IS ecosystem effects


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Sample lecture presentation from HON 305, Global Environment, on ecosystem effects of invasive species.

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IS ecosystem effects

  1. 1. Ecosystem impacts of invasive species HON 305V Dr. Andersen
  2. 2. Why do invasives become so abundant?● Competitive release: Kept in check by co- adapted competitors in native habitat● Release from natural enemies: Kept in check by “the 3 Ps” (predators, parasites, pathogens) in native habitat● Facilitation: Alter habitat to make it more favorable for themselves ● Allelopathy: Poison your neighbors ● Fire regimes: Burn your neighbors homes down
  3. 3. Competitive release vs. natural enemy release● Ecologists have been debating the relative importance of competition vs. the 3 Ps since the 1950s● Still an active topic of research● Real answer seems to be “it depends”
  4. 4. Allelopathy● Yellow starthistle (Centaurea solstitialis) native to Eastern Europe, highly invasive throughout the Western U.S.● Roots produce 8- hydroxyquinoline, toxic to plants that have not co- evolved with C. solstitialis
  5. 5. Altered fire regimes● Cheatgrass (Bromus tectorum), native to Eurasia, now found throughout the Western U.S.● Creates dense stands of dry grass (i.e., fuel) in the hottest driest summer months● Natural grassland fire frequency in non-invaded areas about once every 60-100 years● Heavily invaded areas burn every 3-5 years● Native vegetation not adapted to this high fire frequency● Neither are native wildlife
  6. 6. Effects on invaded habitats● The worst invasive plants can establish near-monocultures that displace native vegetation, and reduce habitat quality for native wildlife
  7. 7. Back to the 3 Ps● Introduced predators can devastate native animal communities● Feral cats● Green tree snakes● Many of the worst offenders are fish
  8. 8. Integrated strategy for combating invasive species● Prevent additional introductions through effective quarantine and regulation● Early detection and rapid response to new outbreaks● Control and management of established problem species through multiple means● Restoration and recovery of natural ecosystems
  9. 9. Giant African Snail (Lissachatina fulica)● Voracious herbivore, major pest (and nuisance) in vegetable and fruit crops, and in gardens● Feeds on a broad range of host plants● Has established throughout Indo-Pacific, Caribbean, Brazil● Found in the U.S. in Florida and Hawaii
  10. 10. Cane Toad (Rhinella marina)● Deliberately introduced into Australia in 1935 to control pest insects in sugarcane● Largest toad species● Eats everything● Toxic to anything that tries to eat it
  11. 11. Feral pigs (Sus scrofa)● Originally native to Europe, Asia, and North Africa● Now found on all continents except Antarctica● Major problem in many areas, including (but not limited to) Australia, Hawaii, Texas● Carry many diseases of livestock and humans including ● Foot and mouth disease ● Brucellosis ● Leptospirosis ● Toxoplasmosis● Rooting and wallowing behavior damages native vegetation, may promote erosion● Opportunistic omnivores (they eat everything)● Impact water resources for wildlife
  12. 12. House sparrow (Passer domesticus)● Native to Eurasia and North Africa● Now found throughout the U.S., and in many other parts of the world● Can out-compete native granivorous (seed-eating) birds● Known to evict many native birds from nests ● Swallows (here on campus) ● Woodpeckers ● Bluebirds ● Wrens ● Purple Martins
  13. 13. Tree-of-heaven (Ailanthus altissima)● Native to Asia● Fast-growing, prolific seed- producer, aggressive root- sprouting; can sprout from fragments● Allelopathic● Thrives in poor soils, tolerates pollution● Can form dense stands and crowd out native vegetation● Roots can damage sidewalks and building foundations
  14. 14. Giant Hogweed (Heracleum mantegazzianum)● Crowds out native species● Dies back in winter, thus can promote soil erosion● Produces toxic sap that can cause skin irritation and blindness● Established in Oregon, Washington, and Pennsylvania● British progressive-rock band Genesis (Phil Collins, Peter Gabriel) recorded a song about Giant Hogweed
  15. 15. Garlic mustard (Alliaria petiolata)● Native to Europe, established in U.S. in th the 19 century● Aggressively competitive, allelopathic● Able to out-compete native forest-floor plants
  16. 16. Russian olive (Eleagnus angustifolia)● Native to southern Europe and western Asia● Displaces native vegetation mainly but not exclusively in riparian (streamside) habitats● Can fix atmospheric nitrogen, shade tolerant● Forms dense stands● Provides poor habitat for native birds
  17. 17. Water hyacinth (Eichhornia crassipes)● Native to tropical South America● Now found in North America, Asia, Australia, Africa, and New Zealand● In U.S. found throughout the southeast, and in California and Hawaii● Chokes waterways, leads to massive amounts of decaying vegetation and reduced flow; reduce dissolved oxygen levels, often leading to fish kills● Shade out other aquatic plants, as well as phytoplankton● Biological control promising● Can be used to make a wicker-like material that can be made into baskets or furniture● Used in World War II in Southeast Asia to fool Japanese pilots into thinking that lakes were open fields safe for landing
  18. 18. ● Questions on the material?● Questions on any of the examples?● Remember competitive release, the 3 Ps, and facilitation. What are the implications of these three mechanisms for control of invasive species?● What kinds of adaptations might species have to cope with really high fire frequencies?● Invasive predators and herbivores can be especially devastating on islands. Can you think of reasons why this might be true?● What are the implications of so many widespread invasive species for our concept of “pristine nature”?● Observations on invasive species youve encountered?