Lesson video

Hello, geographers.

Today's lesson's all about the way in which the world's ecosystems help to regulate Earth's systems, and those are the systems that help preserve life on Earth.

So we're gonna be thinking about the water cycle.

We're gonna be thinking about carbon in the atmosphere and climate change.

And we're also gonna be thinking about something that you probably don't give much thought to, which is about the soil under our feet.

We take it for granted, but perhaps we shouldn't.

Shall we get started? Okay, so today's outcome is as follows.

I can understand how the biosphere regulates the atmosphere and provides important environmental services.

I can understand how the biosphere regulates the atmosphere and provides important environmental services.

So that's what I want you to be able to say by the end of the lesson.

Okay, so we've got some key words to work on today.

These are atmosphere, that's the air above our heads made up of gases, solids and liquids.

We have ecosystem services.

Those are benefits gained from the day-to-day functioning of the world's ecosystems that support human life.

We've got this word regulate, which means to control, for example, the flow of water in a pipe or the temperature in a room.

We've got soil health, the structure, composition and nutrient content of a soil, a measure of soil fertility.

And then lastly, we have the hydrological cycle, otherwise known as the water cycle, of course.

It's the continuous recycling of water in its different states, for example, via rainfall and evaporation.

So those are our key words today, and we're going to be using those throughout the lesson.

Okay, so how is our lesson structured? We have three key questions to answer.

How does the biosphere regulate the atmosphere? How does the biosphere regulate soil health? And then lastly, how does the biosphere regulate water? Firstly, let's get started on this first one then.

So how does the biosphere regulate the atmosphere? These words we use in geography that end in sphere relate to our planetary home that is Earth.

So the atmosphere is the air above our heads, which is made up of gases, for example, oxygen and carbon dioxide, solids, such as dust ejected from volcanoes up into the air, and then liquids, for example, water droplets within clouds formed around condensation nuclei, those solids I was talking about, the particles in the air.

Okay, so that's the atmosphere, whereas the biosphere is the living layer of Earth below the atmosphere.

It includes plants, animals and all other living organisms. So here are the plants.

You'll remember the animals.

And here's an example of, fun fact, something that isn't a plant or an animal but is alive, and that's the fungi.

So these are three examples taken from the temperate, deciduous forest biome.

But of course we know the biosphere's comprised of all the different biomes that we've been studying on Earth.

The biosphere provides us with a wide range of benefits known as ecosystem services.

And these are of global importance, enabling life on Earth.

So we're gonna be looking at how important they are.

So there are different types of ecosystem services provided by the biosphere that support life on Earth, as I was saying.

These are provisioning services, so, for example, the goods that we obtain or abstract from ecosystems, such as food and fuel.

We also have supporting services, so these are processes which support the planet to provide other services.

And these include things like photosynthesis and soil formation.

We've got regulating services that support the healthy functioning of the whole planet, such as carbon storage and water purification.

But also we have cultural services, so benefits gained by human society from living in a healthy environment, such as spiritual wellbeing and happiness.

Now, today, we're gonna focus initially on regulating services because these are the services that moderate environmental phenomenon that affect us, such as climate change, driven by changes in the atmosphere.

So we're thinking about how does the biosphere help to help provide regulating services.

And we're gonna focus therefore on the atmosphere, and think about, to start with, photosynthesis.

Now, you'll remember that photosynthesis is the process by which green plants make food, and it helps to regulate the gaseous composition of our atmosphere.

How does it do this? Well, carbon dioxide is taken in from the atmosphere and stored as biomass, so within plant material.

And oxygen is released into our atmosphere.

And what does that look like, in terms of the formulae? So we've got carbon dioxide plus water with sunlight creates carbohydrates and oxygen.

Our example of carbohydrate here is glucose.

This process of locking away atmospheric carbon is known as sequestration.

The world's biomes are important carbon stores or sinks.

The soil is also a key store of carbon because when living organisms die, their dead biomass adds carbon to the soil.

So we can see in this way that the biosphere is helping regulate the atmosphere.

Why is that important? Well, let's talk greenhouse gases.

