Humans and Their Environment

  • Created by: Katherine
  • Created on: 07-04-13 21:05

Human Impact on the Environment

Humans have an impact on both local and global environments.

Humans often upset the balance of different populations in different ecosystems or/and change the environment so some species find it difficult to survive.

Humans rely on ecosystems for food, water and shelter.

Reasons for an increase in impact:

  • This may be because the population of the world is rapidly increasing, due to modern medicines and farming methods, which have reduced the number of people dying from hunger and disease.
  • Our increasing population puts pressure on the environment, as we take the resources we need to survive. 
  • People are also demanding a higher standard of living, so we use more raw resources and therefore more energy for the manufacturing processes.
  • This has led to us taking more resources, more quickly and many raw materials are being used up quicker than they're being replaced. Eventually they may run out.
  • It also leads to more waste being produced and less space for other species.
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Deforestation is the cutting down of forests.

Deforestation has occurred to:

  • provide timber to use as a building material
  • provide wood to be burnt as a fuel
  • produce paper from wood
  • provide land for agriculture so there can be an increase in the cattle and rice fields to provide more food OR so crops can be grown from which biofuels, based on ethanol, can be produced.
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Problems with Deforestation

Deforestation on a large scale (rainforests) leads to:

  • an increase in carbon dioxide released into the atmosphere because of the burning of wood and the activities of microorganisms which produce carbon dioxide as a waste product of respiration.
  • a reduction in the rate at which carbon dioxide is removed from the atmosphere during photosynthesis and 'locked up' for many years as wood.
  • more methane in the atmosphere released by the cattle and rice fields which replace the forests. Rice fields have ideal conditions (warm & wet) for decomposers which produce and release methane.
  • a reduction in biodiversity, due to the destruction of a large number of species' habitat, putting them in danger of becoming extinct. - Biodiversity is the number of species in a habitat. 
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Biodiversity is the number of species in a habitat. 

Habitats like tropical rainforest contain a large number of different species.

Deforestation destroys habitats which pits many species in danger of becoming extinct so the biodiversity is reduced.

Biodiversity causes lost opportunities:

  • Useful products produced by organisms that became extinct are never discovered.
  • Newly discovered plants and animals can be great sources of food, fibre for clothing and new medicines
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Destruction of Peat Bogs

Bogs are areas of land that are acidic and waterlogged.

Plants don't fully decay when they die because there's not enough oxygen. These partly-rotted plants gradually build up to form peat.

The carbon in the plants is stored in the peat instead of being released into the atmosphere.

Peat bogs are often drained so they can be used as farmland.

Peat is cut up and dried to use as fuel.

Peat is sold to gardeners as compost

When peat bogs and other areas of peat are drained or destroyed the peat starts to decompose, so carbon dioxide is released into the atmosphere, adding to the greenhouse effect.

'Peat Free' composts are coming increasingly more important to reduce the demand for peat, as destruction to peat bog releases carbon dioxide into the atmosphere....

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Climate Change

Levels of carbon dioxide and methane in the atmosphere are increasing and contributing to 'global warming'.

An increase in the Earth's temperature by only a few degrees celcius may cause big changes in the Earth's climate. The consequences:

  • May cause a rise in sea level. - as the sea gets warmer it expands which is can lead to coastal flooding in low-lying places. e.g. The Maldives and Netherlands
  • Higher temperatures will make ice melt, causing the sea level to rise even more.
  • May change weather patterns in many parts of the world. - Many regions may suffer more extreme weather patterns. e.g. longer droughts
  • May result in changes in distribution of species - Some species may become more widely distributed if conditions they thrive in exist over larger areas. Other species may become less widely distributed if conditions they thrive in exist over smaller areas.
  • May cause changes in migration patterns, e.g. some birds may migrate further north, as more northern areas are getting warmer.
  • May reduce biodiversity - If some species are unable to survive a change in the climate, and become extinct. 
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Collection of Data

Scientists are collecting data by:

  • Using satellites to monitor snow and ice cover
  • Using satellites to measure the temperature of the sea surface
  • Recording the temperature and speed of ocean currents
  • Automatic weather stations are constantly recording atmospheric temperatures.

We can use this data as evidence. However not all evidence is reliable.

It is reliable if it:

  • Covers a wide enough area
  • Has a long enough/suitable time scale
  • Lots of scientists have obtained the same results using different methods. 
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Carbon Dioxide

Carbon is present in the atmosphere in the form of carbon dioxide (CO2)

Many processes lead to carbon dioxide being released into the atmosphere. e.g. burning fossil fuels and respiration.

