Transcript English - Invasive Species Specialist Group

MODULE 1
Introduction to Invasive Alien Species
Introduction
• Invasive alien species harm:
– the environment
– the economy
– people
Definition
• Introduction
– The movement by human action of a species
outside its native range. This movement can be
either within or between countries.
Definition
• Alien species
– A species that has been intentionally or
unintentionally introduced to a location, area, or
region where it does not occur naturally
Definition
• Invasive alien species
– An alien species that causes, or has the potential
to cause, harm to the environment, economies, or
human health
Key Point
• An alien species will be considered invasive
only if it has adverse effects on:
– the environment,
– the economy, or
– human health
Invasive Species are
found in
ALL
taxonomic groups
Types of introductions
Alien Species Introductions
Intentional
Legal
Directly released into the wild
Unintentional
Unauthorised
Introduced into captivity
Escaped or intentionally released
Indian House Crow
• Accidental introduction
• Competes with native
birds
• Disease vector
• A nuisance in urban
areas
Salvinia molesta
•
•
•
•
A serious aquatic weed
Forms thick mats
Prevents boat traffic
Ruins fish habitat
Intentional introductions
• Legal
– directly released into the wild
– introduced into captivity
• Illegal / Unauthorised
– smuggling
Unintentional introductions
• ‘Hitchhikers’ and
stowaways
• Trade
• Travel
• Transport
Key Point
• Most of the known invasive invertebrates have
been introduced unintentionally
Key Point
• Natural dispersal tends to play a major role in
the subsequent regional spreading once a
species has been introduced into a country or
region
Process of invasion
1. Introduction
2. Establishment
3. Spread
Process of invasion
Population size
Explosion
phase
Carrying capacity
Lag phase
Time
Can we predict species invasiveness?
• Difficult to identify invasive from harmless
species
• Some characteristics:
– invasive elsewhere
– adaptable
– lack of predators
Key Point
• Precautionary approach
Every alien species must be considered invasive
until proven otherwise
Key Point
• Human alteration of the environment increases
the likelihood of IAS establishing
Land-use changes
• IAS thrive in disturbed areas
Globalisation
• Increasing trade, travel
& transport = increasing
IAS introductions
World shipping routes
Summary
• IAS affect the environment, economy and
human health
• Species invasiveness cannot be easily
predicted
• IAS thrive in disturbed areas
• The rate of IAS introductions is increasing