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Lecture 26: Human Impacts on Biodiversity. EEES 3050 . Human Impacts. Today - Final Lecture! Assignment due Next Thursday – Exam at 10:15. Threats to biodiversity. Global Biodiversity Scenarios for the Year 2100

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human impacts
Human Impacts
  • Today - Final Lecture!
    • Assignment due
  • Next Thursday – Exam at 10:15
threats to biodiversity
Threats to biodiversity
  • Global Biodiversity Scenarios for the Year 2100
  • Osvaldo E. Sala,1* F. Stuart Chapin III,2 Juan J. Armesto,4 Eric Berlow,5 Janine BloomÞeld,6 Rodolfo Dirzo,7 Elisabeth Huber-Sanwald,8 Laura F. Huenneke,9 Robert B. Jackson,10 Ann Kinzig,11 Rik Leemans,12 David M. Lodge,13 Harold A. Mooney,14 Martõ «n Oesterheld,1 N. LeRoy Poff,15 Martin T. Sykes,17 Brian H. Walker,18 Marilyn Walker,3 Diana H. Wall16
  • “For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change…”
  • “For freshwater ecosystems, biotic exchange is much more important.”
climate change



Climate change
  • What is climate change?
    • Changes in temperature and precipitation.
    • Currently, suspected to be driven by human alteration of the carbon cycle.
increase in atmospheric carbon
Increase in atmospheric carbon

Concentration of CO2 at the Mauna Loa Observatory

How does climate change effect ecology?
    • i.e. distribution and abundance of organisms.
    • Changes in range
    • Timing of life cycles
    • Changes in NPP
    • Altering ecosystem properties
    • Altering nutrient cycling
example 1 breeding date
Example 1: Breeding date.
  • Climate change has affected the breeding date of tree swallows throughout North America
  • By Dunn and Winkler
  • Proceedings of the Royal Society of London B. 1999.
    • Prior to this study, most changes in breeding cycles for vertebrates were limited to Europe.
  • Question:
    • If changes in climate are affecting breeding times in Europe, what about North America.
  • Hypothesis:
    • Increasing surface air temperatures are advancing avian reproductive patterns across an entire continent.
    • Compiled and examined 40 years of existing data.
    • Data came from nest-boxes
      • This eliminates potential changes to nest selection.
  • Results:
    • From 1959 – 1991 tree swallows started breeding earlier by 9 days.
example 2 range shifts in marine fishes
Example 2: Range shifts in marine fishes
  • Climate Change and Distribution Shifts in Marine Fishes
  • Allison L. Perry,1* Paula J. Low,2. Jim R. Ellis,2 John D. Reynolds1*
  • Science June 2005
example 2 range shifts in marine fishes14
Example 2: Range shifts in marine fishes
  • Theory:
    • Predicts species should move towards poles due to climate change.
  • Observation:
    • North Sea waters have warmed by an average of 0.6-C between 1962 and 2001
  • Hypothesis:
    • North Sea fish species have shifted their ranges due to climatic changes.
    • Species with fast generation times are more responsive.
    • Studied the demersal (bottom-living) fish assemblage in the North Sea.
    • This group is composed of more than 90 species
    • Used surveys of commercial and non-target fish species.
      • Not really clear how they got this data.
  • Results:
    • Many species were showing a trend of moving north in the North Sea
    • These shifts are correlated with changes in temperature.
land use change
Land-use change
  • Example of land-use change:
    • Deforestation
    • Ag. Land
    • Urbanization
    • Suburban Sprawl
  • Effects on ecology?
    • Loss/alteration of habitat, changing water and nutrient cycles, etc. etc.
example 1 carbon and deforestation
Example 1: Carbon and deforestation.
  • Annual fluxes of carbon from deforestation and regrowth in the Brazilian Amazon
  • R. A. Houghton*, D. L. Skole², Carlos A. Nobre³, J. L. Hackler*,
  • K. T. Lawrence* & W H. Chomentowski²
  • Nature January 2000
    • How did deforestation and regrowth affect the flux of carbon between 1989 and 1998?
Large flux of carbon due to deforestation, primarily as a result of decay.
  • This efflux of carbon is actually almost balanced by the regrowth of forests in this region.
example 2 land use and bird diversity
Example 2: Land use and bird diversity
  • Land Use and Avian Species Diversity Along an Urban Gradient.
  • Robert B. Blair
  • Ecological Applications 1996
example 2 land use and bird diversity28
Example 2: Land use and bird diversity
  • Observation:
    • Urbanization has an obvious impact on the ecology of most species.
  • Hypothesis:
    • Urbanization adversely affects the native bird community.
    • Conducted bird surveys in 5 different land use types ranging from urban to wild.
  • The increase is from widely distributed species at the expense of native species.
biotic exchange i e invasive species
Biotic exchange, i.e. Invasive Species
    • A non-native species that was released (on purpose or accidentally) and is affecting the environment or economy in a “negative” manner.
    • Sometimes called “introduced” species.
      • Usually an “invasive” species is one that is causing harm.
      • Other terms, nuisance, non-native, non-indigenous, …
  • Effects on ecology?
    • From nutrients to ecosystems.
    • From a theoretical standpoint, invasive species are great tools to test questions about stability, competition,
a story in pictures kudzu
A story in pictures… Kudzu
  • Kudzu was introduced to the United States in 1876 at the Centennial Exposition in Philadelphia, Pennsylvania
  • Used for forage in the 1920s
  • the Soil Conservation Service promoted kudzu for erosion control.
    • Hundreds of young men were given work planting kudzu through the Civilian Conservation Corps
  • What has become of Kudzu?
zebra mussels in lake erie
Zebra mussels in Lake Erie
  • A familiar story?
  • What impacts have zebra mussels actually had on Lake Erie?
    • Changes water quality
    • Major declines in native mussels
    • Changes in benthic communities.
    • Link to fisheries?
example 1 zebra mussels and native bivalves
Example 1: Zebra mussels and native bivalves
  • Dramatic Decline of Unionid Bivalves in Offshore Waters of Western lake Erie After Infestation by the Zebra Mussel, Dreissena polymorpha
  • Don W. Schloesser and Thomas F. Nalepa
  • What has been the impact of zebra mussels on native unionids?
example 2 phytoplankton and clarity
Example 2: Phytoplankton and clarity
  • Changes In Planktonic Diatoms And Water Transparency In Hatchery Bay, Bass-island Area, Western Lake Erie Since The Establishment Of The Zebra Mussel
  • Holland, R.E.
  • Journal Of Great Lakes Research 19 (3): 617-624 1993
    • Water clarity has increased.
    • Planktonic diatoms decreased.
  • “Water clarity is aesthetically pleasing, but the capacity of D. polymorpha to remove phytoplankton, as well as abiotic material, from the water justifies concern about consequences for the entire food web.
final thoughts
Final thoughts
  • Ecology as a science:
    • More questions than one can imagine!
    • Very applied.
    • Requires creativity
      • Sometimes more of an art than a science.
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