4.1 The effects of the population explosion
The human population is growing rapidly and the standard of living is increasing.
More waste is being produced. If it is not handled properly it can pollute the water, the air and the land.
The activities of humans reduce the amount of land available for other animals and plants.
Raw materials, including non-renewable resources, are rapidly being used up.
4.2 Land and water pollution
Toxic chemicals such as pesticides and herbicides can pollute the land.
If sewage is not properly handled and treated it can pollute the water.
Fertilisers and toxic chemicals can be washed from the land into the water and pollute it.
Herbicides are used to kill weed plants.
Pesticides kill insect pests.
4.3 Air pollution
When we burn fossil fuels, carbon dioxide is released into the atmosphere.
Sulfur dioxide and nitrogen oxides can be released when fossil fuels are burnt.
These gases dissolved in rainwater and make it more acidic.
Acid rain may damage trees directly. It can make lakes and rivers too acidic, so plants and animals cannot live in them.
Air pollution can cause global dimming as tiny solid particles in the air reflect away the sunlight.
4.4 Deforestation and peat destruction
Deforestation is the destruction or removal of areas of forest or woodland.
Large-scale deforestation has led to an increase in the amount of carbon dioxide released into the atmosphere (from burning and the actions of microorganisms).
It has also reduced the rate at which carbon dioxide is removed from the air by plants.
More rice fields and cattle have led to increased levels of methane in the atmosphere because both rice and cattle produce methane as they grow.
The destruction of peat bogs releases carbon dioxide into the atmosphere.
All plants release carbon dioxide when burnt because carbon compounds are "locked up" in them during the carbon cycle.
4.5 Global Warming
Increasing levels of carbon dioxide and methane in the atmosphere give an increased greenhouse effect, leading to Global Warming - an increase in the temperature of the surface of the Earth.
Global warming may cause a number of changes including:
- climate change
- rising sea levels
- loss of biodiversity
- changes in migration patterns
- changes in distribution of species
Some land has been deforested so that crops can be frown, from which biofuels can be produced.
Ethanol-based fuels can be produced by anaerobic fermentation of sugars from plants.
digestion of starch to sugar by carbohydrase, fermentation (anaerobic respiration) by yeast and distillation
The ethanol distilled from the fermentation product can be used as fuel in motor vehicles.
Pros: efficient, no toxic gases produced, carbon neutral.
Cons: lots of plant needed, so lots of space needed.
Biogas is mainly methane. It is made by the anaerobic fermentation of a wide range of waste substances and plant material containing carbohydrate.
Biogas generators can be small, to supply a single family or large, to deal with the sewage from an entire city.
Many different microorganisms are involved in biogas production.
Biogas is produced by fermentation. The bacteria respire anaerobically using waste carbohydrate.
4.8 Making food production efficient
Biomass and energy are reduced at each stage of a food chain. The efficiency of food production is improved by reducing the number of stages in our food chains.
If you stop animals moving about and keep them warm, they waste less energy, making food production more efficient.
4.9 Sustainable food production
Sustainable food production means producing food in a way which can continue for many years.
It is important to control net sizes and impose fishing quotas to conserve fish stocks, so breeding continues and the decline in numbers is halted.
The fungus Fusarium is grown on sugar syrup in aerobic conditions to produce mycoprotein foods.
Mycoprotein = aerobic
Biogas = anaerobic