Human Interference (Leaving Cert Geography): Revision Notes

Human Interference

The Amazon rainforest has faced unprecedented human interference since the 1970s, when the Brazilian government began actively encouraging industrial development and resource exploitation. This interference has had devastating consequences not only for Brazil but for the entire planet, as the Amazon produces approximately 20% of the world's oxygen and serves as a crucial carbon sink.

The scale of human impact

During the 1970s, Brazil was desperately trying to attract industry and allowed multinational corporations (MNCs) to exploit the Amazon's vast natural resources. Rapid population growth has also contributed to forest clearance for settlement purposes. Today, very few areas of the rainforest remain untouched by human activity.

The major forms of human interference include:

• Deforestation for logging
• Intensive agricultural practices
• Industrial activities
• Settlement and urbanisation

Deforestation

Scale and extent

Since the Brazilian government opened the rainforest for exploitation, roughly 20% of the Amazon has been destroyed - an area of approximately 5.5 million km². While logging may provide short-term economic benefits, the long-term environmental effects are overwhelmingly negative.

The logging industry

Logging represents the primary cause of deforestation in Brazil. Despite improved techniques and greater international awareness about rainforest protection, unsustainable logging continues. The Brazilian government estimates that 75% of all logging in the Amazon is illegal.

The situation worsened in the late 1990s when growing Asian economies had depleted their own timber supplies. Asian logging companies purchased large areas of the Amazon at low prices, leading to further deforestation to supply timber for the global construction boom of the 1990s and 2000s.

Environmental consequences of deforestation

Biodiversity loss

Deforestation destroys the habitats of countless plant and animal species, leading to a significant loss of biodiversity. All rainforest ecosystems are interconnected - removing one component destroys the remaining parts. When trees are cut down, birds lose their homes and food sources, leading to population decline and even extinction.

Soil degradation

• Loss of soil fertility occurs as the forest canopy is removed
• Increased soil erosion happens when torrential rainfall hits exposed ground
• Laterisation - intense leaching occurs as water percolates through the soil
• The lack of plant litter means humus is no longer formed in the soil
• Intense sunlight bakes the soil into hard, impermeable laterite during dry seasons

Climate impact

The Amazon produces roughly half of its own rainfall through evapotranspiration - water evaporated from soil and vegetation into the atmosphere. When tree numbers are greatly reduced, insufficient moisture is evaporated to produce heavy rainfall, causing remaining trees to dry out and die.

Loss of medicinal resources

Rainforests contain over 50% of the world's plant species, and roughly 25% of the world's medicine derives from rainforest plants. Less than 1% of all plant species have been tested for medicinal value, meaning potential cures for serious diseases are being lost as species become extinct.

Intensive agricultural practices

Cattle ranching

Cattle ranching has been responsible for the majority of deforestation occurring in the Amazon from the 1960s to the 1980s. Currently, 75% of deforested areas are used for cattle pasture. Increased demand for beef in the 1980s led to more intense deforestation as trees were cleared by MNCs for ranching using slash-and-burn techniques.

This method proved highly unproductive because many valuable hardwood trees were burned rather than sold. Meanwhile, other areas were being cleared for timber and industry, making the overall rate of deforestation much higher than necessary. Brazil remains one of the world's largest beef producers, with government targets to double beef production between 2014 and 2018.

Cash crop cultivation

Cash crops are widely grown in Brazil to help pay off international debt. Soya bean represents the most widely grown cash crop, exported primarily to the US and UK as animal feed. Originally grown in the south and southeast, increased global demand has shifted production north to the Amazon Basin.

Genetically modified soya bean seeds were developed specifically to grow in the Amazon's climate, leading to intensive cultivation that has made Brazil the second-largest soya producer globally.

Environmental consequences of intensive agriculture

• Slash-and-burn techniques destroy entire ecosystems by removing natural vegetation, which stops the nutrient cycle and leaves soil infertile within a few years
• Land abandonment occurs because clearing new land in the Amazon is cheaper for farmers than using artificial fertilisers to maintain existing farmland
• Soil erosion rapidly occurs on abandoned land, which is washed away into rivers, causing flooding and further ecosystem damage

Industrial activity

As Brazil has become more industrialised, demand for raw materials has increased dramatically. The Amazon Basin contains wealth of valuable materials including iron ore, gold, bauxite and diamonds, leading to increased exploitation over the past 30 years.

Mining

The Amazon Basin's valuable mineral deposits have led to extremely destructive mining operations. Large forest areas are cleared to gain access to proposed mining sites, and additional areas are cleared for temporary housing for mine workers and transportation infrastructure.

Though fewer trees are directly felled by mining compared to cattle ranching, the roads constructed for material transport give illegal loggers better access to the rainforest, increasing overall deforestation rates.

Environmental and social impacts:

• Toxic materials like lead and mercury are washed into rivers, causing water pollution and damaging aquatic ecosystems
• Many indigenous tribes have been displaced or eliminated due to pollution of their water supplies
• Indigenous people have been forced to abandon their homes, with some murdered to intimidate others into cooperating

Hydroelectric power (HEP)

Approximately 79% of Brazil's electricity comes from hydroelectric power, though two-thirds of the country's hydroelectric potential remains untapped. Brazil operates 158 HEP plants with 48 additional dams planned by 2020, with 30 of these located in the Amazon rainforest.

Blast furnaces

The Carajás region contains close to 50 blast furnaces, which have destroyed 75% of local forests. With forest resources running out, illegal logging has occurred in conservation areas and indigenous lands. Despite laws requiring 80% of forest to remain untouched, these regulations are not enforced, resulting in large-scale Amazon destruction.

Settlement

Impact on indigenous peoples

The destruction of the Amazon rainforest has had devastating effects on indigenous tribes who have lived there for thousands of years. Today, an estimated 900,000 indigenous people remain from the 11 million who lived in Brazil when the Portuguese arrived in the 1500s. Over 100 tribes have been completely eliminated.

The most common cause of death among indigenous peoples is contact with outsiders. These isolated populations have not developed immunity to common diseases, making them extremely vulnerable. Statistics indicate that 50% of tribal people die within the first year of contact with outsiders due to diseases like measles, influenza and the common cold.

Urban settlement: Manaus case study

As eastern cities became more densely populated, settlements developed further inland to accommodate rising populations. Manaus exemplifies this rapid urban growth, designated by the Brazilian government as a 'growth pole'.

Originally founded as a river port and rubber trading centre, Manaus has become highly industrialised with modern chemical production, car manufacturing, shipbuilding and electronics industries. This industrialisation has attracted 2 million people who migrated from the east seeking employment.