chapter 20

Foundational Concepts and the Value of Biodiversity

  • Sustainability Mindset: The text emphasizes a quote from "Our Common Journey: A Transition Toward Sustainability" which posits that our planet should be considered as being on loan from our children rather than a gift from our ancestors.

  • Definition of Biodiversity: Biodiversity is defined as the variety of all living things. Maintaining this variety is critical because all organisms interact with one another.

  • Core Beliefs of Conservation Biology:

    • Biodiversity is inherently good for both human well-being and the well-being of nature.

    • The simplification of biodiversity adversely affects all organisms.

  • Levels of Biodiversity Preservation: Conservation biology attempts to preserve nature at three distinct levels:

    • Genetic Diversity: The amount of variation that exists within a species. Having a variety of alleles is essential for populations to adapt to changing environmental conditions.

    • Species Diversity: The number of species that occupy the biosphere. A higher number of species in an ecosystem contributes to increased health and flexibility. This level is determined by the balance between speciation (adaptive radiation) and extinction rates.

    • Ecosystem Diversity: The variety of ecosystems on Earth, such as forests, deserts, grasslands, and oceans.

  • Economic and Material Benefits:

    • Food Resources: Wild plants offer potential new food sources or can provide genetic diversity to strengthen existing crops.

    • Drugs and Medicines: More than 50%50\% of all modern medicines contain natural products derived from wild species.

    • Case Study: Rosy Periwinkle: This plant is used to produce anti-cancer drugs.

    • Biopiracy: Pharmaceutical companies often prospect in tropical countries. Extraction without compensation is termed biopiracy; sharing profits is recommended as an incentive to preserve native species.

  • Ecological Services:

    • Biodiversity facilitates soil formation, waste disposal, air and water purification, nutrient cycling, solar energy absorption, and the maintenance of biogeochemical and hydrological cycles.

    • The total value of these ecological services is estimated at at least $33 trillion\$33\,\text{trillion} per year, which is approximately half of the total world Gross National Product (GNP).

  • Aesthetic and Cultural Benefits:

    • Recreational activities include hunting, fishing, camping, and hiking.

    • Americans spend approximately $730 billion\$730\,\text{billion} annually on nature-based recreation, significantly more than the $81 billion\$81\,\text{billion} spent on automobiles.

    • Ecotourism: Serves as a vital form of sustainable economic development.

    • Existence (Intrinsic) Value: The philosophical belief that organisms have value in and of themselves, independent of human use.

The Biodiversity Crisis and Human Impact

  • State of the Biosphere: Earth is currently experiencing a biodiversity crisis. The extinction rate for vertebrates is significantly higher than it was prior to human intervention.

  • The Human Footprint: The growing human population has a devastating impact on ecosystems worldwide, an effect termed the human "footprint."

  • Primary Causes of Biodiversity Loss: Humans are at the root of the five main drivers of biodiversity loss:

    1. Habitat loss/destruction

    2. Invasive species

    3. Human population growth

    4. Pollution

    5. Overexploitation

Habitat Destruction and Fragmentation

  • Land Alteration: Habitat destruction is the primary threat to biodiversity. Humans have altered more than 50%50\% of the Earth's land, replacing natural biomes like prairies, wetlands, and forests with farms, rangeland, and urban areas.

  • Deforestation: The total removal of trees from a forested area. This process drastically alters atmospheric levels of O2O_2 and CO2CO_2. Trees store carbon, which is released into the atmosphere when the wood is burned.

  • Aquatic Habitat Vulnerability: Freshwater habitats are frequently destroyed by the construction of dams, levees, and the redirection of waterways (e.g., the use of the Colorado River to maintain golf courses in Palm Springs).

  • Fragmentation: This occurs when habitat destruction leaves small, isolated patches of land.

    • Results in a loss of contact between organisms.

    • Leads to inadequate resources and eventual population decline.

Invasive Species

  • Definitions:

    • Introduced Species: Species brought by humans (intentionally or accidentally) to an area where they did not previously occur.

    • Invasive Species: An introduced species that breeds and spreads widely, harming the environment or displacing native organisms.

  • Impact: They change community composition and may introduce diseases to native species. In the United States, there are over 498498 types of invasive plants, animals, and microorganisms.

  • Specific Examples of Invasive Species:

    • Kudzu: An invasive vine.

    • Brown Tree Snake.

    • Zebra Mussels: Spread via ballast water in ships.

    • Purple Loosestrife.

    • Asian Longhorn Beetle.

