Lesson video

Hello, my name is Mr. Marsh and I'm here today to teach you all about desertification, its causes and the strategies we can use to mitigate against it.

So grab everything that you need for today's lesson and let's get going.

So by the end of today's lesson, you will be able to explain the causes of desertification and the strategies used to reduce the risk of desertification.

There are four keywords for today's lesson, and those are: desertification, drought, deforestation, and mitigation.

Desertification refers to the process by which land becomes desert due to climate change, deforestation, or inappropriate agriculture.

Drought refers to a long period of time with little or no rainfall, leading to a shortage of water.

Deforestation refers to the action of clearing a wide area of trees, and finally, mitigation refers to the action of reducing the severity or seriousness of something.

So there are three learning cycles with today's lesson.

And logically we're gonna start with the first learning cycle, which is: What is the threat of desertification? Desertification is the process by which land becomes desert, typically due to drought, deforestation, or excessive agriculture.

It is occurring primarily in regions with very dry or arid climates, and is increasingly prevalent in areas of Africa, for example, the Sahel.

In fact, desertification turns semi arid areas like this into desert areas like this.

Now, desertification is a serious threat to biodiversity.

It degrades soil and removes and reduces vegetation.

This leads to habitat loss and leads to a scarcity of food and water for many of those species.

Ultimately, this threatens the survival of many species and the ecosystem as a whole.

Desertification is a widespread environmental threat affecting biodiversity and communities across the globe, as this map shows.

Areas at risk of desertification exist on every continent with the exception of Antarctica, which is a cold desert.

Now, if we focus on our map in front of us, we're gonna focus primarily on those peachy, orange-colored areas.

These are areas at risk of desertification.

Now, first thing to point out is that it is areas neighbouring existing deserts, which are at risk of desertification.

These semi-arid areas have very fragile ecosystems with very limited rainfall, which is very much seasonal.

Now, as previously mentioned, this shaded area here is the Sahel.

It's the area to the south of the Sahara, and it is the largest area under threat from desertification.

If we're looking closer to home, in Europe there is desertification, primarily in south and eastern Spain.

These are two areas at risk of desertification.

So, learning check.

True or false? Desertification primarily affects arid and semi-arid land, neighbouring hot deserts.

Pause the video here whilst you consider and make your answer.

And the correct answer was true.

Now, once again, I'd like you to pause the video whilst you consider why this statement was true.

So pause the video here whilst you consider your answer.

And the reason it is true is because these areas have fragile ecosystems with already limited and seasonal rainfall, making them especially vulnerable to further soil degradation, climactic changes, and ultimately, desertification.

Really, really well done if you were able to get those two answers correct.

So desertification happens in a series of stages.

First, vegetation cover decreases, by which I mean plants are removed or they die from the soil.

Soil then is more vulnerable to erosion without the presence of those roots holding the soil together.

This erosion could be via wind or perhaps even rain.

Soil over time loses nutrients through leaching and the ability to support plant growth.

This then reduces plant litter, which means even fewer nutrients returning to the soil.

And overall then, this limits the amount of plants that can regrow, thereby leading to desertification.

So another learning check.

Which of the following are involved in desertification? Pause the video here whilst you read through the options and consider and make your answer.

Best of luck.

And there were two correct answers.

It was B: the removal of plant cover, increasing soil erosion, and D: the loss of soil nutrients, reducing soil fertility.

Really, really well done if you were able to identify those two correct answers.

So we're onto our first practise task, and this one asks you to choose and complete the missing stages in this flow diagram to explain how desertification occurs.

The final two stages have already been done for you.

You need to fill in the first three by using the stage descriptors you can see on the right hand side of your screen.

The second practise task asks you to describe the distribution of areas at risk from desertification.

You could include in your answer: the names of continents, compass directions, and the relationship with existing desert areas.

So pause the video here whilst you attempt those two practise questions.

Best of luck.

And now some feedback.

So you were asked to complete the first three missing stages in this flow diagram to explain how desertification occurs.

The first stage was that vegetation cover decreases.

The second is that soil then is more vulnerable to erosion without those plant roots holding the soil together, it becomes very vulnerable to wind and rain erosion.

And finally, soil then loses nutrients and the ability to support plant growth.

Really well done if you were able to get those answers correct.

The second practise question asked you to describe the distribution of areas at risk from desertification.

Your answer may have included any of the following: First thing to say is that every continent has areas at risk of desertification except Antarctica.

Southern and eastern Spain in Europe is at risk of desertification.

Areas at risk of desertification primarily neighbour already existing deserts.

The Sahel, which is south of the Sahara desert, is the largest area at risk of desertification.

And we also see in the Americas and Australia, most desertification is on the western coasts.

So really, really well done if you were able to include any of those answers.

We're on now to our second learning cycle, which is what is actually causing desertification? Now the first cause of desertification is deforestation, for example, removing trees for the use of fuelwood.

The second is overgrazing by cattle, sheep, goat, any farm yard animal grazing on farmland.

Over cultivation, again, farming, this time with crops.

Population growth.

And finally, climate change.

So a learning check.

You just saw the five main causes of desertification.

