Today: Threats to BiodiversityBonuses due... now.

Why are species going extinct?Fig

55.6

data from Canada

Why are species going extinct?

"Global Biodiversity" Chapman & Hall, World Conservation Monitoring Centre, London, 1992

Why is biodiversity important?

Areas with increasing plant biodiversity were less affected by drought.

Fig 55.15

Why are species going extinct?

"Global Biodiversity" Chapman & Hall, World Conservation Monitoring Centre, London, 1992

CB 55.13

Not all habitats are equal

A third to a half of all old-growth species avoid younger (<30-year-old) regrowth.

Ecosystem Fragmentation

63 mi

54 mi

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

Yellowstone NP

CB 55.16

Artificial corridors allow animals to cross fragmented areas

CB 55.16

Fig55.16

Wildlife corridors help maintain biodiversity

Why are species going extinct?

"Global Biodiversity" Chapman & Hall, World Conservation Monitoring Centre, London, 1992

CB 55.6

Invasive species can disrupt an ecosystem

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.

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

Caulerpa Seaweed (Caulerpa taxifolia)

• 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

Slide 37Slide 37

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 billionNapela T.F., Schloesser, D.W., 1992

The brown tree snake (Boiga irregularis)

• Its native in Australia and was introduced to Guam accidentally in the 1950’s

• 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.

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

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.

Hydrilla on Longhorn dam over Town Lake

The level of Lake Austin is lowered in winter to kill the hydrilla and other invasive plants

Why are species going extinct?

"Global Biodiversity" Chapman & Hall, World Conservation Monitoring Centre, London, 1992

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