ecological footprint

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Extinctions - History Historical Mass Extinctions

443 mya 364 mya

251 mya 206 mya

65 mya

Major Mass Extinctions

443 mya 364 mya

251 mya 206 mya

65 mya

Major Mass Extinctions

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The Five Great Extinctions Ordovician

1- End of Ordovician •  When: 450 to 440 mya, two pulses. •  Duration: 10 million years. •  Context: All life marine, very warm period. •  Results: Marine Species – 60 to 85%. •  Cause: Increased CO2 sequestration.

Drop in sea level caused by global cooling. This resulted in rapid loss of habitats and rapid change in ocean temperatures. Then rapid warming at end of ice age.

The Five Great Extinctions

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Devonian 2 - Late Devonian

•  When: 364 mya. •  Duration: 3< million years. •  Context: Fish, plants, insects, amphibians. •  Result: Mostly marine Species, 57 to 83%. •  Cause: global cooling, loss of oxygen in

water and decline of CO2. – Impact. – Plants.

The Five Great Extinctions Permian

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3 - End of Permian •  When: 251 to 261 mya, two pulses. •  Duration: 10 million years. •  Context: Major diversification of marine

and terrestrial life. •  Result: Marine Species 95% and 70%

terrestrial vertebrates, and 83% of insects. •  Cause: global climate and sea level fluctuations.

–  Impact. –  Volcanism, cooling and acidification followed

by abrupt warming. –  Methane hydrate gasification - warming and

acidification.

The Five Great Extinctions

Triassic 4 – End of Triassic •  When: 200 mya. •  Duration: 3 – 4 million years. •  Context: Diversity of reptiles and

amphibians. •  Result: Marine Species 53-80%, majority of

reptiles and amphibians. 50% of all life. •  Cause:

– Impact. – Severe volcanic activity. – Global warming.

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The Door to Dinosaur Diversification The Five Great Extinctions

Cretaceous

Age of the Dinosaurs

Cretaceous

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5 – Late Cretaceous

•  When: 65 mya. •  Duration: <1million years. •  Context: Peak of Dinosaur diversity. •  Result: Marine Species – 47-76%,

extinction of Dinosaurs. •  Cause:

– Impact. – Severe volcanic activity.

The Alverez Iridium anomaly

Around the world is a thin band of clay at the Cretaceous-Tertiary (KT) boundary.

This band is highly enriched for Iridium (Ir).

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Iridium A rare-earth element. Rare in earth’s crust. Common in meteorites. Can be extruded by volcanoes.

What was the source? Extra-terrestrial impact vs. volcanoes.

Comet/asteroid impact. Massive series of volcanic eruptions.

Impact rather than volcanic origin Microtektites

very small glass spheres caused by very high velocity impact (impact, not volcanic) . Strewn fields worldwide.

Microtektites

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Impact rather than Volcanic origin suggested Microtektites

Very small glass spheres caused by very high velocity. impact (impact, Not volcanic). strewn fields worldwide.

Shock quartz Quartz grain with multiple sets of shock lamellae, impact, not volcanic.

Presence of both at Ir anomaly layer strongly supports impact

over volcanic origin of Ir.

Shock quartz

Where was the crater?

North American marine site suggested. Distribution of microtektite strewn fields.

greater abundance and larger grain size of shocked minerals in North American.

Crater appears to be underwater, just off the Yucatan peninsula.

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Extinctions are a natural process.

Why the concern today?

Major Extinctions Processes •  Rapid and intense environmental change.

– Temperature, rainfall, amount sunlight, etc. – Change in CO2 and pH in oceans.

•  Rapid loss of habitat. – Direct destruction. – Loss of plants that could not withstand environmental

changes. •  Rapid declines in populations. •  Secondary extinctions based on biotic

interactions. – Predator – prey. – Plant – pollinator. – Etc.

What happens after an extinction?

Recovery

•  Some species survive and may proliferate rapidly.

•  Slowly new species arise and in some cases explosive adaptive radiations generate new groups.

•  This process takes 10 of millions of years.

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Why are Big and Fierce Animals So

Rare?

The Pleistocene Extinctions Megafauna are animals which weigh more than 100 lbs. North America lost thirty-three genera of megafauna. 70 species or 95% of the megafauna. Worldwide lost 200 genera, most of which were megafauna.

Worldwide Loss of Megafauna during Pleistocene

American Lion Close relative of African Lion

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Saber-toothed Tiger Ambush predator

Dire wolf Larger teeth shorter limbs than Timber Wolf Hyena like lifestyle

Short-faced Bear 1,800 lbs, 5 feet at shoulder

Herbivores lost from America, Europe and Australia

All herbivores > 1000 kg

75% of herbivores 100-1000 kg

41% of herbivores 5-100 kg

< 2% of herbivores < 5kg

1 kg = 2.2 pounds

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Ground Sloths 3,500 lbs and 6 feet tall

North American Camel Related to Llama

Tapir Related to Horses

American Mastodon Browser – Twigs, Leaves 4 to 6 tons, 8-10 ft at shoulder

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Mammoth Grass eater, 10,000 lbs, 10 feet tall

What caused extinction?

What caused extinction?

Climate Change, Overkill, Disease or all of the above?

Environmental Changes

Climate Change

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Land Cover 18,000 yrs bfp

Land Cover 13,000 yrs bfp

Land Cover 11,000 yrs bfp

Land Cover 8,000 yrs bfp

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Land Cover Present

Environmental Changes •  Eliminate food sources. •  Disrupt birth schedules. •  Expose animals to environmental

conditions they are not adapted to.

Changing Ice Volume Arrival of Homo sapiens

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Stone Tipped Spears Worldwide Loss of Megafauna during Pleistocene

Human Migration Corridor

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Pleistocene extinction episodes

Overkill?

Second Order Overkill

New Zealand – about 800 years ago Maori – Arrive 1000 years ago

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Moa – Flightless Birds Madagascar – about 1500 years ago

Polynesians Arrive Giant Elephant Bird

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Extinct Lemurs