Chapter 26: Economic Development and Global Ecology

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Chapter 26 Economic Development and Global
Ecology

• Robert E. Ricklefs
• The Economy of Nature, Fifth Edition

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Looking to the Future

• As the human population continues to grow and
  humans dominate ecological systems worldwide, the
  question of how we can create a sustainable
  future for both humans and other species becomes
  increasingly important
• there is considerable room for pessimistic
  conclusions
• positive steps have been taken in the United
  States
• Clean Air Act (1970)
• Clean Water Act (1972)
• Endangered Species Act (1973)
• But
• In Lebanon?

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Positive Steps Toward Sustainability

• Laws regarding endangered species, clean air, and
  clean water have been implemented worldwide.
• Straightforward ecological and engineering
  solutions exist for environmental problems.
• People worldwide share a concern for the
  environment.

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What can Ecologists Contribute?

• The challenge to ecologists is to provide the
  scientific information needed to develop social
  consensus, build political commitment, and inform
  decision making on issues concerning the
  environment.

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Ecological processes hold the key to
environmental policy.

• Conserving ecological processes is the key to
  maintaining a sustainable biosphere
• the fundamental processes of energy use and
  recycling of materials have built-in mechanisms
  to restore imbalances when these occur
• when consumers increase to high numbers,
  declining birth rates and increasing death rates
  restore a sustainable relationship between
  consumer and resource
• if natural processes are disrupted, ecosystems
  may not be able to maintain themselves

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Human activities threaten local ecological
processes.

• All human activities have consequences for the
  environment
• emphasis on short-term returns can lead to
  collapse of a resource
• one after another of the commercial whale species
  were hunted to near-extinction, forcing the
  industry to turn progressively to less profitable
  species
• many profitable fisheries have collapsed because
  of overfishing

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Human activities threaten local ecological
processes.

• Some consequences of human activities have
  indirect effects
• clearing of watershed land for agriculture or
  timber leads to undesirable consequences
  downstream
• alteration of riverine habitats
• siltation of dams
• damage to reef habitats

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Overexploitation

• Fishing, hunting, grazing, and logging are
  classic consumer-resource interactions
• in natural systems, such interactions come into
  equilibrium
• efficiency of exploitation by consumers and
  resistance to exploitation by resources have
  evolved over long periods
• humans have used technology to escalate beyond
  all natural limits their ability to overexploit
  natural resources, with undesirable consequences
• when resources are exhausted, human populations
  suffer

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Sustainable and Unsustainable Practices

• Consider the lowland tropics
• soils contain few nutrients, with natural
  fertility maintained by recycling of nutrients
  between detritus and living plants
• clearcutting, especially when followed by
  grazing, breaks this cycle, resulting in a badly
  degraded system
• humans have learned to live sustainably in such
  ecosystems through the practice of shifting
  agriculture
• by clearing 1-2 of the land per year and
  cultivating for 2 or 3 years, farmers allow
  sufficient time in fallow for nutrient stocks to
  recover from agriculture

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Introduction of Exotic Species

• Humans have taken other species with them
  everywhere they have traveled for example
• 50,000 nonindigenous species have been introduced
  to the United States
• New Zealand has a predominantly alien flora and
  fauna
• most of the area is occupied by introduced plants
  and animals
• native forests were cut and replaced by
  eucalyptus
• native moas were killed by Maori natives,
  replaced by European transplants

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Why did aliens prosper in New Zealand?

• Of the total New Zealand flora of 2,500 species,
  500 are introduced
• introduced species account for most of the
  vegetation
• why were these species so successful?
• most natural habitats had been disturbed
• because of low diversity and simple structure,
  island ecosystems are generally more easily
  invaded

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Can effects of aliens be predicted?

• Alien species may displace natives, but do not
  necessarily disrupt ecosystems
• introduced species may simply assume the
  ecological roles of natives
• effects of introduced species are hard to
  predict
• aliens may also be disruptive, altering ecosystem
  function and community structure
• Nile perch in Lake Victoria eliminated an entire
  trophic level of planktivorous fish

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Habitat Conversion

• Altering habitats can upset natural processes
• cutting of tropical forests
• breaks the tight cycle of nutrient regeneration
• results in increased erosion
• plowing of prairies set the stage for the dust
  bowl conditions of the 1920s and 1930s in the
  United States
• disruption of mangroves in tropical coastal areas
  have left the land vulnerable to hurricane-driven
  floodwaters
• damming rivers increases silt transport, blocks
  fish migrations, alters downstream ecosystems

