Human influences on the environment

Sulfur dioxide pollution

• Combines with water vapour to form acid rain, damages plants, aquatic life and soil

• Causes respiratory problems in humans

Carbon monoxide pollution

• Binds to haemoglobin, reducing oxygen transport

• Can lead to suffocation and death

Greenhouse gas

A gas that absorbs infrared radiation from the Sun so it remains trapped in the Earth’s atmosphere

5 greenhouse gases

• Water vapour

• Carbon dioxide

• Methane

• Nitrous oxides

• CFCs

How is carbon dioxide produced

During the combustion of fossil fuels

How is methane produced

By cattle as they digest grass

Greenhouse effect process

• The Sun emits rays that enter the Earth’s atmosphere

• heat bounces back from the Earth’s surface

• some heat is reflected back out into space

• some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere – this is normal

Enhanced greenhouse effect

Happens when increasing levels of greenhouse gases from human activities cause the Earth's average temperature to rise above normal, leading to global warming

Consequences of global warming

• Ocean temperatures and water levels rising

• Increasing temperatures

• Changes in or loss of habitats

• Increase in migration

Eutrophication

The process where minerals from agricultural fertilizers are leached into water bodies, leading to excessive plant and algae growth

What causes eutrophication

Fertilizers high in nitrogen enter water bodies, promoting the overgrowth of aquatic plants and algae at the surface.

How does eutrophication affect aquatic plants

Plants below the water surface die due to reduced light levels caused by excessive surface algae growth.

What happens to dead aquatic plants during eutrophication

Decomposers, such as bacteria and fungi, break down the dead plants.

How do decomposers contribute to oxygen depletion

The increased respiration of decomposers uses up oxygen in the water, reducing dissolved oxygen levels

Effect of eutrophication on aquatic life

The reduced oxygen levels make it difficult for aquatic organisms to survive, leading to their death.

How does water pollution occur due to sewage

Sewage enters waterways when sewers overflow or agricultural waste is washed off fields by heavy rain

What effect does sewage have on bacteria in water

Sewage increases the growth of aerobic bacteria that feed on biological waste.

How do aerobic bacteria affect oxygen levels in water

They reduce the availability of dissolved oxygen as they respire

What happens to aquatic organisms when oxygen levels drop

Organisms who are sensitive to oxygen levels die, only organisms that can survive at low concentrations of oxygen survive

How does sewage pollution impact aquatic biodiversity

Biodiversity decreases

What is another risk associated with sewage in waterways

It can increase the number of pathogenic bacteria, posing health risks

Deforestation

The large-scale clearing of trees, usually for agriculture or development.

How does deforestation cause leaching

Without trees to absorb minerals, rain washes soil minerals into nearby bodies of water

What causes soil erosion after deforestation

Without tree roots to hold soil together, it is easily washed or blown away

How does deforestation disturb the water cycle

It reduces transpiration, leading to less water vapor in the atmosphere, reduced cloud formation, and lower rainfall

How does deforestation affect the carbon cycle

It reduces photosynthesis, decreasing carbon absorption, and increases CO₂ emissions when felled trees are burned

How does deforestation contribute to global warming

Less CO₂ is absorbed by trees, and burning trees releases more CO₂, increasing the greenhouse effect