Lecture Outline: Global Ecology And Conservation Biology

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  1. Introduction to Global Ecology and Conservation Biology
    1. Scale of the Problem: Species Count
      1. Approximately 2 million species have been formally named and discovered.
      2. The total number of species is unknown, estimated to range from 5 million to 100 million or more.
      3. The true total will never be known due to ongoing extinction.
    2. Ecology Concepts
      1. The concept of a web of life emphasizes that no species lives in isolation.
      2. The primary concern is the drastic increase in the rate of extinction, especially when caused by human activity.
      3. Biodiversity exists at three different levels:
        1. Genetic diversity: Variety of DNA within one species or population.
        2. Species diversity: Defined by species richness (number of species) and relative abundance (number of individuals per species).
        3. Ecosystem diversity: The number of different kinds of ecosystems (biomes) in the biosphere.
    3. Examples of Critically Endangered Species
      1. Species with fewer than 100 individuals left (e.g., Philippine eagle, river dolphin).
      2. The Marianas bat: A major pollinator hunted as a delicacy.
        1. Rarity increases its value, creating a vicious circle of overhunting that drives it toward extinction.
  2. Four Major Causes of Increased Extinction Rates Due to Human Activity
    1. Loss of Habitat
      1. Main cause is human conversion of land for agriculture and housing.
      2. Habitat fragmentation: Breaking large habitats into smaller pieces.
        1. Fragmentation creates smaller ecological islands, exacerbating the negative effects of the island effect.
    2. Introduced Species
      1. Species are introduced (intentionally or accidentally) into non-native environments.
      2. Accidental introduction examples include rodents on ships or mollusks carried on boats.
      3. Intentional introduction example: Kudzu was introduced to the southeastern US to control soil erosion but outcompetes native organisms.
      4. Attempting to change ecology often leads to unintended consequences because ecology is highly complex.
    3. Overharvesting
      1. Killing elephants solely for ivory tusks; eliminating the market for ivory is essential for conservation.
      2. Bluefin tuna fishing led to an 80% population drop in 10 years after a lucrative market was created by airlifting them to Japan for sushi.
    4. Global Change
      1. Acid Precipitation (Acid Rain/Snow)
        1. Caused by sulfurous compounds (e.g., from burning diesel fuel) reacting with water to form sulfuric acid and other acids.
        2. Acidity changes the chemical environment, causing proteins to change shape (denature), thereby interfering with their function.
        3. Legislative efforts successfully addressed acid precipitation, showing that environmental recovery is possible when the problem is admitted and acted upon quickly.
      2. Global Warming/Climate Change
        1. There is a clear correlation between rising CO2 levels and increasing global average temperature.
        2. Greenhouse gases (e.g., CO2) trap heat (longwave radiation), warming the planet.
        3. Natural CO2 output (respiration) is carbon neutral, but burning fossil fuels releases ancient carbon previously locked out of the cycle.
        4. The increase in atmospheric CO2 is exponential, worsening the problem over time.
        5. Political and economic forces often prevent concerted action on global warming.
      3. Ocean Acidification
        1. The ocean dissolves a large amount of excess atmospheric CO2, mitigating temperature rise.
        2. CO2 reacts with water to form carbonic acid, which releases hydrogen ions (H+).
        3. This continuously makes the ocean more acidic, threatening species sensitive to pH change (e.g., those forming coral reefs).
  3. Ecological Dynamics, Conservation Efforts, and Other Problems
    1. Extinction Vortex
      1. A set of conditions where a small population begins an irreversible decline toward extinction.
      2. The decline accelerates as the population gets smaller because of:
        1. Increased effects of genetic drift (random elimination has a greater proportional impact).
        2. Increased likelihood of inbreeding, which reduces individual fitness by increasing the chance of expressing harmful recessive alleles.
      3. Vortex rescue example: Introducing new individuals to small prairie chicken populations injected genetic variability and reversed the decline.
    2. Conservation Planning
      1. An ecological edge is an abrupt change in conditions that fragments the landscape.
      2. Corridors (natural or artificial bridges) are used to undo fragmentation, allowing organisms to migrate between isolated habitats.
      3. Biodiversity hotspots are ecosystems with high biodiversity that are in severe trouble, serving as priority focus areas for conservation.
      4. Minimum Viable Population (MVP) is the minimum number of individuals required for a species to survive indefinitely and avoid the extinction vortex.
        1. Grizzly bear conservation requires massive land areas (for 500 individuals for long-term survival), leading to political conflict with private land ownership.
      5. Zoned reserve systems (e.g., Costa Rica) involve federally protected core areas surrounded by privately held land that adheres to conservation rules, successfully promoting tourism and economic stability.
    3. Eutrophication and Dead Zones
      1. Caused by excessive runoff of nitrogen-containing compounds (nitrates) from agricultural fertilizer into major rivers (e.g., Mississippi).
      2. Nitrates cause explosive population growth of phytoplankton, followed by zooplankton.
      3. Cellular respiration by massive zooplankton populations depletes dissolved oxygen (O2) in the water, creating a dead zone where fish cannot live.
    4. Biological Magnification
      1. The process where the concentration of toxins (e.g., PCBs, DDT) increases drastically at successively higher trophic levels.
      2. Even low environmental concentrations become devastatingly high in top consumers, interfering with key biological functions (e.g., preventing bird eggshells from hardening).
    5. Pharmaceutical Pollution
      1. Potent drugs (exogenous signal molecules) from human and livestock use enter rivers and streams (e.g., from flushing prescriptions).
      2. Tiny concentrations can have devastating effects on aquatic populations, such as altering the ratio of males to females in fish.
  4. Overall Long-Term Ecological Outlook
    1. Producer Migration Limitation
      1. Unlike animals, plants cannot migrate as individuals as the climate warms.
      2. Calculations show that the rate at which plant ranges can shift (through seed dispersal and new generations) is too slow to keep up with current global warming predictions.
      3. The failure of producers to survive would lead to the collapse of all consumer species.
    2. Human Population and Consumption
      1. Out-of-control human population growth is the fundamental root of most ecological problems.
      2. Although the population growth rate is slightly declining (partially due to government intervention), the overall population size continues to increase dramatically.
      3. The United States uses a disproportionately large fraction of the world’s total energy per capita.
      4. Statistically, having one child, especially in the American lifestyle, negates personal efforts to lead an environmentally green lifestyle.