds of year,s sometimes even thousands or millions of years, and climate is what is occurring over these long periods of time and it helps us choose what kinds of clothes we want to have in our closet.

Things that we might wear now as we enter spring and early summer. Things that we might want to wear in the fall and things that we might want to wear in the winter. Some places are going to be very cold in the winter but other places around the equator might be really warm all year round. So again, weather is what happens day to day and climate happens over a very long period of time.

[Steven] We are on top of a ridge right now at the center. Um before we were down in a little canyon when I was talking about erosion. Um just to recap what Vince said a little bit ago. He's talking about the difference between weather and climate. Weather is what the what happens every day. It rains today. It's hot tomorrow.

Climate is the collection of that over a long long period of time. Many many many years. Now these rocks around me. These are all limestone rocks. You might remember seeing a big giant limestone rock next to me when I was talking about erosion.

The cool thing about limestone when you find limestone is that, now, it doesn't really look like anything special. It's just a gray rock. Nothing, nothing nothing beautiful about it but it tells us something. Tells us that there used to be an ocean. Now, this was once mud, if you can believe it, at the bottom of an ocean. Now, it wasn't just mud at the bottom of the ocean.

It was mud at the bottom of an ocean that was at the equator. Remember where the equator is? On maps and on globes, it's that black line that goes around the middle of the earth kind of like kind of like a belt right around the middle portion of the earth. What is the climate like at the equator?

Think it's cold? Well, it might get chilly up in the mountains but usually the climate around the equator is warm, hot, humid. So, very different place, isn't it? Now, I could tell you that this was all stuff at the bottom of an ocean but if you're doing science, you don't just tell somebody and say that's how it is and then they just automatically believe you. You have to have something to prove it. What is that word?

Starts with an E. It means the same thing as proof. Evidence. You need evidence. So, what kind of evidence do you think that we can find in these rocks that would be proof of an ocean? Fossils, yeah, we can find fossils. Now these fossils are from 300 million years ago when we do find them so, before all the dinosaurs mostly, still a super long time ago so what we're going to do right now is go hunting for some fossils or in other words look for that evidence that proves the ocean was here Crinoid, nice. That's perfect.

Ooh, that's a good one. Alright, here we are with our bag of fossils. Now, fossils, they are evidence. They're cool. There's still evidence. This one really is nice it is really nice seashell we can see the lines in it. That's a piece of evidence because there's no, there's nothing on land that has a shell that opens up like this is there?

There are snail shells, that the snails live on land but not this kind of clam like thing. Yeah, here's another one. It's another shell. Um just like that, like a cup. We can see the lines in there and the shape. This is a really nice shell. It's got both sides to it. So, whereas those that we just looked at had one half of it.

This has the whole creature, and it's all closed up. Definitely nothing on land like that. This one's very cool. Magnifying it makes it look completely different. We can see all sorts of little holes, little kind of tubes in there. This is from something called the sea sponge. This one didn't survive. It's not around anymore. So, what do we call that? Yeah, this one's extinct. This one has more of a texture.

It's from something called a bryzoan. Again, only lives in the ocean. There's no land bryzoans. This one looks like a little stack of discs. So, actually from a stem and then at the top of the stem, there was like little tentacle-ly like arms. It was an animal but it was attached to the sea floor and it would just catch food as it drifts by and then when it caught it, it would move it to the middle. So, what's in the middle? Yeah, the mouth and then it would consume it.

Oh, if it consumes, what is it? Consumer. Here's a little circle. This is from a coral. This type of coral is called horn coral. It's called horn coral because what do you think it looks like? Yeah, it looks like a horn like a bull's horn. So, it would attach to, be attached to a rock. At the top of it, there'd be more little tentacle things and when food drifts by, catches it, consumer or producer?

That's right, consumer. There is our evidence. These are all organisms that live only in the ocean. That is the evidence that tells us that all this limestone was once mud at the bottom of the ocean. There's a word that I used a little bit ago when I was talking about erosion. It's another word that we can use for dirt and sand and things like that. Starts with an S, not soil though.

Sed....sediment. That's right. So, all this stuff, all the sediment, little bits of fossil and stuff is what makes up this limestone rock. Now, all that's the thing, all those are things that lived in the ocean but what about on land? Let's focus on the plants because there are lots and lots of plants on land at this time. What is the gas that plants absorb? Yeah, carbon dioxide and what's the gas that plants release?

