Topic 10.3 Human Effects on Ecosystem Flashcards
The human population explosion
-As people learned to farm plants and animals, more children survived and the populations grew.
-Later: machines enabled us to farm on larger scales, we can change the environment with reservoirs etc, and medicines have developed.
-This means more children are surviving and growing to older ages.
-This then means engines have been developed that burn fossil fuels into the atmosphere, rainforests are being cleared to make room to grow crops etc, and overfishing is occurring.
-All of these activities have been driven by the desire to provide ourselves with food, shelter and goods, are having a major impact on the ecosystems of earth.
Human influences on ecosystems: Climate change
-The fossil record shows us how often the world has gone through ice ages and periods of tropical heat or desertification.
-Global temperatures are increasing, having an inevitable effect on global climate.
-The levels of carbon dioxide and other greenhouse gases in the atmosphere are increasing at an unprecedented rate.
-The difference is that this time it is happening fast and there is growing evidence that they are a direct result of human activities.
Human influences on ecosystems: Depletion of biological resources
-As the population has grown, so has the demand of resources.
-In developed parts of the world people have gone beyond fulfilling basic needs (they eat more food than needed and want a greater variety).
-As a result biological resources are being depleted and ecosystems destroyed- both on land and seas.
Human influences on ecosystems: Loss of biodiversity
Biodiversity is being affected in a number of ways:
-Overfishing
-Habitat reduction
-As a result of climate change
Publishing findings
-When a scientist has carried out research, they publish their findings in scientific journals.
-Before the paper is published:
-Other scientists, who are experts in the field peer review the research.
-If the peer reviewers all agree that the paper is valid and reliable, then the paper will be published.
–> Scientists have to make sure the research they want to publish is at the highest standard
Scientific conferences
-Scientists in the same field regularly meet up regularly at scientific conferences.
-They share data, discuss ideas, and listen to a number of presentations.
-They can take a look at other work in their field, meet up with others, collaborate, and move investigations forwards.
How to evaluate research
-Whether or not to take notice of conclusions.
-Methodology needs to be checked for validity.
-Need to know the size of the study to see if the measurements have been carried out with precision/accuracy.
-If any other scientists have carried out the methodology and have similar results.
-Knowing if anything affected or biased the study.
Intergovernmental Panel on Climate Change (IPCC)
-The IPCC is a body arising from the United Nations Environmental Programme and the World Meteorological Organisation.
-The panel analyses research from scientists all over the world, on climate change and produces regular unbiased reports based on available data to be used by politicians and decision makers globally.
-The role of the IPCC is ‘to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts’.
Greenhouse gases
-Greenhouse gases reduce heat loss from the surface of the earth.
-They maintain temperature at the surface of the earth at a level suitable for life.
-Greenhouse gases include: carbon dioxide, methane and water vapour.
Radiation from the sun: Greenhouse effect
-Some of radiation from the sun is reflected back into space by the atmosphere.
-Some of the radiation is absorbed by the atmosphere.
-Infrared radiation is what makes us feel warm.
-It has a fairly short wavelength.
-It is absorbed by the surface of the earth and then radiated from the surface at a longer wavelength.
-Some of the radiation is absorbed and re-radiated back to the earths atmosphere by greenhouse gas molecules in the atmosphere. This is known as the greenhouse effect.
Evidence for global temperature increases
-UK Met Office have daily weather records going back to 1869.
-Recent weather records also suggest that the earths surface temperature is increasing.
-In 1998 the IPCC gathered a lot of dat to produce a graph of global temperature.
-Other sources of data are called temperature proxies.
Frozen isotopes
-Antarctic and Greenland ice cores are a widely used source of temperature proxies.
-Scientists drill deep down into the ice and then analyse the air trapped in the different layers.
-The oxygen isotopes in melted ice (18O and 16O) reflect the air temperature when the ice layer was laid down.
-Atmospheric carbon dioxide levels can also be measured.
-Analysis from over 300,000 years is shown.
Dendrochronology
Dating of past events using tree ring growth.
-Used to confirm radiocarbon measurements.
Peat bog dating
Using cores taken from beat bogs that show growth patterns over hundreds/thousands of years.
-Used to confirm radiocarbon measurements.
Evidence for increasing levels of carbon dioxide
-The Mauna Loa curve is a series of readings taken at regular intervals at the Mauna Loa observatory on Hawaii.
-The air is sampled continuously at the top of four 7-metre tall towers and an hourly average of CO2 is taken.
-The air is relatively free from local pollutants and scientists believe it is representative of the air in the Northern Hemisphere.
-Ice core data also show clear changes in carbon dioxide concentration.
-CO2 can also be measured in the oceans and seas.
The role of methane
-Methane is a potent greenhouse gas.
-Over 20 it has had a greater effect of global warming than CO2.
-Methane breaks down naturally high in the atmosphere in a series of reactions that eventually form CO2 and water molecules.
-Scientists have calculated that up to 60% of the methane in the atmosphere is now produced by human activity.
