1. Invasive Species
An introduction

2. What is a native species?
normally live and thrive in a particular community.
occupy specific habitats and have specific niches in their native environment.
have natural predators that help to keep their populations in check.
Pink lady's slipper, Cypripedium acaule
Red fox, Vulpes vulpes

3. What is a non-native species?
species living outside its native distributional range
has arrived there by human activity, either deliberate or accidental. 
Non-native species are not necessarily invasive.
Multiflora rose, Rosa multiflora, was introduced for use as an ornamental plant, to control erosion, and to use as “living” fences for livestock.
Zebra mussels (Dreissena polymorpha), were accidentally introduced to North America, and are now found in some Pennsylvanian waterways

4. 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
Japanese stilt grass, Microstegium vimineum, becomes established on recently disturbed areas and outcompetes native plants, reducing biodiversity.

5. Common characteristics of invasive species
Invasive species in general:
Have few natural predators, competitors, parasites or diseases
Rapid reproduction
Fast Growth
Are long-lived
Are generalists (tolerate many different conditions/different foods
Are pioneer species (1st to grow after a disturbance)
Characteristics that make Zebra mussels a good invader include its ability to tolerate a wide-range 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?

6. What traits are common to invasive plant species
Self-compatible
Flower early
Produces abundant seed
Disperse seed widely
Grow rapidly
Spread asexually (don’t need a mate)
Strong competitors
Characteristics that make tree-of-heaven a good invader include its ability to flower early (within 2 years), ability to spread asexually, and fast growth rate.

7. Different Routes of Invasion
Most invasions are due to human activities:
Exotic Plant or pet trade (released/escaped)
Commercial shipping (stow away on a ship or plane)
Tourism
Carry it in
Wind- Seeds can be carried great distances.
Water- Organisms can be transported on natural “rafts”
Ballast Water from ships/boats
In most cases of invasive species, human actions are to blame for their rapid spread.
Seeds that are imported from far away can grow and multiply rapidly in the wild to establish an invasive population. For example, Japanese knotweed (Fallopia japonica) has spread across the UK, outcompeting several native plants for space and light. Similarly, animals that are considered desirable pets often escape and establish feral populations, such as the rose-ringed parakeet (Psittacula krameri) in Richmond Park, London.
Ships move all over the world and have spread rats, mice and many other invasive species to numerous islands, which often has devastating effects on these islands’ biodiversity, and a particularly negative effect on nesting seabirds. Island species are very vulnerable to the threat of invasive species as many islands, such as Australia, New Zealand, Madagascar, the Hawaiian Archipelago, and the Galapagos have a high proportion of endemic and highly specialised flora and fauna which have evolved in isolation over hundreds of thousands of years. In the past, the geographic isolation of these islands has limited immigration of new species, allowing established species to evolve with few strong competitors and predators; however, with the advent of global travel and tourism, the transport of species from all over the world (both accidental and deliberate) has resulted in the introduction of invasive species to ecosystems that are often unable to cope. Islands are more prone to invasion by alien species because of the lack of natural competitors and predators that control populations in their native ecosystems. In New Zealand for example, the introduction of non-native species has caused an irreversible decline in many of the islands’ bird species, such as the kakapo, the world’s only flightless parrot.
Water discharged from ships can potentially transport a huge amount of invasive species. Numerous invasive species are thought to have spread this way, including the zebra mussel (Dreissena polymorpha) and Chinese mitten crab (Eriocheir sinensis).
Seeds of invasive plants can be transported hundreds of miles by cars, on clothes and under shoes. Areas that are visited more often by tourists are more likely to be at risk from the introduction of invasive species.

8. Major events that allow invasive species
Removal of natural barriers
waterfalls, wetlands, land barriers
Development of larger and faster transatlantic vessels-
ships cross 2 weeks, ballast water dumping
Water quality improvements
environmental regulation of pollution improved habitat quality

9. INVASIVE SPECIES PROBLEMS
World-wide problem
Increase in travel and trade open routes
In U.S. costs $137 billion dollars per year
Approximately 42% of Threatened or Endangered species are at risk due to non-native, invasive species.
threaten species diversity
Can cause an imbalance in the natural environment
Out compete native organisms for resources
Change abiotic factors
Threaten agriculture
Endanger the health of plants and animals

10. Impacts of invasive species
Displace native species:
Japanese stilt grass displaces native herbaceous plants, reducing biodiversity, and reducing food available for wildlife species.
Monoculture of Japanese stilt grass, prevents establishment of native herbaceous species
Diversity of herbaceous species increases wildlife habitat

11. Impacts of invasive species
 Reduce ecosystem health and productivity    
Monoculture of Japanese barberry prevents the establishment tree seedlings

12. Impacts of invasive species
Some invasive species kill native species
About ¼ of the hardwood trees in Pennsylvania 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

13. Impacts of invasive species
Indirect impacts:
Hemlock woolly adelgid is killing Eastern hemlock trees throughout Pennsylvania and 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

14. Impacts of invasive species
Economic impacts: Invasive species are responsible for tremendous economic losses through loss in forest and agricultural productivity, spread of diseases that impact humans, among other impacts.
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.

