7.3 Biodiversity and the effect of human interaction on ecosystems Flashcards
Importance of biodiversity
Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem.
Different species depend on each other for:
Food
Shelter
Maintenance of the physical environment
A high biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for these three things.
Consequences of human activity on biodiversity
Many human activities, or consequences for human activities, are reducing biodiversity in individual ecosystems and on a global level. These include:
Producing waste (destruction of habitats to make space for landfill and toxic chemicals from landfill waste can leach into the soil).
Deforestation (destruction of forest habitats that contain high biodiversity).
Global warming (disruption of ecosystems and reduced biodiversity due to flooding of coastal habitats, coral bleaching, increased frequency of extreme weather events and many other factors caused by increasing global temperatures).
Maintaining biodiversity
The future of the human species on Earth relies on us maintaining a good level of biodiversity.
Just like any other species in an ecosystem, humans rely on many other species to survive. For example:
We rely on photosynthetic organisms to produce oxygen, without which we cannot respire.
We rely on pollinator species such as bees to pollinate our food crops.
We rely on many plant species for medicine.
Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction.
Human population
Human population growth globally has been increasing exponentially for the last 150 years.
There are many reasons for this exponential growth, including:
Improved technology leading to an abundance of food = rapid increase in birth rate.
Improved medicine, hygiene and health care = decrease in death rate.
Rapid growth in the human population and an increase in the standard of living mean our negative effect on the environment is also increasing.
As increasingly more resources are used to sustain the growing human population, more waste is produced and more pollution is created.
Unless waste and chemical materials are properly handled, pollution will continue to be created.
Pollution
Water Pollution - caused by toxic chemicals, untreated sewage, fertilisers.
Land pollution - caused by toxic chemicals and discarded rubbish.
Air pollution - sulphur dioxide and nitrogen dioxide.
Peat bogs
Bogs are areas of land that are waterlogged and acidic – plants living in bogs do not decay fully when they die due to a lack of oxygen.
The partly decomposed plant matter accumulates over very long periods of time and forms peat.
The carbon that would have been released into the atmosphere as carbon dioxide (if the plants had been able to fully decompose) is instead stored in the peat.
Peat bogs are also important habitats for many species.
Peat bogs are drained so that the area can be used for farming.
Peat can be dried and used as a fuel.
Peat can be used to produce compost for gardens or farms to increase food production.
Negative impacts of destroying peat bogs
Carbon dioxide is released into the atmosphere when peat is burned as a fuel – this contributes to global warming.
Similarly to fossil fuels, peat bogs take so long to form that peat is effectively a non-renewable energy source.
The available peat bog habitat area for many species of animals, plants and microorganism is decreasing, reducing biodiversity.
Peat bogs are being destroyed faster than they can form – they are being used unsustainably.
Deforestation
Deforestation is the clearing of trees (usually on a large scale).
If trees are replaced by replanting it can be a sustainable practise.
Unfortunately, this is not often the case and unsustainable deforestation is occurring in many places (forests are being cut down faster than they can regenerate).
Unsustainable deforestation is occurring on a large scale in the rainforests of tropical areas for various reasons including:
To provide more land for farming (eg. cattle and rice fields).
To grow crops from which ethanol-based biofuels can be produced.
As the amount of the Earth’s surface covered by trees decreases, it causes increasingly negative effects on the environment and is a particularly severe example of habitat destruction.
Undesirable effects of deforestation include:, Extinction of species , Loss of soil, Flooding, Increase of carbon dioxide in the atmosphere.
Greenhouse gases
A greenhouse gas is a gas that absorbs infrared radiation from the Sun so it remains trapped in the Earth’s atmosphere.
This is important to ensure Earth is warm enough for life, however if levels of these gases in the atmosphere increase it leads to an increase in the greenhouse effect which causes the Earth’s average temperature to rise.
There are many greenhouse gases, the most important are:
Water vapour
Carbon dioxide
Methane
Nitrous oxides
CFCs
Greenhouse effect
The Sun emits rays that enter the Earth’s atmosphere.
The heat bounces back from the
Earth’s surface.
Some heat is reflected back out into space.
Some heat is absorbed by greenhouse gases and is trapped within the Earth’s atmosphere - this is normal.
However, as the levels of greenhouse gases in the atmosphere rise due to human activities the Earth’s average temperature rises beyond normal (an enhanced greenhouse effect), causing global warming.
Consequences of global warming
The consequences of global warming due to an enhanced greenhouse effect include:
Ocean temperatures increasing, causing melting of polar ice caps / rising sea levels / flooding / coral bleaching.
Increasing temperatures causing extreme weather like super storms, flooding, droughts.
Changes in or loss of habitats due to these extreme weather events.
Decreases in biodiversity as food chains are disrupted and extinction rates increase.
Increases in migration of species to new places, including increased spread of pests and disease.
Evidence for global warming
There is scientific consensus (almost all scientists agree) that global warming is happening and that human activities are largely responsible for the most recent warming.
This scientific consensus is based on systematic reviews of thousands of scientific research papers that have been ‘peer reviewed’ by other scientists (the method used by scientists to check each other’s work in order to ensure that
research findings are valid).
Although they can make good predictions, it is difficult for scientists to say for certain what the consequences of global warming will be.
Methods to reduce Negative human impacts on biodiversity
The increasing human population and the activities of humans (including waste production, peat bog destruction, deforestation and our contributions to global warming) are causing a reduction in global and ecosystem-level biodiversity.
Methods to reduce include:
Breeding programmes for endangered species.
Protection and regeneration of rare habitats.
Reintroduction of field margins and hedgerows in agricultural areas where farmers grow one type of crop.
Reduction of deforestation and co2 emissions by some governments.
Recycling resources rather than dumping waste in landfill.
