Topic 4—C: Diversity and classification- 7. Agriculture and biodiversity Flashcards
(14 cards)
Impact of agriculture on biodiversity
Farmers try to maximise the amount of food they can produce from a given area of land
The methods they use reduce biodiversity
- woodland clearance is done to increase the area of farmland. It directly reduces the number of trees and sometimes the number of different tree species. It also destroys habitats so some species could lose their shelter and food source. This means that species will die or be forced to migrate to another suitable area, further reducing biodiversity
- hedgerow removal is also done to increase the area of farmland by turning lots of small fields into fewer large fields. This reduces biodiversity for the same reasons as woodland clearance
- pesticides are chemicals that kill organisms (pests) that feed on crops. This reduces diversity by directly killing the pests
- herbicides are chemicals that kill unwanted plants (weeds). This reduces plant diversity and could reduce the number of organisms that feed on the weeds
- monoculture is when farmers have fields containing only one type of plant. A single type of plant reduces biodiversity directly and will support fewer organisms (e.g. as a habitat or food source) which further reduces biodiversity
Conservation schemes
- agriculture is one way of producing the resources we need from the environment- we need it to produce food and fibres for clothing as well as some medicines and fuels
- biodiversity helps maintain the environment
- it provides us with new sources of food and medicines and it benefits agriculture
- so there needs to be a balance between agriculture and biodiversity
- conservations try to achieve this through conservation schemes
Examples of conservations schemes
- giving legal protection to endangered species
- creating protected areas such as SSSis (sites of special scientific interest). These restrict further development including agricultural development
- the environmental stewardship scheme encourages farmers to conserve biodiversity e.g. by replanting hedgerows
What can you calculate if you need to work out whether there’s a correlation between two variables or not?
Spearman’s rank correlation coefficient
Spearman’s rank correlation efficient formula
Rs = 6 (sum of) d2/ n(n2-1)
D= difference in rank between the data pairs
n= total number of data pairs
- result of the test is a number between -1 and +1
- if the figure is -1 there is a perfect negative correlation between the two variables
- if the figure is +1 then there is a perfect positive correlation
- the closer the figure is to 0 the weaker the correlation is
When you get the result what do you need to find out?
- if it’s statically significant or not
What do you first need to come up with?
A null hypothesis
- it should always be that there is no correlation between the factors your investigating- even if you expect that it will be
What does the result of the spearman’s rank test allow you do decide?
Whether the null hypothesis can be rejected
To determine whether the null hypothesis can be rejected what do you consult?
A table of critical values
What is the result compared to?
The critical value at p=0.05 which corresponds to n for the data your looking at
What does the 0.05 value represent?
The point at which the correlation your investigating would occur 95 out of 100 times so there’s only a 5% chance that the correlation is down to chance
When can you reject the null hypothesis?
If the result of your test is higher than this value
If your result is a negative number what do you ignore when comparing it to the critical value?
The minus sign
What is said if the result is higher than the critical value?
- null hypothesis can be rejected
- result is statistically significant
- positive correlation is unlikely to be due to chance
