Causes of Desertification & Deforestation

Desertification is the degradation of land in dryland environments (arid, semi-arid and dry sub-humid areas), leading to loss of biological and economic productivity.

It is caused by a combination of climatic variations AND human activities (UN Convention to Combat Desertification, 1994).

1. Cattle ranching — Brazil's herd of ~300 million is the world's largest; ~80% of Brazilian Amazon clearance is for cattle pasture.
2. Soy cultivation — ~10% of Brazilian Amazon clearance is for soy (Brazil has ~30 million ha of soy farmland, mostly exported to China and the EU as livestock feed).
3. Palm oil expansion — ~13 million ha of palm oil in Indonesia (Sumatra + Borneo), responsible for the bulk of Indonesia's tropical forest loss.

Other valid causes: logging (legal + illegal), mining, infrastructure (roads, hydropower dams), subsistence + fuelwood collection (especially in Congo Basin).

The Sahel — a semi-arid belt across 12 African countries from Senegal to Eritrea, ~3 million km², with annual rainfall 400-600 mm — is one of the world's most desertification-affected regions.

1. Climate change. Sahel rainfall fell ~20-30% during the 1968-1985 drought, the worst in modern records. Shifts in the Inter-Tropical Convergence Zone (ITCZ) + cooling of the North Atlantic reduced monsoon rains; ongoing global warming has increased the variability and intensity of droughts.

2. Overgrazing. Population pressure (~3%/yr growth in some Sahel countries) means more cattle, goats and sheep on the same land. Animal numbers have exceeded the carrying capacity in many districts. Goats strip vegetation to root level; cattle compact the soil reducing infiltration; the resulting bare soil is wind-eroded.

3. Over-cultivation and fuelwood collection. Cash-crop cultivation (groundnuts, cotton) on marginal land exhausts soil fertility. Most Sahel rural households use wood + charcoal for cooking (~90%+ of rural energy), so trees are cut faster than they regrow — removing the root systems that anchored soils and retained moisture. Lake Chad has shrunk from ~25,000 km² (1960) to ~1,350 km² (2020) — a 90% loss in 60 years — visualising the combined desertification + climate effect.

Brazilian Amazon deforestation in the 2020s has run at ~10,000 km²/yr (INPE PRODES data); ~17-20% of the original forest is now cleared.

1. Cattle ranching (~80% of clearance). Brazil has the world's largest cattle herd, ~300 million animals, and is the world's biggest beef exporter. Land is typically burned ('slash-and-burn'), then converted to pasture. Pasture profitability is low per hectare, but the SCALE is vast.

2. Soy expansion (~10% of direct clearance). Brazil has ~30 million ha of soy farmland, mostly exported to China and the EU as livestock feed. The 2006 Soy Moratorium reduced direct soy planting in the Amazon — but soy still drives INDIRECT deforestation by expanding into cerrado/savanna, which displaces cattle ranching deeper into Amazon.

3. Logging, infrastructure and mining (~10% combined). Illegal logging extracts valuable hardwoods (mahogany, ipê). Roads such as the Trans-Amazonian Highway (built 1970s) and BR-319 open the forest to settlers and ranchers — every 1 km of road can trigger up to ~50 km² of follow-on deforestation. Illegal gold mining in Yanomami territory (~30,000 people threatened during 2019-23 surge) cleared further forest. Hydropower dams (Belo Monte, started 2010) flooded large areas of forest.

4. Policy context. Under the Bolsonaro administration (2019-22) IBAMA (the environmental enforcement agency) was weakened, deforestation rose ~60% above pre-2019 rates. Under Lula (from 2023) enforcement has resumed and the rate has fallen.

Sahel desertification — human causes.

The Sahel's human drivers are mainly subsistence + survival pressures rather than commercial export:

• Overgrazing. Cattle, goats and sheep on land already at carrying-capacity limits. Goats strip vegetation; cattle compact soils.
• Over-cultivation. Cash crops (groundnuts, cotton) on marginal land exhaust nutrients; rotation interrupted by population pressure.
• Fuelwood collection. ~90%+ of rural energy is wood/charcoal; trees cut faster than regrow → loss of soil-anchoring roots.
• Population pressure. Sahel populations growing ~3%/yr; same land must support more people, more animals, more crops.

The drivers feed into a POSITIVE FEEDBACK loop — vegetation loss → higher albedo → less rain → more loss. Lake Chad shrank 90% (25,000 → 1,350 km², 1960-2020) as the combined visible effect.

Amazon deforestation — human causes.

