Biodiversity by linxiaoqin

VIEWS: 4 PAGES: 21

									 What Forms of Pollution are Especially Harmful
               in Ecosystems?
• Air pollution
   – Particulates and Heavy Metals
        • Industrial sources (ex. steel plants) and car exhaust
        • Can be toxic, decrease immunity, and aggravate asthma
   – Acid rain: from nitric acid (car exhaust) and sulfuric acid (coal)
        • Acids increase solubility of some toxic heavy metals
        • Forests decline: Eastern Europe, U.S. Midwest (crosses boundaries)

• Water pollution: point and non-point sources
   – Biomagnification: heavy metals and persistent organic pollutants (POP’s) are difficult
       to metabolize and/or detoxify  concentrate in livers, fats of top predators (ex.
       DDT with egg-thinning effects  endangered bald eagles and pelicans); others
       weaken immune systems or cause feminization (ex. fish in Lake Mead)
   – Eutrophication and Sedimentation: excess plant nutrients lead to algal blooms; when
       algae die, leads to excess decomposition and thus high biological oxygen demand
       (BOD); can lead to fish kills; excess sediment smothers corals and mucous-feeding
       invertebrates; sewage treatment reduces both problems
   – Garbage: dumping in ocean outlawed in United States; plastics build up in central
       Pacific Ocean (center of gyre) and eaten by loggerhead turtles (mistake for jelly-
       fish); seabirds ingest and feel full, regurgitate garbage to their offspring
Figure 55.19
Figure 55.20
Figure 55.18
Noise Pollution Affects Marine
 Mammals (Acoustic Umwelt)
Finally – Proof of Deafness!
    Are Introduced Species a Form of
               Pollution?
• Exotic, non-native species (vs. indigenous species)
• The only pollution that creates more of itself
  – Can be accidental (ex. ship ballast introduces marine
     species via larvae) or purposeful (ex. mongoose in
     Hawaii; many fishes)
  – Can have large effects on ecosystems since native
     species have not co-evolved competitive or anti-
     predation mechanisms
  – Main causes of species extinctions and endangerment in
     Hawaii and Puerto Rico (including many endemic
     species)
  – Often controversial regarding removal or treatment:
     poisoning of Lake Davis (CA) to remove pike; shooting
     goats on Catalina Island
  – Other examples: Africanized (“killer”) bees; brown tree
     snake (Guam); zebra mussels; “Med Fly”
Figure 56.8
       How do Species Become Endangered, and
              How are They Protected?
• Common Characteristics of Endangered Species: small, localized
      ranges (including islands), fragmented populations (often due
      to human activities), low reproductive success
• U.S. Endangered Species Act (ESA): 1973; enforced by U.S. Fish
      and Wildlife Service or National Marine Fisheries Service
   – Endangered status: in “imminent danger of extinction throughout all or
      significant part of its range”
       • Protects habitat; can be applied to a specific sub-population
   – Threatened status: in “forseeable risk” of extinction
       • Examples: white shark (Calif. ESA) with naturally low populations and
              targeted fisheries for sport/jaws; polar bear recent listing
   – Listings: umbrella species chosen to protect entire ecosystem (ex.
       spotted owl chosen to protect old-growth forests); flagship species
       (high profiles, ex. panda, bald eagle); sentinel (bellweather) species
       first to show effects of environmental stress (ex. amphibians exposed
       to air and water pollution); keystone species
   – Controversies: populations difficult to measure; some listings seem
       “crazy” (ex. fly in Colton); is it effective? (few de-listings); habitat
       protection often conflicts with private-land ownership
Figure 56.4
Figure 56.10
  Is Aquaculture the Solution for the Over-
             fishing Problem?
• Over-fishing: 90% of fisheries over continental shelves; led to
     200-mile exclusive-use zones; international fisheries
     include Bering Sea, Gulf of Alaska, Grand Banks,
     Southern Capes (Good Hope, Horn)
   – Due mainly to increased technology: spotter planes, satellite data,
      larger nets and longer long-lines