Carbon dioxide is a greenhouse gas.

This means it absorbs infrared radiation and reradiates it into Earth's atmosphere.

So it functions a bit like the glass in a greenhouse, trapping heat in our atmosphere, trapping heat around our Earth.

Clearly, some carbon dioxide is needed to keep Earth warm enough to support life.

But as a result of human activities, such as or in particular burning fossil fuels, today's enhanced greenhouse effects, that's the term we give to this greenhouse effect plus that we've created by burning lots of fossil fuels, it threatens Earth's support systems, so it threatens to throw them out.

The biosphere's regulating services are therefore needed now more than ever.

And in our diagram, we can see the way we've got incoming short wave radiation, which is reradiated by the Earth as long wave radiation.

And it's this radiation that those greenhouse gases are trapping in our atmosphere.

Okay, quick check for you then.

Regulating services, sorry, are globally important benefits of the biosphere, and they include, A, spiritual wellbeing and happiness, B, keeping climate change in check, or, C, food, fuel and building materials.

Pause the video and discuss with your neighbour or have a think on your own, what's the right answer? Press play when you're ready to check.

And if you said, B, keeping climate change in check, you're absolutely right, well done.

Okay, true or false, the biosphere helps to regulate the atmosphere.

Is that true or false? Now, I'm gonna ask you why in a second as well, so have a think.

Pause the video, talk to your partner and have a think about what you might say when I say why.

Of course, if you said true, you're absolutely right.

But can you think about how, how is it that the biosphere helps to regulate the atmosphere? Well, here's our answer.

For example, green plants photosynthesize, removing carbon dioxide from the atmosphere and releasing oxygen.

This reduces the carbon content of the atmosphere and reduces the enhanced greenhouse effect.

So if you've got some of those terms like photosynthesis and reducing the enhanced greenhouse effect, your answer is effectively explaining how it is that the biosphere is regulating the atmosphere.

So well done.

Okay, practise task for you, I have two for you here.

The first one asks you to describe two ways in which the biosphere helps to regulate the composition of the atmosphere.

And I've got a hint there, just saying can you think about oxygen and carbon dioxide? Then secondly, I would like you to sort out this really rather jumbled definition of our key term, sequestration.

So the hint is four words need to move.

Now, I'm not gonna read this out because it doesn't make much sense.

So I want you to read it out quietly to yourself and think about which words need to move to help these two sentences make sense and define sequestration.

Okay, so I suggest you get a pen out at this point and have a go at writing some answers here and correcting my sentence, and then press play again when you want to check your answers.

Okay, how did you get on then with this first one? Two ways in which the biosphere helps to regulate the composition of the atmosphere.

So your answer might include points like, well, firstly, plants take in carbon dioxide during photosynthesis.

So effectively, that's locking away that carbon in the atmosphere, isn't it? Secondly, as part of the same process, they release oxygen.

So we've got the taking in of carbon dioxide, we've got the releasing of oxygen.

These are both ways in which the biosphere helps to reduce the carbon composition of the atmosphere.

So if your answer was something like that, well done.

Now, our second question therefore was sort this jumble definition of sequestration.

Four words need to move.

Now, how did you get on with this? This was a bit more challenging, wasn't it? So the correct ordering gives us a great definition of sequestration, the locking away of atmospheric carbons, that's carbon in the atmosphere, like the gaseous carbon dioxide.

One example is the storage of carbon within the biomass of green plants.

So that's one example of the way carbon can be locked away by the biosphere.

So if you had that order, well done.

Okay, second part of our lesson, how does the biosphere maintain soil health? How does the biosphere maintain soil health? Now, the biosphere has a key role in maintaining soil health, otherwise known as soil fertility.

Have a look at that picture.

Can you suggest how? Have a think about those ferns and some of those green plants in that image.

What's their role in maintaining soil health? So the biosphere helps to maintain soil health by, firstly, reducing erosion.

So plant roots help to anchor the soil, reducing wind erosion, and leaves intercept the rain, reducing erosion by rain splash.

So reducing erosion.

Secondly, the biosphere improves soil structure.