The Amazon's human drivers are mainly commercial + export-oriented:

• Cattle ranching (~80% of clearance). Brazilian herd ~300m, world's largest; ~10,000 km²/yr cleared in 2020s.
• Soy (~10%). ~30m ha total; exported to China, EU.
• Logging + infrastructure (~10%). Mahogany, ipê hardwoods; Trans-Amazonian Highway + BR-319; gold mining (Yanomami territory).
• Policy. Bolsonaro deregulation 2019-22 saw deforestation rise ~60%; Lula re-enforcement since 2023 has reduced it.

These drivers feed a separate POSITIVE FEEDBACK — less evapotranspiration → less rain → forest dieback. The Amazon is at ~17-20% loss, approaching a 20-25% savannisation tipping point.

Key comparison.

Common feature. Both involve POSITIVE FEEDBACK that locks change in once vegetation is removed. Both also reflect that physical fragility (Sahel rainfall margin, Amazon evapotranspiration dependency) interacts with human choices (grazing intensity, agricultural policy) to produce collapse.

Desertification in the Sahel results from BOTH climate variability AND human pressures; assessing their relative contribution is essential.

The CLIMATE case.

The Sahel sits at the climatic margin between the Sahara (north) and savanna (south). It depends on the Inter-Tropical Convergence Zone (ITCZ) moving north each summer to deliver monsoon rains. Shifts in the ITCZ — driven by Atlantic Multidecadal Variability and global warming — have caused decadal-scale droughts. The 1968-1985 Sahel drought saw rainfall fall ~20-30%, triggering crop failures, livestock losses and famine. Even without any human activity, this rainfall reduction would have caused vegetation loss + desertification in places. Climate models project further drying + greater variability in the Sahel under continued warming, making climate a continuing driver.

The HUMAN case.

Human activities are critical in turning climate stress into severe desertification:

• Overgrazing — increased livestock numbers (cattle, goats, sheep) beyond carrying capacity, especially during droughts when herders gather animals around the few remaining water sources.
• Over-cultivation — cash crops on marginal land (cotton, groundnuts), shortened fallow periods, depletion of soil nutrients.
• Fuelwood collection — wood + charcoal supply ~90%+ of rural Sahel energy; trees cut faster than regrowth.
• Lake Chad water withdrawals — irrigation by Cameroon, Chad, Niger, Nigeria; 90% loss of Lake Chad (25,000 → 1,350 km², 1960-2020) is partly human.
• Population pressure — Sahel populations growing ~3%/yr drives all of the above.
• Conflict + displacement — Boko Haram, Sahel insurgencies; ~50m people food-insecure; displaced people concentrate land use.

The synthesis — interaction matters more than either alone.

Climate and humans interact via POSITIVE FEEDBACK:

• Drought reduces vegetation; humans needing food increase grazing; vegetation removed.
• Bare soil reflects more solar radiation (higher albedo); less convection; less rain.
• Less rain → more drought → more pressure → more bare soil → more albedo → less rain.

This feedback loop is what makes Sahel desertification so destructive — neither climate nor humans alone could create this degree of degradation. Studies (e.g. Charney 1975) showed that human-driven vegetation loss could account for ~30-50% of observed rainfall reduction; the rest was natural climate variability.

Judgement.

Climate variability provides the BACKGROUND vulnerability — without the marginal Sahel rainfall regime, none of this would matter. Human activities provide the TRIGGER + AMPLIFICATION — without overgrazing + over-cultivation + fuelwood collection, the climate stress would not produce widespread desertification. The honest verdict is that desertification is a HUMAN-AMPLIFIED CLIMATE PHENOMENON: ~half the cause is the physical climate envelope, ~half is human use of it. Importantly, this means desertification IS REVERSIBLE through human action — the Great Green Wall (started 2007, target ~8,000 km × 15 km belt across 21 African countries) + farmer-managed regeneration in Niger (~5m ha regreened since 1980s) prove this. Climate cannot be reversed; land management can. The honest policy implication is that EVEN IF climate continues to change, HUMAN CHOICES still determine the Sahel's future.

The Brazilian Amazon is being cleared at ~10,000 km²/yr (INPE 2020s data); ~80% for cattle, ~10% for soy. The question is whether the BLAME (and therefore the SOLUTION) lies with Brazilian farmers who do the clearing — or with global consumers whose demand for beef, soy, leather and timber drives the economics.

The CASE for GLOBAL CONSUMERS.

1. Demand drives deforestation. Brazilian beef + soy is largely EXPORTED. China is the largest buyer of Brazilian beef (~$10bn/yr); the EU is a major buyer of Brazilian soy (used as livestock feed, then meat consumed in Europe). If consumer demand vanished, the economics of clearing forest would collapse.

