Introduced and Invasive Species

Introduced species

Also known as: nonnative, nonindigenous, alien, exotic

Introductions can occur naturally, but now are driven primarily by human factors (esp. trade, travel)

From introduced to invasive

• Vast majority of introductions do not result in establishment of invasives

• However, repeated introductions can lead to invasions (European starlings were introduced 4 times)

• Propagule pressure

Ecological context

• Not just about species attributes• Disturbance can reduce competition

from native plans• Nutrient availability• Community diversity• Enemy release hypothesis

Cozumel Thrasher

Invasives in Canada

Zebra mussel

• Originally native to Russia• First detected in Great Lakes in 1988,

near Detroit/Windsor• Ballast water of ocean-going ships

1992 2001

2010

Leafy Spurge

How do we reduce or manage species introductions?

Canada’s approach to Leafy Spurge

• Biological control: Sheep, Beetles• Elbow Pasture, SK: 1200 sheep

• Reduced spurge density from 80-100 stems/m2 to 20-50 stems/m2 in a few years

• Cattle stocking 36% higher• Beetles: down to 10%

http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1186596698988&lang=eng

Pragmatic approaches

1) Prevention

Pragmatic approaches

2) Eradication: shoot first, ask questions later

video

Pragmatic approaches

3) Management

-Chemical or biological control-Habitat modification-Manual removal-Problem: costs $$$ year after year

What about human values?

The Oatmeal’s Take Video