Invasive Species
An introduction
What is a native species?
Native species are those that normally live and thrive in a
particular community. They occupy specific habitats and have
specific niches in their native environment. They have natural
predators that help to keep their populations in check.
Pink lady's slipper, Cypripedium acaule
Red fox, Vulpes vulpes
What is a non-native species?
•
A species living outside its native distributional range, which
has arrived there by human activity (either deliberate or
accidental).
• Exotic Species
Non-native
species are NOT
necessarily
invasive!!
– from another part of the world
• Introduced Species
– implies introduction but not a threat
• Alien Species
– implies introduction to a particular
ecosystem- may be a nuisance
10% Rule
– Only 10% of introduced exotics will live at all
due to wrong climate, food availability and other
factors
– Of the 10% that live, only 10% will actually
breed and become invasive (EPA estimates)
– 6,500 established invasive species in the U.S.
(USGS)
Invasive Species
Plants
Insects
Diseases
What is a non-native, invasive species?
• A non-native species that adversely affects
habitats and biodiversity.
Emerald ash borer, Agrilus planipennis , has
killed millions of ash trees in the mid-west and
has recently been found in Pennsylvania and
surrounding states. Has not been documented
in Delaware
Japanese stilt grass, Microstegium vimineum,
becomes established on recently disturbed
areas and outcompetes native plants, reducing
biodiversity.
Common characteristics of
invasive species
Invasive species in general:
• Have few natural
predators, competitors,
parasites or diseases
• Have high reproductive
rates
• Are long-lived
• Are generalists
• Are pioneer species
Characteristics that make Zebra mussels a good
invader include its ability to tolerate a widerange of environments, and high reproduction
rate; female mussels release up to 100,000 eggs
ability to tolerate a wide-range of environments
year.
Discussion: how would these characteristics enable a species to become invasive?
Spread of the Zebra Mussel
What prevents species from dispersing
globally?
Geographic Barriers:
Oceans
Mountains
Deserts
Large Lakes
Barriers are in the eye of the beholder: what is a barrier for
one species is not a barrier to another
e.g. mountains may restrict plant distributions, but not birds
Globalization: The key to introduction
Species are being transported across these barriers
at an increasing rate owing to human movement
and commerce.
Major vectors are planes, ships and humans
In some cases, the rate of spread may be 50,000
times greater than by natural dispersal!
Vectors of Invasion
Intentional Release of Target Species into Containment:
- Escapes from zoos and botanical gardens
- Farmed species
- Aquaculture
- Research
Intentional Release of Target Species into the Environment:
- Plants for agriculture, forestry, soil improvements
- Ornamental Plants/Naturalization societies
- Birds and mammals for hunting
- Biological control
- Released pets and pet trade
Vectors of Invasion
Release of Non-Target Species (AKA “Accidental” Releases):
Contaminants or hitchhikers with produce, ornamental plants and aquaculture
Timber
Contaminants of seed stock
Cars
Planes
Hitchhikers with packing material, cargo
Ballast in ships
Tourists/Luggage
Canals/manmade environmental structures
Ballast Water Problem
Global Invader: European Starling
• Habitat generalists, able to exploit a large variety of
habitats, nest sites and food sources
• Large flocks, highly colonial- aggressive and
gregarious
Impacts:
• Seed dispersal
• Agriculture damage
• Outcompete native species (cavity nesters)
60 starlings were released
in Central Park in 1890 by
a Shakespeare fan, the
population today is
estimated at 200 million.
Invasion of the States
Impacts of invasive species
Economic impacts:
Invasive species are responsible for tremendous
economic losses through loss in forest and
agricultural productivity and the spread of
diseases that impact humans.
European starlings, Sturnus vulgaris, spread
diseases to wildlife, livestock, and humans,
damage agricultural crops, and displace
native birds. Their damage to agricultural
crops is estimated at $800 million annually.
Impacts: Economical
Estimated annual costs associated with non-native species:
Group
costs (in millions)
Plants (purple loosestrife, weeds)
34,000
Mammals (feral pigs, rats)
37,000
Birds (pigeons, starlings)
2,000
Fishes
1,000
Arthropods (ants, termites, other pests)
19,000
Mollusks (zebra mussel, asian clam)
1,200
Microbes (plant pathogens, animal disease) 41,000
All organisms
over $136 billion per year
Source: Pimentel et al. 2000 BioScience
Delaware Ecosystems at risk:
• Marine/Estuarine Ecosystems
• Terrestrial Ecosystems
• Freshwater/Riparian Ecosystems
Impacts: Ecological
• Direct competition with native species
• Loss of species diversity
• Disrupts interactions in natural communities
and food webs
• Affects entire ecosystem functions (water
availability and nutrient cycles)
Forest Invader: Japanese Stilt Grass
•
It can become established and live in a
wide variety of habitats
•
Each plant produces hundreds of seeds
that can remain viable in the seed bank
for upward of five years.
