Lesson video

Hello, geographers.

My name is Mrs. Griffiths, and today's lesson is focused on changes in small scale ecosystems. Now this gives us the opportunity to look at a really interesting real world example.

So you made a great choice to learn with me today.

And shall we get started? Okay.

So our outcome for today's lesson reads like this.

I can understand how natural changes and human activities affect the balance of small-scale ecosystems. So that's what I want you to be able to say by the end of the lesson, I can understand how natural changes and human activities affect the balance of small-scale ecosystems. Now let's have a look.

Have we got some keywords today? Some key terms to look at? Okay, so our keywords are as follows.

Biotic.

Living components of an ecosystem such as plants and animals.

Abiotic.

Non-living components of an ecosystem such as soils and climate.

Food web.

A complex interaction or interconnection, sorry, of food chains within an ecosystem.

Habitat.

The natural home or environment in which an animal or plant lives.

And biodiversity.

The variety of plants and animals in the world or in a particular habitat.

So those are our keywords and we're gonna be using those throughout the lesson.

How does our lesson shape up? Well, we've got two key questions to answer.

How does change affect ecosystems? And how has change affected College Lake's ecosystems? So that's the example I mentioned, and we're gonna come back to that because first of all, we're gonna answer this question, how does change affect ecosystems? Okay, so if we define an ecosystem as a community of organisms such as plants and animals that interact with one another and their non non-living environment.

Here's a photograph for us to have a look at.

What might be the living biotic and non-living abiotic components of the ecosystem in this picture? So have a close look at that environment and think about those two sets of components within this ecosystem, the biotic and the abiotic.

What can we identify? Well, within this temperate deciduous woodland ecosystem, I'm sure you spotted that's what it is.

We have firstly, abiotic components such as the temperate climate we have in a country like the UK.

There's the water in the soil and the atmosphere, the bedrock, for example, in this case it's chalk.

And the soil that's created by the weathering of that rock.

We also have biotic components of this ecosystem.

So those are the plants.

And in this image we can see oak, birch, and beech trees as the ones with the silver trunks.

We can imagine the animals that live in this environment, so owls, rabbits and foxes, but also the microorganisms including bacteria and fungi.

So that's thinking about the different components of this temperate deciduous woodland.

Now how do they connect? Of course, plants, animals and other organisms depend on one another for food.

And energy is transferred between them via food chains.

Each food chain forms part of a complex food web.

So we know that nature is a complicated system.

So this is an example of a food web found in a temperate deciduous woodland.

And we can see within this food web we have producers, we have primary consumers and we have apex predators.

So we might call those secondary consumers or for example, where you have the oak leaves eaten by the worm, the thrush then the buzzard.

So we have that perhaps more complicated food chain because we've got that extra stage.

We've actually got the primary consumer being the worm, the thrush coming in as a secondary consumer, and then the buzzard as the tertiary consumer or the apex predator here.

So quick check for you then.

Can you identify a food chain within this woodland web.

Food web that includes secondary and tertiary consumers? Have a think.

Pause the video.

And then press play when you think you know the answer.

Okay, now there's more than one correct answer here, but you might have said, "Well, if we start with fallen oak leaves, those are eaten by a primary consumer, which is snail.

The snail is eaten by a thrush, which is the secondary consumer, which is what I asked you for.

And then the tertiary consumer is that apex predator, it's the bird of prey, it's the buzzard." So if you said that, well done.

So we're thinking today about changes in ecosystems. What might happen in this woodland food web if the rabbit population was say, dramatically reduced by a disease? So have a think what might the impact be? Well, as Sofia says, "If foxes and buzzards.

." "If rabbits were.

." The population was say decimated, "Foxes and buzzards might go hungry because that's their food source." So their population would shrink.

Also, if we look at the rabbits, they're competing with mice, for example, for some of the food on which they survive.

So with the rabbits out of the picture, there would be more food for mice, meaning lots more mice in the long run.

Okay, here's a change for you to think about.

What might happen if foxes were hunted to extinction locally? So think about small-scale ecosystem, what would happen if we took the foxes out of this food web? Pause the video, talk to a partner.

And then press play when you are happy you've got an answer.

Okay.

You might have said something a bit like Izzy.

