HABITAT DEGRADATION

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HABITAT DEGRADATION
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Habitat degradation has been an unfortunate trait
of humans for a long time, at least in recorded
history since the the Phoenicians cut the Atlas
Mountain forests for ship timbers. Even Ptolemy
lamented the loss of the Cedars of Lebanon.
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The ancient arabic name for the mountainous
region of North Africa was land of eternal
shadeToday these are barren sun-blasted slopes.
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Herblock from 1929
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1921
NOW
Cartoonist Ding Darling
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Will we ever recover forests made up of such old
growth giants?? Fortunately, a federal court has
just turned down, as incredulous, a federal
proposal to log one of the last remaining stands
of giant Sequoia redwoods.
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Timber harvest from public lands
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Note without the Okeefenokee, Georgias wetland
losses would be over 60
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The message is that humans have a long
unfortunate history of degrading their ecosystems
and habitats. The good news is that by far the
majority of people recognize the short and long
term bad consequences of degradation. And, they
are willing to pass legislation and assume some
personal cost so that good environmental
stewardship becomes the norm. And, this is not a
rich-poor or cultural divide. What is our role as
academics?
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African oil palm grown in Malaysia for
biodiesel When green is bad.
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Habitat degradation.

• Ratio of BRDR declines, species specific or
  community average
• Vulnerability to external/internal threats
  increases
• Ecosystem properties shift from historical
  conditions such that the characteristic biotic
  community is at risk
• Invasive species do well

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Some examples of degradation

• Native species displaced by invasives (tamarisk
  along desert streams)
• Toxins (macro and micro) increase (heavy metals
  around smelters)
• Nutrients are depleted or some are overly
  enriched (soils versus water)
• Habitat is fragmented (next lectures)

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Dealing with habitat degradation

• Protection legislative, community, incentives
• Restoration after the fact
• Off-site mitigation
• Butcan we really go all the way back once we
  screw up the environment??

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1973
Marshes of the fertile crescent Iraq
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2000
Marsh drained during Saddam Husseins regime
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Date palms..after
Images of the fertile crescent marsh
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Based on the amount of water that can now be sent
into the marsh area, at most the marsh may
recover about 20-30 of its former area. And,
what about the functions and biodiversity of the
marsh ecosystem? How much can be recovered?
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Results of dynamiting reefs for fish. How would
you restore it???
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Large scale land conversion. Note second growth
forest next to farmland.
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Land conversion may leave small areas of natural
habitat with large edge effects
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Large scale clear cuts are a major type of
habitat destruction
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However, small scale clear cuts may have the best
chance of rapid return to the original forest
matrix. Does this mean that the size and
distribution of clear cuts should approximate
natural disturbances such as from tree falls and
storm windfalls?
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Islands of forest are scattered throughout this
harvested forest to maximize forest regrowth..a
sustainable harvest practice. Note this could
also have the negative effects of fragmentation.
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Silvacultural practices can minimize forest
degradation..an example of selective harvesting
and understory protection
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Return of the eastern and southern forests
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Cultivated systems worldwide
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Vegetation change U.S.
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Bird species threatened by land use
???
???
..biofuel plantations
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southern Africa
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wetlands loss, 1780s1980s
Number w/in statethousands of hectares
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Can we mitigate wetland losses and degradation?
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How mitigation currently works. Authorized by
interpretation of sect. 404 of CWA and wetland
preservation legislation. Complex series of
credits Emphasis on trading within
sub-basins Monitoring? New degradation?
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• Exxon Valdez spill along 1900km coast

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Oil spills tell us.

• Some toxics have long-lasting effects.
• Short-term responses may create additional damage
• We really dont know how to assign monetary value
  to imperiled animals and plants in order to
  assign liability.
• Scientists and attorneys need to talk!!

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Increased nitrogen deposition
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More nitrogenless species in prairie
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Coastal dead zones
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Habitat degradation economic and social drivers
New markets Population
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Pharmaceuticals a new kind of pollution

• Biologically very active, tiny amounts (ppb-ppt)
  are significant at lowest levels of detection
• Structurally stable
• May interfere with general biological systems,
  e.g., endocrine disruptors
• May have unexpected effects in non-target
  organism
• Note first three are market-driven properties

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Indian vulture decline.Three species of Gyps
vultures (giant griffon vultures) have declined
97. Role not replaced by other vultures. Now
Bombay uses solar reflectors to decompose
carcasses.
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A solution to pharmaceutical pollution of rivers??

• Constructed wetlands for waste water treatment
  may destroy endocrine disruptors (and provide
  wildlife habitat)

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Habitat fragmentation..future lecture