Topic 23:

Species Extinctions

Western Black Rhino Officially Declared Extinct

Brett Smith for redOrbit.com – Your Universe Online

The western black rhino is now officially extinct, according to the International Union for Conservation of Nature (IUCN). The world’s largest conservation network had considered the rhino, last seen in 2006, “critically endangered” up until it made the official declaration earlier this week.

“Given the wildlife poaching taking place, lack of political will and conservation effort by Cameroon conservation authorities in the past, and increasing illegal demand for rhino horn and associated increased commercial rhino poaching in other range states, it is highly probable that this subspecies is now extinct,” said a statement on the IUCN’s official page for the animal.

The IUCN added that Africa’s northern white rhino is “teetering on the brink of extinction” while Asia’s Javan rhino is “making its last stand” against human activities.

“In the case of the western black rhino and the northern white rhino the situation could have had very different results if the suggested conservation measures had been implemented,” said Simon Stuart, chair of the IUCN species survival commission, in a statement to CNN.

http://www.redorbit.com/news/science/1112998277/western-black-rhino-officially-extinct-110813/

Learning Goals for Day:

The Extinction of Species – example: Passenger Pigeon

Powerpoint Slides

A) Background extinction rates -

            % of species that have gone extinct

            average “life-time” of a species = 3.5-4 million years

            background extinction rates based on fossil record

            record of mass extinctions (e.g. end of age of dinosaurs)  - 5 of them; we are now in the 6th

B) What makes species susceptible to extinction?

1. low population sizes (e.g. grizzlies in San Juans)
2. limited distributions (e.g. island species, including mountain “islands”: Mount Graham red squirrel in AZ)
3. centralized mating areas or migration corridors (e.g. sage grouse)
4. very high specialization or tight symbiotic relationships (e.g. bats that pollinate Agave)
5. be able to give examples of each of these & discuss why this increases susceptibility

C) Human-caused Extinctions

1. Historic:

• Australia – 40k ybp, 13 of 15 genera of large marsupials, lizards, birds extinct
• N. America – 20k ybp, large mammals gone in few 1000 yrs
• Hawaii – 2k ybp, 39+ spp birds lost
• New Zealand – 1k ybp, 13 spp large flightless birds gone

2. Modern:

• accelerating pace of human-caused extinction
• current rates much greater than background (as much as 20 times or more greater)

3. Causes: (why so high?)

• habitat loss
• exotic spp invasions
• over-hunting
• global climate change

Thoughts to consider…

            Why should we care about extinction, and the loss of biodiversity?

           ... it is a question worth pondering.  Think about it, & see Leopold's Round River essay – this could be a good exam essay question…

            Extinction video – questions from the worksheet