Too much carbon dioxide in the atmosphere can lead to global warming.

Carbon dioxide can be sequested (locked up) in natural stores, including:

  • Oceans, lakes and ponds
  • Green plants (Carbon dioxide is removed during photosynthesis and stored as carbon compounds.)
  • Peat bogs 

Storing carbon dioxide is an important factor in removing carbon dioxide from the atmosphere.

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The Greenhouse Effect

The temperature of the Earth is a balance between the heat from the Sun and the heat radiated back into space. 

Gases in the atmosphere naturally act like an insulating layer.

These gases are called 'greenhouse gases'

The main ones are carbon dioxide and methane.

These gases absorb most of the heat that would normally be radiated out into space, and re-radiate it in all directions, including towards the Earth. 

Without greenhouse gases we would get very cold at night.

The Earth is gradually heating up because of the increasing levels of greenhouse gases - global warming

Global warming is a type of climate change and causes other types of climate change. e.g. changing rainfall patterns

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  • Biofuels are carbon neutral.
  • Biofuels can be made by natural products by fermentation.
  • Fermentation is when bacteria or yeast break sugars down by anaerobic respiration.
  • There are two main types of biofuel; ethanol and biogas.
  • Ethanol is made by the anaerobic fermentation of sugar.
  • Biogas is made by the anaerobic fermentation of waste material.


  • Ethanol is made by the anaerobic fermentation of sugar.
  • Yeast make ethanol when they break down sugar by anaerobic respiration.
  • Glucose -> Ethanol + Carbon Dioxide + Energy
  • Sugar cane juices and glucose  dervied from maize starch by the action of carbohydrase can be used.
  • The ethanol is distilled to seperate it from the yeast and remaining glucose before it is used.
  • In some countries cars are adapted to run on gasohol - a mixture of ethanol and petrol. e.g. Brazil
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  • Biogas is mainly methane (70%) and carbon dioxide (30%).
  • Biogas can be produced by anaerobic respiration of a wide range of plant products or waste material containing carbohydrates.
  • Sludge waste from sewage works or sugar factorise is used to produce biogas on a large scale. 
  • It is made in a simple fermenter called a digester or generator.
  • Biogas generators need to be kept at a constant temperature to keep the microorganisms respiring.
  • There are two types of generator; Batch and continuous.
  • Biogas can't be stored as a liquid, as it needs too high a pressure, so it needs to be used straight away.
  • It is used for heating, cooking, lighting or to power a turbine to generate electricity.

Small Scale:

  • Small biogas generators can make enough gas for a small village or family to use for cooking and lighting. 
  • Human wast, waste form keeping pigs and food waste can all be digested by bacteria to produce biogas.
  • By-products are used to fertilise crops and gardens
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Biogas Generators

Batch Generators:

  • Make biogas in small batches
  • They're manually loaded up with waste, which is left to digest, and the by-products are cleared away at the end of each session.

Continuous Generators:

  • Make biogas all the time
  • Waste material is continually fed in
  • Biogas is produced at a steady rate.
  • They are more suitable to large-scale biogas projects

All Biogas Generators Have:

  • An inlet for waste material to be put in
  • An outlet foe the digested material to be removed through
  • An outlet so the biogas can be piped to where it is needed.
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Biogas Generators

Designing a Generator:

  • Cost: continuous generators are more expensive, because waste has to be continuously pumped in and digested material mechanically removed all the time.
  • Convenience: Batch generators are less convenient because they have to be continually loaded, emptied and cleaned.
  • Efficiency: Biogas is produce most quickly at 35'C, so generators in some areas have to be insulated, or kept warm for a fast production. e.g. using solar heaters. Leaks will lead to gases being lost
  • Position: Generators should be situated away form homes as the waste will smell on delivery, and the generator is bet located near to the waste sauce. 
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Advantages of Biofuels - Biogas

  • The raw material is cheap and readily available
  • Biofuels are a greener alternative to fossil fuels. They are carbon neutral, as the CO2 released into the atmosphere was taken in by plants recently.
  • The use of biofuels doesn't produce significant amounts of sulphur dioxide or nitrogen oxides, which cause acid rain.
  • The production of biogas reduces the amount of methane being released into the atmosphere from untreated waste, reducing the effects of global warming.
  • The digested material is a better fertiliser than undigested dung, so people can grow more crops.
  • Biogas saves the need to collects wood or fuel.
  • Biogas generator work as a waste disposal system, getting rid of waste which could cause disease and pollute water supplies. 
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