Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Theoretical ecology wikipedia , lookup
Introduced species wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Occupancy–abundance relationship wikipedia , lookup
Overexploitation wikipedia , lookup
Island restoration wikipedia , lookup
Latitudinal gradients in species diversity wikipedia , lookup
Extinction debt wikipedia , lookup
Lecture 7 Biology 5865 – Conservation Biology Extinction Extinction is the most irreversible and tragic of all environmental calamities. With each plant and animal species that disappears, a precious part of creation is callously erased. M. Soule, 2004 (In Groom et al. 21006) From Conservation Minnesota Magazine – Winter 2009 The U.S. Fish and Wildlife Service estimates that expenditures for wildlife watching are equivalent to the revenues generated from all spectator sports, amusement parks and arcades, non-hotel casinos, bowling centers and skiing facilities combined. Minnesota is no exception. Wildlife watching in Minnesota in 2006 generated an estimated $699 million in retail sales, $1.25 billion in total economic activity, 14,461 jobs, and over $94.6 million in state and local tax revenue. http://library.fws.gov/nat_survey2006_economics.pdf Science 307, 646, 2005. Hawaiian Monk Seal Time Magazine Hawaiian and Mediterranean monk seals are endangered and at risk of extinction with populations dipping below 1,200 and 500 individuals, respectively. Recovery of the Peregrine Falcon •Last survivor, Martha, died in the Cincinnati zoo in 1914 •Why – hunting, egg collecting, habitat loss Extinct United States Birds Labrador Duck – extinct 1878, Over-harvesting eggs and feathers Extinct – 1904 habitat loss – hunting for feathers Great Auk – extinct 1844, hunted for eggs and down Heath Hen – extinct 1932 – hunting, predation of nests Extinction – What is the issue? • Tremendous loss of species over the past 400 years • Thousands, if not tens of thousands, of species are predicted to go extinct in the coming decades (Millennium Ecosystem Assessment 2005) • Present rate of extinction is 100 and perhaps 1000 times faster than the present rate of speciation • Unknown consequences for the future and lost opportunities Worldwide – Species with “Known” Extinctions since 1600 those currently “Threatened with Extinction” Data compiled from Hunter (2002, p.126) & Primack (2010, p. 140). Threat Proportion Known of of Species Extinct Extinction Threatened Mammals Birds Reptiles Amphibians Fish Freshwater mussels Flowering plants 87 1464 27% 131 2065 21% 22 622 8% 5 2279 36% 92 1722 6% 303 ? ? 83 9115 4% United States – Review of Current Status (past 150 years) of Selected Groups of Animals and Plants Presumed Possibly Critically extinct extinct imperiled Mammals 1 0 8 22 3 27 Reptiles 0 0 7 Amphibians 1 1 21 Freshwater fish 16 1 91 FW mussels 17 20 73 Flowering plants 11 126 1,031 Birds From Stein et al. Precious Heritage. (2000) What is the status in Minnesota? - From MN DNR web site Special Endangered Threatened concern Total All species 96 101 242 439 Plants 57 66 133 256 Birds 7 6 15 28 Mammals 0 1 14 15 Fish 0 1 20 21 Mussels 8 12 15 25 Reptiles & amphibians 2 3 9 14 “Background” Extinction Rates - from Groom et al. (2006) • Prior to human dominance on Earth, background rate of extinction (all species) is estimated to have been about 0.1 to 10 species per year • During mass extinctions, rate was 1-2 orders of magnitude greater – hence, perhaps 1 to 1000 species per year • Yet, these are based on the fossil record of marine organisms – unknown whether they can be applied to terrestrial organisms Prediction of Extinction Rates – the Species-Area Model • From E.O. Wilson (1992) – The Diversity of Life, Belknap Press, Cambridge, MA. • Assumes that there is a relationship between number of species and area of habitat - species/area effect • Species/area effect estimated by S =CAZ • S = number of species, A = Area, C is a constant (yintercept) that varies depending on the size of the area, and Z is a constant that measures the slope of the line relating S and A Extinction Rate – Species/Area - 2 • Alternative equation – log S = (log C) + z (log A) – basically the equation of a straight line • Z values often range