Human Impact on Ecosystems

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Human Impact on Ecosystems

• Unit II

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Humans in the Biosphere

• The human population is still growing, but the
  earth is not, and this places increasing demands
  on Earths air, water, land, and living things
• Understanding how humans interact with the
  biosphere is crucial to protecting these
  resources
• Industry technology give humans a strong
  advantage in competing w/ other species for
  limited resources
• Human activity uses as much energy as all of
  Earths other multicellular species combined
• Hunting and gathering, agriculture, industry and
  urban development have significantly transformed
  the biosphere
• Human activities can change the flow of energy in
  an ecosystem and reduce the ability of ecosystems
  to recycle nutrients.

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The Green Revolution

• The green revolution was introduced in the 1950s
  by the government as an effort to greatly
  increase the yields of rice, wheat, and other
  crops
• Using highly productive varieties of certain
  crops
• Using monoculture large fields cleared, plowed,
  and planted with the same crops year after year
• Relied on pesticides, fertilizers, and large
  equipment to support large growing areas
• Benefits increased food production
• Problems depletion of energy and water
  supplies, pest species enabled to reproduce on a
  vast scale, pesticides can be potentially
  harmful, fertilizers can interfere with food webs
  and biogeochemical cycles

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The Industrial Revolution

• The era known as the Industrial Revolution was a
  period in which fundamental changes occurred in
  agriculture, textile and metal manufacture,
  transportation, economic policies and social
  structure (1760-1850).
• Dense human communities
• Human waste products
• Reduction in habitats
• Pollution
• Overuse of wildlife products

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Environmental Resources

• Environmental resources can be classified into 2
  types renewable and nonrenewable
• Renewable Resources can regenerate and are
  therefore replaceable (trees)
• Nonrenewable resources one that cannot be
  replenished by natural processes (coal, oil, and
  natural gas)
• Renewable resources are NOT NECESSARILY
  unlimited! Fresh water is renewable but can
  become limited by drought or overuse.
• Fossil fuels form over hundreds of millions of
  years from deeply buried organic materialswhen
  they are depleted, they are gone forever!!!!

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Sustainable Use

• Sustainable use is a way of using natural
  resources at a rate that does not deplete them
• Land resources
• Forest resources
• Ocean resources
• Air resources
• Water resources
• A sustainable system operates without causing
  long-term harm to the ecological resources on
  which it depends
• Example alternative methods of pest control
  that do not involve harmful chemicals

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Land Resources - Renewable

• Provides space for cities, etc. Important for
  the soils where crops are grown. If managed
  properly, soil is renewable.
• Plowing removes the roots that hold soil in
  placewhich increases the rate of soil erosion
  (wearing away of surface soil by water wind).
• In dry climate parts of the world, a combination
  of farming, overgrazing, and drought has turned
  once productive areas into deserts (a process
  called desertification).
• Prevention contour plowing (plowing across
  slopes of land to reduce erosion, leaving stems
  roots of previous crops to help hold soil)

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Forest Resources

• Forests are dubbed the lungs of the earth b/c
  they remove CO2 and produce O2. They also store
  nutrients, provide habitats and food for
  organisms, limit soil erosion, and protect
  freshwater supplies.
• Forests can be renewable or non-renewable
  depending on the type. For example, an old
  growth forest is considered non-renewable because
  of the amount of time it would take to replace
  the forest.
• Deforestation can lead to severe erosion and loss
  of nutrients and habitats
• Prevention harvest mature trees to promote the
  growth of saplings, utilize tree farms

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Ocean Resources

• The ocean is a vast source of species and food
  supply! In addition, some 75 of the earths
  available oxygen is produced by ocean species.
• The increased rate of commercial fishing has had
  a severe impact on the worlds ocean species!
  Pollution of water systems is also an increasing
  concern!
• Prevention limit catching of certain types of
  fish prevent pollution dumping from industry

10
Air Resources

• Air is used every time we breathe!
• Smog (mixture of chemicals appearing as a
  gray-brown haze) in cities results from
  automobile exhaust.
• A pollutant is a harmful material that can enter
  the biosphere through the land, air, or water!
• The burning of fossil fuels is a major
  contributor to the earths pollution problem and
  can lead to acid rain (gases combined with water
  vapor in the air and form drops of nitric and
  sulfuric acid)can drift for miles before falling
  as acid rain.

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Water Resources

• Although fresh water is a renewable resource, the
  total supply of fresh water is limited!
• Pollution threatens water in several ways
• Protections of the natural systems involved in
  the water cycle are essential for maintaining
  safe, fresh water sources.

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Biodiversity

• Biodiversity is the sum total of the genetically
  based variety of all organisms in the biosphere
• Biodiversity is one of the Earths greatest
  natural resources food, industrial products,
  medicines
• Ecosystem diversity includes the variety of
  habitats, communities, and ecological processes
  in the living world
• Species diversity is the number of different
  species in the biosphere
• Genetic diversity is the sum total of all the
  different forms of genetic information carried by
  all organisms living on Earth today

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Human Threats to Biodiversity

• Habitat Alteration Fragmentation
• Development often splits ecosystems into pieces
  (habitat fragmentation).
• Creates habitat islands.
• Fewer species can survive here and they are more
  vulnerable to further disturbances or climate
  changes.

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Human Threats to Biodiversity

• Demand for Wildlife Products
• Endangered species are now protected from being
  hunted in the US. This is still a problem in
  other parts of the world, such as Africa, South
  America, and Southeast Asia.