2. Embedded deforestation. Studies estimate that ~30-40% of Brazilian agricultural exports carry 'embedded' deforestation. The EU's 2025 Deforestation Regulation explicitly targets this — requiring importers to prove their products are deforestation-free.

3. Price signals. Global beef + soy prices (driven by global demand) determine the profitability of forest clearance. When prices are high, more land is cleared; when prices fall, the rate slows.

4. Indirect drivers. Even consumers not buying Brazilian products contribute — global meat demand has displaced agriculture across the world, pushing Amazonian cattle into forest where they wouldn't otherwise have gone.

5. Tourism + finance. European banks have financed Amazon agribusiness; consumer-funded carbon offsets that don't actually reduce emissions perpetuate the problem.

The CASE for BRAZILIAN FARMERS + GOVERNMENT.

1. The decision is made locally. Forest clearance requires a Brazilian farmer to do the work (or hire workers) + a Brazilian truck to move the timber/cattle. The proximate decision-maker is Brazilian.

2. Domestic policy matters massively. Under President Bolsonaro (2019-22), IBAMA was weakened, fines went unenforced, and Amazon deforestation rose ~60% above prior rates. Under Lula (from 2023), enforcement resumed and the rate fell ~50%. SAME global demand, but very different outcomes — proving that domestic policy is a powerful lever.

3. Brazil is a sovereign nation. It has the right to develop its territory + decide its agricultural policy. Calling for global consumers to dictate is sometimes resisted as 'eco-colonialism'.

4. Indigenous + small-farmer management. Indigenous-managed Amazon land has ~3× LOWER deforestation than non-indigenous land. The choice of WHO MANAGES the forest is a Brazilian/domestic issue.

5. Rural inequality. For some Brazilian farmers (especially settlers in the 'arc of deforestation'), clearing forest is a SURVIVAL STRATEGY in the absence of alternative livelihoods. Blaming individual farmers ignores rural poverty.

The synthesis — shared responsibility.

Neither extreme is right. Amazon deforestation is the product of a CHAIN that includes:

1. Global demand (consumers) →
2. International trade (Cargill, JBS, etc.) →
3. Brazilian government policy (enforcement / deregulation) →
4. Brazilian farmer decisions (local clearance) →
5. Indigenous + local communities (managers or resistors).

EACH LINK in the chain is necessary. Removing any one breaks the chain. The honest framing is shared responsibility + shared agency for change:

• Global consumers can reduce demand (lower meat consumption; choose deforestation-free supply chains).
• Importing countries can regulate (EU Deforestation Regulation 2025; UK Deforestation Action Plan; US potential equivalent).
• Brazilian government can enforce (IBAMA strengthening, satellite monitoring, prosecutions) + invest in alternative livelihoods.
• Brazilian farmers can adopt sustainable agriculture (silvopasture, intensification on existing land rather than clearing new).
• International finance (REDD+, Amazon Fund) can incentivise conservation.

Judgement.

The statement that global consumers are 'the real cause' captures an important truth that is often ignored — without demand, the economics of deforestation would not exist. BUT it underplays the agency of Brazilian institutions, which the Lula vs Bolsonaro contrast shows is enormous. The MOST USEFUL framing is that deforestation is a demand-driven, supply-enabled problem — solving it requires action on both. The EU Deforestation Regulation (2025) is the first serious attempt to bind the demand side; Brazil's improved enforcement under Lula is the supply-side complement. Either alone is insufficient; together they could reduce Amazon clearance dramatically.

The 4GE1 examiner credits candidates who recognise the GLOBAL-LOCAL CHAIN and reach a defensible balanced verdict.

Fragile-environment degradation in the 21st century is the product of an INTERACTION between physical environmental conditions (climate, rainfall, soils, ecology) and human activities (agriculture, energy, policy, demand). Assessing the relative importance requires (a) examining the physical drivers, (b) examining the human drivers, and (c) recognising the interactions + feedbacks that make the two inseparable in practice.

PHYSICAL drivers.

In the Sahel, the climatic margin between Sahara and savanna means that even small changes in rainfall trigger major vegetation responses. The Inter-Tropical Convergence Zone shifts seasonally; its position depends on Atlantic SSTs (Atlantic Multidecadal Variability) and global warming patterns. The 1968-85 drought reduced rainfall by ~20-30% — a physical climate event with severe consequences regardless of human activity. Climate projections suggest the Sahel will see more variable rainfall, more intense droughts and possibly slight average drying through the rest of the century. Soils in the Sahel are sandy + low-organic — physically prone to wind erosion once vegetation is removed.

In the Amazon, the physical baseline is high rainfall (>2000 mm/yr) supported by evapotranspiration that recycles ~50% of the forest's own rain. Recent climate change is producing more severe droughts (2005, 2010, 2015-16, 2023-24 were historic Amazon droughts), making the forest more vulnerable to fire and dieback. Lateritic soils are nutrient-poor — once cleared, fertility collapses in years.