•
Seed can be transported long distances
by water or contaminated hay, seed mix
and soil.
•
Plants also reproduce asexually. They
form roots at the nodes, which allows for
new vegetative stem growth.
•
People can spread stilt grass by carrying
the seeds on their shoes, equipment and
vehicles.
Monoculture of Japanese Stilt grass
prevents the establishment of new tree
seedlings and native herbaceous plants
decreasing the amount of food for
wildlife.
Some invasive species kill native species
About ¼ of the hardwood trees in the Eastern US used
to be American chestnut. The invasive chestnut-blight
fungus killed most American chestnut throughout the
eastern US by 1950.
American chestnut, Castanea dentata, at Grey
Towers National Historic Site in Milford, PA, circa
1905
American chestnut infected with chestnut
blight fungus, Cryphonectria parasitica
Indirect Impacts: Natural Communities
Hemlock woolly adelgid is killing Eastern hemlock trees
throughout the northeast. Eastern hemlock forests play an
important role in maintaining stream temperatures and oxygen
levels favorable for brook trout. Hemlock mortality leads to
increased water temperatures and oxygen levels, and therefore
reduced brook trout populations.
Hemlock woolly adelgid
Hemlock woolly adelgid
infestation
Hemlock mortality along
stream bank
Disturbances: A “root” in the door
The most successful invaders are those that are pre-adapted to
disturbances.
Natural Disturbances
Man-made Disturbances
• mature trees naturally die
• logging
• lightening strikes
• development
•large winds can damage tree crowns
• recreation (trails)
• fire
Stages of Invasion
1. Opportunity (transport)
2. Establishment
3. Spread
(different characteristics may be important at
different stages)
Control Methods
•
•
•
•
•
•
•
Prevention (education, restrictions, monitoring)
Eradication (time sensitive)
Physical (manual & mechanical)
Cultural (ecosystem management)
Biological (natural enemies)
Chemical (pesticides)
Integrated Pest Management (combination of
methods – OFTEN MOST EFFECTIVE)
Side effects of control methods
• Biological – control species can become
invasive, takes a long time to research
• Chemical – may kill native species
• Physical – may miss removing some of the
invasive species
• Prevention – apathy and lack of awareness
Public Outreach: What you can do!
• When boating, clean your boat thoroughly before transporting it to a
different body of water.
• Clean your boots before you hike in a new area to get rid of hitchhiking
weed seeds and pathogens.
• Don’t move firewood (it can harbor forest pests like emerald ash borer).
• Don't release aquarium fish and plants, live bait or other exotic animals
into the wild. If you plan to own an exotic pet, do your research and plan
ahead to make sure you can commit to looking after it.
• Volunteer at your local park, refuge or other wildlife area to help remove
invasive species. Help educate others about the threat.
Laws & Regulations
Federal
- NISA -National Invasive Species Act – ANS
“Aquatic Nuisance Species” Task Force
- Executive Order 13112 on Invasive Species
- The Lacy Act- regulates import and transport
of species
- USDA APHIS
- CDC Center for Disease Control
Delaware Invasive Species Council
Our mission is to “Protect Delaware’s Ecosystems by
Preventing the Introduction and Reducing the Impact of
Non-native Invasive Species.”
USDA Animal and Plant Health
Inspection Services (APHIS)
• Plant Protection and Quarantine (PPQ) regulates the
importation of plants and plant products under the authority
of the Plant Protection Act. PPQ maintains its import program
to safeguard US Agriculture and natural resources from the
risks associated with the entry, establishment, or spread of
animal and plant pests.
• Cooperative Agriculture Pest Survey (CAPS) ensures that new
introductions of harmful plant pests and diseases are detected
as soon as possible, before they have a chance to cause
significant damage. State cooperators carry out surveys for
high-risk pests.
Outreach publication, signage/ Education
materials
BINDERS!!
DISC Website
http://www.delawareinvasives.net/resources