Transcript Document

HABITAT DEGRADATION
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.
The ancient arabic name for
the mountainous region of
North Africa was “land of
eternal shade”
Today these are barren sunblasted slopes.
Herblock from
1929
1921
NOW
Cartoonist Ding Darling
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.
Timber harvest from public lands
Note: without the Okeefenokee, Georgia’s
wetland losses would be over 60%
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?
African oil palm grown in
Malaysia for biodiesel:
When green is bad.
Habitat degradation….
• Ratio of BR:DR 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
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)
Dealing with habitat
degradation
• Protection: legislative, community, incentives
• Restoration after the fact
• Off-site mitigation
But…can we really go all the way back once
we screw up the environment??
1973
Marshes of the fertile crescent: Iraq
2000
Marsh drained during Saddam
Hussein’s regime
Date palms..after
Images of the fertile crescent marsh
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?
Results of dynamiting reefs for fish.
How would you restore it???
Large scale land conversion. Note second
growth forest next to farmland.
Land conversion may leave small
areas of natural habitat with large
edge effects
Large scale clear cuts are a major type of habitat destruction
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?
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.
Silvacultural practices can minimize forest degradation..an
example of selective harvesting and understory protection
Return of the eastern and southern forests
wetlands loss, 1780s–1980s
Number w/in state=thousands
of hectares
Can we “mitigate”
wetland losses and
degradation?
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?
• Exxon Valdez spill along 1900km coast
Oil spills tell us….
• Some toxics have long-lasting effects.
• Short-term responses may create
additional damage
• We really don’t know how to assign
monetary value to imperiled animals
and plants in order to assign liability.
• Scientists and attorneys need to talk!!
Increased nitrogen deposition
More nitrogen=less species in
prairie
Coastal dead zones
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
diclofenac
treat inflamation in cows
Cow carcasses
contaminated with diclofenac
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.
Vultures die from renal failure
97% decline of vultues since 90s
more cow carcasses
more cow carcasses
more anthrax
more dogs
more rabies
A solution to pharmaceutical
pollution of rivers??
Constructed wetlands for waste
water treatment may destroy
endocrine disruptors (and provide
wildlife habitat)
Habitat fragmentation……..future lecture