Impact of Humans

Humans pose a huge threat to lives of animals, plants and their environment

Our impact is so great due to:

• technologies that change the world so quickly
• population increase
• consumption of natural resources, and waste

Human Population Growth

Humans can adapt to survive in almost all habitats and climates. The human population is increasing rapidly and is threatening the environment.

The population will eventually be limited by these factors:

• food and water supply
• disease and pollution
• over-crowding
• sudden changes in climate

Urbanisation & Industrialisation

More and more people are moving into the cities.

The effects:

• increased pollution due to traffic, energy consumption and waste production
• farmland is built on, land taken out of food production
• loss of natural habitats, as cities and roads are built
• rural communities and cultures dissolve as people leave to live in urban areas

Development of industries

The effects:

• non-renewable fossil fuels are used for energy
• release of greenhouse gases speeds up global warming

Effect of Fertilisers

Intensive farming can damage the environment.

1.  Fertilisers containing plant nutrients are sprayed onto fields

2. Plants grow faster and boost crop yields.

3. Rain means may wash nutrients from the fields and into rivers and lakes (this is called run-off).

4. Eutrophication (hyper-nutirtion from fertisiler pollution) occurs which can kill almost everything living.

• Algae grows fast using up lots of oxygen and blocking sunlight
•  Plants begin to die providing food for microbes
• Microbes increase the competition for oxygen
• Water becomes de-oxygenated causing aquatic life to die

Effect of Pesticides

Pesticides used to kill insects and other crop damaging micro-organisms can effect the food chain

• Pesticides can be abosrbed by small aquatic animals
• Fish eat the animals, which have eaten pesticides
• Birds eat the fish
• Pesticides enters food chain

Fishing and Forestry

Fishing

Unsustainability: the using up of resources faster than they are produced so that they will not continue in the future

Example: North Sea Cod are over-fished so are reproducing slower than are being caught. The effect of this means the cod population is heavily declining

Forestry

Humans burn wood or clear land for farming causing deforestation:

Deforestation: 

• destroys habitats
• causes soil erosion leading to barren land and potential flooding
• causes pollution from combustion
• increased levels of carbon dioxide as loss of photosynthesis