Lesson video

Hello, my name's Mr. Jarvis.

Great to be with you again.

Today we're going to be looking at a lesson from the unit, maintaining biodiversity and human impacts.

We're going to be looking at examples of human interactions with ecosystems, including the use of peat.

By the end of today's lesson, you should be able to describe some examples of human interactions with ecosystems, which include the use of peat, eutrofication, and the introduction of non-indigenous species.

There are four key words to today's lesson.

They are; biodiversity, fertiliser, eutrofication, and indigenous species.

You can pause the video at this point if you want some time to read through the definitions, but we will go through them as we go through the lesson.

Today's lesson is broken down into three parts.

First of all, we're going to look at humans' use of peat.

Then we're gonna move on to eutrofication.

And finally, we're going to look at the impact of introducing new species to a habitat.

So if you're ready, let's get started with our first section, which is all about humans use of peat.

Humans help to conserve biodiversity on earth in a number of ways.

We maintain habitats through conservation activities.

For example, here in a wild flower meadow.

We have captive breeding programmes in zoos.

Here's a picture of a tortoises being fed by a zookeeper.

And we have gene banks, they're specific places where seeds and genetic material is conserved for future generations.

However, many ecosystems are negatively impacted by interactions with humans.

Humans have destroyed large areas of peat bogs and peat lands.

Peat bogs are large areas of water logged land.

They have really acidic soil.

And you can see what a peat bog looks like in the picture on the screen.

Peat bogs contain peat, and that's a resource that's useful to humans.

Peat can take thousands of years to form.

It's made of dead plant material that builds up in the soil.

That plant material can't decay completely, as the conditions in the peat bog are both acidic and lack oxygen.

And we call conditions where there's a lack of oxygen anaerobic.

So here's a check.

What conditions in peat bogs prevent plant material from completely decaying? Is it, A-peat bogs work alkaline, B-peat bogs are cold places, C-peat bogs are acidic, or D-peat bogs have a lack of oxygen? I'll pause for a few seconds and then we'll check your answer.

The correct answers are C and D.

The conditions that prevent the plant material from decaying are because the peat bogs are acidic and they have a lack of oxygen.

IE, they're anaerobic.

Well done if you got that.

Peat bogs are unique ecosystems. They have a rich biodiversity.

And plants and animals that live in peat bogs have adaptations that help them to survive in acidic conditions.

And acidic conditions often mean that the soils lack nutrients.

Carnivorous plants get around this by trapping our flies and other insects, sometimes even small amphibians, through either having sticky leaves or having the trumpets that insects can't get back out of.

And as these organisms that are trapped either decompose or are broken down by the plant, they release the the minerals and the nutrients back into the soil to help to improve the conditions for these plants to grow in.

Peat bogs are a natural storer of carbon.

During photosynthesis, plants absorb carbon dioxide from the atmosphere.

And the carbon dioxide is incorporated into carbon containing compounds in the plant.

For example, carbohydrates.

When the plant dies, these carbon compounds don't decompose because of the acidic and anaerobic conditions, and that's when peat is formed.

Peat is really useful for humans.

Peat is used by gardeners to improve the soil to grow food and flowers.

And peat is also burned for fuel to heat homes.

When peat is burned, the carbon it contains is released back into the atmosphere, and this increases the carbon dioxide concentration of the atmosphere.

The destruction of peat bogs also means the destruction of the organisms that depend on them, and that destruction therefore contributes to climate change through the increased concentrations of carbon dioxide, and reduces biodiversity because habitats are being destroyed.

Peat is being used more quickly than it's being made.

70% of the peat sold in the UK is in the compost that's sold to gardeners.

And the UK government has put plans in place to ban the sale of compost to gardeners if it contains peat.

Alternative composts can be made from bark, garden waste, and even coconut husks.

And you can see some different examples on the screen.

The government has set out plans and provided finances to restore, manage, and protect peat lands because of their rich biodiversity.

And here is one such area, the Great North Bog.

This is helping to tackle threats of climate change and declining biodiversity.

The Great North Bog is a large area of protected peatland in Northern England.

So here's a check.

Which of the following processes takes place slowly in peat bogs and peatlands? Is it A-photosynthesis, B-decomposition, or C-respiration? I'll give you a few seconds, and then we'll check your answer.

The correct answer is B, decomposition.

