Over-exploitation of resources
Quiz: Gill et al. 2009 3. Describe Figure 2. What chronology does this figure suggest?
New Vocab: Gill et al. 2009 Coprolite fossilized dung Coprophilous dung lover Edaphic soil Megafauna(l) large animals Paleoecology study of fossils/dead ecology No-analog no equivalent conditions on Earth today Insolation solar exposure
How many extinctions have humans caused (directly or indirectly)?
Over-exploitation of resources
What caused the megafauna extinction? Climate? Altered habitat Loss of food sources Thermal tolerance (more applicable to reptiles) People? Hunted to extinction Slow growing/reproducing organisms cannot repopulate fast enough
Paleobiology tells us: Climate Change causes extinctions
Lots of climate changes (glacial/interglacial) during the megafauna extinction Cooper et al., 2015
BUT: Megafauna loss precedes other ecological changes Gill et al., 2009
BUT: Megafauna loss precedes other ecological changes Human expansion in Australia Rule et al., 2012
Mystery of the megafauna extinction Climate Altered habitat Loss of food sources Thermal tolerance (more applicable to reptiles) People Hunted to extinction **For N. America and Australia Slow growing/reproducing organisms cannot repopulate fast enough
Spatially, extinctions occur in regions where humans were evolutionarily novel Megafauna lost Human invasion
Timing of megafauna extinction coincides with human arrival Australia Americas New Zealand
Humans hunted megafauna Holes in mammoth bones containing fragments of stone and/or bone projectiles Bones found in Siberia Nikolskiy & Pitulko, 2013
Evidence that humans played a substantial role in megafauna extinction Spatial pattern match between novelty of humans and amount of megafauna loss Timing of human arrival on continents matches extinction events Taxonomic bias towards large mammals and flightless birds (yummy)
Megafauna extinction climate + people Barnosky et al., 2004
Australia lost 21 mammals + 7 flightless birds (~90% of species >10 kg)
Giant Wombat (Diprotodon) Largest known marsupial Extinct ~50,000 years ago in Australia
Red = extinct N. America lost 33 mammals (~80% of species >10 kg)
Short-faced Bear (Arctodus simus) Once ranged throughout the US Weighed up to 1500 lbs Likely ran as fast as 30 mph Extinct 11,000 years ago in N. America
S. America lost 50 mammals (~80% of species >10 kg)
Glyptodon Related to armadillos, but 3 m long and weighing 2 tons Extinct 10,000 years ago in S. America Glyptodon Fossil in Vienna Natural History Museum
Shell close-up Glyptodon
Extinctions in recent human history Counts of species extinct or extinct in the wild since 1500 IUCN/NYTimes
Great Auk (Pinguinus impennis) Flightless birds of N. Atlantic 2.5-3 ft tall Extinct in 1852 Naïve to predation
Dodo (Raphus cucullatus) Flightless birds on Mauritius (S. Indian Ocean) ~3 ft tall Extinct in 1662 Naïve to predation
Steller s Sea Cow (Hydrodamalis gigas) Huge (9 m) marine mammal in N. Pacific Extinct 1768 Hunted to extinction within 30 years of initial discovery
Collapse of North Atlantic Cod Fisheries
California grizzly bear (Ursus arctos californicus) Hunted to extinction (danger to livestock and people) - extinct in 1924
Eastern Elk (Cervus canadensis canadensis) Habitat loss + hunting Extinct 1877
Extinct birds of Hawaii (sample) Causes: Habitat loss Avian malaria Rats & cats
Land snail extinctions Regnier et al., 2015
Land snail extinctions Causes:??? Habitat loss Invasive species Giant African Snail (introduced via pet trade) Rosy Wolf Snail (carnivorous) introduced to control African Snail
What drives modern extinctions? Over-exploitation & direct hunting Habitat loss Invasive predators & pathogens Climate change (on the horizon)
Small Groups Discussion Go through remaining questions from Gill