Overexploitation Flashcards Preview

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Flashcards in Overexploitation Deck (17):

Whats is the definition of a protected area provided by the IUCN

clearly defined geographic space, recognised, dedicated and managed, through legal or other effective means, to
achieve the long-term conservation of nature
with associated ecosystem services and cultural values


Define over-exploitation

harvesting/ using resources at rates which exceed the ability of these populations to regenerate


What are the requirements required for sustainable exploitation

Rate of resources harvest must be less than or equal to rate of resource renewal


Why are large organisms (e.g rhinos and tuna) more susceptible to exploitation`

They have low intrinsic max. reproductive rates


What data supports the idea that overexploitation is a significant cause of human induced extinction

D.S.Wilcove et al. (1998) found that that OE threatened 17% of endangered species mentioned in US recovery plans


How much is the legal wildlife trade worth

the legal wildlife trade in 2005 was worth $293 billion (Roe 2008)


What is the largest threat to large, tropical invertabraates

Over hunting by indigenous communities (Cunnningham et al., 2009)


An example of overexploitation in amphibians

1 billion frogs per are shipped from Indonesia to France and the US to use in food Warkentin et al. 2009


What evidence is there to suggest that humans have been OE organisms for millenniums

Flint spearheads
made by western European CroMagnons
became gradually smaller due to the decreasing size of prey (Martin 1984).
Mega fauna becoming extinct after humans colonise initially people free areas


Example of a modern megafauna nearly driven to extinction by OE

Bison bison existed in the tens of millions in the 1850s but were driven to near extinction by the 1900s


Why is mahogany so vulnerable to commercial extirpation

beautiful pliable wood
natural distributions in forests experiencing rapid conversion rates
low-density populations
non-pioneer late secondary plant


Why are is it difficult to implement sustainable forestry and give an example

There is a lack of financial incentive. Economic logic dictates that trees should be felled whenever their rate of volume
increment drops below the prevailing interest
rate (Pearce 1990).
In Bolivia mahogany trees can felled at 40cm in diameter. At this size they increase by 4% yearly whilst on average mahogany prices increase by 1%. But in Bolivia the real interest rates are >10% so there is an economic incentive to cut down all trees of any value (Gullison 1998)


What are the current global trends in fisheries

Since the 1990s, first time global catch has levelled off despite continuing growth in effort and technology. Aquaculture is still increasing (Reynolds and Peres 2005)


What does it mean to fish down marine food webs?

OE targets large fish until they disappear, and turn to increasingly small fish (Pauly et al. 1998)


Describe the typical harvesting trajectory of fisheries

When a population of fish is found, new fisheries tend to join quickly as the catch/effort is high. Technology and ability to fish in aggregations maintain high catches even when MSY has been passed. Before overfishing is recognized young fish stop showing up in the nets and the yield quickly drops.


Describe the logic of overexploitation

If the rate of population increase of exploited
species is lower than the monetary growth rate of
alternative investment options, then
overexploitation always pays off


How much of the world's fish stocks are fully fished or over exploited