Earth Sciences 2240F/G Lecture Notes - Lecture 2: Background Extinction Rate, Holocene Extinction, Mastodon
11 Jun 2018
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The Holocene Mass Extinction
1.0 Introduction
• Holocene extinction referred to as the 6th mass extinction within the
Phanerozoic Era is ongoing accelerated loss of species on Earth
• ¼ of species on earth may become extinct by 2125 and up to 3
quarters by 2200
• almost entirely biological: humans and human practices primarily
responsible
o habitat destruction, over-exploitation, pollution and climate
change
• of estimated 10 million species on earth, as of 2008 only 1.8 million
species documented
o 47,677 analyzed by International Union for the Conservation
of nature and 17, 291 considered threatened
• 6th is equal event if not greater than previous extinctions, most of
which have occurred on time scale of 100,000 of greater
• comparision: all of earths large mammals and most birds will be
extinct in 40,000 years
• total background extinction rate of one species per year
• climate facts driving extinction
o beginning of PETM period-most recent period of warming we
can make comparisons with-until its end, the rate of heating
from released GHG was about 0.025 C per 100 years
o comparison- rate of heating during period of global warming
during Cretaceous was 0.000025 C per 100 years
o rate of warming today 1-4 C per 100 years
• i.e. amount of GHG in atmosphere is much less important than rate
at which they are added
• cretaceous, lots of CO2 added, but lifeforms had plenty of time to
either adapt or migrate, so no significant extinctions
• during PETM, rate of addition slow enough that most life adapted or
moved, but some ocean floor extinctions occurred
• rate today is so fast most life forms do not have a hope
2.0 The Extinction Facts
• split extinction into waves
2.1 The First Wave: Spread of Modern Humans 40,000 BP to 1800
• more than half genera of large animals over 44 kg disappeared
(giant deer and bison)
• at 11000 BP, megafauna in NA and Eurasia terminated (mastodons
and saber-toothed tigers)
• Hawaii, arrival of Polynesians exterminated over 2000 bird species
(15% of world total)
• Eurasia, first extinctions from overkill after migration of humans
from east Africa
find more resources at oneclass.com
find more resources at oneclass.com
The Holocene Mass Extinction
• NA, Clovis culture (Paleo-Indian group that appeared at end of last
glacial period) arrived in NA at 13,400 BP and produced first
extinction from overkill at 12,260 BP
• 18000 BP-11,500 BP, global warming may have eliminated food
sources or exposed animals to extreme climates
• latter half, extinctions occurred on Hawaii and New Zealand from
overkill and invasive species introduced by Stone Age farmers
• also disease that jumped from humans to newly encountered fauna
2.2 The Second Wave: Spread of Europeans 1500-1970
• 869 extinctions from 1500-1970
• 90 species of mammals (sea cows sea mink), result of expansion
and migration
• 70x greater than background extinction rate of mammals
• great auk and passenger pigeon among birds killed off
• majority of second wave (72%) occurred on islands; arrival of
Spaniards in Caribbean terminated 36 species of mammals
• second wave primarily due to colonial European expansion
• in order of importance, causes are: over exploitation, habitat
destruction and introduction of invasive species from home
2.3 The Third Wave: Globalization, 1970-2100
• species pops have deteriorated world wide
• greatest numbers of threatened birds, mammals and amphibian’s in
tropical regions around the globe
• 21% mammals, 12% birds and 30% amphibians threatened
• amphibians grown to highest risk, after surviving 300 my even
through end-permian and end-cretaceous extinctions
• since 1970, humans have cut down 40% of worlds forest cover
o i.e. habitat destruction is primary cause of extinctions in this
wave
o continues at accelerated pace, with 15,000,000 hectares of
deforestation annually, size of New Brunswick
o highest rates in Indonesia and South America
o primary reasons for deforestation is to get more arable land
to grow food
o demand for food is expected to double in next 30 eyars
o as pop of humans grow, urbanization becomes a factor: we
kill bears, deer and all other wild creatures that appear in out
towns
• Over exploitation:
o An increasing threat, we use other species for food, medicine
and fuel, and destroy biodiversity by capturing many for pets
or zoos
o Examples:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
1. 0 introduction: holocene extinction referred to as the 6th mass extinction within the. 2. 0 the extinction facts: split extinction into waves. Spaniards in caribbean terminated 36 species of mammals: second wave primarily due to colonial european expansion in order of importance, causes are: over exploitation, habitat destruction and introduction of invasive species from home. Northern leopard frog: fertilizer run off causing eutrophication and dead zones (result of nutrient loading form mississippi river, Oregon and california: 1980s extinctions of amphibians from climate related increases in chytridiomycosis (a deadly skin disease) which currently affects over 200 species of amphibians. Provide a net energy gain, ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Have environmental benefits, relative to fossil fuels they displace, ghg emissions are reduced by 12% by production and combustion of ethanol and 41% by biodiesel.
