Lessons from the Anthropocene •  There have been 5 major ex6nc6ons •  These are a7ributed to –  Asteroid impacts –  Climate change •  They usually occur over millenia •  A sixth ex6nc6on is in progress Relevance •  Once species become intelligent (fi) they can supercede their ecosystems. •  They become an ac6ve par6cipant in their own des6ny. •  All the rules per6nent to evolu6on change. Geological Timespans: Eons •  Hadean –  Ends ~4 Gya with indirect evidence for life (kerogens) •  Archean –  Ends ~2.5 Gya with first O2 catastrophe •  Proterozoic –  Ends ~0.54 Gya with first animal fossils Hadea, Archean, Proterozoic comprise the PreCambrian •  Phanerozoic –  now Geological Timespans: Eras Phanerozoic –  Paleozoic •  Ends with forma6on of Pangea ~ 250Mya –  Mesozoic •  Era of the dinosaurs •  Ends with the KT event ~66 Mya •  Periods: Triassic, Jurassic, Cretaceous –  Cenozoic Geological Timespans: Periods Cenozoic Era •  Paleogene –  ends with ice ages @ 23Mya •  Neogene –  ends 2.58 Mya •  Quaternary Geological Timespans: Epochs Quaternary period •  Pleistocene –  Ends 11,000 years ago –  Ex6nc6on of many large mammals •  Holocene –  Begins with Older/Younger Dryas climate changes The Anthropocene Epoch That epoch when human beings affect the Earth’s ecosystems •  Start about 1850 CE? •  Synonymous with the Holocene? Recap: Evolu6onary Mechanisms •  In a stable ecosystem, predators and prey are in equilibrium •  Most species are not extremely mo6le •  Oceans and mountain ranges are significant barriers •  Evolu6on proceeds in small isolated popula6ons Invasive Species •
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Transported to new ecosystem Out of equilibrium with the ecosystem Some fail to thrive Some thrive in absence of natural prey •  If the number of invasive species is small, ecosystem can rebalance Humans as an Invasive Species •  Homo Heidelbergensis ~ 1.8 Mya •  Homo Sapiens “Out of Africa” ~ 75,000 ya •  Technology permi7ed adapta6on to wide range of climates •  Populated en6re Old World by ~30,000 ya •  Populated en6re New World by ~15,000 ya •  Populated Polynesia by 900 CE Humans as an Invasive Species Carried useful and not-­‐so-­‐useful species •  Beasts of burden •  Ca7le •  Edible plants •  Rats •  Human parasites Humans as an Invasive Species Two effects: •  Direct impact on the environment •  Indirect impact on the environment Direct Impact: Ex6nc6on of Large Mammals •  Large animals have few natural enemies •  Most large animals have a reproduc6on strategy of few young infrequently •  Hun6ng, combined with environmental stresses, can explain ex6nc6on of large mammals ~ 10,000 years ago •  Did not occur in Africa Indirect Impact: Removal of geographic barriers Pangea Pangea: Confluence of all con6nents into one super-­‐con6nent ~300 – 200 Mya Pangea and the P-­‐T Ex6nc6on •  Removal of ocean barriers •  Species can migrate freely •  Climate affected by con6nental distribu6on •  Pangea forma6on defines Paleozoic-­‐Mesozoic border •  Permian-­‐Triassic Ex6nc6on event was the largest –  96% of marine species –  70% of terrestrial species –  57% of families; 83% of genera Parallels with Today Increase in invasive species from: •  Rapid intercon6nental travel •  Trade in exo6c species Ex6nc6on leads to drops in bio-­‐diversity Other Effects •  Agriculture affects ecosystems and the atmosphere •  Agriculture –  reflects more sunlight than forests –  produces more CO2 than forests –  Reduces bio-­‐diversity L Will humans survive the Anthropocene? •  We are part of an ecosystem •  The ecosystem is changing rapidly Technology to the rescue? Overpopula6on Earth has a carrying capacity •  We need sufficient –  Fresh water –  Food •  We need space for plants and animals Carrying Capacity is unknown •  Es6mates range 4 -­‐ 16 billion Human Popula6on Growth Why the Popula6on is Growing h7p://www.eoearth.org/view/ar6cle/153596/ How Long Un:l the Earth is Full? Exponen6al Growth •  Y=tX, X>1 The Meaning of Exponen6al Growth •  A constant percentage increase per 6me •  e.g, a 2% popula6on growth is exponen6al. •  The doubling 6me is 70/ the percentage growth (70 ~ 100 ln(2) = 69.3) The Meaning of Exponen6al Growth •  In a doubling 6me, Y doubles •  5% annual interest means your money doubles in 70/5 = 14 years •  A crime rate that doubles in 10 years is growing at 7% per year •  A popula6on that grows at 2% per year doubles in size in 35 years The Meaning of Exponen6al Growth •
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Consider a test tube with one bacterium. The size of a bacterium is ~1 μm (10-­‐4 cm) Volume of the bacterium ~ 10-­‐12 cm3 The bacterium divides every 30 minutes. The volume of the test tube is 40 cm3. You can fit 4x1013 bacteria in the test tube How long un6l the test tube is full? The Meaning of Exponen6al Growth •
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Doubling 6me is 30 minutes % growth = 70/30 =2.3% per minute There is room for 40/10-­‐12 = 4 x 1013 bacteria in the test tube. When is the test tube full of bacteria? Awer ln(3 x 1013)/ln(2) doubling 6mes Awer 44 doubling 6mes, there are 2x1013 bacteria •  In another 30 minutes the test tube is full. The Meaning of Exponen6al Growth •  There are now 7 billion people on Earth •  Popula6on growth is about 1.14% per year •  The surface area of Earth is about 4.5x1014 m2 •  About 25% of the Earth is land. •  Each person has, in principle, about 16,000 sq m The Meaning of Exponen6al Growth •  Define the Earth as full when each person has 1 sq m. •  That requires 16,000 6mes the present popula6on, or about 1014 people on Earth. •  Current doubling 6me is 70/1.14 = 61 years •  At the current rate, that will take 14 doubling 6mes, or 840 years! The Meaning of Exponen6al Growth Suppose we cap Earth at its current popula6on, and start colonizing extrasolar planets. •  Assume one Earth-­‐like planet per star •  We fill the galaxy (4x1011 stars) in 36 doubling 6mes. That’s only 2200 years! In the space of one hundred and seventy-­‐six years the Lower Mississippi has shortened itself two hundred and forty-­‐two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idio6c, can see that in the Old Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing rod. And by the same token any person can see that seven hundred and forty-­‐two years from now the Lower Mississippi will be only a mile and three quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascina:ng about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. Life on the Mississippi, by Mark Twain