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Human Threats to Biodiversity

• Introduced Species
• the accidental or intentional introduction of new
  plants animals into an area.
• invasive species -a new species able to reproduce
  rapidly because their new habitat lacks the
  natural population controls they face in their
  old habitat.
• Cane Toads in Austraila
• Kudzu in America
• African Bees in South America

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Kudzu
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Conserving Biodiversity

• Today, conservation efforts focus on protecting
  entire ecosystems as well as single species
• Most often, the need to protect biodiversity is
  greatest in countries that are least able to do
  so. These are known as hot spots immediate
  danger of extinction of species as a result of
  human activity
• Example rainforests are found in developing
  countries

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Biological Hot Spots

• In an effort to locate problem areas and set up a
  list of conservation priorities, conservation
  biologists identify hot spotsplaces where
  significant numbers of habitats and species are
  in immediate danger of extinction as a result of
  human activity.

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Changing the Future

• Many biologists are now concerned about the
  biological effects of 4 types of global change
• The thinning, or depletion of the ozone
• Global warming
• Acid Precipitation
• Biological Magnification

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A Thinning Ozone

• Our atmosphere contains a concentration of ozone
  gases called the ozone layer. Ozone molecules
  consist of 3 oxygen atoms.
• Function absorbs harmful UV radiation before it
  reaches Earths surface (global sunscreen).
• Studies suggest that the ozone has been gradually
  thinning since 1975.
• The problem of thinning ozone is caused by CFCs
  (chlorofluorcarbons) used as propellants in
  aerosol cans, to produce plastic foam, and as
  coolants in a/c systems. In cold atmospheres
  such as in space, CFCs allow UV to break apart
  ozone molecules.
• The US has joined other countries in phasing out
  the use of CFCs.

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Ultraviolet Radiation
A threat to the continuation of life
Visible
Infrared (IR)
UV
Humans DNA damage Cancer Crops Productivity
decrease Ocean plants Death?
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Ultraviolet Radiation
stratospheric ozone layer
UV
destroy
CFCs refrigeration electronics foam
packaging spray propellants
1996 CFC decrease noticed 2006 stabilization?
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Size of the Antarctic Ozone Hole
North America
30
20
Antarctica
Average Area millions sq km
10
0
1979
2001
Prediction 50 years to return to 1980 size
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Global Warming

• Earths temperatures remain within a range
  suitable for life because of the biospheres
  natural insulating blanket the atmosphere
• Carbon dioxide, methane, water vapor, and other
  gases trap heat energy and maintain Earths
  temperature range
• The function of these gases is similar to glass
  in a greenhouse they trap the heat energy of
  sunlight inside Earths atmosphere.
• The natural situation in which heat is retained
  by this layer of greenhouse gases is called the
  greenhouse effect.
• These greenhouse gases allow solar energy to
  penetrate the earths atmosphere, where much of
  the sunlight that hits the Earths surface is
  converted to heat energy and reflected back into
  the atmosphere.
• The same greenhouse gases do not allow the heat
  to readily escape the atmosphere, but instead,
  trap it inside. The Earth is heating up!

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Global Warming

• Human activities may be causing climate change by
  increasing carbon dioxide concentration in the
  atmosphere!
• Rising atmospheric CO2 - since the Industrial
  Revolution, the concentration of CO2 in the
  atmosphere has increased greatly as a result of
  burning fossil fuels.
• Human-produced greenhouse gases include carbon
  dioxide CO2 , methane CH4, nitrous oxide N2O
• The predicted consequences of global warming
  include
• sea level rise
• increased plant primary productivity
• increased storm severity
• changes to patterns of rainfall
• changes to ocean circulation patterns

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Acid Rain

• The burning of wood and of fossil fuels,
  including coal and oil, releases oxides of sulfur
  and nitrogen that react with water in the
  atmosphere, forming sulfuric and nitric acid,
  respectively.
• The acids eventually fall to Earths surface as
  acid precipitation rain, snow, sleet, or fog
  that has a pH of less than 5.2.
• This acid precipitation lowers the pH of streams
  and lakes and affects soil chemistry and nutrient
  availability.
• The main causes of acid rain are emissions from
  ore smelters and electrical generating plants.

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Ecological Effects from Acid Rain in Lake System

• Changes begin to occur as soon as a lake starts
  to lose it natural bases or alkalinity.
• A large reduction in the number of plankton
  invertebrates.
• The rate of decomposition of organic matter
  decreases
• Direct effects on fishes reproductive cycles.
• A calcium deficiency in fish leads to bone
  malformation.
• Fish can suffocate as their gills become clogged
  with aluminum hydroxide.
• Songbirds are effected by eating insects
  contaminated with toxic metals.

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Biomagnification
In biomagnification, there is a tendency for
pollutants to concentrate as they move from one
link in a food chain to anothertop level
carnivores suffer the most harmful effects of
biomagnification.
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Biomagnification DDT

• Dichlorodiphenyltrichloroethane (DDT)
• Used as a pesticide from 1939-late 1960s fat
  soluble compound - it is not broken down by
  metabolic processes in bacteria, plants, or
  animals
• When DDT is picked up by organisms, they do not
  eliminate it from their bodies. As a result,
  something unexpected happens. DDT is picked up,
  concentrated, and stored by aquatic plants and
  algae.
• When herbivores eat those plants, they
  concentrate DDT to levels ten times higher than
  levels found in plants! When carnivores eat
  herbivores, the toxic substance is concentrated
  further in a process called biological
  magnification.
• The worlds production has substantially
  decreased since it was banned in the West
• Detected in mud of deep sea and snow ice of
  Antarctica