Presentations text content in Effects of biological invasions on large-river ecosystems
Slide1
Effects of biological invasions on large-river ecosystems
Dave Strayer, Cary Institute of Ecosystem Studies
Slide2Conclusions
Like other threats being discussed here
Biological invasions have large, varied effects on large-river ecosystems and the services they provide to people
These effects vary enormously across rivers
These effects are increasing over time
Invasions interact with other threats (Havel et al. 2015)
We generally understand the causes of invasions
Unlike other
threats
Much
of this understanding is more qualitative than
quantitative
Effects
of the next invasion are hard to
predict
Invasions
grow on their own, and are long-lasting or
irreversible
Actions
of individual people can have large
consequences
Incorrect
folk wisdom about invasions impedes
control
Current
measures to control invasions are not very
effective
Management
should be matched to the attributes of invasions
Slide3Hudson example 1: zebra mussels
Strayer, Frontiers Ecol. Environ, 2009
Also blocks water intakes
Controlled in water intakes ($105-106/yr in Hudson, >$300 million in North America)
Slide4Hudson example 2: water-chestnut
Caraco
et al., Tall et al.
Ecol. Appl., 2011
Slide5The number of invasions varies hugely
Leprieur
F, Beauchard O, Blanchet S, Oberdorff T, Brosse S (2008) Fish Invasions in the World's River Systems: When Natural Processes Are Blurred by Human Activities. PLoS Biol 6(2): e28. doi:10.1371/journal.pbio.0060028http://journals.plos.org/plosbiology/article?id=info:doi/10.1371/journal.pbio.0060028
But number of invasions ≠ effects
Fish only, so underestimates actual number of invasions
Slide6The number of invaders rises over time
Mills et al. (1996, updated); Jackson & Grey 2013
But number of invasions ≠ effects
Underestimates actual number of invasions
Slide7We generally understand causes of invasions
Deliberate releases
(game/food fish, ornamental spp.)
Contaminants of recreational equipment (including water)
Ship fouling
Bait bucket releases
Escapes from aqua/agriculture
Aquarium and water-garden releases
Ballast water
Canals
Slide8…but not all the important details
Aquarium and water-garden releases
fashion
culturalnorms
educationof owner
availability ofthe species
regulations aboutpurchase and release
economics
?
Slide9Understanding is more qualitative than quantitative
Propagule
pressure vs. establishment rate
Establishment rate vs. intensity of effects
Spatial variation in effects
Temporal variation in effects
Strength of effects on different parts of the ecosystem
Effects of different kinds of invaders
Context-dependence of effects
Gallardo et al.,
Global Change Biology
(2016)
Slide10Effect of next invasion is hard to predict
Slide11Invasions grow on their own, and last for a long time
Dave Brenner, MI Sea Grant
Slide12Invasions grow on their own, and last for a long time
Dave Brenner, MI Sea Grant
Slide13Dave Brenner, MI Sea Grant
Invasions grow on their own, and last for a long time
Slide14Inaccurate folk wisdom is widespread
Invaders go away after a while
Invaders are not bad (or that specific species are good – “zebra mussels clean up the water”)
Natural selection ensures that the best ecosystem results after invasions (the strong survive, and strong is good)
We can eat them or something if they get to be a problem
Slide15Actions of individual people can have large consequences
Rob
Emens, NC Sea Grant
http://www.dpi.qld.gov.au/extra/aquaticinvaders/add_Overview.html
Slide16Optimal management should recognize unique attributes of invasions
As long as new invasions are frequent, ecosystems will be unstable, and managers will need to be nimble
Invaders persist and grow once established
Focus on pre-establishment control
Learn how to motivate policy-makers in “preventative ecology”
Focus post-establishment management on specific goals (not “kill ‘
em
all”), and be willing to spend real $$$
Actions of individual people matter
Educate people
Better understand what motivates their behavior
Take decision-making power away from individuals (i.e., remove many more species from commerce)
Slide17Conclusions
Like other threats being discussed here
Biological invasions have large, varied effects on large-river ecosystems and the services they provide to people
These effects vary enormously across rivers
These effects are increasing over time
Invasions interact with other threats (Havel et al. 2015)
We generally understand the causes of invasions
Unlike other
threats
Much
of this understanding is more qualitative than
quantitative
Effects
of the next invasion are hard to
predict
Invasions
grow on their own, and are long-lasting or
irreversible
Actions
of individual people can have large
consequences
Incorrect
folk wisdom about invasions impedes
control
Current
measures to control invasions are not very
effective
Management
should be matched to the attributes of invasions
Effects of biological invasions on large-river ecosystems
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