FW 404: Invasive Species, 12/2

Invasive Species (mostly plants)

“On a global basis..the two great destroyers of biodiversity are, first habitat destruction and, second, invasion by exotic species” - E. O. Wilson

Definitions

  • Native species: present at the time of European exploration (early 1500s)

  • Non-native species: occur in a given place as a result of direct or indirect, deliberate or accidental actions by humans

    • also alien, introduced, exotic, or non-indigenous

  • Benign non-natives depend on humans for survival

  • Invasive non-natives survive and reproduce without human intervention (in this case, the same as naturalized)

  • Natives cannot be invasive, but instead “aggressive” or “weedy”

    • ex: sweetgum

Big Picture in US

  • 50,000 non-native species

  • 20,000 non-native microbes

    • hard to measure

  • 4,500 non-native invertebrates

  • 140 fish, 100 birds, 20 mammals

  • 25,000 non-native plants

  • 5,000 invasive plants

  • 17,000 native plants

How are plants introduced?

  • ornamental (miscanthus, spirea, privet)

  • wildlife food (autumn olive)

  • erosion control (kudzu, sericea)

  • packing material (Japanese stiltgrass)

  • timber producer (Paulownia)

Invasive Plants

  • prolific seed producer

  • long seed viability

  • adaptations for dispersal

  • vegetative reproduction

  • tolerates extreme conditions

  • allelopathic

  • favor disturbance

Japanese stiltgrass has invasive characteristics.

Ecological Effects

  • invasive plants reduce native diversity

  • invasive plants alter structure

  • plant diversity = wildlife diversity

    • ex: butterflies and host plants

  • altered plant structure = changes in wildlife community

Oriental bittersweet climbs onto native canopy.

Buffelgrass promotes fire that kill saguaro.

Cogangrass increases fire intensity in longleaf pine forests. 

Miscanthus increases fire intensity in western NC.

Avoid Invasive Ornamentals

  • Chinese privet

  • Callery pear

  • english ivy

  • periwinkle

  • heavenly bamboo

  • mahognia

  • autumn olive

  • kudzu

  • wisteria

  • Japanese stiltgrass

  • porcelainberry

The Future

  • generally takes 100 years for plant to become invasive

    • today’s invasives introduced in 1800s

    • today’s introductions = tomorrow’s invasives

  • Nandina invading suburbs

  • porcelainberry invading

Solutions

  • don’t plant non-natives

  • manage existing native communities

  • clean logging equipment

  • scout for invasives before management

    • disturbances promote invasives

  • how to manage invasives:

    • accept them as the new norm?

    • pull and other mechanical means

    • herbicides!

  • Logging equipment can spread invasives

  • fire is not a good way to manage

TOPHAT

Northern bobwhite and other upland gamebirds have experienced declines around the world because:

A

grasslands/shrublands have been converted to farmland

B

advancement in herbicides allows better weed control on farmland

C

fire has been excluded from many landscapes

D

all of the above

E

none of the above