Today: Threats to Biodiversity Bonuses due... now.

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Today Threats to BiodiversityBonuses due...
now.
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Why are species going extinct?
Fig 55.6
data from Canada
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Why are species going extinct?
"Global Biodiversity" Chapman Hall, World
Conservation Monitoring Centre, London, 1992
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Why is biodiversity important?
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Areas with increasing plant biodiversity were
less affected by drought.
Fig 55.15
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Why are species going extinct?
"Global Biodiversity" Chapman Hall, World
Conservation Monitoring Centre, London, 1992
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CB 55.13
Not all habitats are equal
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A third to a half of all old-growth species avoid
younger (lt30-year-old) regrowth.
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Ecosystem Fragmentation
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Yellowstone NP
63 mi
54 mi

• 466 mi of roads
• 950 mi of backcountry trails
• 97 trailheads
• 287 backcountry campsites

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Artificial corridors allow animals to cross
fragmented areas
CB 55.16
CB 55.16
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Wildlife corridors help maintain biodiversity
Fig55.16
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Why are species going extinct?
"Global Biodiversity" Chapman Hall, World
Conservation Monitoring Centre, London, 1992
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Invasive species can disrupt an ecosystem
CB 55.6
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Nile Perch (Lates niloticus)

• Introduced to Lake Victoria in 1954 to increase
  fish yield
• Caused extinction of 200 endemic fish species
  through predation, and competition
• Fish caused indirect increased erosion on land,
  causing higher nutrient levels in the lake.

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Water Hyacinth (Eichhornia crassipes)

• Introduced as ornamental plant around the world
• Now in 50 countries on 5 continents including US
• In California it replaced the native pennywort
  (Hydrocotyle umbellata) which occupies a similar
  habitat, leading to a marked decrease in
  invertebrate communities
• Limits water transport, reduces oxygen and light
  levels in the water

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Caulerpa Seaweed (Caulerpa taxifolia)
Slide 37
Slide 37

• Introduced into Mediterranean by Monaco Aquarium
  in 1984 by dumping aquarium waste into the sea.
• Hardier clone than the tropical species which
  seemed to have developed in the aquarium.
• Smothers natural seagrass beds while being toxic
  to herbivores.
• By 2000 covered 131km2 in several Mediterranean
  countries.

Meinesz A, Belsher T,et al 2001 / Thibaut T,
Meinesz A
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Zebra mussel (Dreissena polymorpha)

• Spread from its native range in the Baltic Sea
  via ballast water
• Spreads in Europe and North America
• Kills native molluscs, changes ecosystems, and
  damages infrastructure
• Estimated annual damage in US 3 billion

Napela T.F., Schloesser, D.W., 1992
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The brown tree snake (Boiga irregularis)

• Its native in Australia and was introduced to
  Guam accidentally in the 1950s
• Overall responsible for the extinction of 3 out
  of 4 seabirds 9 out of 13 forest birds 3-5 out
  12 reptile species on the Island of Guam.
• This snake caused the extirpation or serious
  reduction of most of the island's 25 resident
  bird species on the main island of Guam.

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• How Many Invasive Species Are There in Texas?
• 67 terrestrial plants
• 12 aquatic/wetland plants
• 10 mammals
• 4 birds
• 7 fishes
• 11 insects
• 11 mollusks and crustaceans

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Hydrilla verticillata Aquatic invader covering
nearly 100,000 surface acres of water in Texas.
Spreads rapidly, in one Texas lake it covered 23
acres in 1999 but over 200 in 2000. Depletes
water of oxygen and blocks sunlight killing off
many native plants and animal species.
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Hydrilla on Longhorn dam over Town Lake
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The level of Lake Austin is lowered in winter to
kill the hydrilla and other invasive plants
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Why are species going extinct?
"Global Biodiversity" Chapman Hall, World
Conservation Monitoring Centre, London, 1992
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