Can you now try to remember what those five were? Pause your video here whilst you consider and make your answer.

And the five correct answers were: deforestation for the removal of trees for fuel, wood, overgrazing, over cultivation, population growth and climate change.

Really, really well done if you were able to identify those five answers.

Let's now start looking at those causes in a bit more detail, starting with deforestation.

Now, trees and shrubs are removed by communities because they need the wood to burn for fuel.

Typically, a lot of these areas at risk of desertification can be found in low income countries, and therefore they need this wood to burn for fuel.

This deforestation removes that vegetation that is holding the soil in place with their roots.

Without this vegetation, the soil is very much exposed to wind and rain, which leads to erosion and nutrient loss or leaching.

And as these nutrients are lost and the soil erodes, the land struggles to support new plant growth, gradually turning it into a barren, desert-like conditions.

Next we have overgrazing.

And overgrazing again leads to desertification as livestock eat plants faster than they can grow back.

Soil again is left unprotected to nutrient loss and soil erosion.

And in the Sahel, this is a big cause of desertification.

Overgrazing can strip the land of vegetation, causing soil degradation, turning once fertile areas into now desert-like areas.

Over-cultivation intensively farms the land to the point where soil nutrients and fertility are completely lost.

This happens by the intensive farming completely uses those nutrients.

Land then is not given time to recover and restore those lost nutrients.

The soil becomes infertile, crops struggle to grow and the lack of vegetation cover makes soil vulnerable once again to erosion.

All of these factors combined leads to the land becoming desertified.

Climate change is increasingly a cause of desertification.

Increase in temperatures and altered rainfall patterns represent a major challenge for those areas at risk of desertification.

This is because climate change can increase the frequency and intensity and duration of drought.

So drought is a long period of time without rainfall.

Longer periods without rainfall then inevitably reduces the amount of plant and vegetation cover there.

This dry soil then is exposed to erosion and nutrient loss.

Finally, the soil degrades, becoming infertile, leading once again to desertification.

Population growth sees the increased demand for land, food and resources.

This leads to land being deforested, overgrazed and over cultivated.

High population growth in the Sahel, for example, has led to the expansion of agriculture into fragile and arid areas.

All of this accelerates soil erosion and land degradation and ultimately leads to desertification.

And did you know that the Sahel's population has actually grown from 21 million in 1960 to 103 million in 2020 and is projected to grow to 500 million by 2050? Clearly this is going to be an increasing cause of desertification in the Sahel.

So a learning check.

How does overgrazing contribute to desertification? Pause the video here whilst you read through the options.

Consider your answer and make your answer.

Best of luck.

And the correct answer was A: overgrazing removes that vegetation cover, leads to soil erosion and ultimately, desertification.

Really, really well done if you were able to identify that correct answer.

So we're on now to our practise task, and this asks you to fill the gaps to explain how deforestation and climate change can cause deforestation.

You have six gaps to fill and the words are presented at the bottom of the screen.

So what I'd like you to do right now is pause the video whilst you complete this practise question.

Best of luck.

So, some feedback.

Deforestation contributes to desertification by removing vegetation that stabilises soil, leading to increased erosion.

Without plant cover, soil is exposed to rain and wind, losing vital nutrients needed for new growth.

Climate change worsens desertification by raising temperatures and altering rainfall patterns, accelerating evaporation and reducing soil moisture.

In regions like the Sahel, infrequent rain and prolonged droughts hinder vegetation recovery, further degrading soil and rendering it unproductive.

So really, really well done if you were able to identify those six correct answers.

We're on now to our third and final learning cycle, which is How can desertification be mitigated? Managing desertification involves implementing strategies to prevent, slow or reverse soil degradation.

Effective mitigation of desertification focuses on a few different things: It looks to restore vegetation cover, improve soil health, conserve water resources, promote sustainable land use practises, for example, through sustainable agriculture.

Any methods and technology used to mitigate certification must be appropriate for the areas they're being implemented.

This means they must be: Affordable: technology should be cost effective, especially for use in regions with limited funds.

It must be accessible: the materials and tools required to implement these strategies should be available locally, reducing dependence on external sources such as external charity organisations or external governments.

And finally, they must be simple and understandable.

The technology used should be easy to understand and maintain, so it can be used effectively by local people with minimal training.

So, learn and check.

Which statement is correct? Is it Izzy's? "Appropriate technologies to combat desertification are those which are government-led and rely on external sources for support." Or is it Aisha? "Appropriate technologies to combat desertification are those which are are affordable, easily accessible, simple and easy to understand for local people." So I would like you again to read through Izzy and Aisha's responses.

Pause the video whilst you consider and make your answer.

Best of luck.

And the correct answer was Aisha.

Yes, appropriate technologies to combat desertification are those which are accessible, affordable, and easy to understand for local people.

Now desertification is due to a lack of water and nutrients in the soil.

Therefore, conserving these is absolutely crucial.

And this can be done by a number of different strategies: the first of which is terracing.

And as you can see on the image, these are stepped fields literally dug into the side of a hill.