Izzy says, "Rabbits, mice and thrushes would increase in number with fewer predators.

Buzzards would be better fed with less competition for food and so could grow in number too." So we've got some similarities with the last change that we looked at where you've got the removal of a predator, so they're preyed as well, but also animals that were competing for food that they benefit as well.

So I'm sure you've had both of those ideas, but I just wanted to flag those for you there.

Okay, so this is a different diagram.

So this is a diagram, it's a way of representing this woodland ecosystem and a particular food chain in terms of bars that are used to represent each trophic level.

So each position within the food chain.

And each bar is drawn in a way that is proportional to the weight of biomass in that layer.

So you can see that we have a lot more plant material needed to feed the snails that would support the thrushes, which would be needed to support a small population of buzzards.

And if I just add in those names for the trophic levels, that just reminds you about who are the producers, consumers and tertiary consumers in particular, those apex predators within this ecosystem.

So that's a different way of looking at a food chain.

Thinking about change again, what might happen if some trees in this woodland ecosystem were felled? What might happen if some trees in this woodland ecosystem were felled? Pause the video, talk to your partner.

And then press play when you want to hear the answer.

Okay.

So if we remove some trees from this woodland ecosystem, clearly there'd be less food for the snails.

This would reduce their population and therefore the biomass in that trophic level.

And it would also reduce the population of birds, both thrushes and eventually the buzzards.

So if you said something like that in answer to how would felling some trees in this environment have an impact on this ecosystem? Great job.

So we're thinking about change and how change affects different ecosystems. Clearly changes can disrupt the balance of these different components, and we can see how complex different natural systems are.

But we have to remember that change can be natural or it can be as a result of human activities.

So let's focus in on natural change to start with.

Natural change can take place on different timescales.

Now, if we think about slow change, that can actually have few harmful or hugely impactful effects for plants and animals because they have time for plant and animal adaptation.

However, what we're witnessing today with climate change is that the climate is changing quite rapidly at a more rapid rate than has previously been experienced.

And scientists today are doing research into whether these more rapid changes in our weather patterns could mean that some plants and pollinators, pictured here, this is the insect that pollinates flowers, will actually be.

Eventually be out of step.

So the insects perhaps come out of hibernation ahead of the the flowers being created.

So could these things be somewhat out of kilter as a result of climate change? But of course, there are extreme weather events.

So we're not just talking about slow change.

We could have rapid events that have devastating impacts on ecosystems. Can you think of an example? Well here's one, drought.

Drought particularly affects wetland habitats.

What's the impact? Well plants dry out as water evaporates.

With that reduction in the volume of water, we get a decrease in water quality plus less food affects the animals 'cause we know the plants dried out.

Fish will die of course, without water and amphibians will go elsewhere.

So a particular, a local small-scale ecosystem will be affected by that out-migration.

Of course in nature, we don't just have drought, but we also have storms. And storms fell trees.

In fact, millions were lost in 2021 in the UK as a result of 90 miles per hour winds of Storm Arwen.

An oak tree felled in the storm might have provided a habitat for more than 2,000 other species.

So we can't underestimate the impact of the loss of these mature trees.

Here's a check for you.

Drought affects wetland habitats because.

Now three possible answer there, A, B, and C, but only one of them is correct.

Talk to your partner about that one.

And then press play when you're ready to hear the answer.

Okay.

And if you said C, you're absolutely right, well done.

Drought affects wetland habitats because there's an out-migration of amphibians which affects food chains.

Good.

Let's move on.

Okay, so let's think about, we've thought about natural change.

What about human activity? Human activities such as agriculture can affect ecosystems. And we've got two images there of agriculture in the UK.

Have a good look at those images.

How is it that farmers are having an impact on small-scale ecosystems? What do you think? Well, if we think about change, clearly some agriculture can harm ecosystems, disrupting their delicate balance.

Thinking about the complexity in the sort of food webs and things that we've seen.

So for example, hedgerows are removed or woods can be cleared and cut down to allow fields to be en enlarged.

And that results in a loss of habitat.

Pesticides are used to reduce weeds, insects and fungi which would otherwise affect the crop.

So farmers are acting to protect their harvests.

But of course, this reduces biodiversity in the environment.

