Lesson video

Hello and welcome to today's lesson in the unit maintaining biodiversity into human impacts.

My name's Mr. Jarvis and I'm gonna be taking you through today's lesson.

Today, we're going to be looking at negative human interactions with ecosystems and impacts on biodiversity.

By the end of today's lesson, you should be able to describe negative impacts of humans on biodiversity in different ecosystems. Today, there are five key words.

They are biodiversity, urbanisation, deforestation, greenhouse gas, and climate change.

The definitions of those words are on the screen now.

You can pause the video to read through them or we'll cover them as we go through today's lesson.

Today's lesson is divided into two parts.

First of all, we're going to look at the impact of humans on ecosystems, and then we're going to look at the changing climate and how that impacts on biodiversity.

So if you're ready, let's get started with our first part, which is all about the impact of humans on ecosystems. Biodiversity is the range of different living organisms that live in a place.

The higher the number of different organisms that live in the ecosystem, the greater the biodiversity.

So here's an example.

Arctic habitats don't have a high biodiversity.

It's a really harsh environment and very few species can live there.

On the flip side, coral reefs have a really high biodiversity.

Coral reefs contain lots of food, shelter, and places for different species to reproduce.

And you can see the difference in the biodiversity of the two habitats just by looking at the pictures on the screen.

The coral reef has a huge number of different species, so it has a high biodiversity.

If one species is removed from an ecosystem, it can impact all of the other species, and the fewer the species there are within an ecosystem, the greater the impact there is when a species is removed.

So for example, here's a picture of a red panda eating bamboo.

The loss of bamboo habitats is causing the red panda to become endangered because there are fewer species within that ecosystem, so removing bamboo actually is having an impact on the number of red pandas.

When an ecosystem has a high biodiversity, the impact of removing one species is less, and that's because the other species will fill the niches or gaps left by species that have been removed.

Organisms rely on each other.

They are interdependent.

Interdependence means where species rely on each other, and that includes humans.

Humans need high biodiversity to survive because we rely on organisms for food, materials, and medicines.

And here's an example.

Coffee beans contain caffeine.

Chemicals from plants form the basis of many human medicines.

Caffeine is one of them.

However, human activity results in biodiversity being reduced.

So why is having a high biodiversity important for humans? Is it, A, humans need to be able to grow large fields of crops such as wheat to provide food? Is it because, B, humans rely on many different organisms for food, medicines, and resources such as materials? Or is it C, humans eat a wide range of foods? I'll pause for a few seconds and then we'll check to see if you've got the right answer.

The correct answer is B.

Having a high biodiversity is important for humans because we rely on many different organisms for food, medicines, and resources such as materials we're building.

Well done if you got that.

The human population has increased significantly.

I've plotted the number of humans, the population of humans on a graph, and you can see that human population has increased significantly in the last 2000 years.

From 10,000 BC to 1,700 BC, the human population grew by about 0.

04% each year.

The black death pandemic is shown in this graph.

It killed 25% to 50% of all humans in Europe.

And you can see there's a kink in the graph.

Since 1800, the population of humans has increased dramatically.

It's moved from that 0.

04% increase each year to something much more significant, and you can see that the population is doubling really quickly.

1975 saw the population just over 4 million.

By 2000 is over six, and it's estimated to reach 10 billion people by 2058.

As the human population increases, our activity often has negative impacts on biodiversity, and these include increased land use for resources such as growing food and fuels.

The picture on the screen shows a rice paddy field.

Rice is one of the main staple foods that humans eat, but the problem is that it's large expanses of one single producer, and that limits biodiversity.

Increased urbanisation has an impact on biodiversity too, as we destroy habitats to make way for buildings and roads and transport systems and increased production of waste and pollution has a big impact on biodiversity because of the way that we get rid of our waste and because of the chemicals that we use in the environment.

So here's a check.

Why is biodiversity decreasing as the human population increases? Is it, A, ecosystems are being destroyed as humans use land to grow single crops for food? Is it B, ecosystems are being protected as nature reserves for humans to visit and relax? Or is it C, ecosystems are put under pressure as a result of pollution and waste produced by humans? I'll pause for a few seconds and then we'll check your answer.

The correct answers are A and C.

Biodiversity is decreasing as the human population increases because ecosystems are being destroyed as humans use more land to grow single crops for food, and the ecosystems are put under pressure as a result of pollution and the waste that humans produce.

Well done if you got both of those answers.

There is a significant impact on how humans use land as the population grows.

Land has been used for farming to provide food for the population, and crops are grown in large field.

That means that hedges that border those fields are often removed and the hedges are really important habitats for organisms to live in.