15. Invasive Species by State
What area of the US has the highest # of invasive species? Why??

16. Controlling Invasive Species
Controlling invasive species once they have become established is difficult.
Control is also usually very expensive!
Main ways that invasive species are controlled:
Physical control
Chemical control
Biological control
Prevention
Controlling invasive species once they have become established can be difficult, and in some cases it may even be impossible.
Control is also usually very expensive!
There are four main ways that invasive species are controlled:
- Physical control
- Chemical control
- Biological control
- Prevention
These will be discussed in more detail on the slides to follow.
Image: A team of conservationists clearing Pleomele halapepe stand of invasive plants.

17. Physical Control of Invasive Species
Controlling plants:
Mechanical – excavation, weed whipping, etc.
Removal of plants by hand
Installation of growth barriers
Controlling animals:
Culling (selectively remove)
Trapping and hunting
Putting up barriers or fences
Controlling invasive plants:
There are a number of approaches to physically controlling an invasive plant species. These can range from mechanical excavation or hand removal to the installation of growth barriers to suppress or stop invasive plants encroaching onto a site.
There are many things to consider when choosing an appropriate control method, and a single control method will not work for all species. For example, strimming plants can be effective in controlling some species, such as Himalayan balsam, but only if it is done to young plants before the seed heads have developed. Strimming would not be effective for woody species, such as rhododendron, as it does not affect root growth. Similarly, for species such as Japanese knotweed, strimming would result in the plant fragments being dispersed over a wide area, exacerbating the problem.
Controlling animals:
Culling – e.g. culling of the red deer in the UK to restrict the damage it causes to forestry, agriculture and the natural environment (e.g. browsing red deer (see photo) can prevent the regeneration of woodland)
Trapping and hunting
Putting up barriers or fences
Image: Red deer (Cervus elaphus) feeding on tree leaves. Red deer are native to most of Europe, southwest Asia and North Africa; however, it has been introduced to Australia, New Zealand and Argentina, as well as a range of other countries, where it can cause serious damage to native species and habitats. Even in the UK, red deer are periodically culled to prevent the population becoming out of control
Unintended Side Effects – may miss removing some of the invasive species

18. Chemical Control of Invasive Species
Chemical control involves applying poison to eliminate invasive species
E.g. Eradication of rats on Henderson Island
Use rodenticide (rat poison)
Insecticides & pesticides
to control insect pests
Herbicides (weed-killer)
to control plants
Chemical control of species:
Eradication – e.g. removal of rats from islands where they are having devastating effects on nesting seabirds. A large scale eradication project was recently carried out on Henderson Island to protect the native seabirds such as the Henderson petrel, whose populations were in serious decline.
As rats are extremely prolific breeders, the only feasible way to achieve the eradication of the species on a large and rugged island such as Henderson is by spreading bait containing a rodenticide (rat poison).
On Henderson, Brodifacoum, the active ingredient in many household rat poisons, was used to eradicate the rats.
Video – rat predating on Henderson petrel chick:
Find out more about the eradication of rats from Henderson Island: &
Unintended Side Effects – may kill native species

19. Biological Control of Invasive Species
Uses a living organism to control invasive species
This organism may eat the invasive species or cause it to become diseased
Biological control agents must be carefully assessed before release to ensure the control species will not become invasive itself
Biological control uses a living organism to reduce or eliminate the population of the invasive species.
The organism may eat the invasive species or cause it to become diseased - it relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role.
Control agents are often brought from the original habitat of the invasive species.
Images – L: seven-spot ladybird; R: harlequin ladybird – feeding on aphids
Ladybirds are often used as biological control agents to control aphids in greenhouse production of crops. Ladybirds are natural predators of aphids, and so one way of controlling aphid numbers is to release more ladybirds into an area to help control the aphid infestation. Depending on the level of pest infestation, as many as 5,000 to 200,000 ladybirds per acre (1 to 50 per square metre) per week could be mass-released.
However, biological control is risky. Proposals for biological control must be carefully assessed to ensure the control species does not become invasive and cause as much damage as the species to be controlled. One example of this is the harlequin ladybird. The harlequin ladybird spread to the UK after being imported from East Asia to Europe for commercial pest control of crops, and it is now affecting populations of the UK’s native ladybird species, as it is bigger than native species, better protected and able to outcompete native species for food resources.
Seven-spot ladybird
Harlequin ladybird
Unintended Side Effects – control species can become invasive

20. LAWS & REGULATIONS – FEDERAL
NISA – National Invasive Species Act - ANS “Aquatic Nuisance Species” Task Force
Executive Order on Invasive Species – coordinates activities of government agencies (NCIS)
The Lacy Act – regulates import and transport of species
USDA APHIS – US Dept. of Agriculture Animal and Plant Health Inspection Service
CDC – Center for Disease Control

21. What can you do? Buy native plants.
When boating, clean boat before putting it into a different body of water.
Clean your boots before hiking a new area.
Don't take home any animals, plants, shells, firewood, or food from different ecosystems.
Never release pets into the wild.
Volunteer at your local park, refuge, or other wildlife area to help remove invasive species. Most parks also have native species restoration programs.