For most of human history, farming worked by moving: move the herd to fresh grass, move the field to fresh soil. Then, in about twenty years in the middle of the twentieth century, we learned how to stay put and force the land to keep producing. That change fed billions of people and damaged an enormous amount of soil. Both halves of that sentence are examinable.
📘 What you need to know
Nomadic pastoralism herds livestock between pastures in a seasonal cycle, suited to arid and semi-arid environments.
Slash-and-burn (shifting cultivation) clears and burns forest, crops the land for a few years until the soil is depleted of nutrients, then moves on and lets the forest regenerate.
Traditional systems are sustainable at low population density, but become unsustainable as populations grow and land becomes scarce.
The green revolution was a set of research, development and technology initiatives in the 1950s and 1960s, also called the third agricultural revolution.
Its key initiatives were high-yielding varieties, improved irrigation, synthetic fertilisers and pesticides.
It raised food production and incomes, but caused soil degradation, water pollution, biodiversity loss, economic inequality and sociocultural disruption, and it did not reach everywhere.
Synthetic fertilisers supply nutrients immediately but degrade soil, pollute water and depend on fossil fuels.
Sustainable alternatives for soil fertility include fallowing, organic fertiliser, herbal mixed leys, mycorrhizae, continuous cover forestry and agroforestry.
Traditional practice 1: nomadic pastoralism
Definition
Nomadic pastoralism is a form of agriculture in which livestock is herded to different pastures in a seasonal cycle.
The classic example is Bedouin communities in the Middle East, who traditionally move camels, goats and sheep across desert regions to find grazing land.
Characteristics
Relies on natural pasture and water sources rather than grown feed or irrigation.
Adapted to arid or semi-arid environments where crops would fail.
Minimal permanent settlements, because the people move with the animals.
Seasonal changes control movement — the herd follows the rain and the grass.
There is a logic here worth spelling out: in a dry environment, grass grows back slowly. Moving on before the pasture is stripped gives it time to recover. Nomadic pastoralism is not a primitive version of ranching — it is a system built around giving land time to regenerate, which is exactly what modern sustainable grazing tries to reinvent.
Traditional practice 2: slash-and-burn
Definition
Slash-and-burn agriculture is a method in which forest is cut down and burned, and crops are grown on the cleared land for a few years until the soil is depleted of nutrients.
Some Indigenous peoples in the Amazon rainforest traditionally practise slash-and-burn to grow crops such as cassava and maize.
The whole system depends on the length of step four. Give the forest twenty years and it works; give it three and you get permanent degradation.
Characteristics
Sustainable in low-density populations.
Allows regeneration of forest over time.
Relies on a rotating cycle of land use rather than staying on one plot.
Where traditional practices run into trouble
Challenge
What happens
Environmental impact of slash-and-burn
Deforestation and loss of biodiversity where forest is cleared
Environmental impact of pastoralism
Overgrazing and soil erosion can occasionally result if herds stay too long or grow too large
Population growth
Traditional methods become unsustainable as populations grow and land becomes scarce, leading to overuse of land and resources
Modernisation
Some Indigenous peoples have been observed transitioning to more sedentary lifestyles, which changes how the land is used
Read the mechanism carefully. Neither system fails because the method is bad. Both fail when too many people use them on too little land, so the rest period disappears. Write that in an exam and you are explaining rather than describing.
The green revolution
The green revolution refers to a series of research, development and technology initiatives that took place between the 1950s and 1960s, aiming to increase agricultural production and food security globally. It is also known as the third agricultural revolution.
The four key initiatives
Initiative
What it involved
Example
High-yielding varieties (HYVs)
Breeding crops such as wheat, rice and maize to produce higher yields
IR8 rice, known as “miracle rice”, developed in the Philippines
Improved irrigation
Development and expansion of irrigation infrastructure, turning arid and semi-arid land into highly productive farmland
The Indus Basin Irrigation System in Pakistan
Synthetic fertilisers
Chemical fertilisers supplying essential nutrients to crops. Their production depends on nitrogen fixation, which relies on fossil fuels
Widely applied to HYV cereal crops
Pesticides
Chemical pesticides applied to protect crops from pests and diseases
Used alongside monoculture planting
Notice how the four initiatives lock together. High-yielding varieties only deliver high yields if they are given plenty of water and nutrients, so they pull irrigation and fertiliser in behind them. And because everyone plants the same high-yielding variety, the fields become genetically uniform, which makes pests spread easily — which pulls in pesticides. This is why you cannot adopt half a green revolution.
Do not treat this as a “was it good or bad” question. It is a question about who gained, who paid, and over what time scale.
Positive consequences
Increased food production — significant increases in crop yields and food availability, helping to relieve hunger and food shortages in many regions.
Economic growth — agricultural economies were boosted and farmer incomes rose. Mexico became a major wheat exporter as a result of green revolution practices.
Technological advancement — it led to further agricultural research and innovation.
Negative consequences
Environmental — overuse of chemical fertilisers and pesticides caused soil degradation and water pollution, and intense monoculture caused loss of biodiversity.
Economic inequality — larger, wealthier farmers gained more than small-scale farmers, and farmers who could not afford the new technologies took on increased debt.
Sociocultural — displacement and loss of traditional farming practices, and an increase in rural to urban migration as agricultural labour demands changed.
Selective implementation — the green revolution was not universal. It did not reach all developing nations, and regions without access to the necessary resources and infrastructure saw limited benefits.
