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Invasive Species in Context
Gary Lovett
Forest Ecologist
Cary Institute Science and Management Forum: Invasive Species in the Hudson Valley
Saturday, March 21, 2015
Zebra mussel Multiflora rose Emerald ash borer
Alien invasive species: Unwanted byproducts of global trade
Largest shipping routes in 2007 (Kazula et al. 2010)
0
500
1000
1500
2000
2500
1750 1800 1850 1900 1950 2000 2050
Value of U.S. Imports(Billions of 2010 $ per year)
Val
ue
of
Imp
ort
s (B
illio
ns
of
2010
$ p
er y
ear)
Trade goes both ways…
Smooth cordgrass (Spartina) invasive in Asia Grey Squirrel invasive in Britain
Red eared slider invasive in many places Fall webworm invasive in China
Focus on Early Stages of Invasion
Likelihood of successful eradication decreasesCost of control efforts increasesCosts shift from importer to general population
Graphic from Department of Environment and Primary Industries , Victoria, Australia
Economic Costs of Invasive Species
• An economic “externality” to importers. Costs largely paid by the public
• Economic costs are not yet fully reckoned
• One estimate of aggregate cost: $120 billion per year in the U.S. (Pimentel et al. 2005)
• Does not include non-market values
Most Important Pathways of Introduction
Terrestrial plants• Plant trade• Intentional
introductions
Forest pests• Plant trade• Wood packing
material (crates, pallets, spools)
Aquatic species• Plant trade• Ballast water• Ship hulls• Canals• Pet trade• Aquarium trade
Plants Herbivores
Plant pathogens
Predators
Decomposers
Native primary producers
Detritus and dead organic matter
Native predators
Native decomposers
Native herbivoresAilanthus
Gypsy moth
Beech bark disease
Nightcrawler
Snakehead
• Water use
• Physical structure
• Fire
• Wildlife habitat
Other Ecological Impacts
Introduced Forest Insects and Diseases:Impacts and Options
The Rogue’s Gallery(A Partial List)
• Chestnut blight
• Dutch elm disease
• Gypsy moth
• Hemlock woolly adelgid
• Balsam woolly adelgid
• White pine blister rust
• Dogwood anthracnose
• Emerald ash borer
• Beech bark disease
• And the list goes on and on……
• And waiting in the wings:
– Asian longhorned beetle
– Sudden oak death (Phytophthora ramorum)
– Sirex wood wasp
From Liebhold et al. Diversity and Distributions (2013)
Biological Pollution
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0
100
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1750 1800 1850 1900 1950 2000 2050
Cu
mu
lati
ve v
alu
e o
f im
po
rts
(Tri
llio
ns
of
20
10
$)
Cu
mu
lati
ve N
um
be
r o
f P
est
s
All Insect Pests
WoodBorers
Value of Imports
All insects: 2.6 per year
since 1850
Wood borers: 1.2 per year since 1985
0
100
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500
600
700
1750 1800 1850 1900 1950 2000 2050
Cu
mu
lati
ve N
um
ber
of
Pest
s
All Insect Pests
WoodBorers
All insects: 2.6 per year
since 1850
Wood borers: 1.2 per year since 1985
The number of insect pests has continued to increase…
… but not as fast as trade
Data from Aukema et al. 2010
Death of trees
Warming of streams may impact fish
Impacts of Forest Pests Reverberate Though the Ecosystem
Short- and long-term changes in carbon storage
and nutrient losses
Decline of some bird species
Decline of old-growth forests
Hemlock Woolly Adelgid
Economic Impacts• Impacts of invasive insects estimated at > $5B per year
– Forestry impacts small compared to urban and suburban impacts
– Largest costs borne by homeowners and municipal governments
– Costs include takedown and replacement of street trees and yard trees, lost property value
Worcester, MA eradication of Asian longhorned beetle
Before After
Photos from APHIS PPQ
(from Aukema et al. 2011)
Focus on Major Pathways of Introduction
Live plants for horticultureWood packing material
• Current regulations require heat treatment or fumigation of wood packing material
• Have been shown to be partially effective, reducing pest introductions by 30-50%
• Could still result in the number of wood-boring beetle species tripling by 2050!
• Current regulations for most plants require a certificate from country of origin and an inspection upon entry
• Estimated to intercept only 28% of imported insects on live plants
Leung et al 2014 Liebhold et al 2012
Can This Problem be Solved? Eradication of established pests is
virtually impossible, but we can slow their spread and buy some time
Biological control has potential but is difficult and risky
Action is needed at the federal level to control the major vectors: live plants for the nursery trade and wood packing material
Policy Options to Prevent Establishment
What can you do about this?
• Use native rather than imported plants in landscaping
• Don’t move firewood
• If managing a forest in response to pest outbreaks, consider:• Impacts of harvesting on the ecosystem• Impacts of pesticides• Long-term health of the tree population
• Recognize that this is a national problem of border protection and complain loudly to your representatives in Congress