Extinction and threats to biodiversity

4.2 Evaluating Biodiversity and Vulnerability

Remember Extinct is FOREVER!!

Two major causesNatural Causes (Non-Human)Human Causes

Causes of Extinction

Volcanic EruptionsDroughtMeteorsGlaciers and ice ageCompetition and Predation

Natural Causes (Non-Human)

H-Habitat destruction and fragmentation

I- Introduced speciesP-PollutionP-Practices of agricultureO-Over hunting

Human Causes (HIPPO)

Dodo Bird – Extinct

Degradation: reducing the quality of available habitat Ex. Logging, agriculture, sewage

Fragmentation: splitting a single large, contiguous system into many disconnected areasEx. Putting a road through a wilderness area, or

building a dam across a riverLoss: Disappearing of an entire habitat

Ex. Paving natural area for building sites, converting prairies to farmland or residential subdivisions

Habitat Destruction/ Fragmentation

Organisms that are living in an environment outside of its normal range or natural environment

Many are transported by accidentBiocontrol: Species transported intentionally to

control other “problem” species populationsCharacteristics:

Fast growth/reproductionLive in wide range of environmentsUsually harmful to environment Outcompete native organisms for local food

sources Leads to extinction of native organisms

Invasive Species (Alien, exotic, non-native)

Asian CarpKudzuRabbitsStarlingsCane Toads

Examples of Invasive Species

“the vine that ate the South” and “The Green Menace”.

Grow up to 1 foot in a day!

Introduced from Japan as quick ground cover to prevent soil erosion

Kudzu

Asian Carp

Originally imported to clear algae from catfish ponds in the southern USA,

Flooding allowed some carp to escape into the Mississippi River and its tributaries where they quickly became MANY carp

Pose a strong threat to the Great Lakes

Asian Carp

“The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.”

-Thomas Austin in 1859

(Released 24 rabbits)1950 ~ 600 million

rabbits1951 ~ 100 million

Rabbits

Government Drugged Watering Hole

Today starlings are blamed for agricultural losses of up to $800 million annually in the United States, as well as being implicated in a number of deadly plane crashes.

~ 60 were released in New York’s Central Park in 1890.

Starlings

Cane Toad

Good Example of biocontrol! In 1937 cane toads were released in

Australia's sugar cane plantations to control insect populations

By 1938 ~60,000 cane toads left sugar cane fields for more natural habitat (ate all majority of insect populations and outcompeted native amphibians for food)

Can grow up to 15 inches and eat anything!

Cane Toad

Toxins added to the environment lead to a loss or degradation of habitat.

Pollution

Farming causes habitat loss and reduces biodiversity because of…Monoculture: Farming of only one crop on a

large scalePesticides: Often lethal to many non-pest

speciesHerbicides: Lethal to species other than the

weeds

Practices of Agriculture

Collecting, and harvesting wild populations: unregulated, it can diminish local populations or even drive some to extinction Tasmanian tigerdodoNorth American sea minkPrairie buffalo Blue whale

Over Hunting

Fossil Records reveal average “lifetimes” of species.

Extinction occurs naturally and is referred to as the background rate of extinction

Humans have lead to a 1000x extinction rateEstimated 137 species lost each day

50,000 species a year

Rates of Extinction

The Earth has experienced 5 mass extinctionsMass Extinctions

Extinction # 1 ~445 MYA Ordovician Stage – Dramatic loss of sea level due to forming Antarctica -57% Extinct

Extinction # 2 ~ 370 MYA Devonian Stage – Changes in sea level and global cooling stage -50% Extinct

Extinction #3 ~250 MYA Permian Stage- Breaking up of Pangea change ocean currents- 83% Extinction

Extinction #4 ~200 MYA Triassic Stage – Climate warming from volcanic eruptions -48% Extinct

Extinction #5 ~65 MYA Cretaceous – Asteroid impacting the earth – 50% Extinct

Extinction Events

Mammals: ~ 1 million years

With approximately 5,000 mammals the background rate is 1 every 200 years

In past 400 years 89 extinctions have been recorded.45x background rate.

Over 50 extinctions have occurred in the past century100x background rate

Average Lifespan of mammals

Organisms that are…Limited habitatExtremely specialized nicheLow reproductive potential Require a large territory MigratoryValuable economically (hunted)Vulnerable to pollutionIncompatible with civilization

may be more likely to go extinct

Characteristics of Vulnerable Species

Contain ½ of Earth’s known speciesMost species have specialized

nichesHumans disrupt environment for

loggingChanging one part of ecosystem

alters the entire web of relationships

Breakdown of rainforest likely lead to extinction of 10% worlds species in 25 years

Regeneration rate is slow due to poor soil quality (rapid year round nutrient cycling depletes soil)

Rainforest Vulnerability

4.2.5 Red List Criteria

Red List CriteriaIUCN (International Union for Conservation

of Nature) Red list used to determine extinction riskSpecific Aims:

Provide system that can be applied consistentlyImprove evaluation of different factors which

affect the risk of extinction

Factors used to determine listPopulation size: how many organisms of the species still

exist?Reduction in population size: are the numbers falling

rapidly or slowly?Numbers of mature individuals: if many of the remaining

individuals are already at or past their reproductive peak, the species is likely to decline even further

Geographic range and fragmentation: wide geographic range makes the species less prone to

extinctionfragmented habitat makes it more difficult for populations

to interbreedQuality of habitat: degraded habitat supports fewer

individuals

CategoriesExtinct (Ex) – No reasonable doubt that the

last individual has died. Determined after exhaustive surveys of animals known range and expected habitats

Endangered (E)- Survival is unlikely if causal factors continue operating. Drastically reduced populations and habitat

Vulnerable (V) – Near endangered if causal factors continue. Numbers are abundant but are under threat from serious factors (overexploitation, habitat destruction)

Rare (R) – Small world populations that are at risk. Unexpected threat could easily cause a critical decline (small geographic disturbance)

Unknown (K) – Suspected to fit in one of the above categories but there is a lack of information

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