Desertification Response

The desert does not march

The picture most people carry is of dunes advancing across farmland like a slow tide. That is not what desertification is, and an answer built on it will not score. The United Nations defines it as the degradation of land in arid, semi-arid and dry sub-humid areas, resulting from climatic variations and human activities. The land does not get swallowed from the edge. It is worn out from within: vegetation thins, the soil loses its structure and its nutrients, wind and the occasional violent downpour strip away what is left, and ground that used to grow a crop no longer will. The scale is large. Drylands cover something like 40 per cent of the land surface of the planet and around 2 billion people live on them. India's own government atlas puts close to 30 per cent of the country's land in a degraded condition. The Thar Desert and the semi-arid land around it sit at the sharp end of this: roughly 200,000 square kilometres carrying about 83 people per square kilometre, the highest population density of any desert on Earth, on 120 to 240 mm of rain a year. What makes the topic difficult, and interesting, is that the causes will not separate cleanly. A drought thins the grass; thinner grass means the same herd grazes it harder; harder grazing means less root to hold the soil when the rain finally comes; and the family doing the grazing has no other way to eat. Climate and human pressure are not two lists, they are a loop. This module follows that loop and then works through the three families of response the specification asks you to name and explain.

Five terms, three of them causes

The first is the process itself, the next three are the human pressures that drive it, and the last is the response category students most often fail to name properly.

Order the degradation spiral

These six stages describe how productive dryland becomes unproductive. Put them in the order they follow.

• A growing population needs more food, more grazing and more fuel from the same land
• Vegetation cover thins as it is grazed, cropped and cut faster than it regrows
• Bare soil is exposed to the sun, the wind and the occasional heavy downpour
• The fertile topsoil is blown or washed away, and what remains is compacted
• Yields fall, so still more land has to be cleared or grazed to produce the same amount
• The land will no longer support the use it once did, and the cycle has tightened

Why does losing the plants matter so much?

Almost every cause of desertification works by removing vegetation. Which answer best explains why that single change does so much damage?

• Vegetation is doing four jobs at once. Roots bind the soil together so wind and water cannot carry it off; the canopy intercepts rain so that it reaches the ground gently rather than hammering the surface and sealing it; shade and shelter cut evaporation and slow the wind at ground level; and dead leaves and stems return organic matter that holds moisture and nutrients. Remove the plants and all four go together, so the soil erodes faster, absorbs less of what little rain arrives, dries out sooner and grows less, which makes recovery harder still.
• Without plants there is no shade, so the land becomes too hot for crops.
• Plants create rainfall, so removing them stops rain falling.
• Without plants there is nothing for animals to eat, which is the only real problem.

Three families of response, each with a scheme

The specification groups the strategies exactly this way, so learn them in these three boxes. Each column gives the idea, a real named scheme, how it works, and what limits it, because a strategy without a mechanism and a limit is only a list entry.

Match each measure to what it changes

Name it, explain it, limit it

The examiner report on this key element says the same thing every year, and the specification note repeats it: strategies must be named and explained, not listed. A sentence that reads "strategies include tree planting, water management and appropriate technology" tells the examiner only that you have memorised three headings. Use a three-part move for each strategy you bring. Name the actual scheme and where it is. Explain the mechanism, which means saying what physically changes: what the water does now that it did not do before, or what the wind can no longer do. Limit it, by saying what the strategy depends on or cannot fix. The third part is what separates the top band, because it shows you are evaluating rather than reciting, and almost every strategy in this topic has an obvious limit once you look for it. Two further habits. First, resist the temptation to treat the causes as a tidy split between climate and people. The strongest answers show the loop: a dry year forces harder use of the land, and harder use makes the next dry year worse. Second, be careful with blame. Overgrazing and fuelwood cutting are not carelessness, they are what people do when there is no alternative, which is exactly why appropriate technology matters as a category: it works by giving people a different option rather than by asking them to want less. And keep the command word in view. "Explain the causes" wants the process. "Assess the effectiveness of strategies" wants a judgement, and the criterion that usually works best here is whether a scheme can be maintained locally once the funding and the attention have moved on.

Complete the desertification facts

Desertification is the degradation of land in dry regions caused by climatic variation and human activity, which means it is not the desert marching outwards but existing dryland losing its _____. Around _____ billion people live on the drylands at risk, and India classes close to 30 per cent of its own land as degraded. Human causes include overgrazing, over-cultivation and the cutting of _____ for fuel, and each of them works by removing the vegetation whose roots hold the soil together. Responses fall into three groups. Rebuilding traditional earth check dams known as _____ in Rajasthan recharges the groundwater; planting belts of trees slows the wind at ground level; and _____ pits in Burkina Faso concentrate scarce water and manure at the root of each plant.

