Lessons from the Anthropocene

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 (f i ) 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 O 2 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 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 CO 2 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?

Y=t X, X>1 Exponen6al Growth

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 Consider a test tube with one bacterium. The size of a bacterium is ~1 μm (10-4 cm) Volume of the bacterium ~ 10-12 cm 3 The bacterium divides every 30 minutes. The volume of the test tube is 40 cm 3. You can fit 4x10 13 bacteria in the test tube How long un6l the test tube is full?

The Meaning of Exponen6al Growth Doubling 6me is 30 minutes % growth = 70/30 =2.3% per minute There is room for 40/10-12 = 4 x 10 13 bacteria in the test tube. When is the test tube full of bacteria? Awer ln(3 x 10 13 )/ln(2) doubling 6mes Awer 44 doubling 6mes, there are 2x10 13 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 4.5x10 14 m 2 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 10 14 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 (4x10 11 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