Introduced Invasive Plants in California

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Introduced Invasive Plants in California
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• Since the arrival of Europeans, approximately
  1,000 plant species have been introduced in CA
• 140 species listed by the CA Exotic Pest Plant
  Council as Plants of Greatest Ecological Concern

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How Invasive Plants Effect Native Biodiversity

• Displace native species
• Change the way a normal ecosystem operates
• Can be hazardous to native fauna
• Reduces biodiversity

4
European Beachgrass

• captures sand, decreasing natural sand movement,
  and causing the dunes to increase in height
• unsuitable as habitat for nesting snowy plovers
• Displaces three particular species of plants
  including beach layia which is federally listed

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Scotch broom

• Interferes with the establishment of forests and
  invades natural areas.
• Overruns pastures, utility corridors and
  roadsides increasing the maintenance costs of
  these operations.
• Displaces the native plant species and the
  wildlife that depend on them.
• Broom infested areas create a fire hazard.

6
Yellow starthistle

• Native to Eurasia
• First found in Alameda county in 1869
• Infests 42 of California
• Lethal to horse if consumed
• Decreases range forage quality
• millions of dollars in losses probably occur from
  interference with livestock grazing
• Depletes soil moisture

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Tamarisk

• Starting in the 1850s, several species of
  tamarisk were imported to the United States as
  ornamentals and for use in erosion control.

• Starting in the 1850s, several species of
  tamarisk were imported to the United States as
  ornamentals and for use in erosion control
• Aggressive invader of desert riparian habitats
• Forms impenetrable thickets that suck up water
  leaving other plants, birds and fish high and dry
  (up to 300 gallons a day!)

8
Water hyacinth

• Escaped ornamental aquatic plant
• Has invaded the Sacramento-San Juaquin Delta
• Clogs boating waterways
• competitively exclude native submersed and
  floating-leaved plants
• Low oxygen conditions develop beneath water
  hyacinth mats

9
Arundo

• chokes riversides and stream channels
• interferes with flood control
• crowds out native plants

• It ignites easily and can create intense fires.
• grows vertically without any horizontal
  branching and does not provide shading to the
  in-stream habitat, which can lead to increased
  water temperatures and reduced habitat quality
  for fish and other aquatic wildlife