18.18 Maintaining Biodiversity

1. Threats Leading to Extinction

• Current Human-Caused Mass Extinction:
  • Unlike previous natural mass extinctions (e.g., asteroid impact 65 million years ago), the current wave is largely driven by human activities.

Key Causes of Extinction

• Habitat Loss:
  • Deforestation: Loss of tropical forests threatens species like orangutans.
  • Wetland Drainage: Destroys habitats for water-dependent species.
  • Pollution: Air, water, and soil pollution negatively impact many species’ survival.
• Over-Exploitation:
  • Hunting & Poaching: Killing animals for sport, food, or commercial products (e.g., elephants for ivory).
  • Overfishing: Depletes fish populations, disrupting marine ecosystems.
• Climate Change:
  • Rising Temperatures: Forces species to shift habitats or face extinction.
  • Rising Sea Levels: Floods coastal habitats, impacting coastal and marine biodiversity.
  • Ocean Acidification: Damages coral reefs, threatening high-biodiversity ecosystems.
• Invasive Species:
  • Introduction of Non-Native Predators: E.g., Cats and rats in New Zealand led to extinction of 53 flightless bird species.
  • Competition from Invasive Species: Outcompetes native species for resources.
• Interspecific Competition:
  • Resource Competition: Species that share limited resources may outcompete each other.
  • Historical Example: In North America, cat species that arrived from Asia outcompeted many native dog species.

2. Reasons for Maintaining Biodiversity

A. Ecological Reasons

• Ecosystem Stability and Resilience:
  • Ecosystems with high biodiversity are more resilient to environmental changes, pollution, and other disruptions.
• Keystone Species:
  • Definition: Species that have a disproportionately large impact on their ecosystems.
  • Example: Sea otters control sea urchin populations in kelp forests; without otters, sea urchins overgraze kelp, destabilizing the entire ecosystem.
• Interconnectedness of Species:
  • Loss of a single species can disrupt food webs, affect other species, and lead to cascading ecosystem changes.

B. Economic Reasons

• Medicinal Resources:
  • Many drugs are derived from plants, animals, and microorganisms.
• Examples:
  • Antibiotics from fungi and bacteria.
  • Cancer drugs: Paclitaxel from the Pacific yew and Madagascan periwinkle.
• Threat to Medicinal Resources: Habitat loss threatens the survival of species that could provide future medical treatments.
• Biotechnology and Industrial Uses:
  • Taq Polymerase: Enzyme from the thermophilic bacterium Thermus aquaticus, used in DNA replication for research and forensics.
  • Extremophiles: Organisms living in extreme conditions (e.g., deep-sea vents) may have enzymes useful in industrial processes.
• Ecotourism:
  • Income and Jobs: Countries with rich biodiversity (e.g., Belize, Malaysia) attract tourists, boosting local economies and creating employment.
  • National Parks and Conservation Areas: Protecting biodiversity can also support sustainable tourism.
• Agricultural Value:
  • Wild Crop Relatives: Provide genetic diversity needed for crop resilience.
    • Example: Wild rice (Oryza longistaminata) in Africa provides disease resistance genes.
    • Example: Andean wild potato species offer resistance to diseases like blight.
  • Genetic Resources for Future Agriculture: Wild relatives of crops provide genes for traits like drought tolerance, pest resistance, and improved yield.

C. Aesthetic Reasons

• Enjoyment and Inspiration:
  • Many people derive pleasure and inspiration from nature, including artists, writers, and photographers.
  • Biodiversity in Art and Culture: Natural landscapes, animals, and plants are sources of artistic and cultural expression.

D. Moral and Ethical Reasons

• Moral Responsibility:
  • Many people believe that humans have a duty to protect other species and prevent unnecessary extinction.
• Stewardship of Earth:
  • Belief that humans are caretakers of the Earth, with a responsibility to maintain biodiversity for future generations.
• Rights of Other Species:
  • Ethical argument that all species have an inherent right to exist, independent of their utility to humans.

E. Environmental Reasons

• Ecosystem Services:
  • Carbon Sequestration:
    • Forests and peat bogs absorb CO₂, which helps mitigate climate change.
  • Water Cycle Maintenance:
    • Plants contribute to the water cycle through transpiration, providing moisture that eventually replenishes freshwater sources.
  • Soil Fertility and Nutrient Cycling:
    • Decomposers (e.g., bacteria, fungi) recycle nutrients, maintaining soil health for plant growth.
    • Pollinators: Insects and other animals pollinate crops and wild plants, essential for food production and plant reproduction.
  • Waste Breakdown:
    • Microorganisms break down organic waste in ecosystems, preventing pollution and providing nutrients for other organisms.

Summary of Reasons to Maintain Biodiversity

1. Ecological: Stability and resilience of ecosystems; keystone species maintain balance.
2. Economic: Sources of medicines, biotechnology, ecotourism income, and genetic diversity for agriculture.
3. Aesthetic: Natural beauty provides enjoyment, inspiration, and cultural significance.
4. Moral/Ethical: Responsibility to protect species and preserve biodiversity.
5. Environmental: Ecosystem services that support life, including carbon sequestration, water cycle, and nutrient recycling.

Threats to Ecosystems and Biodiversity

Examples of Conservation Needs

1. Keystone Species Conservation:

• Sea Otters: Protecting sea otters helps maintain kelp forest ecosystems, benefiting many species.

1. Wild Crop Relatives:

• Wild Rice and Maize: Protecting habitats of wild rice in Africa and maize in Mexico preserves genes needed for disease resistance in crops.

1. Medicinal Plants:

• Madagascan Periwinkle: Habitat loss threatens this plant, a source of anti-cancer compounds.

1. Ecosystem Conservation:

• Coral Reefs: Important biodiversity hotspots that support fisheries and protect coastlines from storms.

Question Review

1. List of Threats to Ecosystems:

• Habitat destruction, climate change, over-exploitation, invasive species, pollution, and competition.

1. Five Reasons to Maintain Biodiversity:

• Ecological: Ensures stability and resilience of ecosystems.
• Economic: Provides resources like medicines, ecotourism income, and agricultural resilience.
• Aesthetic: Offers enjoyment and inspiration from nature.
• Moral and Ethical: Humans have a duty to protect other species.
• Environmental: Ecosystem services like carbon sequestration, water purification, and nutrient recycling are essential for life.