Lesson video

This lesson is called, "Climate Change and Biodiversity, forests and oceans", and is from the unit, "Maintaining biodiversity and human impacts." Hi there, my name's Mrs. McCready, and I'm here to guide you through today's lesson.

So, thank you very much for joining me today.

In our lesson today, we're going to describe the importance of forests and oceans in combating climate change, and the impact of human activities on forests and oceans.

Now, in our lesson today, we're gonna come across a number of keywords, and they're listed up here on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

Now in our lesson today, we're going to start off by looking at climate change and the effect on forests, before we consider climate change, and the effect on the oceans.

So, are you ready to go? I certainly am, let's get started.

There are many different types of forests, and I'm sure you probably know that already.

For example, tropical rainforests, that possibly was one of the first ones which came to mind.

Temperate forests like the ones we have here in the UK, and then other various forests such as mangrove forests, maybe you visited those in southern Florida, for instance.

These different forests are all examples of very complex ecosystems with many different organisms, plants, animals, and many other different kingdoms of organisms besides, all living together in a complex ecosystem.

There are many different trees and other plants coexisting within a forest.

And this rich habitat supports many animals and fungi, to live throughout it as well.

Now, undisturbed forests support many, as yet undiscovered species of plants and animals.

More than 8,600 new plant species have been discovered since 2020 alone, and, many more forests have yet to be fully investigated, and their treasures unearthed.

Now, forests have an important role in managing climate change, because trees capture carbon dioxide from the atmosphere, and store it as biomass via the process of photosynthesis.

So the carbon dioxide in the atmosphere is being converted into plant matter, through the photosynthesis process, and stored therefore, within the plants.

Therefore, forests are carbon sinks, places where carbon is stored, and forests acting as carbon sinks are very important, because they store a quarter of the world's carbon emissions.

Now, as human activities release lots of carbon dioxide into the atmosphere, the role of trees and therefore forests, within this process to manage, and mitigate the activities of humans, will be really, really important.

Forests have other roles as well.

For instance, they stabilise water flow through the landscape, which prevents flooding and soil erosion as well.

So, forests provide a very complex number of different roles within ecosystems. So, which of the following are natural functions of forests? Carbon capture and storage, habitat creation, or providing material for furniture.

I'll give you five seconds to think about it.

Okay, so hopefully you have identified that carbon capture and storage, and habitat creation are both natural functions of forests.

Well done.

Now in 1900, 48% of the Earth's surface was covered with forests, but by 2018, this had reduced to 38%, a 10% loss in just over a century.

Now, deforestation is the destruction of forested areas, the cutting down of many, many trees.

And, once forests have been cut down, it takes a very long time, several decades at least, to regrow that rich biodiversity and habitat, that was found within the ecosystem of the forest.

Remembering that there are many organisms that are living within the forest, not just the trees.

Now, deforestation is happening at an increasingly fast rate, and a very alarming rate at that.

According to data from the Global Forest Watch, between 2001 and 2023, the UK lost 15% of the forest cover, that existed in the year 2000.

And that is just in that short period alone.

Nevermind all the deforestation that had happened up to that point.

Even more alarmingly, in 2019, the Amazon rainforest lost the equivalent of one football pitch of forest every minute, due to accelerating deforestation, and that rate still persists.

So, deforestation is causing huge destruction to many, large areas of forest, across the globe.

Now, there are several drivers for deforestation, and agriculture is the biggest reason for it.

Now, agriculture takes the form of growing crops, or grazing livestock.

So, forestry is cleared, so that crops can be grown or livestock can be grazed.

Now, sometimes the crops that are grown, are being grown in order to feed the livestock that are grazing.

So sometimes, twice as much forest is deforested, in order to provide twice as much land for crops, and for animal grazing.

Therefore, reducing meat consumption, and changing our diets, is a very important way, that we can have over influencing, and reducing the level of deforestation that is happening across the globe.

Now, when forests are deforested, when forests are cleared, a technique called slash-and-burn is often used.

Now this is a rapid, but quite a final way of destroying a forest.

First of all, slashing happens, and this involves clearing trees using heavy machinery, to fell trees rapidly and decisively.

And then, burning methods follow after that.

And this causes the complete destruction of the forest, and all the other organisms that were living within that space.

This method wholly destroys forests, and it also releases great quantities of carbon that was stored within the biomass of all the organisms that were living within the forest, back into the atmosphere, particularly through the burning process.

So, slash-and-burning, and deforestation, are enormously consequential for climate change, and the progress of that on earth.

Another cause of deforestation is forest fires, and this is becoming an increasing cause of deforestation.

In fact, in 2023, 43% of forest loss that year, was caused by forest fires.

So, nearly half of the forest that we lost in 2023, was lost due to forest fires.

