Population Changes and Environmental Damage

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Population Changes and Environmental Damage

• Due to natural causes, changes in climate, human
  activity, and the introduction of invasive, and
  non-native species

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Natural Causes
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Natural Causes

• Population Densities change relatively little
  through time, although annual fluctuations in
  density occur in response to various factors.
• Factors regulating population size are
  responsible for temporal fluctuations. These
  include the following density-dependent factors
  and density-independent factors.

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Density-Independent Factors
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Density-Independent Factors

• 1) Weather - unfavorable weather can limit
  breeding success or cause deaths in the
  population
• 2) Food Supply - abundance of food is often
  dependent on climate, and in poor years food
  supply may limit population size.
• 3) Habitat Limitation seasonal or annual
  changes can affect resource levels such as
  nesting sites or availability of nesting
  materials.
• (2) and (3) help set a limit for Carrying
  Capacity of the habitat.
• Because they are more important at high
  densities, they can be considered
  density-independent or density-dependent factors.
  

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Density-Dependent Factors
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Density-Dependent Factors

• 1) Predation focuses most intensely on eggs and
  young.
• Acts more strongly at high densities. Keeps
  populations below the theoretical carrying
  capacity in some cases.
• 2) Competition if resources are limiting, only
  a given number of individuals may persist in a
  given habitat (the number that can persist is the
  carrying capacity).
• At at high densities (near the carrying capacity)
  it becomes very important.
• 3) Parasites and Disease have the greatest
  effect at high population densities. Can be
  important factors regulating population sizes in
  some cases.

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Climate Changes
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Changes in Climate

• Climate has been changing over hundreds and
  thousands of year
• In response temperate zones shift from coniferous
  to deciduous with changes in the dominant species
  of trees.
• Quick changes, can species keep up?
• Increased burning of fossil fuels increases CO2
  level

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Impact of Changing Climate

• Current difference between temp. at poles and
  equator is a major driving force for atmospheric
  circulation.
• Warming happening more quickly at the poles
• Will change atmospheric circulation patterns and
  rainfall distribution patterns
• Higher temp more evaporation and great ability
  of the atmosphere to hold moisture.
• Some regions drier and some wetter
• Increased droughts and increased rainstorms
• Widespread water concerns droughts, floods,
  water quality
• Rising sea level

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Effect on Populations

• Rate of climatic warming could outpace the
  ability of species to migrate northwards.
• Plant species that cant migrate trap both
  themselves and other dependent organisms in
  inhospitable climates.
• Remember, not all organisms can adapt to the
  environmental changes and evolution takes years!

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Human Activity
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Human Activity

• Physical Alteration of Habitats
• Responsible for 36 of known extinctions
• Conversion
• From natural habitat to human use
• Fragmentation
• Reduced habitat can not support the critical
  number during adverse years
• Simplification
• Removal natural debris such as of fallen logs and
  dead trees diminishes microhabitats.

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Human Activity

• Pollution
• Oil spills
• Chemical spills
• Destroy or alter habitats
• Urban sprawl

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Introduction of Invasive, Non-native Species
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Introduced Species

• Displace native species
• Reduce biodiversity
• Reduce farm and forest productivity
• Affect human and animal health
• Contribute significantly to land degradation
• Many introduced plant species have become
  invasive weeds, noxious weeds or both and are
  among the most serious threats to the natural
  environment.