IB Environmental Systems and Societies

1. Topic 2.7
Measuring changes in a system
http://www.youtube.com/watch?v=
xMQ0Ryy01yE

2. 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

3. 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

4. The International Nuclear Event Scale
Chernobyl, Ukraine, 1986
Kyshtym, Russia, 1957
Three Mile Island, USA, 1979
Windscale, UK, 1973

5. 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

6. 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)

7. 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/
2014/02/environmental-
impact-assessment.html

8. The Three Gorges Dam Project
http://edroness.blogspot.mx/2014/0
2/the-three-gorges-dam-project-
china.html

9. 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