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Impacts of invasive species:from species to ecosystems.
Centro de Ciências do Mar do Algarve
Aschwin Engelen
General introduction invasions
• 3 big global human impacts on nature:– global climate change
General introduction invasions
• 3 big global human impacts on nature:– global climate change
– habitat destruction and fragmentation
General introduction invasions
• 3 big global human impacts on nature:– global climate change
– habitat destruction and fragmentation
– biological invasions– In 2002, the European Council (Environment) noted that the introduction of IAS is one of the main recorded causes of
biodiversity loss and causes serious damage to economy and health.
Biological invasions
• Under the Convention on Biological Diversity (CBD),invasive alien species (IAS) are those that areintroduced, establish, naturalize, and spread outside oftheir home range, and whose impacts involve significantharm.
• What are invasive species?
• Currently 97 registrated in Portugal (ISSG database)
http://www.issg.org/database/welcome/
Biological invasions
Acacia mearnsii
acácia-negraCodium fragile spp. tomentosoides
Crassostrea gigas
Gambusia affinis
Gambuzia
Opuntia stricta
Carpobrotus edulis
Examples Portugal
Linepithema humile (the Argentine ant)
Oxyura jamaicensis (ruddy duck)
Procambarus clarkii
Biological marine invasions
• Causes:– disruption of natural barriers
• large water masses: oceans, seas
– ship hull and ballast water
• cultivation of exotic species
• Impacts– economical: uncertain for most marine invasions
– ecological: ranging from single species replacement to entire ecosystems
• Costs?– There are only two estimates of the total cost of invasive
species at the national level, both relating to the United States.
• 1993: 79 species over 85 yrs 97 billion dollars
• 2000: annual costs 137 billion dollars
Seaweed Invasion impacts on Humans
•Physical hindrance of small boats with outboard engines of up to 20 h.p.
•Clogging of intake pipes, both of boats and industrial installations
•Floating mats foul commercial fishing lines and nets
•Floating debris tends to be concentrated by buoyant fronds forming floating mats
and creating an eyesore
•Large mats of weeds are eventually cast up on shores and cause problems when
rotting, i.e. producing offensive smells on resort beaches
•Dense growths of S. muticum on oyster beds: difficult to see cultured oysters
relocation of oysters
•Loss in amenity and recreational use of water areas, e.g. swimming, skiing, sail
boarding, dinghy sailing and fishing
Ecological invasion impacts
Light Nutrients Sulfide TempEnvironmental factors
Macrophyte interactions
Community level
Ecosystem level
Canopy forming seaweedsMat forming seaweedsHealthy, denseseagrass bed
Ecological invasion impacts
Light Nutrients Sulfide TempEnvironmental factors
Macrophyte interactions
Community level
Ecosystem level
Seaweed density/biomass
Ab
iotic fa
cto
r
Effect of macrophyte
on abiotic factors
Canopy forming seaweedsMat forming seaweedsHealthy, denseseagrass bed
+Synergistic effects
Density threshold
Ecological invasion impacts
Light Nutrients Sulfide TempEnvironmental factors
Macrophyte interactions
Community level
Ecosystem level
Seaweed density/biomass
Ab
iotic fa
cto
r
Effect of macrophyte
on abiotic factors
Canopy forming seaweedsMat forming seaweedsHealthy, denseseagrass bed
Density threshold
+Synergistic effects
Density threshold
Associated community
composition
Ecological invasion impacts
Light Nutrients Sulfide TempEnvironmental factors
Macrophyte interactions
Community level
Ecosystem level
Seaweed density/biomass
Ab
iotic fa
cto
r
Effect of macrophyte
on abiotic factors
Canopy forming seaweedsMat forming seaweedsHealthy, denseseagrass bed
X
X
X
X
X X P7
Density threshold
+Synergistic effects
Density threshold
System metabolism
Foodweb structure
Macrophyte decomposition
Associated community
composition
Impacts of invasive species
•Large global problem, goes hand in hand with globelization
•Large impact economically and ecologically
•Characteristics of the invader and the recipient
system determines impact