Man’s Impact on the
Environment
Threats to Biodiversity
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Biodiversity has three components:
– Genetic diversity. This is the pool of genetic information and variations found
in the biosphere.
– Species diversity – The number of different life-forms found on the planet.
Almost 2 million species have been described to date.
– Ecosystem diversity – The unique assemblages of interact communities
scattered around the globe.
When populations are reduced and/or species become extinct, genetic information
is lost forever without us ever knowing its potential benefit to both that species,
and to mankind.
There is a list of threatened and endangered species (both in the U.S. and
worldwide). At present 24% of mammalian species are endangered and
approximately 20% of freshwater fish have gone extinct or are threatened with
extinction. Many plants , insects, and other invertebrates are also imperiled.
Coral reef and tropical forest ecosystems have been and are being seriously
impacted by man’s activities. In the late 1990’s, illegal wild fires, that were set to
clear rainforest in Borneo, caused so much severe air pollution in Singapore,
Malaysia, and the surrounding region that the governments of those countries
called a regional conference to address the issue.
Importance of biodiversity
• Plants , microbes, and animals contain a vast genetic diversity that
may in the future provide many needed products for mankind.
• About 25% of all pharmaceuticals contain chemicals derived from
plants.
• Many companies are ‘bioprospecting’ for useful enzymes and
drugs. They do this by screening for useful enzymes in microbes
that live in unusual or extreme habitats, by looking for cancer
fighting chemical in marine invertebrates (sponges don’t get
cancer), or by searching tropical forests for potential
pharmaceuticals.
• Healthy ecosystems controls runoff and erosion. They can absorb
excess nutrients before they cause europhication. They provide
the pollinators needed for agricultural crops, and provide
organisms for the biological control of agricultural pests.
• We don’t know what future discoveries can improve our lives, but
we do know that this won’t happen if we lose the biodiversity upon
which it depends.
Exotic plants in South Florida
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South Florida has many invasive
exotic plants which dominant
and/or overrun native plant
communities. Miami-Dade
County’s Department of
Environmental Resource
Management (DERM) has a long
list of plants that are forbidden to
sell or plant in South Florida.
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The picture to the right shows
Burma Reed, a large (10-12 ft.
high) invasive grass, in front of a
thicket of Brazilian pepper
(Schinus).
Three problem species can be
seen on the next page.
Exotic plants in South Florida
(left) air potato – who needs Kudzu!, (upper right) castor bean – seeds are
toxic, (lower right) Brazilian pepper – related to poison ivy, red fruit spread by
birds.
Exotic animals in South Florida
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More than 30 lizards and 3 species
of exotic snakes are established in
Florida (most can be found in
South Florida. The number
increases every year. The Tokay
gecko (right) is large (10-12
inches), vocal, and common in
South Dade.
There are 63 species of introduced
fish in the South Florida drainage
basin. The peacock bass from
northern South America (right) was
introduced by state fisheries
biologists to attempt control of
tilapia populations. Local tilapia
species are native to parts of
Africa.
Chemical pollution in the environment
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Biological magnification is the
reason that species at the top of
the food chain are more toxic than
those at lower trophic levels.
Compounds, such as DDT and
PCBs, have in the past and are
presently causing environmental
problems. On the next page there
is an illustration of biological
magnification.
Oil spills can destroy or disrupt
local coastal ecosystems and/or
communities.
Loss of large parts of the ozone
layer have been attributed to the
use of chlorofluorocarbons in
aerosol cans. That is way these
compounds have been banned in
air-conditioners and refrigeration
units
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Mercury is a naturally-occurring
toxic trace element which has a
complex cycle between the Earth’s
crust, atmosphere and oceans.
Some mercury is released by
natural processes but the
predominant emissions to the
atmosphere result from human
activities
Mercury deposited in wetlands,
lakes and streams can be
converted by natural bacteria into
methylmercury, a toxic form that is
accumulated and biomagnified at
each link in the food chain. In
some circumstances, the result is
sport fish that would be toxic if
eaten by humans and prey fish
that may be toxic to wildlife that
eat them.
Chemical Pollution
• Eutrophication, caused by the
runoff of nitrates and other
nutrients from the land, has
created large areas that are
devoid of oxygen. There is a
major dead zone in the Gulf of
Mexico off the Mississippi
River Delta.
• Sea areas starved of oxygen
will soon damage fish
stocks even more than
unsustainable catches, the
United Nations believes.
(BBC News Monday, 29
March, 2004) .