So we have animals, such as earthworms, that burrow within it, creating spaces which allow rain water to infiltrate, and plant roots do the same.

Oh, and Alex, he's stuck on the worms here.

"I know a farmer "who says he employs millions of workers on his farm, "and they all live underground (laughs)." Well, we know they're earth worms, don't we? Thank you, Alex.

And then thirdly, we have recycling nutrients.

So the biosphere is helping to main soil health by recycling nutrients.

Now, what does that mean? Well, nutrients such as nitrogen are recycled within any given ecosystem.

And this natural system can be shown as the movement between three different stores.

Those stores are the biomass, so living things, the litter, so dead organisms, such as leaves, and the soil.

So we have biomass linked to litter, so we're talking about leaves, branches, skeletons of animals that have died, nothing to do with crisp packets, and the soil store.

And those are all linked.

So nutrients continually move around between the three stores by processes such as littering.

So this is where, for example, deciduous trees lose their leaves in autumn, where litter is broken down in the process of decomposition, and nutrients are released into the soil.

And then we have plant uptake, where nutrients are taken from the soil back up into plants.

So here's our example of just explaining what I've talked you through there.

Plants will take their nutrients for the soil as they grow.

Eventually, their leaves will fall to the floor, which will add nutrients to the litter store.

But in time, those leaves will decompose, where the leaves break down, and this adds nutrients to the soil ready for plant uptake again.

And as we've said, this is a continual process that is ongoing.

Decomposers of course help with nutrient cycling, and we've got the example in the image there of fungi, fungi that are living in and on the leaf litter.

So fungi and bacteria take this similar role.

They break down dead plant and animal material and waste, such as faeces, meaning that these nutrients are available for reuse.

So what is decomposers doing? They're directly absorbing nutrients by living in or on organic matter, and they're returning those nutrients to the soil in the form of an organic substance called humus.

Quick check for you then.

True or false, littering is when leaves transfer nutrients from the biomass to the soil store.

Is that true or false? And if you said false, can you explain why? Well, the answer we have here is that organic matter containing nutrients, so we're thinking about leaves falling from trees, are transferred to the litter store, but not directly to the soil store.

To reach the soil, decomposition of the litter must take place.

So if your answer includes some reference to the fact that decomposition hasn't taken place yet, so we don't transfer nutrients straight from the tree, via the process of littering, to the soil, but there's this process of decomposition in between, then that's brilliant.

Another check for you here.

Complete the following sentences, fungi and bacteria break down something.

This process of decomposition returns something.

Okay, pause the video, discuss with a partner, and then press play when you're ready to check your answer.

Okay, so I have fungi and bacteria break down dead leaves in the litter store, and this process of decomposition returns nutrients to the soil store ready for plant uptake.

Well done for having a go at that one.

Okay, so it's worth talking about processes that add nutrients to an ecosystem, and these are called inputs.

So let's have a think about what we're talking about here.

So we're talking about rainwater that washes material into the litter from the atmosphere.

We're also thinking about weathering, which releases nutrients from the bedrock into the soil.

Within this system, there are also losses.

Can we think of some examples? Well, there's runoff.

So some material is washed out of the litter and lost to the system, perhaps as particles.

We also have leaching.

So we have rainwater entering the soil, perhaps dissolving nutrients in the soil, and washing that away into the local river.

So a quick recap, examples of inputs here are rainwater washing chemicals out of the atmosphere and weathering releasing chemicals from the bedrock and adding those to the soil.

Non-examples of inputs would be runoff.

This is a loss.

It's a loss from the litter.

Leaching, this is a loss of nutrients from the soil as water moves through it.

Again, a loss, not an input.

Human activities can have an impact on that process of nutrient cycling.

Can you think of an example that might affect this cycle? Well, one example is deforestation, and that's the large scale felling or clearance of trees.

This reduces not only the biomass, but in time will reduce the litter and the soil stores.

And you can imagine how that might happen.

Quick check for you.

True or false, nutrient recycling means plants absorb all of the nutrients released into the soil by decomposition.

