Sustaining Biodiversity: Saving Species & Ecosystem Services – Study Notes

Core Case Study – Disappearing Honeybees

  • Bees are keystone pollinators. Roughly \frac{1}{3} of global food supply originates from insect–pollinated plants.
  • Modern agriculture depends almost exclusively on one managed honey-bee species (Apis mellifera).
  • Crisis: Colony Collapse Disorder (CCD)
    • Annual hive losses in Europe & the U.S. ≈ 30\text{–}50\% of colonies.
    • Suspected drivers: pesticides (neonicotinoids), parasitic mites (Varroa), fungal pathogens, nutrition stress, monocultures, climate change, 5G/EMF hypotheses (mentioned anecdotally).
  • Emerging farmer responses
    • Breeding mite- and fungus-resistant strains.
    • Maintaining on-site colonies; reducing pollination outsourcing.
    • Diversifying floral resources → better bee nutrition (cover crops, hedgerows).
  • Take-away: Failure to protect bees ➔ cascading loss of pollination services, jeopardising food security & ecosystem stability.

Historic Lesson – Passenger Pigeon

  • Once most abundant North-American bird (billions).
  • Commercial hunters used:
    • “Stool pigeons” (live decoys).
    • Giant nets.
    • Setting nesting trees on fire.
  • Extinct by 1900 → iconic example of anthropogenic extermination.
  • Archaeological record reveals five previous mass-extinction events; current human activity may herald a sixth.

Human Modification of the Biosphere

  • ≥ 50\% of terrestrial surface disturbed: wetland filling, grassland/forest conversion to cropland or urban areas.
  • Aquatic systems likewise degraded (dams, pollution, overfishing, invasive species).

Extinction Vocabulary

  • Background extinction: natural rate ≈ 1 species per 10^{6} species per year (derived from marine-fossil data).
  • Current measured rate (birds & mammals): \approx1\% of species/100 yrs → \approx10^{-4} species/species/yr.
    • Thus present rate \approx100\text{–}1000\times background (some estimates up to 10^{4}\times).
  • Projected by 2100: \approx10^{4}\times background.
  • Mass extinction: loss of 50\text{–}90\% of species in short geologic interval.
  • Biological extinction: no living members remain.
  • Regional extinction: gone from normal range.
  • Functional (ecological) extinction: numbers so low the species no longer fulfils its ecological role (→ trophic cascade).

Visualising Rates

  • Hypothetical 0.1\% annual rate:
    • 5\,\text{million} species → 5\,000 extinctions/yr; \approx200 yrs until 1\,000\,000 species lost.
    • At 100\,\text{million} species: 100\,000/yr.

Ecological Smoke Alarms – Endangered vs. Threatened

  • Endangered: numbers so low extinction imminent.
  • Threatened (Vulnerable): still viable now but trending downward.
  • Additional terms:
    • Regionally extinct (e.g., gray wolf in much of U.S.).
    • Functionally extinct (e.g., some coral species no longer build reefs).

Iconic Contemporary Cases (population figures)

  • Mexican gray wolf ≈ 42 individuals (AZ/NM forests).
  • California condor 226 (up from 9 in 1986).
  • Whooping crane 437.
  • Sumatran tiger <500.

Species Currently Threatened (illustrative list)

Grizzly bear, African elephant, blue whale, giant panda, northern spotted owl, Florida panther, mountain gorilla, black rhinoceros, etc.

Traits Predisposing Species to Extinction

  • Low reproductive rate (K-strategists) → blue whale, rhino.
  • Specialized niche → giant panda (bamboo diet).
  • Narrow distribution → desert pupfish.
  • High trophic level → Bengal tiger, bald eagle.
  • Fixed migration routes → sea turtles.
  • Rarity, commercial value, need for large territories.

Taxonomic Threat Percentages

  • Fish 34\% (freshwater species 51\%).
  • Amphibians 32\%.
  • Mammals 25\%.
  • Reptiles 20\%.
  • Plants 14\%.
  • Birds 12\%.

Why Preserve Biodiversity?

  1. Ecosystem services (support life & economy):
    • Pollination, nutrient cycling, pest control, climate regulation, genetic reservoirs.
  2. Economic goods: food, fuel, timber, fibre, medicine, ecotourism.
  3. Recovery from mass loss takes 5\text{–}10\,\text{million yrs}.
  4. Ethical / intrinsic: many hold that species have a right to exist independent of human utility.
  5. Decision problem: limited resources → which species get priority?

Nature’s Pharmacy Examples

  • Pacific yew (Taxus brevifolia) → Taxol for ovarian cancer.
  • Rosy periwinkle (Catharanthus roseus) → vinblastine/vincristine for Hodgkin’s disease & leukemia.
  • Rauvolfia serpentina → reserpine for hypertension & anxiety.
  • Neem tree (Azadirachta indica) → multi-purpose: medicinal, insecticidal, contraceptive.
  • Foxglove (Digitalis purpurea) → digitalis for heart failure.
  • Cinchona → quinine (malaria).

Drivers of Species Loss – HIPPCO

H – Habitat destruction, degradation, fragmentation (greatest single threat).
I – Invasive (nonnative) species.
P – Population growth & overconsumption.
P – Pollution.
C – Climate change.
O – Overexploitation.

Habitat Loss / Fragmentation

  • Large continuous habitats sliced by roads, farms, urban sprawl → smaller \“islands\”.
  • National parks & reserves themselves can become habitat islands.
  • Range reductions documented for:
    • Indian tiger, black rhino, African elephant, Asian elephant (maps show historic vs. present distribution).

Invasive Species

  • Beneficial introductions exist (e.g., crops) but many invaders lack predators/parasites in new range.
  • U.S. hosts ≈ 7,100 harmful invasive species. Examples:
    • Deliberate: purple loosestrife, European starling, Africanized honeybee, hydrilla, feral pigs.
    • Accidental: zebra mussel, brown tree snake, Asian long-horned beetle, Argentine fire ant.
  • Impacts: crowding out natives, altering food webs, economic costs >\$100\,\text{billion}/yr globally (figure implied).
  • Mitigation hierarchy: Prevention > early detection > rapid response.
    • Research screening/ID programmes.
    • International treaties restricting ballast-water discharge, plant/animal trade.
    • Public education (exotic pets, ornamental plants).

Population, Pollution & Climate

  • Growing human numbers & per-capita resource use intensify land-use change & extraction.
  • Pollution: toxins bioaccumulate, biomagnify → top predators & sensitive species disappear (e.g., DDT & raptors).
  • Climate change shifts temperature & precipitation belts: some species migrate poleward/up-slope, others cannot.

Overexploitation

  • Commercial hunting/fishing (passenger pigeon precedent).
  • Poaching for ivory, rhino horn, bushmeat, exotic pet trade (hyacinth macaw example).

Future Outlook & Ethical Question

  • Extinction & ecosystem-service loss likely to accelerate over next 50\text{–}100\,\text{yrs} under business-as-usual.
  • Biodiversity hotspots face disproportionately high extinction rates because of intense human pressure on limited ranges.
  • Societal trade-off: expanding wildlife ranges vs. land for agriculture & settlement.
  • Key policy tools: habitat protection/restoration, invasive-species prevention, sustainable harvest quotas, pollution/climate mitigation, captive breeding & reintroduction.