Well done if you got that right.

Humans use resources from the environment.

One resource that's used is peat.

Peat bogs are destroyed to remove peat.

I'd like you to give two examples of how humans use the peat that's removed from peat bogs.

And then secondly, I'd like you to explain how the removal of peat is harmful to the environment.

You'll need to pause the video at this point, write down your answer, and then when you're ready to check your answers, press play, and we'll see how well you've done.

Good luck.

So first of all, I asked you to give two examples of how humans use peat that's removed from peat bogs.

Your answers should have been, gardeners use compost to grow plants and crops, and humans burn peat as fuel, for example, for heating or cooking.

Well done if you got those.

Next, I asked you to explain how the removal of peat is harmful to the environment.

You may have included that decay or combustion of peat releases carbon dioxide back into the atmosphere, and that increases global warming, and contributes to climate change.

And clearing large areas of peat bogs means that species no longer have a habitat in which they can survive.

This means that biodiversity decreases.

Well done if you got that.

That brings us to the second part of today's lesson, which is all about eutrofication.

So if you're ready, let's move on.

Farmers want to make sure that they maximise crop growth and yield, and this is so that farmers can feed the ever increasing human population.

Farmers add fertilisers to the soil to make sure it stays fertile for a long period of time.

Fertilisers contain all of the mineral irons that plants need to grow well, which include nitrates.

Farmers use both manmade fertilisers, and also natural fertilisers such as manure.

Organic products are grown without the use of manmade chemicals.

Nitrates are minerals that are essential for plant growth.

And the plants take the nitrates from the soil using their roots, and they then use those nitrates to help make proteins.

That helps to improve the crop yield, because proteins help organisms to grow and repair.

So here's a check.

Why do farmers use fertilisers? Is it A-to prevent pests from eating crops, B-to make sure that seedlings germinate, C-to ensure that soil contains the minerals that plants need for healthy growth, or D-to ensure that plants get the water that they need? I'll pause for a few seconds, and then we'll check your answer.

The correct answer is C.

Farmers use fertilisers to ensure that the soil contains the minerals that plants need for healthy growth.

Well done if you got that.

Overuse of fertilisers, including organic fertilisers such as manure, can impact environments.

And this is because minerals, particularly nitrates, get washed into rivers and lakes, and that causes algae to grow quickly, and forms a blanket which eventually blocks out the light from the plants that are living underneath.

And without the light, the water plants are unable therefore to photosynthesize, and eventually die.

There's a large increase in the number of microorganisms that then have to decompose the dead plants.

And these microorganisms respire and remove lots of oxygen from the water.

And this reduces the oxygen levels, and causes other organisms such as fish to die.

And in turn, they are decomposed by microorganisms, removing even more oxygen from the water.

And eventually the oxygen levels fall so low that the water can no longer support any aquatic animals.

And that's what we call the process of eutrofication.

Eutrofication can be reduced by using less or targeting the use of fertiliser to prevent nitrates and other minerals from being washed into water.

By constructing areas of wetlands that help us to act as filters and absorb those minerals from the water that's being washed away and towards the rivers.

Or by treating affected bodies of water through oxygenation or removing algae.

And here's a picture of some paddle wheel aerators and pumps that are used to help oxygenate water.

Here's a check.

What causes eutrofication? Is it A-a buildup of pollutants in the atmosphere, B-the use of pesticides in farming, C-the use of fertilisers in farming, or D-increasing atmospheric carbon dioxide concentration? I'll pause for a few seconds, and then we'll check your answer the correct answer is C.

The use of fertilisers in farming is what causes eutrofication.

Well done if you got that.

So here's a task.

Farmers use organic and artificial fertilisers to help them provide enough food to feed the increasing human population.

Fertilisers provide plants with minerals such as nitrates that help them to grow well.

I'd like you to explain why using too much fertiliser can have a negative impact on aquatic habitats.

You'll need to pause the video, write down your answer, and then we'll check to see how well you did.

Good luck.

So, how did you find that? I asked you to explain why using too much fertiliser can have a negative impact on aquatic habitats.

You might have included the following points.

Minerals such as nitrates get washed into aquatic habitats, and that can lead to eutrofication.

Eutrofication is where plants such as algae grow really quickly.

This blocks out light from plants below the surface, and prevents them from photosynthesizing, and eventually those plants will die.