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Irrigation

• Benefits of irrigation are often offset by
  substantial environmental problems
• environmental costs associated with
  infrastructure (dams, canals, etc.)
• lowered water tables where wells are used
• reduction of groundwater quality (through
  introduction of pesticides and fertilizers)
• accumulation of salt in irrigated lands
• transmission of diseases by aquatic organisms

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Fertilization and Eutrophication 1

• Inorganic fertilizers (e.g., nitrates,
  phosphates) inevitably make their way into
  aquatic systems
• fertilization of aquatic systems (eutrophication)
  leads to overproduction
• waters are no longer attractive for recreational
  use
• decaying organic matter can lead to deoxygenation
  of water and fish kills

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Fertilization and Eutrophication 2

• Addition of organic wastes poses a serious
  problem for water quality
• organic matter increases biological oxygen
  demand, decreasing oxygen levels
• killing fish and other obligate aerobes
• cutting migration routes for other species
• Problems associated with eutrophication can be
  avoided by
• cutting off or diverting sources of nutrients
• improving treatment of organic wastes

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Toxins

• Toxins are poisons
• these chemicals kill animals and plants by
  interfering with normal physiological functions
• many toxins occur naturally, but humans have
  increased their accumulation in the environment
• various classes of toxins exist, including
• acids
• heavy metals
• organic compounds
• radiation

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Acids

• Two principal sources of acidity are associated
  with human activities
• acid mine drainage
• oxidation of sulfur and thiol in mine wastes by
  bacteria creates sulfates, which become sulfuric
  acid in mine drainage
• mine drainage may be sufficiently acidic as to
  sterilize aquatic environments downstream
• acid rain, the result of combusting fossil fuels

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Acid Rain

• Burning of coal and oil releases nitrogen oxides
  and sulfur dioxide into the atmosphere
• these gases dissolve in raindrops, creating
  acids
• pH of rain may drop to as low as 3-4
• consequences of acid rain have been especially
  severe in industrialized areas
• direct impacts of acidity on aquatic systems
• depletion of fertility in terrestrial systems
• Reducing emissions of sulfur and nitrogen oxides,
  reductions in energy use are solutions to acid
  rain.

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Heavy Metals

• Mercury, arsenic, lead, copper, nickel, zinc, and
  other heavy metals are toxic even in low
  concentrations
• these enter the environment as byproducts of
  mining, manufacturing, fungicides, fuels
• emissions of heavy metals from smelting
  operations have been especially troublesome
• emissions adversely affect mosses, lichens,
  fungi, other soil organisms, vascular plants, and
  higher animals
• adverse effects may extend many km downwind of
  smelters

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Organic Compounds 1

• Organic compounds have been introduced to many
  ecosystems in the form of pesticides
• classes include
• organomercurials (methylmercury)
• chlorinated hydrocarbons (DDT)
• organophosphorus compounds (parathion)
• carbamate insecticides
• triazine herbicides
• these compounds may accumulate in ecosystems with
  adverse effects on unintended targets

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Organic Compounds 2

• Can the adverse effects of pesticides be reduced?
• modern pesticides and efficient delivery systems
  can reduce unintended impacts
• alternatives to chemical warfare against other
  organisms can be explored
• bioremediation (using biological agents to
  restore habitats) can be explored
• Another anthropogenic impact caused by organic
  compounds is oil spills (3-6 x 106 tons
  annually)
• oil kills by coating organisms, disrupting
  membranes

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Radiation

• Of special concern are extremely energetic (short
  wavelength) forms of radiation and subatomic
  particles emitted by disintegration of atomic
  nuclei
• low levels occur naturally as background
• extreme radiation hazards are posed by nuclear
  power plants, nuclear wastes of various kinds,
  and nuclear war
• even peaceful uses of nuclear materials are
  limited by problems associated with disposal of
  long-lived wastes

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Atmospheric Pollution

• Pollution of the oceans and atmosphere are of
  particular concern
• circulation leads to widespread distribution of
  pollutants far beyond their sources
• of greatest concern are two anthropogenic effects
  on the atmosphere
• destruction of the ozone layer
• increase in carbon dioxide, other greenhouse gases

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The Ozone Layer and Ultraviolet Radiation