between 0.15 and 0.35 based on a variety of previous studies • A Z value of 0.30 translates into a simple rule of thumb – if the area is reduced by 90 % then the number of species it supports will be halved (Fig. 7.10 in Primack 2006) • Wilson then chose the rate at which tropical forest habitats are decreasing - he chose 1.8 % per year (from Myers 1989) Extinction Rates Species/Area - 3 • With different z values: 1. z = 0.30, then 0.54 % species lost per year, 2. z = 0.35, then 0.63 % species lost per year, and 3. z = 0.15, then 0.27 % species lost per year • Wilson then used “conservative” estimate of 0.27 % species lost per year and multiplied this by a “conservative” estimate of the number of species in the tropical forests - 10,000,000 species • Result is 0.27 x 10,000,000 = 27,000 species going extinct per year!!!! From Groom et al. (2006) Extinction Rate – Species/Area - 4 • Analysis assumes – (neither of which is probably reasonable) – species have broad geographic ranges - those with small geographic ranges may be eliminated earlier, and – suitable habitat will remain within the ranges of most species. • Background or normal extinction rate is assumed to be about 1 to 10 species per year • Estimated extinction rate in this example varies between 2700 to 27,000 times greater than the background extinction rate in tropical forests – is this a mass extinction period? • About 1,000,000 years is the “typical” life span of a species • Note - tropical forests are estimated to contain one-half of the species on Earth Extinction Rates – Direct Observation – from Groom et al. (2006) • IUCN (International Union for the Conservation of Nature) Red List documents 844 extinctions since 1500, a loss of 2.2 % of all evaluated species and 0.04 % of all described species • Certainly an underestimate because all species are not described • Corrections made by using the best-known groups of species Extinction Rate – Direct Observation - 2 • For example, 100 birds and mammals have gone extinct between 1900-2000 • Hence, 15,333 species of birds and mammals – 0.65 % loss per century or 1 bird or mammal species per year • Compared with the historical record for birds and mammals – 0.0003 species per year • Hence, 333 times greater than background rate of extinction “we estimate that 6300 affiliate species are “coendangered” with host species currently listed as endangered. Current extinction estimates need to be recalibrated by taking species coextinctions into account.” “If a species is at risk of extinction, its close relatives have a higher than average chance of being at risk” Not on web site Mass Extinctions and Global Change • Estimates from the fossil record indicate that about 99.9% of all species that have ever lived have gone extinct • Extinction has been a constant process over the 3.5 billion year history of life on earth End of the Pleistocene (about 11,000 ybp) 33 genera went extinct in less than 1000 years in North America - the cause ? 1. Over hunting by humans crossing over from Siberia to Alaska, or 2. Significant and rapid climate change Island Species - read Song of the Dodo – by Quammen Species are particularly vulnerable to extinction – many examples in Primack (2010) • Extinction of 11 species of moas (large flightless birds) by the Maoris in New Zealand • Hawaiian islands - 44 species of endemic land birds out of 82 went extinct between the arrival of Polynesians and the Europeans - probably a combination of habitat changes, disease, and over hunting Defining Extinction • Extinction is hard to define - e.g., cahow is a rare seabird thought to be extinct since last seen in 1621, but rediscovered in 1906 and a breeding colony discovered in 1951 (Hunter, 2002) • Rule of thumb is that a species is extinct after no evidence of its existence after 50 years • Consider the Ivory-billed Woodpecker - may be extinct in North America but a few may be surviving in pine forests of eastern Cuba, Arkansas, Florida?; had not been seen since the 1950's but potential sighting in Arkansas in 2004 – observation under severe scrutiny and questionable • Basic problem in extinction rates is that most species have never been described - “centinelan extinctions” according to Wilson (1992)