Now, forest fires are becoming more common, because the climate is changing, and as the climate changes, the risk of wildfires is increasing.

This is because extreme heat, extended periods of drought and high winds, are all becoming more common, and these all increase the risks of wildfires, and how quickly and far they spread.

So, which of the following is a cause of deforestation? A, slash-and-burn land clearance.

B, increasing carbon dioxide emissions, or C, illegal logging.

I'll give you five seconds to think about it.

Okay, hopefully you chose both A and C, as causes of deforestation.

Well done.

Now I've already said that forests act as carbon sinks.

They absorb carbon dioxide from the atmosphere through the process of photosynthesis, and store it within their matter for long periods of time.

So, destruction of forests, reduces the ability for a forest to be a carbon sink.

And forest destruction comes in lots of different ways.

Fragmenting a forest, by dividing it up into smaller pieces which are unconnected to each other, plus other processes such as logging, and obviously forest fires, as we've already discussed, all contribute to deforestation, and the reduction of a forest, in its ability to be able to store and absorb carbon from the atmosphere.

So, deforestation destroys the ability for a forest to absorb carbon out of the atmosphere, and store it for a long time, therefore, reduces its ability to act as a carbon sink.

But, what, if anything, can we do to halt this damage? Well, firstly, we need to protect the forest that we still have.

We can protect forests against illegal logging, land use changes, and forest fires.

So, we can essentially prevent forest land from being converted and destroyed.

We also need to give good reason for reducing deforestation in the first place.

So, for instance, land which is being converted from forest to agricultural land, needs to stop.

But, in order for that to stop, we need humans that need to find more efficient ways of growing food, so that we can shift away from having to grow animals to feed us, and towards growing a more plant-based diet, which is much more efficient, requires less land to grow, and therefore, will have a much smaller impact on forest land.

We also need to replant forest that we have already lost.

Now, as I've already said, this is going to take a long time for forests to regrow, and establish the great biodiversity and richness, that is present within the already established forest ecosystems. But we certainly need to try.

So, planting trees to expand and repopulate existing forests is certainly one other thing that we need to do, in order to restore forest land and reduce deforestation.

So, which pupil suggests a suitable approach for reducing deforestation? Lucas says, "We should ban wooden furniture because this would reduce logging." Alex says, "If we stopped using paper and used our computers instead, trees wouldn't get cut down." And Aisha says, "We should all reduce the amount of meat we eat, to stop forests being converted into farms." But who is suggesting a suitable approach for reducing deforestation? I'll give you five seconds to think about it.

Okay, so hopefully you've chosen Aisha, as suggesting the most suitable approach.

Well done.

So what I'd like you to do now, is to consider this scenario.

In the pictures you can see, that deforestation is taking place on an enormous scale in Brazil.

The photographs show satellite images of deforestation, in Brazil, in a 15 kilometre by 45 kilometre area, over the period of 14 years.

So, what I'd like you to do is, by considering those photographs, describe why forests are important in managing climate change, suggest why the forests are being deforested, and suggest how deforestation could be reduced, and prevented.

So, pause the video and come back to me when you are ready.

Okay, let's see what you wrote.

So firstly, I asked you to describe why forests are important in managing climate change, and you should have said that, trees act as carbon sinks, because they absorb carbon dioxide from the atmosphere, and store it for a long period of time.

Then I asked you to suggest, why the forests are being deforested, and you should have said that, trees may be being cleared for agricultural land, including grazing animals and growing crops, for either humans or animals.

And you should have said that, some trees may be lost to wildfires.

Then I asked you to suggest how deforestation could be reduced and prevented, and you might have included that, deforestation could be reduced, by protecting the land to prevent illegal logging, and deforestation.

Reducing deforestation in the first instance, by things like changing our diet, to reduce the demand for land, and by replanting trees to recreate forests.

So, just review your work over, and check that you've got everything.

Well done.

Now let's move on to the second part of our lesson, which is going to be looking at climate change, and the oceans.

So, oceans cover 70% of the earth's surface, and store 97% of the world's water.

And by doing so, they provide vital habitats for many, many different organisms. They also significantly affect the weather across the globe, and they also impact coastal regions, where large numbers of people live around the globe.

Now, just like forests, oceans act as carbon sinks, and they also absorb about a quarter of the carbon dioxide, that is emitted by the activities, that we undertake as humans.

So, forests and oceans have an equal role to play, in removing carbon dioxide out of the atmosphere, following our activities.

By absorbing carbon dioxide out of the atmosphere, what they are helping to do, is reduce the accumulation of carbon dioxide in the atmosphere, and this directly slows global warming.

So, which of the following describes a key role of the oceans? Providing fresh water for drinking, providing habitats for human life, and acting as a carbon sink.

