overexploitation

Question 1

what is over exploitation

Answer 1

the harvesting of a renewable resource faster than it can be produced
of threated or near threatened species 72% are being over exploited for commerce, recreation or subsistence

Question 2

give some examples of species which have been made exitinct by overexploitation

Answer 2

the passenger pigeon was once one of the most numerous bird species in the world with a population of 1-5 billion individuals in the early 1800s but the commercilisation of piegon meat as cheap food lead to europeans hunting the birds on a massive scale leading to massive population declines.

Question 3

what is the maximum sustainable yield model

Answer 3

the maximum rate at which new individuals are added to a population is one quater the product of the intrinsic growth rate times the carrying capacity
if harvesting exceeds the maximum rate at which individuals are added to a population then the pop will not maintain a positive growth rate and will decline to extinction

MSY depends on the rate of pop grwoth and the carrying capacity

Question 4

what is a fixed harvest quota

Answer 4

if the quota is too high the population will be driven to exinction
harvesting will be sustainable if the initial pop levels above maximum sustainable yield but will lead to declines if pop dips below it

lower quotas are safer- only lead to decline if pop goes below N1 on graph

Question 5

what is a proportional harvest

Answer 5

when all equilibria are stable including maximum sustainable yeild

Question 6

why are maximum sustainable yields considered simplistic

Answer 6

they fail to account for the size or age structure of populations as well as key demographic and environmental stochasticity that can alter species population growth rates and carrying capacity which arent fixed parameters but can vary through time

Question 7

what is commercial overexploitation

Answer 7

the unsustainable harvesting driven by legal or illegal markets e.g. fishing shows 33% of fish are overharvested resulting in population crashes
over exploitation of commerically viable species is common especially in countires lacking strong regulations and enforcement or have no incentives for species protection

Question 8

give a example of a species which has been commercially over exploited

Answer 8

the newfoundland cod whose population crashed by 99%- didn’t lead to extinction but population was unable to bounce back to original numbers

Question 9

how have quotas been used to help combat commercial overexploitation

Answer 9

help to fish sustainably but bycatch can cause some issues with 25-75% of the harvest in fishing operations being dumped back into the sea dead or dying
this can be combated by improving fishing equipment or technology as well as rasing public awarness helping people choose sources of seafood more wisley

Question 10

give an example where legislations have been introduced to help combat the effects of commercial fishing

Answer 10

whaling
- larger species were targeted and crashed first closley followed by smaller species
- 1986 the international whaling commission banned commercial whaling to allow stocks to recover
some species recovered such as the humpback hwale but others less so such as the blue whale despite being protected since 1966

Question 11

why, despite protection, do some species which have been commercially overexploited not bounced back

Answer 11

• even after populations recover they still have genetic diversity
  e.g. pinnipeds were hunted almost to the point of extinction in 18th and 19th centurary for blubber but research found that 11 species show genetic signs of severe bottlenecks with effective population sizes declining to less than 500

Question 12

in what instances was genetic diversity lower after commercial exploitation

Answer 12

1) if the species went through bottlenecks
2) if the species have small current population sizes
3) if the species breed on land (easily accessible by human hunters)

Question 13

what are the main solutions to combat commercial over exploitation

Answer 13

1) certification schemes e.g. marine/forestry stewardship council which boost standards across industries

2) international agreements such as CITES

Question 14

what are the different CITES appendixes

Answer 14

I= trade permitted only under exceptional circumstances
II= trade strictly controlled
III= request for assistance in controlling trade of species protected in a specific country

Question 15

what areas are vulnerable to subsistence overexploitation

Answer 15

High human density
new road/transport

links enabling access

increasing commercial trade

Question 16

what is meant by recreational overexploitation

Answer 16

the target and overexplotation of largest and most fecund individuals for ‘fun’ e.g. recreational fishing or trophy hunting
- can lead to population declines
- restocking programmes boost numbers but can damage natural populations e.g. hybridisation of non native species, invasive species

Question 17

give an example of cases where recreational overexploitation as causes population declines

Answer 17

hunting and habitta loss reduced the Bengal tiger populations in India from 40,000 to less than 1,800 in a mere 100 yrs

Question 18

why might there be public defences when measures are put in to stop recreational hunting

Answer 18

in many places in many families it is a cultural experience passed down from generation to generation

recreational hunting can also be a major contributer to local economies e.g. outdoor industry association reported that 34 billion dollars was spent on hunting trips, equipment and licences