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 Extinct 1904 habitat loss hunting for feathers Labrador Duck extinct 1878, Over-harvesting eggs and 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). Known Extinct Threat of Extinction Proportion of Species Threatened Mammals 87 1464 27% Birds 131 2065 21% Reptiles 22 622 8% Amphibians 5 2279 36% Fish 92 1722 6% Freshwater mussels 303?? Flowering plants 83 9115 4%
United States Review of Current Status (past 150 years) of Selected Groups of Animals and Plants Presumed extinct Possibly extinct Critically imperiled Mammals 1 0 8 Birds 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 From Stein et al. Precious Heritage. (2000)
What is the status in Minnesota? - From MN DNR web site Endangered Threatened Special 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 =CA Z 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)