Humans and their Environment
Humans often upset the balance of different populations in natural ecosystems or change the environment so that some species find it difficult to survive.
With so many people in the world, there is a serious danger of causing permanent damage not just to the local environments but also to the global environment unless out overall effect is managed carefully. Humans rely on ecosystems for food, water and shelter.
Scientists collect 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 atmostpheric temperatures
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
Humans and their Environment 2
- Developed countries - High standard of living
- Developing countries - Low standard of living
Impact humans make -
- Non renewable resources being used a lot (coal oil ect)
- Raw materials being used up rapidly
- Land is being used up by dumping waste, buildings, farming, transport networks and quarrying
- More waste is being produced = More polution
- Water - sewage, fertiliser or toxic chemicals
- Air - with smoke and gases such as sulfur dioxide = acid rain
- Land - with toxic chemicals such as pesticides and herbicides which may be washed from the land into waterways
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.
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.
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....
The term biodiversity refers not only to the number of different species. It also refers to all the variations within and between species, and all the differences between the habitats and ecosystems that make up the Earth’sbiosphere.
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.
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.
Carbon dioxide can be sequestered in...
- Green plants
- Peat Bogs
Storing carbondioxide is an important factor of removing carbon dioxide from the atmostphere
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
- 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
- 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 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
- 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.
- 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 for the digested material to be removed through
- An outlet so the biogas can be piped to where it is needed.
Bacteria involved in the experiment works best at 30 degrees
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.
At each stage in a food chain, less material and less energy are contained in the biomass of the organisms. This means that the efficent of food production can be improved by reducing the number of stages in food chains.
The efficencu of food production can also be improved by restricting energy loss from food animals by limiting their movement and by controlling the temperature of their surroundings.
(Because energy is lost through faeses, respiration, movement and maintaining body temperature)
Factory farming = Lifestock (Birds ect)
Intensive farming = All types of farming (animals and wheat ect)
.....This can be done through factory farming where you.....
- Prevent animals from moving around too much - This conserves energy which can be used to increase biomass
- Keeping their surroundings warm - This preserves energy that would be used to maintain body temperature, so that is can be used to increase biomass
There are two main types of factory farming
- The chicken is kept in a small cage which prevents much movement. This cuts down energy use in muscle contraction so less energy is transferred out of the food chain
- Kept indoors - less heat energy is transferred into surroundings
Zero-grazing dairy farming
- Cows produce 10x their normal milk yeild
- Stand on concrete floors, and may become lame
- Vast quantaties of animal waste created, add to green house gases
Advantages and Disadvantages of Factory Farming
- Less energy is transferred out of the food chain, so more energy is avaliable for human consumption
- It is less labour intesntive, as the animals are all contained in a limited area
- There is less risk of attack from predators such as foxes
- Production costs cheaper
- There is a greater risk of dicease spreading through the animals as they are in close contact
- Some people feel that the technique is inhumane or cruel to animals
- Some people belive that the quality of the product is poorer compared to free range
Calculating Energy Efficeny
Calculating Energy Efficiency (Calculations)
This bullock has eaten 100 kJ of stored energy in the form of grass, andexcreted 63 kJ in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kJ. So how much has been used up in respiration?
The energy released by respiration
= 100 - 63 - 4 = 33 kJ
Only 4 kJ of the original energy available to the bullock is available to the next stage in the food chain, which might be humans.
The efficiency of this energy transfer is:
4/100 × 100 = 4%
As the population has grown so has the demand for fish.
If fish are caught at a quicker rate than the remaining fish are able to reproduce, the fish stock with decline. Trying to harvest more fish than the sea can produce is an example of unsustainability.
Why are the size of fish declining?
- When people fish they use nets that only catch the big fish and leave the baby and small adult fish
- This means the small adult fishes will have small fish
- Eventually all fish will be small - This is articifical selection (Humans are only selecting the big fish)
The EU places regulations to conserve fish stocks.....
Setting fishing quota's- One boat can only catch a certain amount of fish
Limiting net size
The increasing demand for food has led scientists to investigate alternative ways of obtaining food through microorganisms.
Mycoprotein is a high-protein food produced from the fungal biomass of a soilfungus called Fusarium . It also has a high fibre content, and is low in fat with no cholesterol. This makes it a healthy, vegetarian alternative to meat.
Mycoprotein is grown in a fermenter - an apparatus for growing cultures on a large scale.
It grows quickly, its better for you than meat, and its very sustainable.