Synthetic fertilisers
Synthetic fertilisers are chemical compounds applied to soil to supply essential nutrients for plant growth. Their purpose is to maintain high commercial productivity in intensive farming systems.
Advantages
Disadvantages
Immediate nutrient supply to crops
Soil degradation over time
Increased crop yields and faster growth
Water pollution from runoff
Predictable and easy to apply at scale
Dependency on fossil fuels for production
Here is the trap in this section. Synthetic fertilisers feed the plant, not the soil. They add nutrients but no organic matter, so soil structure, water-holding capacity and the soil organisms all decline over time, and the crop becomes more dependent on the next application. The sustainable methods below do the opposite — they feed the soil and let the soil feed the plant.
Sustainable ways to keep soil fertile
Method
What it is
Benefits
Fallowing
Leaving land uncultivated for a period
Allows soil to recover and regain nutrients, and reduces the need for synthetic fertilisers
Organic fertiliser
Using manure from farm animals or human waste (humanure)
Improves soil structure and fertility, and reduces the need for synthetic fertilisers
Herbal mixed leys
Planting a mixture of herbs and grasses
Provides diverse nutrients to the soil and improves soil health and biodiversity
Mycorrhizae
Symbiotic fungi that enhance plant nutrient uptake
Increases plant access to nutrients and reduces the need for synthetic fertilisers
Continuous cover forestry
Maintaining a continuous canopy of trees
Prevents soil erosion, because roots bind the soil and the canopy intercepts rain, and increases soil organic matter and fertility
Agroforestry
Integrating trees and shrubs into agricultural landscapes
Improves soil health, reduces soil erosion and provides additional income from fruit or timber
Worked examples
WE 1
Explain why shifting cultivation can be sustainable
Explain why slash-and-burn agriculture can be sustainable in some circumstances but not in others. (4 marks)
Point 1: how the system works
Forest is cleared and burnt, the ash releases nutrients, and crops are grown until the soil is depleted of nutrients.
Point 2: the recovery stage
The plot is then abandoned and the forest regenerates, restoring nutrients and organic matter, so it can be cropped again later.
Point 3: when it works
At low population density there is enough land for long fallow periods, so each plot fully recovers before it is reused.
Point 4: when it fails
As population grows and land becomes scarce, plots are reused too soon, forest cannot regenerate, and the result is deforestation, biodiversity loss and permanent soil degradation.
Sustainability depends on the length of the fallow, not on the method itselfthe marks are in the comparison — give both the working case and the failing case
WE 2
Evaluate the green revolution
Evaluate the consequences of the green revolution. (6 marks)
Positive 1: food
Crop yields and food availability rose sharply, relieving hunger and food shortages in many regions.
Positive 2: economy
Farm incomes and agricultural economies grew; Mexico became a major wheat exporter.
Negative 1: environment
Overuse of fertilisers and pesticides caused soil degradation and water pollution, and monoculture reduced biodiversity.
Negative 2: equity
Wealthier farmers benefited most, while those who could not afford the technology fell into debt.
Negative 3: reach
It was selectively implemented and did not reach regions lacking infrastructure and resources.
Judgement
It succeeded on its own terms of raising output, but it transferred costs onto soils, ecosystems and poorer farmers, so it is not sustainable in its original form.
Large short-term gains, significant long-term and distributional costsan evaluate question needs a judgement at the end — not just a balanced list
WE 3
Compare two ways of adding nutrients
Compare and contrast the use of synthetic fertiliser with the use of organic fertiliser for maintaining soil fertility. (4 marks)
Similarity
Both supply nutrients to the soil that support plant growth and crop yields.
Difference 1: speed
Synthetic fertiliser gives an immediate nutrient supply; organic fertiliser releases nutrients more slowly as it decomposes.
Difference 2: soil structure
Organic fertiliser adds organic matter and improves soil structure, while synthetic fertiliser adds no organic matter and can degrade soil over time.
Difference 3: wider impacts
Synthetic fertiliser depends on fossil fuels and can pollute water through runoff; organic fertiliser reduces the need for synthetics and uses waste already on the farm.
One feeds the plant quickly, the other feeds the soil slowlycompare and contrast means you must give at least one similarity, not only differences
💡 Exam tips
Learn the green revolution dates: 1950s to 1960s, and the alternative name, the third agricultural revolution.
Have one named example per initiative: IR8 rice, the Indus Basin, Mexico and wheat.
Say that synthetic fertiliser production depends on nitrogen fixation and therefore on fossil fuels. It is an easy extra mark.
For traditional systems, give the characteristics, not just the definition.
Know all six sustainable fertility methods by name — they are a common short-answer target.
In evaluate questions, finish with an actual judgement.
⚠ Common mistakes
Calling slash-and-burn simply destructive. It is sustainable at low population density; the problem is shortened fallow periods.
Saying the green revolution fed the whole world. It was selectively implemented and missed many regions.
Confusing nomadic pastoralism with ranching. Nomadic herders move seasonally and keep minimal permanent settlements.
Treating synthetic fertiliser as purely bad. It gives immediate nutrients and higher yields; the costs are long term.
Forgetting the social costs. Rural to urban migration and lost traditional practices are examinable consequences.
Mixing up fallowing and crop rotation. Fallowing leaves land uncultivated; rotation changes which crop is grown.
Up next: Protecting and Restoring Soil — the conservation techniques that stop soil being lost in the first place, sorted into the three groups examiners expect you to use.
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