HUMAN POPULATION

Noadswood Science, 2012

Human Population

To understand the impact of rapid growth in the human population

Friday, April 21, 2023

Developing & Developed

Look at the following – a recent scene from the Glastonbury festival and a shanty town in South America

What issues are involved with this many people?

Developing & Developed

In a given area if the population becomes this vast there is a huge strain on resources needed: space / shelter; food; water (and mates)

There is also a great strain on removal of waste This impacts not only human populations, but any surrounding flora

and fauna

Human Population Projection Human beings compete with other living things for resources

and space – as the world’s population continues to increase, and standards of living improve, there is serious danger of a permanent change to the global environment

Human activities have led to the pollution of the environment, and a reduction in the amount of land available for other animals and plants, which makes it difficult for some species to survive

There is a need to achieve a level of development that also sustains the environment for future generations…

Human Population Projection Like all living things, humans exploit their surroundings for

resources – before the beginning of agriculture about 10,000 years ago, small groups of humans wandered across large areas, hunting and gathering just enough food to stay alive

Population numbers were kept low because of the difficulty of finding food

The development of agriculture led to a population explosion that has accelerated enormously during the past 500 years – unlike other species, humans can adapt to and survive in almost all habitats and climates

Human Population Projection Using the data in the table below plot a graph showing how the

human population has changed over the last 10’000 years: -

YearHuman Population Numbers

(Thousands)

8’000 BCE 5’000

6’000 BCE 10’000

4’000 BCE 20’000

2’000 BCE 35’000

0 200’000

2000 CE 6’000’000

Human Population Projection Human population graph over the past 10’000 years: -

Human Population

In the last 200 years or so the human population has grown very quickly – why? We can grow more food We can cure and prevent illness or disease We have no natural predators Standard of living has improved (electricity, fuel, heat,

cars etc…)

Standards Of Living

People in the developed world enjoy a high standard of living, with abundant food, cars and comfortable housing

People in the developing world have a lower standard of living, but many countries are catching up quickly

Strains on the global environment include: - Non-renewable energy resources (e.g. coal, oil and

natural gas) are being used up rapidly Raw materials are being used up rapidly More waste is being produced More pollution is being caused

Waste

Pollution is the addition of substances to the environment that may be harmful to living organisms

Population growth and increases in the standard of living cause more waste to be produced – If this waste is not handled correctly, it leads to pollution

Pollution can be categorised into the following: - Land pollution Water pollution Air pollution

Land Pollution

Most rubbish is buried in landfill sites and not all of it comprises safe materials – even common household items can contain toxic chemicals such as poisonous metals (many smoke alarms contain radioactive americium)

Industrial waste is also discharged onto the land – many farmers apply pesticides to improve their crops, but these can damage living things (toxic chemicals can be washed from the land into rivers, lakes and seas causing eutrophication)

Eutrophication in the Caspian Sea (turbidity in North)

Water Pollution

Water pollution is caused by the discharge of harmful substances into rivers, lakes and seas

Many aquatic invertebrate animals cannot survive in polluted water, so their presence or absence indicates the extent to which a body of water is polluted

Pollutant Typical Effect

Fertilisers Damage to aquatic ecosystems

SewageDamage to aquatic ecosystems and

humans

Toxic chemicalsDamage to aquatic ecosystems and

humans

Air Pollution

The most common source of air pollution is the combustion of fossil fuels

Pollutant Effect

Smoke

Deposits soot on buildings and trees, causing them damage – permeates the air,

making it difficult for living creatures to breathe

Carbon monoxide Poisonous gas

Carbon dioxideGreenhouse gas that contributes to global

warming

Sulfur dioxide Contributes to acid rain

Deforestation

Humans have been cutting down trees for thousands of years to clear land for farming and building, and for wood to use as a fuel or building material

Forestry is sustainable as long as forests are allowed to replace themselves, or are replanted after felling, but often this is not done – the result is that the world’s forests are steadily shrinking

Crops being grown for biofuels, based on ethanol, is now also playing a major part in deforestation

Deforestation

The world’s forests have changed greatly over the last 10’000 years

Deforestation

The world’s forests have changed greatly over the last 10’000 years

Deforestation

Deforestation leads to: - Forest habitats being destroyed Soil erosion increasing, which causes barren land,

flooding and land slides Atmospheric pollution is caused when forests are cleared

by burning trees

Deforestation also leads to a loss of biodiversity – this refers not only to the number of different species, but also to all the variations within and between species, and all the differences between the habitats and ecosystems that make up the Earth’s biosphere

Deforestation

Deforestation

The loss of forests reduces biodiversity and we run the risk of losing organisms that might have been useful in the future - for example as sources of new medicines

There is also a moral responsibility to look after the planet and its resources

Global Warming

The atmosphere is a thin layer of gases, surrounding the Earth

Certain gases in the atmosphere trap heat, reflecting it back to the Earth’s surface, warming it

This is similar to the glass in a greenhouse, which traps heat inside it (trapping of heat by the Earth’s atmosphere is known as the greenhouse effect)!

Without this atmosphere the Earth would be too cold for life to exist