Quarries have dug up large areas as humans mine for rocks and mineral ores.

And here's a picture of a limestone quarry.

Look at the picture of the big dumper truck that's on the screen and show you the scale of how much and how big this area is.

There's significant impact on how humans use land due to deforestation that clears land for human activities.

And fossil fuels are extracted from the earth and used to produce plastics, and plastics of course are one of the biggest pollutants of our land.

Another example is how more land is used for building houses, factories, and roads as more people start to live in urban areas.

And that's what we call urbanisation.

Here's a picture of Tokyo.

It's an area of high urbanisation and you can see the densely packed towers of houses and also all the shops and roads that make up Tokyo City.

All of these activities destroy the natural habitats of other organisms and reduce biodiversity.

More humans produce more waste and processing waste, even recycling takes up land, but a lot of our human waste ends up in landfill and toxic chemicals can be released from that waste into the soil.

And of course, much of that waste takes absolutely ages to break down.

Things like plastics that are not biodegradable end up in landfill and stay there for hundreds if not thousands of years.

Human activities release chemicals into the environment and these can pollute the air, the water, and the land in different ways.

For example, pollution from burning fossil fuels can cause acid rain.

And where acid rain falls onto habitats, it can, if it's strong enough, kill the organisms that are living there.

Fertilisers and pesticides can pollute water and build up in food chains, and toxic chemicals can pollute the soil and kill organisms. Here's the picture of Chernobyl in the Ukraine.

It was a nuclear disaster where the reactor exploded and contaminated land for miles around with radioactive waste, and even now, the levels of radioactivity some 40 years on almost are too high for many organisms to live there.

So here's a check.

Why does human land use reduce biodiversity? Is it A, that it destroys habitats and the organisms within them? B, the use of the land means no other species can live there? Or C, it creates additional habitats for plants and animals? Again, I'll pause for a few seconds and then we'll check your answer.

The correct answer is A.

Humans' land use reduces biodiversity because it destroys habitats and the organisms that live within them.

Well done if you've got that.

Let's move on to our first practise task.

There are two parts to this task.

First of all, the human population is increasing and more household waste is being produced.

Describe one way that household waste affects our environment.

And secondly, farming techniques have changed in the last 100 years, fields have been made larger and hedgerows removed.

Describe why more land is used for farming and how an increase in farming has decreased biodiversity.

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 to see how well you've done.

Good luck.

So how did you find that? I hope it wasn't too tricky.

Let's check your answers and see how well you've done.

So first of all, I said that the human population is increasing and more household waste is being produced.

Describe one way that household waste affects our environment.

And your answer might have included that more waste could increase pollution.

This may have a negative impact and negative effect on organisms and reduce biodiversity within the environment.

Or you could have said that more waste means that it will take more land to process that waste, and there will be more land needed for landfill, and habitats will again be destroyed, and that will reduce biodiversity.

Well done if you got either of those in your answer.

The second question talked about farming techniques and how they've changed over the last 100 years, fields having been made larger and hedgerows removed.

I asked you to describe why more land is used for farming and how an increase in farming has decreased biodiversity.

Here are some answers again that you might have included.

An increasing population needs more foods, so more lands needed to grow crops or to raise animals.

And large machinery has seen an increase in the size of the fields.

Habitats have been destroyed to provide land for crops and animals.

Hedgerows have been cut down to make larger fields and chemicals such as pesticides will kill organisms, and the loss of habitats and that increased use of pesticides will reduce biodiversity.

Well done if you've got either of those in your answer.

That brings us to the second part of the lesson, which is all about the changing climate and biodiversity.

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

Earth is kept at an ideal temperature for life to exist, and this is because of something we call the greenhouse effect.

The greenhouse effect is a good thing and it is a good thing because it keeps the earth at a temperature where life can exist.

Here's a picture of the sun and the earth, and the earth is surrounded by the atmosphere.

Infrared radiation from the sun, sometimes called IR radiation passes through the atmosphere and is absorbed by the earth's surface.

We feel that infrared radiation on a warm sunny day.

We can feel how the radiation is warming us and the planet.

Some of that infrared radiation is reflected back out into space and some of the infrared radiation is absorbed and re-radiated from the earth's surface.

So in effect, the earth's surface is warming up and that's giving out that heat into the atmosphere.

Greenhouse gases absorb that radiation and that's then radiated in all directions and that warms the lower atmosphere.

So here's the illustration of that, that the earth is giving out that infrared radiation and then that's scattered throughout the atmosphere.

And it's done by the greenhouse gases.

Greenhouse gases are the gases that basically radiate and keep the atmosphere warm.

And those gases include water vapour, carbon dioxide, and methane.