The oxygen. Plants need the carbon dioxide. Animals like us or bugs need the oxygen. There was so much oxygen on earth at that time that many of the insects that we have today that are tiny were huge, giant cockroaches, giant dragonflies. Because there was so much oxygen in the atmosphere it allowed them to grow larger. When trees die, they hold on to a lot of that carbon from the carbon dioxide.

So, if we have billions and billions and billions of plants and trees on Earth living absorbing carbon dioxide, releasing oxygen, and then holding on to that carbon dioxide, something's going to change in the atmosphere. Carbon dioxide is a kind of gas that hold on the heat. It's called the greenhouse gas because of greenhouses where you grow plants. It's always warm in there.

Um so, if there's lots and lots of oxygen and declining amount of carbon dioxide in the atmosphere, eventually the air is not going to get warm and hold a lot of heat. The air is going to get, yeah it's going to get colder. So that causes a change, a change in the climate, and a change over time. if an organism, a plant, or an animal, or whatever thing that is living cannot survive in a colder place, what might happen? It might die. If they all die, yeah, that's right.

They went extinct but if they can change, what's that word? They can adapt, then they might survive and of course, if they can move, they might move but that's like an adaptation as well. So the earth went from a warm humid plant covered place to a colder place with lots of ice. What do you think we called that period of time? I think you got it, yeah, an ice age, because the temperature went down, the ice covered more of the earth, and so that changed the kind of organisms that were able to survive in certain place.

That ice age, do you think it lasted forever? Of course not. The planet's climate is always changing. If you have enough time go by, change is going to happen. So, the changing that happened after that ice age allowed organisms like this salamander that we have a fossil of in our museum to become a successful creature and eventually, things changed again, out that salamander went.

The giant salamander didn't survive the, until now. Um so, what we need to remember is that the climate on Earth is always changing, but usually over very long periods of time, and a long period of time is over millions and millions of years. Right now, the atmosphere, the climate is warming and that's happening over just a couple hundred years. We'll talk about that in another video though.

[Vince] So, in this video, we've been learning about how ecosystems change over time. Let's think about that minute. How do ecosystems change over time? Sometimes those changes happen really rapidly like with a forest fire. Sometimes those changes happen over a very very long period of time like the fossils that we've been looking at.

Other times those changes happen cyclically or over seasons like the flooding. Or on a daily basis we have weather. Now how do scientists know ecosystems change over time? What do they need to do? They need to make observations. Sometimes they can make measurements. Now, in this activity for the video, we're going to make an observation log and I'm going to show you an observation log I made and explain how one works.

So, here's mine. You can see I've divided the paper into four columns. The first column says time and date. Column two says observation one, column three says observation 2, and the last column says observation three. We want you to choose three different things that you can observe. We'll ask you to first choose weather, because everybody can observe the weather, and then you'll notice that I selected a plant or flower that I want to observe really closely, and the third thing is my trash can. In the first column, we put the time.

So, we'll put the 9 AM and we'll put the date. Today is April 23rd, 2020. The next column says weather. So, what's the weather like today? Well, it's windy, it's sunny, maybe about 70°, or warm if you don't know the temperature. Whatever you can figure out for the weather you'll put there. Then tomorrow, I'm going to look at the weather again at the same time and make some observations.

Maybe it's cloudy, maybe it's a little cooler or warmer. Whatever it is, I'll go ahead and write that down. In the second observation, I chose a flower and in this case, this flower was say yellow and halfway open. Tomorrow, maybe the flower is a little more open. Maybe it's all the way open. In a couple days, maybe that flower has died or the petals have fallen off. Whatever you observe, go ahead and write that down and then the last column is my trash can.

I'm going to pretend that today my trash can was empty and then tomorrow, maybe there's just a little bit of a trash in there maybe it's 10% full so I might write 10% then the next day is half full and then eventually it's going to fill up and it's going to be taken out to the trash and then it'll be empty again. Whatever you observe, are observing, go ahead and write those things down. You can be creative in your second and third observation.

You do not have to select what I've selected. You may choose to go outside and observe all the animals and insects and birds that you've been able to observe, or you may choose to stay inside and maybe you look at things that you're eating every day, or things your aunt or uncle or brother or sister or whoever's in your house, maybe something they're eating. Whatever it is, choose three different things that you're going to observe and observe them for seven to 10 days or maybe two weeks. At the end of your observation period, we're going to ask you to analyze your observations.

You're analyzing data and the way you do that is you look for patterns and things that might have changed or may have stayed the same over your week to two weeks of observations. Because ultimately, what we're looking for is change over time. How has the weather changed over time? How has this flower? Or how has the trash can changed? If it's changed, indicate that. If it hasn't, write about that too.