Transcript Biodiversity - Mr. Fouts' Home Page

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 jellyfish); 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 antipredation 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 Overfishing 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