Is that true or false? And remember, I'm gonna ask you to explain your answer in a moment.

So have a think.

Now, you probably said false, didn't you? Well done, can you explain that? Okay, so the answer we had was that not all nutrients are available for plant uptake.

Some nutrients are lost from the soil via leaching.

So it's not a closed system, we haven't just got that complete cycling, but we are having some losses as well as inputs to the system.

So if you mentioned a process like leaching or losses via runoff, good job.

So another check for you, what would be the impact of deforestation on the size of the three stores in this nutrient cycle? What would be the impact of deforestation? That's right, all three stores would reduce in size over time, a bit like this.

And this diagram we use to represent the relationship between stores and processes within a natural system.

So here in geography, we're using circles for the stores and we're using arrows to represent those processes.

It's typical to see different diagrams for different biomes, but also different biomes that have been affected by human activity.

And typically, within these diagrams, you would reduce the size of the circles to show the way that those stores have been reduced.

Okay, practise task for you then.

Describe what is meant by the term nutrient cycling.

What is meant by the term nutrient cycling? Can you explain that in a sentence or two, sorry, describe that process in a sentence or two? Then, secondly, I'd like you to use the following words to complete this explanation of why deforestation harms soil health.

So you have a paragraph there to complete.

And I've got one, two, three, four, five, six blank spaces.

And then we have a box of six words for you to use.

Okay, so I suggest you get a pen or a pencil out at this point.

I want you to have a go at that description task, and trying to complete that paragraph.

And then press play again once you want to check your answers.

Okay, how did we get on? Describe what is meant by the term nutrient cycling.

I'm interested to see if you could do that in just very few words.

Laura's got quite a succinct answer for us, quite concise.

She said, "A set of physical processes "that together form nature's recycling system.

"Together, these enable the reuse of nutrients "in dead and waste material "by other living things again and again." I like that last bit.

It tells us that this is an ongoing process, isn't it, of recycling, of ongoing recycling.

Second question then, use the following words to complete this explanation of why deforestation harms soil health.

And I've just put up the completed paragraph there for you to have a look at.

How did you get on? Let's read out the completed paragraph then.

Soil health depends on the ongoing addition of nutrients via littering and decomposition.

However, the large scale felling of trees, remember that's deforestation, means that the biomass store within this system is drastically reduced in size.

This in turn reduces the amount of organic material added to the litter store, and as a result reduces the amount of nutrients added to the soil store by decomposers.

Did you get those words in the right place? If you do, this paragraph should make sense, yes? Brilliant.

Okay, third section of our lesson then, we're thinking about this third question, how does the biosphere regulate water? So we're thinking about the water cycle, otherwise known as the hydrological cycle, which is the continuous recycling of water in its different states.

And here's a diagram that would probably be quite familiar to you.

We can see how water evaporates from the sea into the atmosphere as water vapour, condensing as clouds, and then falling in the form of precipitation to reach the land surface, travelling via surface runoff back into the sea.

But of course, it's not that simple, and the biosphere performs a role in this diagram, although perhaps it's not flagged right here.

Let's have a look at what role the biosphere plays within the water cycle.

So for example, forests, but also lots of different leafy plants play a key role in helping to regulate the movement of water, reducing flood risk.

Can you suggest how? Well, one process is interception, and there's a really great image here, isn't there, showing the raindrops collecting on leaves.

So if raindrops collect on leaves rather than falling to the ground, this creates a temporary store of water.

Infiltration is another role.

So plant roots enable water to infiltrate the soil, and this reduces the volume that travels directly to the river via surface runoff.

So water's going to infiltrate into the soil, that might create a temporary store, and it doesn't travel over land directly to the river.

Thirdly, we've got this process of evapotranspiration, which is the transfer of moisture from the leaf surface and via the pores of leaves during photosynthesis back to the atmosphere.

And these are three different ways in which many plants, certainly forests, play a key role in helping to regulate the movement of water and reducing flood risk.

Quick check for you, what's the difference between interception and infiltration? And if you said something like this, well done.

So we have interception is the storage of rainwater on the surface of leaves above the ground, whereas infiltration involves plant roots, which are in the ground.

