EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk

EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk

EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk due to: – environmental stochasticity u Random variation in habitat quality u Extreme cases = catastrophes

Environmental Stochasiticity Examples – variable rate of increase Muskox population on Nunivak Island, (Akcakaya et al. 1999)

Environmental Stochasiticity - Example of random K v Serengeti wildebeest data set – recovering from Rinderpest outbreak –Fluctuations around K possibly related to rainfall

EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk due to: – demographic stochasticity u Random variation birth/death rates – “good” years and “bad” years

EXTINCTION PROCESSES EXTINCTION PROCESSES v Rare species are at risk due to: – genetic stochasticity u Random variation in gene freq. due to: – Genetic drift – Bottlenecks – inbreeding

EXTINCTION PROCESSES EXTINCTION PROCESSES A. Specialization – habitat restriction u proboscis monkeys and mangrove swamps

EXTINCTION PROCESSES EXTINCTION PROCESSES A. Specialization – habitat restriction – range restriction u golden-lion tamarins

EXTINCTION PROCESSES EXTINCTION PROCESSES A. Specialization – habitat restriction – range restriction – body size and home-range size u maned wolf Photo by Pete Oxford

EXTINCTION PROCESSES EXTINCTION PROCESSES A. Specialization B. Catastrophes – earthquakes, asteroids – 5 mass extinctions – Cretaceous-Tertiary extinctions

EXTINCTION PROCESSES EXTINCTION PROCESSES A. Specialization B. Catastrophes – the human catastrophe – humans have caused 75% of extinctions since 1600

HUMANS AND EXTINCTION HUMANS AND EXTINCTION A. Role of Overexploitation – Lessons from North America

HUMANS AND EXTINCTION A. Role of Overexploitation – Bison A. Role of Overexploitation – Bison presettlement: ca. 60 million presettlement: ca. 60 million used food, hides used food, hides weapon against Native Americans weapon against Native Americans by 1889: only 600 by 1889: only 600

HUMANS AND EXTINCTION HUMANS AND EXTINCTION A. Role of Overexploitation B. Role of Exotics – introduced organisms – cause of 20% of extinctions since 1600

HUMANS AND EXTINCTION HUMANS AND EXTINCTION B. Role of Exotics – Feral Pigs u game species u destroy understory and groundcover u effect on brown honeycreeper u expensive to exterminate Po’ouli, n = 3 on 2/03

HUMANS AND EXTINCTION HUMANS AND EXTINCTION B. Role of Exotics – Domestic Cats u domesticated to kill pests u in 1/3 of U.S. households u humans support high densities

HUMANS AND EXTINCTION HUMANS AND EXTINCTION v Cats: Effects on Native Wildlife – Wisconsin: 19 million songbirds, 140,000 game birds per year – Great Britain: 50 million small mammals per year – Australia: endangerment of eastern barred bandicoot Photo: Ian McCann

HUMANS AND EXTINCTION HUMANS AND EXTINCTION C. Role of Human Population Size – most abundant mammal (Suzuki) – currently about 6.7 billion – stabilize at ~9 billion by 2042

HUMANS AND EXTINCTION C. Role of Human Population Size – Habitat Destruction – Habitat Disturbance – The “human footprint” on habitats is today’s biggest threat to mammals 1. Human density 2. Land transformation 3. Access to areas 4. Electrical power infrastructure

CONSERVATION AND HUMAN RESOURCE USE  Humans use ca. 40% of total terrestrial NPP

CONSERVATION AND HUMAN RESOURCE USE  Humans use ca. 40% of total terrestrial productivity  Land pre-empted for agriculture and cities: extinction of 5% of land mammals Richmond, VA – USDA photo

CONSERVATION AND HUMAN RESOURCE USE  Humans use 20-30% of total terrestrial productivity  Agriculture pre-emption: extinction of 5%  Energy pre-emption: extinction of 10% more of land mammals Texas oil wellsRussian coal power plant

CONCLUSION  Conservation will fail unless: – human population is controlled – human resource use is moderated