EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at riskRare species are at risk
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at riskRare species are at risk
Time (years)
10 20 30 40 50 60Po
pu
lati
on
s P
ersi
stin
g (
%)
0
20
40
60
80
100
N < 16
N = 16-30
N = 31-50
N = 51-100
N > 100
Bighorn Sheep on Mountain Ranges
Source: Berger (1990, Cons. Biol. 4:91-98)
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– environmental stochasticityenvironmental stochasticity
Random variation in habitat qualityRandom variation in habitat quality Extreme cases = catastrophesExtreme cases = catastrophes
Environmental Environmental StochasiticityStochasiticity
Examples – variable Examples – variable rate of rate of increaseincrease
Muskox population on
Nunivak Island, 1947-1964
(Akcakaya et al. 1999)
Environmental Environmental StochasiticityStochasiticity- - Example of random KExample of random K
Serengeti wildebeest data set – recovering from Serengeti wildebeest data set – recovering from Rinderpest outbreakRinderpest outbreak– Fluctuations around K possibly related to rainfallFluctuations around K possibly related to rainfall
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– demographic stochasticitydemographic stochasticity
Random variation birth/death ratesRandom variation birth/death rates– ““good” years and “bad” yearsgood” years and “bad” years
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– genetic stochasticitygenetic stochasticity
Random variation in gene freq. due Random variation in gene freq. due to:to:
– Genetic driftGenetic drift– BottlenecksBottlenecks– inbreedinginbreeding
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization– habitat restrictionhabitat restriction
proboscis monkeys and mangrove proboscis monkeys and mangrove swampsswamps
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization– habitat habitat
restrictionrestriction– range range
restrictionrestriction golden-lion golden-lion
tamarinstamarins
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization– habitat habitat
restrictionrestriction– range range
restrictionrestriction– body size and body size and
home-range home-range sizesize
maned wolfmaned wolf
Photo by Pete Oxford
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization
B. CatastrophesB. Catastrophes– earthquakes, asteroidsearthquakes, asteroids– 5 mass extinctions5 mass extinctions– Cretaceous-Tertiary Cretaceous-Tertiary
extinctionsextinctions
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization
B. CatastrophesB. Catastrophes– the human catastrophethe human catastrophe– humans have caused 75% of humans have caused 75% of
extinctions since 1600extinctions since 1600
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
A. Role of OverexploitationA. Role of Overexploitation– Lessons from North AmericaLessons from North America
HUMANS AND EXTINCTION
HUMANS AND EXTINCTION
A. Role of Overexploitation– Bison
A. Role of Overexploitation– Bison
• presettlement: ca. 60 millionpresettlement: ca. 60 million• used food, hidesused food, hides• weapon against Native weapon against Native AmericansAmericans• by 1889: only 600by 1889: only 600
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
A. Role of OverexploitationA. Role of Overexploitation
B. Role of ExoticsB. Role of Exotics– introduced organismsintroduced organisms– cause of 20% of extinctions cause of 20% of extinctions
since 1600since 1600
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
B. Role of ExoticsB. Role of Exotics– Feral PigsFeral Pigs
game speciesgame species destroy destroy
understory and understory and groundcovergroundcover
effect on brown effect on brown honeycreeperhoneycreeper
expensive to expensive to exterminateexterminate
Po’ouli, n = 3 on 2/03
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
B. Role of ExoticsB. Role of Exotics– Domestic CatsDomestic Cats
domesticated to domesticated to kill pestskill pests
in 1/3 of U.S. in 1/3 of U.S. householdshouseholds
humans support humans support high densitieshigh densities
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
Cats: Cats: Effects on Native WildlifeEffects on Native Wildlife– WisconsinWisconsin: 19 million songbirds, : 19 million songbirds,
140,000 game birds per year140,000 game birds per year– Great BritainGreat Britain: 50 million small : 50 million small
mammals per yearmammals per year– AustraliaAustralia: endangerment of eastern : endangerment of eastern
barred bandicootbarred bandicoot
Photo: Ian McCann
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
C. Role of Human Population C. Role of Human Population SizeSize– most abundant mammal most abundant mammal
(Suzuki)(Suzuki)– currently about 6.7 billioncurrently about 6.7 billion– stabilize at ~9 billion by 2042stabilize at ~9 billion by 2042
HUMANS AND HUMANS AND EXTINCTIONEXTINCTION
C. Role of Human Population SizeC. Role of Human Population Size– Habitat DestructionHabitat Destruction– Habitat DisturbanceHabitat Disturbance– The “human footprint” on habitats The “human footprint” on habitats
is today’s biggest threat to is today’s biggest threat to mammalsmammals1.1. Human densityHuman density2.2. Land transformationLand transformation3.3. Access to areasAccess to areas4.4. Electrical power infrastructureElectrical power infrastructure
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE
Humans use ca. 40% of total terrestrial Humans use ca. 40% of total terrestrial NPPNPP
www.usda.gov
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE Humans use ca. 40% of total terrestrial Humans use ca. 40% of total terrestrial
productivityproductivity Land pre-empted for agriculture and cities: Land pre-empted for agriculture and cities:
extinction of 5% of land mammalsextinction of 5% of land mammals
Richmond, VA – USDA photo
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE Humans use 20-30% of total terrestrial Humans use 20-30% of total terrestrial
productivityproductivity Agriculture pre-emption: extinction of 5%Agriculture pre-emption: extinction of 5% Energy pre-emption: extinction of 10% more of Energy pre-emption: extinction of 10% more of
land mammalsland mammals
Texas oil wells Russian coal power plant
CONCLUSIONCONCLUSION
Conservation will fail unless:Conservation will fail unless:– human population is controlledhuman population is controlled– human resource use is moderatedhuman resource use is moderated