Microorganisms and decomposers break down the dead plants.

These organisms use lots of oxygen from the water to respire.

Animals in the water then don't have enough oxygen to survive, and biodiversity is reduced.

Well done if you've got some or all of those answers correct.

That brings us to the third part of today's lesson, which is all about the impact of introducing new species to a habitat.

So if you're ready, let's move on.

Most of the organisms we see around us are what we call indigenous species.

And that means that they occur naturally in the ecosystem.

As more humans travel globally, there's been an increase in the introduction of organisms from one part of the world to another.

Here on the screen we've got some of the UK's indigenous or native species.

Some species are intentionally introduced.

Grey squirrels were introduced into the UK in the late 1800s in many stately homes.

And the grey squirrel is well adapted to live in the UK.

It was able to escape from those stately homes and outcompete the indigenous red squirrel.

The grey squirrel is an example of an invasive species, a species which outcompetes the indigenous species.

Japanese knotweed was introduced in the UK in the 1850s as an ornamental garden plant.

And the plant grows rapidly from rhizomes or roots that it produces really quickly in the summer months.

And those roots are so strong that it can damage house foundations.

It's kept in check in its native Japan by a large native ecosystem of vigorous growing plants such as bamboos, grasses, and lots of natural invertebrate species which feed on it.

However, in the UK, it outcompetes other species, and that reduces biodiversity in the habitat.

And there's no native species that feed on the plant, and so it grows unchecked.

Chinese mitten crabs are another example of an introduced species.

They're transported by ships.

And so here's a picture of a Chinese mitten crab.

They're native to southeast Asia.

The first UK record was in London in 1935, but they're now found around the UK coast.

The crabs can damage river banks, and outcompete indigenous species.

They also can block water outlets and damage fishing nets.

The increase in human global travel can have huge consequences for humans' health, food production, and biodiversity.

Travel is really important in the spread of diseases which infect humans or other species.

And half of the emerging pest plants and diseases are attributed to human travel.

Introduced species can quickly become invasive, as we saw with the grey squirrel.

They can spread quickly as a result of having no native predators, no native parasites or diseases, no native competitors that would normally limit their population size.

And here's another example, the red signal crayfish.

It's an invasive species in the UK.

Invasive species can have a large negative impact on biodiversity in a habitat.

And some countries have strict laws about introducing non-indigenous species.

So here's a check.

A species which is introduced and now competes an indigenous species is called a, A-introduce species, B-a native species, or C-an invasive species? I'll pause for a few seconds, and then we'll check your answer.

The correct answer is C, it's an invasive species.

Well done if you got that.

That brings us to our final check for today's lesson.

The red signal crayfish was introduced into the UK from America in the 1960s.

And since its introduction, the number of indigenous white clawed crayfish have declined.

Explain how the introduction of the red signal crayfish may have led to the decline in the white clawed crayfish numbers.

You'll need to pause the video at this point.

Write down your answer.

And then when you're ready, press play, and we'll check your answer.

So I asked you to explain how the red signal crayfish introduction may have led to the decline in the white clawed crayfish numbers.

Some possible explanations include that the red signal crayfish are predators of the white clawed crayfish.

There's competition between two species for the same resources, for example, food and shelter.

And it might be that the red signal crayfish outcompetes the white clawed crayfish for these resources.

It might be that the red signal crayfish may carry parasites or diseases which have a greater impact on the indigenous white clawed crayfish species.

All of the above would result in the population of the white clawed crayfish reducing in number.

Well done if you got any of those answers.

That brings us to the summary of today's lesson.

We've seen that humans positively interact with ecosystems by protecting habitats and conserving biodiversity.

Humans also negatively impact ecosystems. The use of peat as a fuel and to improve the soil for flowers and plants has destroyed peat bogs.

And that's reduced biodiversity in those ecosystems. Farmers use fertilisers to help produce food for the increasing human population, but it's led to eutrofication and a reduction in biodiversity.

The introduction of species from other parts of the world has seen some indigenous species outcompeted, and that has reduced biodiversity too.

And by protecting peat bogs, and reducing peat use, and through careful use of fertilisers, human impacts on ecosystems can be reduced.

Thank you for learning with me today.

It's been great learning with you as always.

And I look forward to seeing you again sometime soon.

Bye-bye for now.