I'll give you five seconds to think about it.

Okay so, hopefully you have chosen the final option, acting as a carbon sink, as a key role of the oceans.

Well done.

Now, many marine organisms, as you probably already know, are protected by a shell, which is made of a compound called calcium carbonate, and this includes quite a range of different organisms, including plankton, snails, and bivalves such as clams. And, all of these organisms provide essential food and nutrients for larger animals, such as other bivalves, fish, and whales.

So, these are organisms, which are fairly low down in the food chain, and therefore, provide a food source for organisms further on through the food chain.

Now, carbon dioxide, when it's stored in the ocean, it acidifies the water.

Now this is problematic for organisms, which create shells using calcium carbonate, because, by acidifying the ocean water, this reduces the ability of marine organisms, to create shells using calcium carbonate.

And this means, that their ability to survive and reproduce reduces, because they aren't able to make the shells that they require, for them to survive for properly with.

So, ocean acidification, directly impacts the ability of organisms which have to make shells out of calcium carbonate, to survive, which, because these are providing a significant food source for organisms further down the food chain, impacts organisms further down the food chain, that feed on those organisms. So by acidifying the ocean, by it absorbing more carbon dioxide out of the atmosphere, directly impacts many, many organisms within the food chain, because of the reduction in the ability for organisms to make hard shells in acidic oceans.

So let's see how that might impact a specific organism.

Let's look at the walrus.

So the walrus lives on Arctic sea ice, and it uses the ice as a diving platform.

They dive down to the surface of the ocean, and find clams there, pick them up and they eat them, and that's what they feed on.

Now, ocean acidification, is reducing the ability of clams to make shells, which is reducing the ability of clams to survive, and therefore, the availability of clams is being reduced.

And this is the walruses' primary food source.

So, ocean acidification, is reducing, the food supply of the walrus.

So, the oceans are becoming increasingly acidic.

True or false? Okay, you should have said that that is true, but why? Can you explain that? Well, hopefully you said, that when oceans absorb carbon dioxide, they become more acidic.

They are also storing increased amounts of carbon dioxide due to human activities.

Well done if you said both of those.

So, let's look at the oceans from a different perspective.

The earth receives radiation from the sun, primarily in the form of visible light.

And that visible light, some of it, is reflected straight back into space.

The rest of it is absorbed by the earth's surface, and then re-radiated, as infrared radiation, as heat.

Now that heat, that infrared radiation is absorbed, and then re-emitted by greenhouse gases in the atmosphere, such as carbon dioxide.

And by bouncing the heat around the earth, this causes the greenhouse effect.

And the greenhouse effect, helps to keep the planet warm enough for life to be maintained, and it also warms the oceans.

So, it's very useful up to a point.

But warmer oceans can absorb less carbon dioxide.

So, the warmer the ocean gets, the less carbon dioxide it can absorb.

This means, that more carbon dioxide remains in the atmosphere, and this increases the greenhouse effect.

So we've got these competing problems going on, with ocean acidification happening, as the ocean is absorbing carbon dioxide out of the atmosphere, but the reduction in its ability to do so, by the warming of the planet through the greenhouse effect.

Now, warmer oceans, let's stick with that for the moment.

Warmer oceans cause sea levels to rise, because warm water takes up more space than cooler water, and so, the sea will rise.

Warm oceans also change the ocean currents that diverts them in different ways from their standard routes around the globe.

It also means that, weather patterns are altered, because oceans impact the weather significantly, and warmer oceans, impact weather in different ways, from cooler oceans.

It also, drives the melting of sea ice.

So, ice that is floating on top of the sea, melts faster, because the sea itself is warmer.

So, we've got sea levels rising and sea ice melting, as well as, changing currents and changing weather patterns, all caused by having warmer oceans.

Now, warmer oceans, also impacts organisms that are living within or around the sea and the oceans.

So, for instance, and you may well already know this, that during periods of stress, such as an increase in water temperature, coral expel the algae that live in their tissues.

The algae provide the coral with the colour that they have, and also provide them with nutrients as well.

in a symbiotic relationship, in a relationship which benefits both the coral and the algae.

Now, when coral expels the algae, it changes their colour, and we call that coal bleaching, because the coral loses its colour.

And you can see that, in the picture there, the white coral, which has become bleached, as it has expelled algae from it, compared to the browner, more earthy colours of the coral, which still has its algae.

Now, coral can survive without algae, however, it is more risk of starvation and disease, because it does not have the algae anymore.

So, it is much more likely to die, as a result of having expelled its algae, and it has expelled its algae, because the sea temperature has increased, and put it under stress.

Let's look at another example.

Let's go back to that walrus.