Spot the three accurate desertification claims

Select the THREE statements that are true.

• Desertification is the loss of productivity in land that is already dry, rather than the physical advance of dunes across farmland from the edge of an existing desert.
• Climatic and human causes reinforce one another: a dry year thins the vegetation, which means the same herd grazes what is left harder, which leaves less root to hold the soil when rain eventually returns.
• Irrigation can itself cause degradation, because water evaporating in intense heat leaves its dissolved salts behind in the soil, which has happened along stretches of the Indira Gandhi Canal.
• Desertification happens mainly because dryland farmers are careless with their land.
• The Great Green Wall has already met its target of restoring 100 million hectares across the Sahel.
• Appropriate technology means bringing in the most advanced equipment available so that results come quickly.

A 9-mark assessment, marked

"Appropriate technology is the most effective way of reducing the risk of desertification." Use a case study to assess this view. [9 marks] In the Thar Desert and the semi-arid land around it, where roughly 83 people live on every square kilometre and rainfall runs at only 120 to 240 mm a year, the pressure on the land comes from grazing, cultivation and fuelwood cutting by a growing population. Appropriate technology has real strengths against this. Zai pits in Burkina Faso, hand-dug and filled with manure, concentrate scarce water and nutrients at the root of each plant rather than spreading both thinly, and low-cost drip irrigation delivers water at the base of the crop so that far less evaporates and less salt is left in the soil. This meant that a farmer can act without waiting for a government scheme, using local materials and local labour, which is exactly why such measures survive after outside funding stops. However, their reach is small. Each pit must be dug by hand and each drip kit bought and learned, so coverage grows slowly across a region of 200,000 square kilometres. Water and soil management can work at a larger scale: the revival of johads in Alwar district from the mid 1980s saw villagers rebuild thousands of earth check dams across around a thousand villages, holding monsoon runoff until it seeped down and recharging wells that had run dry, which restored water to whole communities rather than single fields. Tree planting is larger still in ambition, and weakest in delivery, since the Great Green Wall launched across the Sahel in 2007 aimed at 100 million hectares by 2030 and has run far behind, partly because saplings planted without anyone to tend them do not survive. I partly agree with the statement. Judged by cost and by whether a measure lasts once attention moves elsewhere, appropriate technology is the most effective, because it is owned locally and needs nobody's permission. Judged by the area that can be treated at once, water and soil management does more, and the johads show that a traditional method organised by villagers can be both local and large. The honest conclusion is that the categories overlap, and that what the successful schemes share is not their technology but the fact that the people living there run them. What earned the marks: every strategy named with its place and date, then explained by mechanism and then limited; a case study used throughout rather than mentioned once; two stated criteria doing the judging; and a conclusion that identifies what the successful schemes actually have in common instead of declaring one category the winner.

Find the two that explain rather than list

Five sentences about anti-desertification strategies. Three of them only name a measure. Tap the TWO that explain how it actually works.

• A low earth bank across the valley holds the monsoon runoff in a shallow pond long enough for it to seep downwards and refill the wells beneath.
• Tree planting is used as a strategy in the Sahel and in Rajasthan.
• Planting the belt across the prevailing wind slows the air at ground level, so blowing sand is trapped and less moisture is stripped from the soil.
• Some farmers use drip irrigation instead of flooding their fields.
• Strategies include water management, tree planting and appropriate technology.

Build the causal loop sentence

Assemble a sentence that shows the climatic and human causes reinforcing one another.

Four decisions on degraded land

Each stage is a real choice facing people managing dryland. Pick the response that has actually worked, and note which of the three families it belongs to.

• Your village in semi-arid Rajasthan has watched its wells run dry over two decades. The monsoon still comes, but the rain runs straight off the hard ground and away down the valley within hours.
• Herd numbers have grown with the population and the grazing is visibly thinner every year. Simply telling families to keep fewer animals is not going to work, because the animals are their savings.
• Every household cooks on wood, and the shrubs within walking distance of the village have almost gone. The women walk further each year to gather it.
• Irrigated fields near the canal are developing white crusts after hot weather, and yields are falling on land that the canal had only recently made productive.

Explain the causes

Explain the causes of desertification on the fringes of hot deserts. [9 marks]

• Desertification: the degradation of dryland, not the advance of the desert
• A real region named
• For each cause, what is physically removed or changed and what follows
• Causes reinforce each other as a loop, not two separate lists
• No blaming the people involved: these pressures come from having no alternative