Accidents happen and the accidental pollution of ponds via leaks of farm waste can occur, which of course, will kill the organisms living in those ponds.

And fertilisers.

Fertilisers which contribute nitrates to local waterways can cause eutrophication.

Let's have a look at that in some detail and what's eutrophication about? Well, if you imagine the farmer has applied a nitrate rich fertiliser to his or her fields, what happens next is as a result of heavy rain, run-off carries those nitrates into the river.

The impact of that is effectively the fertilisation of that riverine environment.

And we get the rapid growth of algae resulting.

But the problem with that rapid growth of algae is it actually starves other organisms like fish, of oxygen in the river.

So that's eutrophication.

Another impact of human activities in small-scale ecosystems. All of those aren't great, but also agriculture can support the functioning of these natural systems. And no doubt, when I asked you that question originally you were thinking, "Well actually I can think of the things that farmers are doing to support nature." So for example, some farmers are increasingly replanting hedgerows.

So hedgerows are going back into the fields because there's a recognition that they're creating corridors for wildlife.

Wetland areas are also created by some farmers on their land.

And this is creating additional habitat that might have previously been lost.

And some farmers are protecting strips of wildflowers around their fields.

So around the edge of the fields, they're actually not sewing the crop right up until and spraying the fertilisers and pesticides right up to the edge of the field.

But they're protecting a strip of wildflowers.

And that creates a very biodiverse environment if you imagine that occurring around every field or a large number of fields within a farm.

So and in the UK, farmers receive government funding to protect key habitats for wildlife in order to conserve or restore biodiversity and.

We're hearing of this, aren't we? We're hearing about the restoration of biodiversity and the importance of it.

Okay, so a check for you.

With a partner, I'd like you to list ways in which agriculture affects small-scale ecosystems. Hint, think about damage but also restoration.

So I'm gonna give you a bit of time to think about that.

So pause the video and then press play when you wanna check your list.

Okay, well done for having a go at that task.

You may have listed the following, and I've got a number.

So hedgerow removal.

The idea that some farmers are ripping out hedgerows to enlarge fields.

This leads to a loss of habitat, isn't it? We've also got hedge planting, which is quite the reverse.

It's the creation or restoration of habitats within the rural environment.

The creation of wetland areas.

This is the creation of habitat.

As opposed to the pollution of ponds which leads to the loss of aquatic creatures.

The use of pesticides to protect the crop can have that impact on grass and plants and animals a loss of biodiversity.

Conversely, wildflower strips that are protected around the edge of the field supports a habitat for those animals, those same animals.

And then lastly, the use of nitrate-rich fertilisers, depending on the way that the fields are planted and the climate can lead to the eutrophication of local river systems and the loss of fishes.

So congratulations if you've got all of those.

And if you've got quite a few of them, well done as well.

Okay, next quick check for you then.

True or false? Changes that affect ecosystems are always created by people.

What do you think? Pause the video and then start it again when you have an answer.

Okay, now you may well have said, "Well, that's false." It's not true that changes that affect ecosystems are always created by people.

But can you give me an answer? Can you explain your answer? Okay then.

The answer we had was that naturally-occurring, sorry, extreme weather events have a dramatic impact on ecosystems. For example, storms, we also had droughts, didn't we? But storms in particular fell trees on which many animals depend.

So well done if you came up with that as your explanation.

Okay, so I've got a practise task for you here.

Let's have a look at it together first.

So question one says, suggest what impacts an extreme weather event might have on an aquatic ecosystem such as a pond.

So let's write something in your own words.

It might be a list of bullet points, or maybe you can give me some linked sentences on that one.

Then question two says, sort the following human activities associated with agriculture into two categories.

One category disrupts ecosystems, the other restores ecosystems. And we've got different activities which I will let you read through there.

Okay? So I'm gonna give you a little bit of time to have a go at those.

And then when you've got your answers, press play on the video and we'll have a look at what I had.

Okay, so question one.

Your answer might include something like this.

So Jun has written us a description of what might be the impacts of an extreme weather event.

In this case, a drought.

Let's read it through.

"A drought could result in aquatic plants drying out.

Fish and other animals could die due to the loss of their habitat as the pond water evaporates.

Due to a lack of food, amphibians might migrate elsewhere, meaning it could take years for the pond's ecosystem to fully recover." And I like that because he's.