So, we were looking at walruses earlier, and the problems that they have feeding on clams, because of the reduction in clam populations through ocean acidification.

Well, walruses have another problem as well, that they use sea ice to give birth to their young.

It's a platform for them to come out of the water, and live on.

Now, the ice platforms are melting, and retreating in shallower waters, because of the rising ocean temperature.

And this means, that walruses are losing habitat to live on, and diving platforms to feed from, and space to raise their young.

So, walruses have a two-pronged attack on them.

They are both being affected by reduction in food source through ocean acidification, and they're also being targeted through a reduction in landmass, because of ocean warming as well.

Another example of an animal which is affected by ocean warming, is the kittiwake.

Now the kittiwake is a bird which lives on land, but hunts out to sea.

And populations of kittiwakes are really important in the UK.

And UK has a significant number of, highly important, world breeding sites for kittiwakes.

But, populations of kittiwakes have declined significantly in the UK, over the last 20, 30, 40 years.

So, since 2000, there has been a 43% reduction in the kittiwake population, in the UK.

43%.

So, nearly half of the kittiwake population has disappeared, in the last 25 years.

And the population of kittiwakes is reducing because, these birds feed on sand eels, and sand eel numbers are declining, because of warmer sea temperatures.

So, you can see how, sea temperatures impact organisms often at the lower end of the food chain.

But that means, that the implications of that, are far reaching, because many organisms, higher up the food chain, are then also impacted as a result.

So, who describes a likely outcome of ocean acidification and warming? So Laura says, "Clams find it harder to make shells in acidic oceans and dolphins feed on clams so may starve." Izzy says, "Warmer oceans will be more pleasant to live and swim in, so more animals will move to warmer waters." And Jun says, "Warmer seas will dissolve more gases in them, which will make them more bubbly and frothy." But who is correct? I'll give you five seconds to think about it.

Okay, so hopefully you have said that Laura is correct.

Well done if you did.

So, what I'd like you to do in our final task today, is to consider this example.

Now, data published in 2024, shows an increase of 0.

6 degrees centigrade in average global ocean temperatures, over the past 40 years.

So, in the last 40 years, the ocean temperature has on average increased by 0.

6 degrees centigrade.

Now, migratory marine animals such as the sea turtle as pictured, are changing their migration patterns in response to this change.

So, what I would like you to do, is to firstly describe the role of the oceans, in maintaining a stable climate, and then suggest why climate change has caused changes in migration patterns in sea turtles, and I'd like you to include as many factors as possible.

So, pause the video now, and come back to me when you are ready.

Okay, let's see what you wrote.

So firstly, I asked you to describe the role of oceans in maintaining a stable climate.

And you should have included that, oceans absorb a quarter of the carbon dioxide in the atmosphere, and this reduces the amount of greenhouse gas in the atmosphere, so reduces the rate of global warming.

You might also have said, that the oceans absorb excess solar radiation or heat, that cannot be reflected into space.

Well done if you included all of those points.

Then, I asked you to suggest why climate change has caused changes in migration patterns in the sea turtles, and to include as much as you possibly can.

So, you might have included that, the warming oceans causes changes in ocean currents, and this means that sea turtles may be forced to take different migratory routes through the oceans.

It also means that their food sources may be relocated by the changing currents, or by the warmth of the ocean.

And also, impacted by the fact that the oceans are absorbing carbon dioxide, which is acidifying them.

Acidification of the oceans may affect the abundance of food sources for turtles, because organisms lower down in the food chain cannot produce shells, and this will therefore impact the availability of food for the sea turtles.

So, you might have included all of those points.

If you've missed anything out, then do add it into your work now.

Well done.

Okay, we've come to the end of our lesson today now.

So, thank you very much for joining me.

In our lesson today, we've seen how forests and oceans are both carbon sinks, and each of them absorb about a quarter of the annual carbon dioxide emissions that humans put into the atmosphere.

So, they play, a great part in global warming, and the maintenance, the reduction of that.

Now, deforestation of forests contributes to climate change by removing carbon sinks, which is what forests are, and it also causes significant habitat and biodiversity loss.

Now, deforestation can be prevented, by protecting forests, by reducing the drivers for deforestation, such as agriculture, and by replanting forests as well.

We've also looked at oceans, and we've seen how carbon dioxide uptake by oceans leads to the acidification of oceans, and this in turn reduces the ability of some marine organisms to form shells.

And this therefore, has quite a significant impact on food webs.

We've also seen how oceans absorb most of the excess heat that is radiating around the earth, and by doing so, warmer oceans cause changes to the weather patterns, ocean currents, and to sea levels.

So, I hope you found this lesson very interesting, and I would like to thank you very much for joining me today.

I hope to see you again soon.

Bye!.