EE Lecture 35: Drivers of biodiversity decline Flashcards
outline the main aspects of drivers of biodiversity decline
habitat loss
overexploitation
introduced species
chains of extinction
give an example of an extinction where multiple factors contributed to the extinction
when did it go extinct
why did it go extinct
on the island of Raiatea -v. restricted range to start with
Partula turgida (snail)
died out 01/01/96
went extinct due to Euglandina rosea - the native snail popn which predated on them
then the final straw was a microsporidian disease
what does decline in popn normally resulkt from
an interaction between driver and species’ biology
discuss overexploitation in prehistory
megafaunal extinction
why do large species tend to be the most vulnerable
theyre slower to recover
more appealing for hunting
possible danger to human
slower reproductive rates
give an example of a very large mammal that was once v abundant but now extinct
American buffalo
discuss overexploitation in human history
on islands, timings of extinction fits human colonisation MADAGASCAR:1000AD -giant aye aye and sloth lemur AUSTRALIA:5000BC -giant marsupial ground sloth NZ:1350AD -giant moa
when did humans colonise madagascar, which species did this cause decline of
1000AD
extinction of giant aye-aye and sloth lemur
when did humans colonise australia
which species did this cause decline of
5000BC
giant marsupial ground sloth
when did humans colonize NZ
which species did this cause decline of
1350AD
giant moa
how is overexploitation happening at present
rising demand for animals
the theory of maximum sustainable yield
what is the MSY
the theory of maximum sustainable yield
what is the logistic model of a popn growing towards its carrying capacit
dN/dT = rN(1-N/K)
K -caryring capacity
r-intrinsic rate of increase
what curve should the logistic model of a popn growing towards its capacity look like
a sigmoidal curve
time on x
N on y
at what carrying capacity is the max rate of popn grown
when N=K/2 which = rK/4 individuals per year
what two rates need to be thought about when working out MSY
harvesting rate
recruitment rate
what is habitat loss aka wrt declining biodiv
fragmentation
what has habitat loss been driven by
the expansion of the human pop and its economy
what does dispersal between habitat fragments require
corridors
whayt did gareth hardin propose
the tragedy of the commons
what was the tragedy of the commons
suggests why we use biodiversity unsustainably
what effect can habitat loss have on species
edge effects
What are edge effects
changes in population that occur at the boundary of two habitats.
Areas with small habitat fragments exhibit especially pronounced edge effects that may extend throughout the range.
why are introduced species drivers of biodiversity decline
outcompete
predate
knock on effect
give an example of a knock on effect leading to biodiv decline due to introduced species
foxes kill birds, droppings dont fertilise ground, vegetation changes
what are chains of extinction
loss of one species affects another
give an example of chained extinction
In Aleutian Islands, sea lions gone, so killer whales eat all the sea otters os the kelp forest disappears
what is the millenium ecosystem assessment
gives a status on the main threats over the last century
give an example of introduced species leading to extinction
Harlequin vs native ladybirds
-recent invasion in britain and belgium
what are the current threats to each biome outlined by the millennium ecosystem assessment
habitat change climate change invasive species overexploitation pollution
what were the first threats to make a difference to biodiversity decline
overexploitation and introduced species