Jun's actually thought about the timescale of the impact of that drought.

So it might go beyond the initial weeks and months of the drought itself.

Then you're asked to sort out these human activities into two categories.

The ones that disrupt ecosystems and the ones that restore ecosystems. This is how we've sorted it out.

Is this what your table looks like? So in terms of disrupting ecosystems, we've got the removal of hedgerows to enlarge fields, use of pesticides to protect crops and the use of nitrate-rich fertilisers.

But on the flip side, we've got farmers creating wetland areas, planting hedges, and protecting those wildflower strips around fields.

All helping to restore nature and restore biodiversity and those small-scale ecosystems. Okay, so we have answered how does change affect ecosystems? But we do need to think about how has change affected College Lake's ecosystems? So this is our example, this is our real world example.

But first of all, let's have a look at this photograph.

What do you think are the different components of this ecosystem in the picture? Well, thinking back to what we talked about in the first half of this lesson, you've got the idea of abiotic components.

So this includes the climate, it includes the water in the lakes.

We've got the chalk bedrock we can see in the photograph, that's that light-colored rock or cliff face and the shallow soils that overly that created by the weathering of the rock.

But say, well, in the foreground, mostly we can see the plants, trees, grasses and flowering plants, mosses.

So there's lots of living things in this environment, lots of living components, and we can imagine all the different birds that live in this marshland environment and the fish in the lake.

As well as perhaps the microorganisms, the bacteria, and the fungi in this space.

So College Lake, a home for nature.

College Lake is a nature reserve that has developed on the site of a former chalk quarry.

And this is an example that's useful for us to use to illustrate some of what we've been talking about in the first half of the lesson.

It's located near Pitstone in Buckinghamshire, which is in the southeast of England.

And today it provides lake, marshland and grassland habitats for more than a thousand species of wildlife.

So it's a great resource for nature, it's a home for nature.

But it hasn't always been so biodiverse.

And this is where the change bit comes in.

The site where College Lake is found today was once an arable farm known as College Farm.

But in the 20th century, the site became a chalk quarry and cement works.

So take a look at that photograph.

How much nature do you think was evident in this place at that time? In fact, as an industrial site, it was described as being a white lunar landscape, devoid of nature.

But industry ceased on site in 1991.

And I can hear you saying to me, "Well, what happened next?" Well, today it's a biodiverse site, and here's an example of the chalk grassland on the site.

So what happened next was after the quarry closed the original plan had been to return the site to agricultural use, which you can remember was the original use of the site.

But instead what happened is it's become a public nature reserve.

So today the site provides a range of different natural habitats.

And these habitats provide a much greater variety of species, a home than would've been typical of an arable farm on chalk soil.

How did this chalk pit become a home for nature? You're telling me there's this bit of the story missing, isn't there? Absolutely.

And here's a view from the bird hide at College Lake.

Well, in fact, what happened is the site was abandoned by industry and the deep holes left behind after the quarry closed have long since been flooded.

Flooded by runoff, flooded by rainfall, and also rising groundwater.

The grasses and flowering plants grew and seeded on the banks around the lake.

And a local wildlife trust, so it's the Berks, Bucks and Oxon Wildlife Trust, also known as BBOWT, now manages College Lake.

And one of the jobs it has is to create paths and hides to enable public access.

So it's a site managed by conservationists, but also lots and lots of volunteers as well.

Quick check for you then.

Chalk grassland is one of a number of different types of ecosystem or habitat found at College Lake.

Is that true or false? Pause the video and press play when you think you know the answer.

Yep, you're absolutely right.

This is definitely true, but can we explain why? Have a think about that, please.

And then I'm gonna need your answer in a moment.

Okay, so the site provides lake, marshland, and chalk grassland ecosystems. Well done if you said something like that.

Another check then.

True or false? College Lake is located in the area that has never experienced human impact.

Is that true based on the story? I know you're telling me that's false, but can you explain why? Why is it not true to say it has never experienced human impact? Pause the video, have a think.

How would you phrase it? Well, I can hear you say human activities have had an impact on the site and you would be listing for me agriculture and quarrying, which dramatically changed the site.