    • Asian Carp: Imported in the 1960s1960\text{s} and 1970s1970\text{s}; voracious filter feeders that compete with native life, costing the region $200 million\$200\,\text{million} annually.

    • Lionfish: Likely introduced via the aquarium trade; a rapid breeder and predator capable of wiping out coral reef species.

    • Burmese Python: Invading the Everglades.

    • Giant African Snail: Can grow to 20 cm20\,\text{cm} (8 in8\,\text{in}); eats over 500500 kinds of plants and carries a parasite causing meningitis in humans.

    • Feral Hog: Introduced for hunting in the 1930s1930\text{s}; causes $1.5 billion\$1.5\,\text{billion} in annual damage.

Pollution and Biomagnification

  • Water Pollution:

    • Eutrophication: A process where added nutrients (nitrogen and phosphorus from fertilizers/sewage) cause a massive increase in phytoplankton and algae blooms. When the algae die, their decay depletes the oxygen in the water, creating "dead zones" (e.g., the Gulf of Mexico near the Mississippi River).

    • Chemical Pollutants: Examples include pharmaceuticals like birth control pills and industrial chemicals like BPA.

    • Endocrine Disruptors: Chemicals that mimic, inhibit, or enhance hormone activity. Studies show fish exposed to sewage effluent develop high levels of vitellogenin (egg protein) in males, leading to intersex fish (testes containing oocytes).

  • Biological Magnification (Biomagnification): The process by which toxins become more concentrated in organisms at higher trophic levels.

    • Examples: PCBs, DDT, mercury.

    • PCB Concentrations in Lake Michigan: Phytoplankton (0.025 ppm0.025\,\text{ppm}) (\rightarrow) Zooplankton (0.123 ppm0.123\,\text{ppm}) (\rightarrow) Smelt (1.04 ppm1.04\,\text{ppm}) (\rightarrow) Lake trout (4.83 ppm4.83\,\text{ppm}) (\rightarrow) Herring gull eggs (124 ppm124\,\text{ppm}).

  • Air Pollution:

    • Smog: A visible haze in the lower atmosphere, often from burning coal and oil in industrial regions.

    • Acid Deposition: Sulfur and nitrogen oxides from fossil fuel combustion mix with water to form acids that alter soil and water chemistry.

    • Greenhouse Effect: Gases such as CO2CO_2, methane (CH4CH_4), and nitrous oxide (N2ON_2O) trap infrared radiation in the atmosphere, warming the Earth and leading to climate change.

    • Ocean Acidification: As CO2CO_2 concentration increases in the atmosphere, it dissolves in seawater, decreasing the pHpH and threatening marine life.

Overexploitation

  • Definition: Harvesting a species at a rate that exceeds its ability to rebound or reproduce.

  • Historical Examples:

    • Great Auk: Driven to extinction.

    • Atlantic Cod: Stocks off the East Coast of Newfoundland collapsed in 19921992.

    • Atlantic Bluefin Tuna: Facing similar threats from overharvesting.

Conservation Strategies and Legislation

  • Addressing Habitat Destruction:

    • Movement Corridors: Areas of habitat that connect isolated wildlife populations separated by human activity (e.g., overpasses or underpasses for roads).

    • Yellowstone to Yukon (Y2Y) Conservation Initiative: An ambitious effort to create a string of parks and reserves from Alaska to Wyoming, including the reintroduction of wolf populations.

  • Addressing Invasive Species: Prevention strategies include not planting invasive species, cleaning boats and boots after use, and not releasing exotic pets into the wild.

  • Addressing Pollution & Overexploitation:

    • Rachel Carson: Wrote Silent Spring in 19621962, highlighting the dangers of pesticides and leading to the ban of DDT.

    • Management Plans: Successful hunting and fishery plans utilize knowledge of biology and migratory patterns to prevent illegal harvesting.

  • Environmental Legislation (Nixon Era and Beyond):

    • NEPA (1970): National Environmental Policy Act; framework for environmental protection.

    • Clean Air Act (1970): Controls air pollution.

    • Clean Water Act (1972): Governs water pollution.

    • Endangered Species Act (ESA) (1973): Protects species in danger of extinction. Bald eagles have successfully recovered due to this act.

    • RCRA (1976): Resource Conservation and Recovery Act; governs solid and hazardous waste disposal.

    • CERCLA (1980): Comprehensive Environmental Response, Compensation, and Liability Act (Superfund); facilitates clean-up of hazardous waste sites like Rocky Flats, CO.