Yeah, they break up that ground surface which enables water to enter the soil.

Any similarities between those two processes? So we thought about the differences, any similarities? Pause the video.

Okay, well, there are some similarities because both involve the temporary storage of water, both reduce the volume of rainwater that travels directly to the river as surface runoff, and therefore they're contributing to reducing flooding.

Perhaps your answer said something like that.

If it did, well done.

Another check for you.

Evapotranspiration, it's a long word, isn't it, is the transfer of water, dot, dot, dot.

Pause the video, discuss this with a partner, have a think, and restart it when you know the answer.

And of course, the answer is B, from plant leaves to the atmosphere.

So evapotranspiration is the transfer of water from plant leaves to the atmosphere, well done.

Now, interestingly, in recent years, scientific research has shown that there's a link between the large scale felling of tropical rainforest and changes in regional weather patterns.

We have a headline there.

"Breaking news, scientists link loss of tropical rainforest "to fall in regional rainfall." Such a reduction in local and regional rainfall could have a negative impact on agriculture, and provides a strong argument for conservation of the rainforest biome.

So this is research that scientists have undertaken in the Amazon, and recently published their findings, that actually large scale felling does lead to a loss of regional rainfall.

Here's a diagram which shows how deforestation has a range of impacts on the hydrological cycle locally.

So let's have a think about what the numbers on that diagram might mean.

So here, we can see the forest on the right hand side of the diagram, but most of it's been cleared, hasn't it, between the top of the hillside and the river.

So what's been the impact of that? Firstly, we've got reduced interception and increased erosion by, for example, rain splash.

Secondly, we've got reduced infiltration and groundwater storage.

So water isn't being stored underground if it can't infiltrate into the soil because the lack of vegetation breaking up the soil surface.

Thirdly, we've got an increased surface runoff.

The water has to go somewhere, doesn't it? And remember, that's the rapid, that's the most rapid route to the river.

And then fourthly, we've got increased risk of flooding due to this runoff we spoke about.

And also the erosion, which you can see in the picture in that cross section of the river channel is filling the river channel with sediment, which is reducing the volume of the river channel and reducing its ability to cope with and hold the water.

And then lastly, we've got reduced evapotranspiration from the earth's surface there.

So there aren't the plants that are transpiring because they've been cleared.

So check for you, what will be the impact of these changes on the weather? So I'm talking about one to five that we've just spoken about.

Pause the video, have a talk to your partner.

And I'm sure you had an answer a bit like Andeep's here.

"The loss of tree cover and reduced evapotranspiration "means less moisture in the atmosphere, "fewer clouds and less rain." So that's the impact on the weather.

Practise task for you, then, can you write labels for numbers one to five on my diagram to show how deforestation leads to changes in the hydrological cycle of the rainforest? I'd like you to include some of the processes below.

So we've got condensation, erosion, evapotranspiration, flooding, infiltration, interception, rainfall, runoff and storage.

So I suggest you grab a pen, pause the video and have a go at that task now.

How do we get on with writing labels for your diagram? Well, your first label should say something like reduced interception and increased erosion is our first impact of deforestation in this environment.

Secondly, we have reduced infiltration and groundwater storage.

Thirdly, increased surface runoff.

And fourthly, increased risk of flooding due to this runoff and erosion.

So we talked about that sediment filling the river channel.

And then, lastly, reduced evapotranspiration, meaning less moisture in the atmosphere to condense effectively, fewer clouds and less rain.

If you had all five of those, you are doing brilliantly.

Okay, so what have we talked about today? We've been talking about the biosphere and the way it provides us with a range of globally important environmental services.

So it regulates the composition of the atmosphere, helping to balance its gaseous components and return moisture to the atmosphere.

It maintains soil health as part of the nutrient cycle.

And it regulates the hydrological cycle, reducing flood risk.

These ecosystem services provides us with strong arguments for the conservation of the biosphere, and that helps us to understand all the different reasons why conservation of our ecosystems are so important.

Thanks for taking part today, and I look forward to seeing you again really soon.