But also today, it's actively managed by conservation work, which has helped conserve its varied habitats and enable public access to this local home for nature.

So well done on that.

Let's have a think about change then.

Going back to the idea of change.

Are people bringing about change even today? Well, yes.

As part of the wild life trust management of College Lake, sheep have been introduced to graze the steep banks of these lakes in autumn and winter.

The breed that was selected was a mountainous Hebridean islands sheep.

Okay? So it was a Hebridean sheep that were chosen to graze the banks of this lake environment.

Can you think about why that might be? Well, as Izzy says, "The Hebridean islands are mountainous, so sheep bred there must be well suited to living on steep slopes, just like those steep banks that we've seen that are situated around the lakes at College Lake." We've seen that in the photographs, haven't we? Now what was the impact of introducing sheep to graze the banks of the lakes in autumn and winter, and why was that done by conservationists? So let's have a think about what the impact was.

So sheep were introduced in the autumn and winter of one particular year.

And the following spring, summer, what happened was there was a reduced growth of dominant.

Otherwise dominant grasses, allowing more flowering plants to thrive, such as rare orchids.

Not only that but the knock on effect was that by the summer, a greater range of flowers meant there was more nectar to support a larger population of insects, as well as a greater variety.

So we got more biodiversity on site.

And of course, you'll remember from what we've been thinking about in the first half of the lesson in terms of food chains and food webs, the greater range of insects had an impact on birds.

So birds nesting on site had a greater food source supporting more successful breeding, boosting population numbers.

And in turn, that benefited birds of prey on site.

So College Lake attracts birds like hobby and sparrowhawk, and both populations benefited and their numbers were boosted as a result of greater population of nesting birds.

Okay, now those points have been summarised on my slide here.

And I'd like to check.

Can you reorder these statements to show how changing one component of College Lake's grassland ecosystem affects the others? So just summarise what I've talked you through here.

So you need to look at statements, A, B, C, D and E.

Read them through and put them into the correct order.

Now, if you just want to jot down those five letters in the correct order once you've read the statements, I'm gonna give you a few moments to do that.

And then press play when you think you have an answer.

Okay, and well done to those people who have the answer C, B, D, A and E.

So C, sheep graze the banks of College Lake in autumn/winter.

B, this leads to a reduction in dominant grasses allowing flowering plants to thrive.

Then D, more flowers mean more nectar to support insects.

And then this in turn means that small birds have more food boosting their number.

And then of course, birds of prey benefit, in turn boosting their numbers too.

So congrats if you've got that order.

We're making sense of this now, aren't we, in terms of this real world example? Okay, so I've got a practise task for you now.

I'd like you to explain the impact of grazing sheep on the grassland ecosystem at College Lake in your own words, but I've provided you a few words to use.

I'd like you to include these six words, consumer, population, primary, producer, tertiary and secondary.

Okay, I'm going to give you a few moments to do that.

And then when you've had a go writing that explanation, then restart the video to have a look at the feedback that I'm gonna give you.

Okay, now that was quite a tricky task.

Let's have a look at what we have here.

I'm sure your answer is brilliant, but this is the answer we have.

So let's have a look at how we've used those key terms. As sheep graze the banks of College Lake, grasses are fewer in number.

This means that there's more space to grow, more light, as well as more nutrients in the soil for flowering plants.

That's the main driver for grazing this area with sheep.

With a greater variety of producers, use that term, there is more nectar for insects, also known as primary consumers, to feed on boosting their numbers also.

Those insects are eaten by small birds, and so the small bird population of secondary consumers has grown.

And this supports a larger number of tertiary consumers, such as sparrowhawks at the top of the food chain.

So one small change has really transformed this grassland ecosystem.

Great.

Well, we've covered a huge amount in this lesson.

Let's just have a look at it in summary.

Ecosystems are finely balanced, meaning a change affecting one component may affect many others.

Such changes are brought about by natural events, storms that fell trees, for example, as well as human activities like agriculture and conservation.

College Lake is a nature reserve that includes a range of small-scale ecosystems, one of which we've focused on, which was chalk grassland.

And the introduction of sheep to graze the grassland has reduced the growth of dominant grasses and enables a more biodiverse plant and animal community to thrive.

Well, as I said, we've covered a huge amount and thank you for working along with me really well.