And the idea is that this causes the water to flow downhill much more slowly, thereby encouraging more moisture absorption in the soil and also reducing leaching by which I mean nutrient loss from the soil, thereby keeping the soil much more hydrated and much more rich with nutrients.

The second is drip irrigation.

Again, looking at the image, this is where water is dripped directly onto the roots of vegetation, rather than using perhaps a spray over a wide area where there may be some plants and there may not be some plants.

Through drip irrigation, it reduces water wastage.

The third and final one is rainwater harvesting.

And it's just collecting and storing rain water in tanks for people to use in fields and homes.

It's about using the limited water resources that the areas do, in fact, receive from time to time.

Now, desertification is also due to a lack of vegetation cover and poor soil management.

Now this can be addressed in the following ways: The first one is afforestation, by which I mean planting trees.

Planting trees can help stabilise the soil as roots bind the soil together, which reduces soil erosion.

It reduces nutrient loss from rainfall and wind, and this therefore improves moisture and nutrient retention, thereby making the soil much more fertile.

The second thing is a better agricultural practise.

This is crop rotation, because growing the same crop year after year on the same land reduces soil fertility, but rotating and mixing crops can restore nutrients, for example, nitrogen, which again, therefore leads to a much healthier soil.

Now, China's Great Green Wall is just one strategy which aims to combat desertification.

It has created a 4,500 kilometer-long chain of human-planted forest strips across northern China to slow the expansion of the Gobi Desert, as this illustration on the left hand side of your screen shows.

This is what is intended through their afforestation programme.

Desertification has already slowed with the percentage of land classified as desertified dropping from 27.

2% to 26.

8%.

Yes, a small decrease, but a decrease nevertheless.

Palm frond fencing is also another strategy which can mitigate the effects of desertification.

It uses the leaves and stems of palm trees, which are often readily available in semi-arid areas.

Now, therefore, it's a cost effective option with some areas which are being affected by desertified being low economically developed, it reduces the need for international dependency.

And palm trees are readily available in this area.

So they have a supply of the resource needed to implement this strategy.

It is simple and effective to create, and it is effective at trapping soil and water, thereby reducing soil erosion.

Afforestation can also be used to support the economic development of local communities tackling desertification.

How? In sub-Saharan Africa, the United Nations has supported local communities in planting acacia trees.

These provide fuelwood, shade and fodder for animals, all while protecting against soil erosion.

Furthermore, the gum, as you can see in the image in front of you, can also be tapped from the tree by local people.

The gum can then be sold since it's actually a key ingredient in a variety of different products, such as a stabiliser in food and the cosmetic industries.

So therefore, they're gonna be able to gain money from a strategy which is also doing its job in combating desertification.

So a learning check.

What I'd like you to do is look at the six different strategies that we can use to mitigate desertification.

I would like you to match the strategy A, B, C, D, E, F, with the image shown.

So pause your video here whilst you consider and make your answer.

So the correct answers were: F was palm frond fencing.

We then have rainwater harvesting, we have terracing, we have crop rotation, we have afforestation, and finally we have drip irrigation.

So really, really well done if you were able to identify those six correct answers.

We're on to our final practise tasks now.

And the first one says to match the sentence beginning to the sentence end.

And the second practise task asks you, using your own knowledge and evidence from the image, annotate how palm frond fencing is an example of appropriate technology to mitigate desertification.

So what I'd like you to do right now is pause the video whilst you attempt those two questions.

Best of luck.

And the feedback.

So, the correct answers were: Rainwater harvesting collects and stores the limited rainwater in tanks for people to use in fields and homes.

Terracing creates step fields to slow water movement and encourage moisture retention and reduce nutrient loss from the soil.

Drip irrigation drips water directly onto the roots of vegetation to reduce water wastage.

Afforestation plants trees to stabilise the soil and reduce erosion and improve moisture retention.

Finally, crop retention moves crops and livestock to different fields to allow soil recovery and prevent over-cultivation.

The second practise question asks you to annotate this image of palm frond fencing to show how it's an example of appropriate technology to mitigate desertification.

Now, you may have had some of the following: The first of which is that palm trees are readily available to local communities in semi-arid regions, thereby it's a readily available building resource.

It's very simple and effective to create, and little expertise is actually required to construct it.

It's very effective.

It traps the soil and water behind the fence, thereby reducing soil erosion and nutrient loss.

It's extremely cost effective and this is very important for those semi-arid regions with low economic development.

And finally, it therefore reduces the need for international dependency.

Local communities can solve the problem by themselves.

So really, really well done if you were able to include any of those answers that you see in front of you.

So a summary: Desertification is a process by which land becomes desert due to climate change, deforestation or inappropriate agriculture.

It generally occurs in arid and semi-arid areas, bordering existing deserts.

The causes of desertification include climate change, population growth, removal of fuelwood via deforestation, overgrazing over cultivation, and soil erosion.

The use of appropriate technology, though, ensures strategies to mitigate desertification are affordable, easy to use and readily accessible.

Techniques such as afforestation, drip irrigation, palm frond fencing, and terracing are all examples of this appropriate technology.

So thank you very much for being with me today and I will see you on the next lesson.

Goodbye.