   – Biggest problems: bycatch; fishing at low trophic levels; subsidization
      and flags of convenience (escape international treaties)
       • Trawling degrades habitat and has high level of bycatch
   – Shark fisheries: mainly for shark-fin soup  finning
       • Sharks do not support fisheries due to low reproductive potential
   – Reserves replacing quotas and size limits; easier to enforce and
      evidence that they work (most fishes with planktonic larvae)
• Aquaculture and Mariculture (marine aquaculture)
   – Shrimp, salmon, lobster mainly for feeding relatively wealthy; all use
      fish meal and contribute to over-fishing (net loss of biomass)
   – Tilapia and shrimp farms often destroy coastal wetlands/mangroves
   – Dense populations lead to disease  antibiotics enter ecosystems
   – Escapes common; concern over effects on natural gene pools
Figure 56.9
Figure 54.24
 Is the Ozone Layer Still Threatened?
• Stratospheric Ozone Depletion
  – Ozone a component of smog in lower atmosphere; in
      upper atmosphere, shields Earth from UVB radiation
  – Chlorofluorocarbons (CFC’s) lighter than air, rise to
      upper atmosphere, where they stick to ice crystals;
      each molecule able to destroy many ozone molecules
      (most during summer); Antarctic ozone hole detected in
      1985, Arctic ozone hole detected in early 1990’s; global
      ozone declining (ex. Toronto, UV increased 5.3% per
      year from 1989-1993)
  – Effects of UV: skin cancers, stress immune systems,
      coral bleaching, reduces productivity of phytoplankton
  – International Response: Montreal Protocol (1987) phased
      out production of CFC’s, but existing CFC’s stable
      (long-lived; ex. freon)
Figures 55.23-55.25
     What Evidence Supports the Theory of
              Global Warming?
• A theory, supported by multiple lines of evidence (that
      current observed warming trend is due largely to
      human-caused influences)
  – Greenhouse Effect: greenhouse gases trap warm air in lower
     atmosphere (esp. carbon dioxide, methane, and carbon
     monoxide)
  – Combustion of fossil fuels adds CO2 to atmosphere; deforestation
     is often via burning (combustion) and loss of trees reduces
     uptake of carbon dioxide; more cattle  more methane
     (proposal for effort to measure this effect laughed out of U.S.
     Congress as “cow-fart study”)
  – Observed: rise in atmospheric CO2; global atmospheric and
     oceanic warming; rising sea levels (Tuvalu, Kiribati, other
     Pacific islands flooding); retreat of mountain glaciers, Arctic ice
     thinned, Antarctic ice shelves apparently breaking up;
     tropical diseases and insects spreading; regional climates
     shifting, affecting species ranges and causing extinctions;
     widespread coral bleaching; lower heating costs on the
     “bright side”
Figure 55.21
       What are the Predicted Effects of Global
      Warming and the International Response?
– Predicted: approx. 6°C rise by 2100; warming of tundra releases more
    CO2, melting of polar ice reduces reflection of energy by white ice and
    accelerates melting (vicious cycles); melting of West Antarctic ice sheet
    would raise sea level by 20 feet, flooding London, New York, Florida,
    New Orleans (among others); cooling of Northern Europe due to likely
    disruption of Gulf Stream current by melting Arctic (more icebergs will
    also endanger ships); rise in intensity of tropical cyclones due to
    warmer water temperature
– Debate among specialists is mainly regarding the ocean’s role in the
    absorption of CO2 (but note that levels steadily rising in atmosphere,
    corresponding to steady rise in combustion/emissions)
– Public debate mainly regarding Earth’s natural cycles of warming/cooling
    and lack of “definite proof”; also regarding economic costs of reducing
    carbon emissions
– International Response: Rio Earth Summit (1992) – agreed that Global
    Warming is serious problem and response needed by year 2000
    (George Bush Sr. signed); Kyoto Accord (1998) – signed by nearly all
    nations; Copenhagen (Dec. 2009); Adapt (?): sea walls planned in
    Thailand and Bangladesh

								
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