Global warming
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Virtually all atmospheric scientists believe that the evidence for global
warming is overwhelming. Many politicians are reluctant to accept this
evidence, because it means that something REALLY must be done to limit
greenhouse gas emissions. Part of the rise in global temperature may be
due to long term atmospheric cycles, however man’s activities have probably
been the major contributing factor. The data below was collected at Mauna
Loa, Hawaii.
Global warming
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The greenhouse effect is shown in the illustration below. An average
temperature rise of only a few degrees (Celsius or Fahrenheit!) can lead to
significant sea level rise and altered rainfall pattern. The real problem is that
if we wait too long to control green house gases, it may take a long time to
see positive change. It’s like trying to stop a freight train when there is a
truck on the track ahead. You can hit the brakes when the train is 200 yards
away from the truck, but it won’t stop for another ½ mile!
Critical habitat
• Critical habitat is the set of environmental conditions necessary to
maintain a species. It may be mature long-leaf pine forests for the
red-cockaded woodpecker, or old growth forests for the northern
spotted owl.
• It is necessary to determine the habitat needs of a species, before
a management plan can be developed. Since not every species
can be saved, it is also important to determine the keystone
species in order to best protect the overall community structure.
Landscape ecology and movement corridors
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A goal of landscape ecology is to study
human land use patterns and make
biodiversity conservation a priority.
When habitats are fragmented by
human development is sometimes
possible to develop movement
corridors to connect pieces of high
quality habitat. These may spans
distances of many miles or they may be
local man-made corridors to protect
wildlife.
To the right is an animal bridge in Braniff
National Park, Canada, however you
don’t need to go to Canada to see
movement corridors.
Drive across Alligator Alley (I-75)
between Ft. Lauderdale and Naples and
look the edge of the road. The whole
road is fenced to prevent animals from
being killed while crossing the highway.
Periodically there are bridges, with
animal corridors beneath, which allow
deer, Florida panther, raccoons, and
other animals to cross from north to
south without risk of being hit by traffic.
Protected Areas
• Not everything can be protected, so scientists are focusing on
protecting biodiversity hotspots. These are small areas that have a
relatively high number of species. Hotspots can be seen in purple
on the map below. Because of their great diversity, these hotspots
are also at great risk from development.
• Fisheries biologists are using NO FISH zones to protect breeding
stocks, and nursery grounds. A large no-fish zone has been
established in the waters near Dry Tortugas National Park, and a
no-fish zone exists in Merritt Sound by Cape Canaveral.
Restoration ecology
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The goal of restoration ecology is to
develop ways to return degraded
ecosystems to conditions as similar as
possible to their natural, predegraded
state.
These techniques have been used to
bring spawning salmon back into rivers
and streams where they once bred.
Controlled burns are sometimes used
(see the illustration lower right).
Bioremediation uses plants and
microbes to remove toxic chemicals for
polluted areas. This has been used
successfully to help clean-up oil spills.
The on-going Everglades Restoration
Project is one of the largest restoration
projects ever attempted, and is still
many years from completion.
Kissimmee River project
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The Kissimmee River runs from the
lakes of central Florida to the northern
edge of Lake Okeechobee. It was a
meandering river full of ox-bow bends.
Water moved slowly. Too slowly for
man. A plan was developed and
implemented to channelize the river.
(see lower right).
Now the river ran straight and fast.
Unfortunately it also now dumped huge
amounts of nutrients into Lake
Okeechobee, triggering vast algal
blooms that threatened the health of the
lake.
This lead to the Kissimmee River
Restoration Project. The goal was to
un-channelize the river and reestablish
its meandering nature. This would slow
water flow and allow nutrients to be
filtered out, before the water entered
Lake Okeechobee.
So far the project has been very
successful in reducing the nutrient load
into the lake. This is an example of how
restoration efforts can reverse
environmental damage
Zoned reserves
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Zoned reserves are protected
areas that are surrounded by
zones in which there is human
habitation, but the land is
protected from extensive
alteration.
Costa Rica has used the concept
of zoned reserves to protect much
of its biologically diverse land. The
government and people of Costa
Rica should be commended for
their attempts to both manage their
rich biological resources, and work
towards a plan for sustainable
development.
Hopefully more countries will
follow their example.
Sustainable development
• Our goal should be sustainable development. Both using and
protecting resources in such a manner that they are available to
the generations that come after us.
• Sustainable development will depend not only on continued
research and application of ecological knowledge. It will also
require us to connect the life sciences with the social sciences,
economics, and humanities. Conservation and restoration of
diversity is only on side of sustainable development; the other key
facet is improving the human condition. Public commitment and
cooperation of nations are essential to the success of this
endeavor.
• Each of us must play our part, no matter how small, if this is to
become a reality.