Transcript Evolution

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
2010
2001
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/displayafficher.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