And it's that natural phenomenon that we know is the greenhouse effect.

So here's a check.

Which of the following are examples of greenhouse gases which are found in the Earth's atmosphere? A, oxygen, B, methane, C, nitrogen, D, carbon dioxide.

I'll pause for five seconds and then we'll check your answer.

The correct answer is B, methane, and D, carbon dioxide.

Well done if you got that right.

One of the others that isn't in that list is water vapour.

Here's another.

True or false? The greenhouse effect is a good thing.

And then justify your answer.

Is it because A, the greenhouse effect is causing Earth's temperature to increase? Or B, the greenhouse effect is essential to maintain the planet to temperature that allows life to exist.

Again, I'll pause for five seconds and then we'll check your answer.

The correct answer is that it's true.

The greenhouse effect is a good thing and that's because B, the greenhouse effect is essential to maintain the planet to temperature that allows life to exist.

Well done if you've got both.

Carbon dioxide levels in the atmosphere are changing.

Here's a graphic.

Here's some carbon dioxide in the atmosphere.

The carbon dioxide is taken in by trees and other plants via the process of photosynthesis.

We're burning fuels both in our cars and through power stations and organisms give out lots of carbon dioxide through the process of respiration, and that keeps the levels of carbon dioxide in the atmosphere in balance.

However, humans have increased carbon dioxide levels in the atmosphere by burning more and more fossil fuels.

And so that's adding more carbon dioxide into the atmosphere.

We're also finding that through deforestation that we've cut down the number of producers that take in carbon dioxide from the air via the process of photosynthesis.

And so overall, we've not got a balance of carbon dioxide in the atmosphere.

We are putting more carbon dioxide into the atmosphere than photosynthesis and our producers are able to take back out.

And the evidence is suggesting that human activities are contributing to climate change.

And this is partly as a result of the increase in carbon dioxide in the atmosphere, which is changing the weather patterns.

That's what climate change is, a long-term change in the weather patterns.

So let's look at the data from Mauna Loa in Hawaii.

This has been taken over a large number of years back from the 1960s and we can see that that it shows that carbon dioxide concentrations in the atmosphere are steadily over time.

It also shows yearly fluctuations.

In the summer, plants grow and take in CO2 and in the winter, the plants die, they decompose, and that releases CO2 back into the atmosphere and that explains for the wiggly line that we get in the graph.

Another greenhouse gas, methane, also has been increasing in the atmosphere and methane is produced by microbes in the digestive system of cows.

Humans farm cattle and that increases the amount of methane gas that's released into the atmosphere because we've got high populations of cattle and sheep that release methane into the atmosphere.

Increasing the population of cattle will also release the increase levels of carbon dioxide produced by respiration.

Methane in the atmosphere is also increased through growing rice for humans to eat.

Here we've got a picture of a paddy field and rice is one of the main foods, one of the staple foods of humans.

The PADI fields contain methane emitting bacteria and they're a source of atmospheric methane gas.

Landfill sites don't just take up the land.

They are also another source of methane.

Bacteria which decompose organic matter release both methane and carbon dioxide into the atmosphere.

So here's a check.

How can humans change their behaviour to release less methane into the atmosphere? Is it A, they eat more rice and less meat? B, they eat more meat and less rice? C, they ensure that all waste is put into landfill? Or D, they reduce how much meat is eaten? I'll pause for a few seconds and then we'll check the answers.

The correct answer is D, reduce how much meat we eat.

If we reduce the amount of meat that we eat, we reduce the population of cattle that we farm and that reduces the amount of methane being put into the atmosphere.

Well done if you've got that.

The greenhouse effect is important in maintaining the optimum temperature for life to exist on earth.

And as the levels of greenhouse gases increase in the atmosphere, the greenhouse effect increases too.

So the more methane, the more carbon dioxide, and the more water vapour we put into the atmosphere, the greater the greenhouse effect becomes because more infrared radiation is re-radiated back into the earth.

And that's causing a really small but significant increase to the surface as temperature of the earth.

There's evidence to suggest that the earth's surface temperature is increased by not 0.

5 degrees centigrade or celsius since the 1970s.

And that doesn't sound very much, but an increase in less than three degrees may significantly speed up climate change and cause sea levels to rise due to melting of polar ice.

Climate change may give rise to several severe and unpredictable weather events such as really intense storms, more droughts, and more rainfall and floods.

As the earth's surface temperature increases, the ocean temperature increases too, and that causes evaporation and releases more water vapour.

We know that water vapour is also a greenhouse gas, so the more water that evaporates, the more greenhouse gases there are in the atmosphere, the increase in temperature of the water also reduces the quantity of carbon dioxide that can be dissolved in the oceans.

