Transcript Human Impact on Biodiversity

Human impact on
biodiversity
Snow leopard (Panthera uncia)
© 2016 Paul Billiet ODWS
What are the human activities that
are causing a loss of biodiversity?
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Over exploitation
Islandisation
Habitat destruction
Pollution
Introduction of alien species
© 2016 Paul Billiet ODWS
Over exploitation
• Over hunting
• Over fishing
• Clear felling forests
BBC
Clear felling in the Amazon forest
Mongabay.com
American bison skulls waiting to be ground for fertiliser (1870)
© 2016 Paul Billiet ODWS
The passenger pigeon
(Ectopistes migratorius)
© 2016 Paul Billiet ODWS
Songbird foundation
The passenger pigeon
(Ectopistes migratorius)
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Estimated population early 1800s 3 to 5 billion
Extinct in 1914
Reason: Excessive over hunting
The arrival of railways and the telegraph during the period
1860-1890 increased the mobility and co-ordination of the
hunters.
© 2016 Paul Billiet ODWS
Enter the realm of the living
dead
• 1895 a single flock remained
of an estimated 250 000 birds
• A hunt in April 1895 killed
200 000 and maimed 40 000
About 5 000 escaped
• The population was below
the point where it could
recover.
Hunting passenger pigeons
© 2016 Paul Billiet ODWS
The last survivor
• By 1912 the last male bird
died in captivity
• On 1st September 1914 the
last female died in Cincinnati
Zoo.
Martha
© 2016 Paul Billiet ODWS
Islandisation
• Dividing and isolating
populations of species so
that they cannot breed
together
• The human barriers can be
as big as a city or as small as
a road.
ubc
© 2016 Paul Billiet ODWS
Habitat destruction
• The total loss of an
organism’s habitat will
lead to its extinction
• Tropical forests are
disappearing at a rate of 76
000 km2 per year
• This results in the estimated
loss of 4000 to 6000 species
per year.
© 2016 Paul Billiet ODWS
NASA earth observatory
Pollution
• E.g. plastic bags are killing
marine turtles that mistake
them for jellyfish, their
natural food
• Displacement of ecosystems
due to global warming
• If species (e.g. trees) cannot
disperse fast enough they
will become extinct.
© 2016 Paul Billiet ODWS
NOAA Coris
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Introduction of alien species
• Species introduced
accidentally (e.g. rats)
• Species introduced
deliberately (e.g. foxes in
Australia)
• These will increase in
numbers and out compete or
heavily predate native
species
• The aliens have little or no
natural predators to control
them
• Kiwis v rats and cats in NZ.
© 2016 Paul Billiet ODWS
Invasive animals cooperative research centre
European starling (Sturnus vulgaris)
• Between 1890 and 1891, 160 of
these birds were released in Central
Park New York.
• By 1942 they had spread as far as
California.
• An estimate population of between
140 and 200 million starlings now
exist in North America
• One of the commonest species of
bird on Earth
© 2016 Paul Billiet ODWS
European starling (Sturnus vulgaris)
Current distribution
CJKrebs (1978) Ecology
© 2016 Paul Billiet ODWS
The Colorado Beetle (Leptinotarsa
decemlineata)
• A potato pest from North America
• It spread quickly through Europe
© 2016 Paul Billiet ODWS
© P Billiet
The Colorado Beetle (Leptinotarsa
decemlineata)
Begon, Townsend & Harper (1990) Ecology
© 2016 Paul Billiet ODWS
Biological pest control
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Control of pest species using the natural predators
No toxic chemicals involved
Ecological risks
The predator may turn on other non-pest species.
© 2016 Paul Billiet ODWS
Prickly pear cactus (Opuntia
stricta)
• Native of N and S america
• 1839 Introduced into Australia
planted as hedges
• The population got out of
control
• 1880 classified as a pest.
© 2016 Paul Billiet ODWS
The invasion spreads
© 2016 Paul Billiet ODWS
Year
Area invaded
/ ha
1900
4 000 000
1920
23 500 000
1925
24 300 000
Biological control agent Cactoblastis
cactorum
• 1920 Search in the prickly pear’s
native habitats found 50 insect
species that eat it
• 12 were released in Australia
• One species was effective at
controlling it,
the moth Cactoblastis cactorum
from Argentina.
Larva Cactoblastis
Adult moth
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A success story
• Complete control of the cactus achieved by 1940
• Today the cactus is found locally distributed
• As soon as its numbers increase the moth population
increases and the cactus is brought under control.
© 2016 Paul Billiet ODWS