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Daehler and Strong [2] suggest that invasive
exotic pose the most severe threat to native plant diversity in many
nature reserves.
- Exotic plants pose a severe threat to over 7 million hectares of
Federal lands in the western U.S.
- Annual losses to leafy spurge (Euphorbia
esula) - $144 million.
- $20 million needed annually to control hydrilla (Hydrilla
verticillata) in 35,000 hectares of Florida waterways.
- Mediterranean fruit fly - $100 million in 1981 to eradicate
from San Francisco Bay area. (Helicopters, aerial spraying
of malathion.)
- Congressional Office of Technology Assessment report ``Harmful
Non-Indigenous Species in the United States,'' OTA-F-565 (Washington,
D.C.: U.S. Government Printing Office, September 1993).
- Evaluated impacts of 79 non-indigenous species (NIS) introduced
from 1906-1991.
- Cumulative losses estimated to be $97 billion.
- More recently Pimentel et al. [12] estimated
that ``the approximately 50,000 nonindigenous species in the United
States cause major environmental damage and losses totaling
approximately $137 billion per year.''
Kent Holsinger