Topic 2.7

Measuring changes in a system

http://www.youtube.com/watch?v=xMQ0Ryy01yE

Ecological Gradients

• These occur where ecosystems meet or where an ecosystem ends

• They occur due to gradual changes in biotic and abiotic factors close to such boundaries

• They are usually measured using transect quadrat sampling (random quadrat sampling alone is not sufficient). – A belt transect is a transect with width (1-2 m) throughout

which quadrat sampling is carried out.– The belt can also be spilt into squares. Sampling locations

can then be chosen using a random number generator

Measuring Abiotic and Biotic Changes Due To A Specific Human Activity

• On 26th April 1986 there were two explosions at the Chernobyl Nuclear Plant in Ukraine which blew a hole in the top of the reactor

• Radioactive particles escaped into the atmosphere over a 10 day period

• There was widespread contamination over much of western Europe – affecting humans, soil, plants and animals

http://edroness.blogspot.mx/2014/01/point-source-pollution-incidents.html

The International Nuclear Event Scale

Chernobyl, Ukraine, 1986

Kyshtym, Russia, 1957

Three Mile Island, USA, 1979

Windscale, UK, 1973

Responses to the Chernobyl Accident• Local firefighters from the nearby town of

Pripyat arrived and over 3 hours extinguished the external fires, receiving large radiation doses. Sand, lead and clay were dumped into the reactor by helicopter

• A concrete shell was build around the reactor. Radiation is still leaking from it and it requires repairs

• Pripyat was evacuated and is now a ghost town

• Dykes, dams and concrete walls were constructed to try to prevent radioactive contamination of soil and water

• Satellite imaging and radiation detectors were used to track the plume of airbourne radiation that was released

Environmental Impact Assessments (EIAs)

• These became law in the US in 1969 and are being increasingly used around the world

• They are a method of predicting possible impacts on the environment prior to any major project, and helps to decide if it should go ahead

• In some countries they have legal status, in others they just supply information for decision-making (in some they may be ignored in favour of economic benefits)

Environmental Impact Assessments (EIAs)

• The first stage is always a baseline study to assess the status of the environment prior to the project– Habitat types and area– Species present– Biodiversity– List of endangered species– Hydrology– Human population and requirements– Soil types and quality

• The quality of an EIA depends to a large extent on the quality of the baseline study

• All EIAs are speculative to some extent due to the inherent complexities of ecosystems http://edroness.blogspot.mx/2

014/02/environmental-impact-assessment.html

The Three Gorges Dam Project

http://edroness.blogspot.mx/2014/02/the-three-gorges-dam-project-china.html

Questions

1. Briefly describe the stages of primary succession

2. What is P/R ration and how does it change as succession proceeds

3. List the characteristics of a typical climax community

4. What is plagioclimax. Give examples of how humans may cause it