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Introduction to Wildlife & Fisheries Conservation WFSC 304 Lecture 9: Vulnerability to Extinction Defining Extinction • Extinction is hard to define • Rule of thumb is that a species is extinct after no evidence of it exists for 50 years • Cahow—rare seabird thought to be extinct since 1621, but rediscovered in 1906 and a breeding colony discovered in 1951 (Hunter, 2002) • Ivory-billed Woodpecker - may be extinct in North America but a few may be surviving in pine forests of eastern Cuba, Arkansas, Florida. Not seen since 1950 but potential sighting in Arkansas in 2004. • Basic problem in extinction rates is that most species have never been described “centinelan extinctions” according to Wilson (1992) • Even so, we know that a large fraction of defined species are vulnerable: Suppose a taxon is vulnerable. What does the conservation biology groundwork to prevent extinction look like? Tapir case study here (Patrícia Medici TED talk; 11:32) baby tapir Part of extinction vulnerability is low population size and endemism (go hand in hand). Here is a look at the number of endemic plants reported by state. Geological record of extinctions Nearly all species that have ever lived have gone extinct Extinction has been an everpresent but dynamic process over the 3.5 billion year history of life on earth 5 major ancient crashes Plus a 6th (current) crash Cause of 5 major ancient extinction waves? We basically still don’t know, but the meteor hypothesis isn’t very strong: Wikipedia: Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously exposed land. Evidence of marine regressions and transgressions occurs throughout the fossil record, and these fluctuations are thought to have caused or contributed to several mass extinctions, among them thePermian-Triassic extinction event (250 million years ago) and Cretaceous–Paleogene extinction event (66 Ma). At the time of the Permian-Triassic extinction, the largest extinction event in the Earth's history, global sea level fell 250 m (820 ft). #6: Late Pleistocene/Anthropocene (about 11,000 ybp) 33 genera went extinct in less than 1000 years in North America Very clearly demarcated—terrestrial vertebrates over 97# Similar extinctions in Europe, Asia and Australia Some causes discussed in Science Daily article Cause? o Probably: Over hunting by humans Extinction took place in NA at precisely the time humans entered and spread (13.8-11 kbp) Speartips (see 3rd and 7th papers on my website) found in many megafauna carcasses o Possibly (or exacerbated by): Rapid climate change Good video on extinction topic here (9:11) Good article on mammoth extinction: http://www.slate.com/articles/health_and_science/animal_forecast/2013/02/pleistocene_extinction_did_climate _change_or_humans_doom_mammoths_sabercats.html Interesting megafauna tangent—giant arctic camels evolve in NA, later go extinct here but descendants adapt to desert: Nat. Geogr. article The North American Megafauna was huge and wild. Giant beavers, actual lions (larger than those in Africa), rhinos, etc. Tasmanian wolf/tiger Extinct @ 1900 Video from last zoo captives Both sexes have pouch Madagascar Its climate and geological diversity have given rise to a highly diverse group of animals and plants, while isolation has resulted in 70-90 % of all its plants and animals are endemic to the island Its ecosystems are highly degraded, its human population rapidly expanded from 2.5 million in 1900 to 12 million in 1990 Conservationists are closely watching Madagascar because there are so many endemic species to be lost but many efforts are on-going to 1. protect some ecosystems, 2. foster ecotourism, 3. encourage sustainable development, and 4. improve land use practices