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THREATS

THREATS. There are big catastrophic threats and…. …There are smaller chronic threats, but they can, over time, have big effects !. ???. Per cent of taxa imperiled in the United States. Range of vulnerability within taxa. Meaning of threat.

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THREATS

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  1. THREATS

  2. There are big catastrophic threats and…..

  3. …There are smaller chronic threats, but they can, over time, have big effects !

  4. ???

  5. Per cent of taxa imperiled in the United States

  6. Range of vulnerability within taxa

  7. Meaning of threat Threats are any external event or process that degrades ecosystem functions, reduces biodiversity, or places populations at risk of extinction.

  8. CATASTROPHICTHREATS • Hurricanes (categories 3-5) • Major river floods • Extensive droughts • Wildfires • War • Virulent disease • Others??

  9. Catastrophic events often leave long legacy effects • Ecosystem functions may be changed • Some ecosystems may be lost and others created • Species may disappear regionally • Invasive species may become more common • New diseases may emerge

  10. But, where there is a long history of similar catastrophic events, resiliency may dominate • Belize and Nicaragua experience frequent hurricanes. Costa Rica does not. How do these forests respond? Belize and Nicaragua forest trees resprout (coppicing). Costa Rica trees, same species, generally do not. A hurricane is a greater catastrophe for Costa Rica

  11. Legacy of H. Mitch • Traditional farms more resilient • Poor land use more vulnerable • National Parks more resilient • Riparian zones scoured • Mangroves have slow recovery but most not damaged • Rat populations elevated

  12. Hurricane Katrina

  13. Legacy of H. Katrina • Poor land use made wetlands more vulnerable • Wetland losses made New Orleans more vulnerable (Env. Service example) • Cold water churned up in Gulf increased fish production • Coastal mosquito populations greatly increased. • Massive amounts of dead wood (termites, CO2)

  14. Large floods • Spatial scales can be hundreds of square miles • Exacerbated by loss of riparian wetlands and urban watersheds • Coastal effects can include increased “dead zones”

  15. Dartmouth Floodwatch keeps track of floods on weekly basis

  16. Mississippi flood of 1988

  17. Photos of “dead zone” off Oregon’s coast. Lethal conditions begin when oxygen levels drop below 1.5 milliliters per liter of sea water.

  18. Global distribution of coastal “dead zones” As of 2007, 400 major dead zones, double the number found two years ago. Will Georgia join the map??

  19. Forest fires Illustrate complex interactions and cascading effects

  20. Fire adapted systems recover quickly. Lodgepole pine recovery from Yellowstone fire of 1988. But recovery of other trees much slower.

  21. Post-fire effects on grizzly bears

  22. High elevation Whitebark pine seeds are lipid-rich and important for bear hibernation fat. Bears raid Red squirrel middens. Yellowstone fire destroyed many Whitebark stands.

  23. Without Whitebark seeds, bears foraged more around campsites. Also, bears foraged more around creek mouths at Yellowstone Lake for fish, but this is where many hotels were built. The result was that for several years following the Yellowstone fire, there was an increased number of bear-human interactions.

  24. Dispersal of Whitebark seeds depends on Clark’s Nutcracker.

  25. Clark’s Nutcracker depends on conifer forests and on seeds available following fires. Post fire timber salvaging may impact Clark’s Nutcracker populations. ???

  26. An enigma?? Before the great fire of 1929, most of Glacier National Park was a cedar-hemlock forest. Was Clark’s Nutcracker absent? Forest is now mostly pine. How did this get colonized?

  27. And, one more interacting factor. White Pine Blister Rust, invading from Europe is killing Whitebark Pine.

  28. Forest fires in westernUnited States. 1970-1984 compared with 1985-2000 • Fire duration change from 7.5 to 37.1 days • Four fold increase in number of major fires • Six fold increase in size of fire • Snow melt 1-4 weeks earlier • …and pattern continues through 2008

  29. Forest fire con’t • Ave. temperature increase ca 0.9 C • 7/7 climate change models suggest temperature increases of 2-5 C by 2040-2069, plus decreased ppt. • Expect doubling of fires (minimum) • Currently forest fires (worldwide) add equivalent of 40% of fossil fuel C into atmosphere. What next??? Westerling et al. 2006. Science 313: 940-943

  30. Take home message… Catastrophic events often trigger long-lasting complex consequences

  31. CHRONIC THREATS • Habitat destruction (gradual) • Habitat fragmentation (bit by bit) • Invasive species (handful of villains) • Pollution (shifting from PS to NPS) • Disease (from the subtle to the obvious) • Climate change (the big unknown) • Etc etc etc

  32. But..does it have to be this way?

  33. Disease is a central component in shaping populations and communities

  34. Emerging diseases. Red dots emerging diseases for first time; blue dots re-emerging diseases.

  35. A new fungal disease “White nose syndrome” is killing most northeastern US bats

  36. Disease and amphibian decline

  37. Pollution Most worrisome are endocrine disruptors that are potent at parts per billion

  38. Orca (Killer Whale) muscle tissue * Males **Females * **

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