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Unformatted text preview: t destroyers
of biodiversity are:
1. habitat destruction, THE PROBLEM OF INTRODUCED SPECIES
• Zebra mussels
Introduced from Caspian Sea
750,000 per m2
Reduce phytoplankton levels
Loss of fish
pipes and 2. invasion by exotic
• The Nature Conservancy /
University of California, Davis
Wildland Invasive Species Team • http:// tncweeds .ucdavis .edu
European bull thistle in
Yosemite National Park THE PROBLEM OF INTRODUCED SPECIES
• African honeybee
• Wanted to cross-breed with
• Aggressive towards
humans and animals
• Ten deaths in U.S. Invasive? Invasive Introduced Species
• Weed : an organism growing in a given area where it is not wanted by
humans. May be native or non-native.
• Introduced / Non-native / Exotic / Alien / Non-indigenous: species
introduced to an area outside their original range by human activity —
directly or indirectly / intentionally or unintentionally.
• Invasive: non-native species that spreads from its site of introduction
into new areas.
– Some authors limit this definition to those species having a
measurable effect on native wild communities.
– By either definition, only a tiny fraction of the tens of thousands of
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