Extinction Conservation

Extirpation

elimination of a species in a particular location

(i.e., local extinction), but continues to exist elsewhere

Extinction

total disappearance of a species throughout its range

Extinction and extirpation are the

evolutionary result of the natural progression of speciation

Background Extinction

• Species are always going extinct (normal process)

• Vast majority of ALL species that have ever lived are now extinct (>96% of all mammal species since Cretaceous (66 MYA) are extinct

• Average life span of species from fossil record ~ 4 million years

Mass extinction

• Large ‘die-offs’ of species in a relatively short time span (at least 60% of species within 1 million years)

• Worldwide, affecting many species, genera, families

• After mass extinction, some remaining taxa undergo adaptive radiations as they fill out vacated niches

Mass extinction rates are _______ than background

HIGHER

5 major mass extinction events

– Ordovician

– Devonian

– Permian

– Triassic

– Cretaceous

Causes of Mass Extinction

Major changes in temperature associate with mass extinctions

- ↑volcanism at all of these times (plus a major meteor strike at 1

+6th humans!

Ordovician

• Extinction of mostly marine invertebrates (at that time all known animal species lived in the oceans)

• Subsequent rise of fishes, origin of amphibians

Devonian

• Extinction of many marine invertebrates and

76% of marine and freshwater fish families (loss of Ostracoderms, Placoderms, Acanthodia)

• Subsequent radiation of amphibians on land, origin of reptiles

Permian

• The most sever mass extinction, often called the Great Dying

• First to significantly affect terrestrial life

– Tetrapod genera reduced by 75%

– 90-95% of marine species disappeared

– 78% of reptile and 67% of amphibian families went extinct (insects also affected)

• Major change in marine and terrestrial communities

• Earth’s biotas took a long time to recover (~10 MY), with subsequent radiations of reptiles, origin of mammals

+Heightened volcanic activity and consequent changes in climate and atmosphere occurred

+Hypoxia at higher latitudes contributed to marine die-offs

Triassic

• Many long-established marine invertebrates and many

terrestrial vertebrates went extinct (e.g., ammonoids, mussels, clams, scallops, several reptile families)

• Proliferation of reptiles (dinosaurs) follows

Cretaceous

• Extinction of all non-avian dinosaurs, flying and marine reptiles

– 61% tetrapod families became extinct

– 70-80% reduction of marine biodiversity

– Many plants and shelled organisms went extinct

• Mammals subsequently proliferated

Causes of Cretaceous Mass Extinction

• Large meteor hit in Yucatan (equivalent to 10 billion WWII atomic bombs)

• Increased volcanic activity, increased ash/cloud cover

• Limited sunlight lead to environmental changes

– “Impact” winter (difficult for ectotherms)

– Collapse of photosynthesis (affect vegetation and food chain)

The 6th Mass Extinction

• Recent history suggests Earth is in the 6th major mass extinction: current extinction rate significantly larger than background extinction, faster rates than ever before

• This mass extinction is unique in that it is caused by a single

species (humans)

• Population declines and extinctions are global; and more

heavily affect large species

+N. America = a 3 billion bird decline over 50 years! > puts populations and species in peril

+-Risk: amphibians > reptiles > birds/mammals

+Current amphibian extinction rate 200X higher than background! (Herps at risk)

+Shark and ray abundance has declined by 50% since 1970

Human Population Growth Leads to

• Habitat loss and fragmentation

• Overfishing/hunting

• Invasive/introduced species

• Toxicity / contaminants

Much of current Amphibian declines associated with spread of….

chytrid fungus (Bd: Batrachochytrium dendrobatidis)

-Bd originated in Asia (Korean peninsula), and began spreading globally in the 1900s due to the pet trade

Solutions

• No simple solution to current extinction

• Proposed solutions (many of which are being implemented)

– Wildlife sanctuaries / refuges

– Ecosystem / habitat restoration

– Management projects

• wildlife corridors

• repopulation programs

• genetic restoration

• captive breeding

– Invasive species management

– Green initiatives