HUMAN drivers.

In the Sahel:

• Overgrazing by cattle + goats beyond carrying capacity.
• Over-cultivation of marginal land for cash crops (cotton, groundnuts).
• Fuelwood collection (~90%+ of rural energy).
• Population growth (~3%/yr in some Sahel countries).
• Lake Chad over-abstraction (90% loss 1960-2020 reflects irrigation withdrawals + climate).
• Conflict + displacement (Boko Haram, Sahel insurgencies) concentrate land pressure.

In the Amazon:

• Cattle ranching ~80% Brazilian Amazon clearance (Brazil 300m herd, world's largest).
• Soy ~10% (~30m ha total Brazilian soy area).
• Logging (legal + illegal); mining (illegal gold in Yanomami territory).
• Infrastructure (Trans-Amazonian Highway, BR-319) opens access.
• Government policy (Bolsonaro deregulation 2019-22 saw deforestation rise ~60%; Lula re-enforcement halved it from 2023).
• Global demand (China beef, EU soy) pulls the agriculture into the forest.

INTERACTIONS + FEEDBACKS — neither cause works alone.

The crucial point is that human and physical drivers do not operate independently — they INTERACT through positive feedbacks:

• In the Sahel, drought (physical) + overgrazing (human) → vegetation loss → higher albedo (physical) → less rainfall (physical) → more drying → more overgrazing pressure. The feedback locks the system into degradation.
• In the Amazon, climate-driven drought (physical) + forest clearance (human) → reduced evapotranspiration → less rainfall → more drying → more fires → more forest loss. The 20-25% deforestation tipping point would convert the eastern Amazon to savanna self-sustainingly.

So 'physical vs human' is a false binary. Physical conditions create the VULNERABILITY; human activities provide the TRIGGER + AMPLIFICATION; feedbacks LOCK IN change.

The 21st-century context — humans now ALSO drive the physical.

A complication: in the 21st century, human activities (greenhouse gas emissions) are CHANGING THE PHYSICAL BASELINE itself. Sahel rainfall variability + Amazon drought frequency are themselves partly anthropogenic via climate change. So the 'physical drivers' increasingly contain a human-decision component. This collapses the human-vs-physical distinction further. The 4°C of cumulative warming over the Arctic, the more severe Amazon droughts, the shifting ITCZ patterns are all consequences of GLOBAL human emissions, magnified locally.

Quantitative judgement.

If we attempt a rough split:

Amazon degradation is MORE HUMAN-DOMINATED because clearance is overwhelmingly commercial. Sahel degradation is MORE EVENLY SPLIT because rainfall variability provides such a large physical component. BUT in both cases, humans are now the dominant driver because (a) human actions provide the trigger, (b) human emissions amplify the climate baseline, and (c) human policy choices determine whether degradation continues or is reversed.

Policy implications.

The judgement matters because it shapes solutions:

• If degradation is mostly 'physical' (climate), responses are limited to adaptation.
• If degradation is mostly 'human', responses can address the drivers directly.

The Sahel Great Green Wall (started 2007, ~21 African countries, ~$33bn pledged at One Planet Summit) is a human-action response. Farmer-managed natural regeneration in Niger has regreened ~5m ha since 1980s. These prove human action can REVERSE desertification even as climate continues to challenge.

The Brazilian Amazon under Lula since 2023 has seen deforestation FALL ~50%, also through human policy choice (IBAMA enforcement, satellite monitoring, prosecutions). The EU Deforestation Regulation (2025) addresses the demand side.

In both cases, HUMAN INSTITUTIONS — international policy, national enforcement, indigenous land rights, agricultural subsidies — are the operational levers. Physical conditions set the limits; human choices determine the outcomes within those limits.

Verdict.

In the 21st century, fragile-environment degradation is OVERWHELMINGLY HUMAN-DRIVEN even when physical climate stress provides the trigger. This is true for Amazon deforestation (~80%+ human) and for Sahel desertification (still ~half human, with the physical half itself partly human via climate change). The MOST CONSEQUENTIAL DRIVERS — global beef and soy demand, Brazilian agricultural policy, Sahel land-management practices, climate-change emissions — are all human decisions. The PRACTICAL IMPLICATION is that protecting fragile environments depends primarily on HUMAN INSTITUTIONS — international policy, national enforcement, indigenous rights, market regulation, and emissions reduction. Pearson 4GE1 mark schemes reward candidates who reach a defensible balanced verdict that emphasises HUMAN AGENCY without ignoring physical preconditions.