• Ozone (O3) is molecular oxygen in a highly
  reactive form
• ozone readily oxidizes organic molecules
• anthropogenic ozone near the earths surface is a
  byproduct of combustion of fossil fuels
• nitrous oxide (NO2) combines with oxygen to form
  ozone in the presence of sunlight
• high levels of ozone are damaging to human
  health, crops, and natural vegetation

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Ozone in the Upper Atmosphere

• Naturally occurring ozone in the upper atmosphere
  absorbs ultraviolet radiation
• ozone thus shields earths surface from damaging
  effects of UV radiation
• reaction of chlorine with ozone in the upper
  atmosphere breaks down ozone
• chlorine has increased as result of emissions of
  CFCs (chlorofluorocarbons)
• depletion of stratospheric ozone at high
  latitudes has been referred to as ozone holes

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Damaging Effects of Ozone Depletion

• Depletion of stratospheric ozone leads to
  increased UV radiation at the earths surface
• Consequences include
• damage to DNA and resultant cancers
• reduced photosynthetic production by plants
• Ozone depletion is now addressed by conventions
  phasing out use of CFCs
• Vienna Convention for Protection of the Ozone
  Layer (1985)
• Montreal Protocol (1987)

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Carbon Dioxide and the Greenhouse Effect 1

• Carbon dioxide (CO2) is a naturally occurring
  atmospheric component, at about 280 ppm in the
  preindustrial atmosphere.
• CO2 and several other atmospheric gases form an
  insulative layer, passing visible light, but
  absorbing longwave radiation emitted by the
  earth
• referred to as the greenhouse effect

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Carbon Dioxide and the Greenhouse Effect 2

• CO2 levels have varied considerably during
  earths history
• at times in the past when CO2 levels were high,
  earth was much warmer
• CO2 levels are now creeping upward as a result of
  combustion of fossil fuels and forest clearing
• CO2 level is now 350 ppm and increasing
• we are now faced with increasing global
  temperatures and related effects (such as rising
  sea levels)

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Carbon Dioxide and the Greenhouse Effect 3

• Humans now add carbon to the atmosphere at a rate
  of about 7 billion tons annually
• the oceans absorb about 2.4 billion tons
• this is insufficient to balance anthropogenic
  additions, so atmospheric levels will continue to
  rise
• Most effects of increased atmospheric CO2 and
  global warming will be negative
• increasing drought stress in arid environments
• inundation of coastal areas by rising sea level

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Human ecology is the ultimate challenge.

• If we are to leave a habitable world for future
  generations, our top priority must be to achieve
  a sustainable relationship with the rest of the
  biosphere. This will require
• putting an end to population growth
• developing sustainable energy sources
• providing for regeneration of nutrients and other
  materials
• restoring deteriorated habitats

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Increase in Oil and Energy Prices
Population Growth
Over Demand for Fish
Arable Land
Over Demand
Droughts
Unsustainable Fishing Practices
Food Production
Biofuel and Food Competition
Self Sufficiency Rate
Sea Food Supply
Increase in Speculative Trading
Fisherman Income
Rise in Food Prices
Food Deficit
Market Policies
Food Security
Direct Compensating Variation (DCV)
Poverty
Use of Cultivable Lands
Desert Areas
Salination
Rise in Extreme Poverty
Water Shortage
Urban Expansion
Overgrazing
Migration to Urban Areas
Over Demand
Climate Change
Desertification
Farmers Low Income
Population Growth
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Future Scenarios

• Potential consequences of unrestrained population
  growth and human impacts are devastating
• energy and material shortages
• many living in poverty and disease
• a badly polluted environment
• escalating social and political strife
• The future need not be like this

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Positive Alternatives

• Humankind has the choice of adopting a new
  attitude toward its relationship with nature. We
  are a part of nature, not apart from nature.
• To the extent that our intelligence, culture, and
  technology have given us the power to dominate
  nature, we must also use these abilities to
  impose self-regulation and self-restraint.
• We have succeeded famously in becoming the
  technological species. Our survival now depends
  on our becoming the ecological species and taking
  our appropriate place in the economy of nature.

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Summary 1

• The key to human survival is the development of
  sustainable interactions with the biosphere.
• Local threats to integrity of natural systems are
  overexploitation of resources, introductions of
  exotic species, habitat conversion, irrigation,
  eutrophication, and production of toxic materials.

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Summary 2

• Global threats to integrity of natural systems
  include depletion of stratospheric ozone and
  global warming caused by increasing atmospheric
  carbon dioxide.
• Solutions to the environmental crisis will
  require new attitudes promoting sustainability
  and self-restraint.