TESC 211 The Science of Environmental Sustainability Autumn 2011UWT

Species extinctions are a natural process and through out most of Earth’s history have occurred at an average rate of % per year. “Extinction is forever”

There have been five mass extinctions when 50-95% of species became extinct within a relatively short period of time. Recovery of biodiversity from a mass extinction event typically takes several million years. Extinction is often categorized as being of one of three levels: Local extinction Ecological extinction Biological extinction

Local extinction no longer found in an area found elsewhere loss of one or more populations e.g. Arctic fox has not been found in the British Isles for ~12, 000 years but is found through out northern Europe

Ecological extinction reduced population size no longer able to perform function in ecosystem e.g. American Bison once dominated the grasslands of North America, now most of cultivated in captivity for hides and meat.

Biological extinction species can no longer be found anywhere Irreversible loss of natural capital e.g. Thylacine (Tasmanian tiger), Dodo, Tyrannosaurus Rex, Homo Habilis.

It is estimated that current extinction rates are at least 100 times greater than the back ground extinction rate. Why? Human activities have disturbed ~50% of the Earth’s surface water Human activities have disturbed 50-80% of the Earth’s land surface. Anticipated that by the end of the century extinction rate will reach 0.1% - 1% ( ,000X background rate)

A t a 1% annual extinction rate: within a century >50% of all species would be lost It would take 200, 000 human generations to recover these species. 20 times longer than humans have occupied the planet

Why be concerned about extinctions and loss of biodiversity? Species provide economic and ecosystem services 62% of all cancer drugs derived from tropical forest plants Food Raw materials Pest control Eco-tourism Lion skin ~$1000 Lion sighting tours $500, 000 Intrinsic value, quality of life etc

What speeds up the rate of extinctions? The most significant causes of extinctions can be summarized by the acronym HIPPCO: Habitat destruction, degradation and fragmentation HIPPCO: Invasive species deliberately introduced accidently introduced

What speeds up the rate of extinctions? HIPPCO: Population increased demand on ecosystem services more land diverted to human uses “SEVEN billion people will call planet Earth home from this Monday (10/27/2011). That is the projected date at which the number of people alive will pass the seven-billion milestone, according to a landmark study of global population pressures released overnight by the UN Population Fund.” Mark Kenny, The Advertiser 10/27/2011