Lecture20_Extinctions

Also cooling occurred in cause early pleistocene with

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Unformatted text preview: no; would have been largely synchronous globally, and is not. also, cooling occurred in Cause? early Pleistocene with no extinction of large mammals Climate change? no; extinctions occurred without replacement by new taxa; many vacant niches Competitive exclusion? remain unfilled still Human hunting (Martin, 1984)? most plausible; can explain high selective, asynchronous,and patchy patterns The 6th mass extinction Are we causing a mass extinction? W hat’s the evidence? 1 in 8 birds, 1 in 4 mammals, 1 in 5 invertebrates, 1 in 3 amphibians and half of all turtles face extinction Paleoclimate - study with stratigraphic record or isotopic record Stratigraphic —> desert —> tropical —> glacial Cross-bedded sandstone, coal beds, glacial till Isotopic —> oxygen isotope data in ice cores warming .7C over 20th century Atmosphere: increase shown from Mauna Loa records Increase of green house gases Climate models Effects of Climate Change - glacial retreat; sea-level rise; extreme weather events (flood, drought, etc.); changes in agricultural yield; species extinction; increases in range of disease vectors Coral Reef Bleaching 2/3 of polar bears will disappear by 2050 due to loss of habitat and pray Major loss 50-90% of penguins over last 50 years due to loss of habitat and pray...
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