And so some of the carbon dioxide from the oceans is released into the atmosphere and that further increases atmospheric carbon dioxide levels and that increases the greenhouse effect too.

So here's a check.

Increasing ocean temperatures have led to, A, more CO2 dissolved in the oceans.

B, the same amount of CO2 dissolved in the oceans.

Or C, less CO2 dissolved in the oceans.

I'll pause for a few seconds and then we'll check your answer.

The correct answer is C.

Increasing ocean temperatures have led to less CO2 being dissolved into the oceans.

Well done if you got that.

As the earth gets warmer, all species including humans will be impacted.

This is because habitats will be lost as areas become flooded due to rising sea levels.

As the climate changes where organisms can survive will change.

Some organisms may even become extinct because of that loss of habitat.

And here's a picture of some polar bears on floating ice.

As the ice polar caps are melting, the polar bears are finding it more and more difficult to hunt for food and to have a habitat that helps them to survive.

And migration patterns will change as climates become hotter or colder, which affects the availability of food.

There's strong evidence that the climate is changing as a result of human activity and climate change will result in many organisms no longer being adapted to their surroundings and they may become extinct.

If producers are not able to survive, all of the organisms within a food chain will be impacted, and the planet's biodiversity will reduce significantly.

So here's another check.

Why some species become extinct as a result of climate change? Is it A, they might not adapt quickly enough to warmer temperatures? B, they might not adapt quickly enough to colder temperatures? C, the organisms they rely on for food might become extinct? Or D, changes in the habitat mean that it's no longer providing the species with a place to shelter and reproduce? I'll pause for a few seconds and then we'll check your answer.

Did you get the answer right? The correct answer is all four answers are correct.

All of those reasons are examples of why a species might become extinct as a result of climate change.

They might not adapt quickly enough because of the warmer or colder temperatures.

The organisms they rely upon for food might become extinct or there may be changes in the habitat, which means that it no longer provides a place that shelters them, that provides them with food, and enables them to reproduce.

Well done if you got that right.

Let's move to our second practise task.

The graph shows carbon dioxide concentration in the atmosphere from 1990 to 2015.

I'd like you to first of all describe two patterns in the graph.

And then secondly, name two human activities that affect the concentration of carbon dioxide in the atmosphere.

And thirdly, what impact could increasing carbon dioxide levels have on biodiversity? And explain your answer.

You'll need to pause the video, write down your answers, and then when you're ready, press play and we'll check to see how well you did.

Good luck.

So let's go through the answers.

I hope you didn't find it too tricky.

First of all, I asked you to describe two patterns that you can see in the graph.

Well, first of all, there's an overall increase in the levels of carbon dioxide.

The graph is steadily going upwards as a trend.

And secondly, there are yearly peaks and troughs of carbon dioxide concentration.

We talked about how that was as a result of plants taking in carbon dioxide through photosynthesis during the summer, and as the plants die and decompose, giving out carbon dioxide in the winter months.

Secondly, I asked you to name two human activities that affect the concentration of carbon dioxide in the atmosphere.

They are combustion and deforestation.

Well done if you got those.

The third question was what impact could increasing carbon dioxide levels have on biodiversity? And I asked you to explain your answer.

You might have included the following, increasing carbon dioxide levels will cause more global warming.

The temperature of the earth's surface will therefore begin to increase, and that will cause climate change.

So for example, more storms, droughts, and floods.

Climate change may destroy habitats through things like floods, droughts, might kill plants and remove foods for consumers, and temperature rises may melt ice and cause additional floods.

There may be changes in migration patterns of animals, and all of the factors are likely to reduce the biodiversity of ecosystems. Well done if you've got any of those points in your answer.

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

We've seen that high biodiversity is important for humans as we rely on lots of organisms for food, resources, and medicines.

Human population is increasing rapidly and we are using more land for resources such as food and fuel and for urbanisation, building large population areas, and roads, and other infrastructure.

As more land is needed, habitats are destroyed.

For example, by deforestation and as we destroy more and more habitats, biodiversity is lost.

Greenhouse gases such as carbon dioxide and methane and also water vapour keep earth at temperatures which help to sustain life.

And that's the third process called the greenhouse effect.

As the greenhouse gases increase as a result of human activity, the Earth's temperature increases further.

And this results in climate change.

And it's really important to stress that even very small increases in temperature of the Earth's surface can have a significant change on the climate and on climate change.

And climate change will mean that some organisms are not able to survive and this will reduce biodiversity.

Well, thank you for learning alongside me today.

It's been great as always learning with you and I look forward to seeing you all again soon.

Take care.

Bye-Bye for now.