Myth 3: Extinction Is Unnatural and Bad, But Easy to Accomplish — Key Concepts

Myth 3: Extinction Is Unnatural And Bad, But Easy To Accomplish

• Myth presented: People kill individual creatures, and we could save all species today if we tried. The reality counters this:

  • Extinction is natural in a finite universe; the ultimate fate of all species is extinction. Hence, extinction is natural.
  • Some species are vulnerable, but many are persistent; it is difficult to cause extinction of many pests and disease carriers.
  • MOST SPECIES THAT HAVE EXISTED ON EARTH HAVE GONE EXTINCT. We do not know enough to save all species today; there are limits of time, money, energy, and interest.
  • If the universe ends, all life ends; eventually all species go extinct.
  • Fossil records suggest an average extinction rate of about one species per year, though recent papers may claim higher rates. Among mammals, average persistence ≈ 750{,}000 years, suggesting humans already exceed the average persistence of our kind.

• Additional Reality: The hardest way to drive a species extinct is to hunt every individual; easier is to destroy habitat or introduce a novel parasite.

• The discussion is not about wanting more extinctions; it’s about understanding why extinctions happen so we can reduce them.

• The notion that humans are causing massive extinctions has become fashionable, exemplified by Elizabeth Kolbert’s book The Sixth Extinction: An Unnatural History.

  • The book describes five mega-extinctions in the distant past and predicts a sixth due to human activity, implying humans have great power to affect life on Earth.
  • The author notes arrogance in believing we can control all life on Earth and questions why we haven’t controlled diseases like malaria or invasive species like Burmese pythons in the Everglades.

• Practical counterpoints to the “we can save all species” premise:

  • Invasive species (e.g., Burmese python, Melaleuca in the Everglades) illustrate limits of control.
  • We should shift focus to deciding which species we can help effectively, rather than pursuing an impossible universal save.
  • A pragmatic reformulation offered: do them no harm for the species we wish to keep around.

• A plan emerges: reduce extinctions by understanding causes, focusing on feasible actions, and applying industrial/scientific methodology: figure out how extinctions occur, assess tools we already have or can develop, then act.

• The Role of Science in Determining Likely Extinctions

  • Two approaches have been used to save endangered species: (1) scientific analysis; (2) informal observations, experience, and judgment. Often mixed.
  • The author argues the role of science has been limited because: knowledge about many species/ecosystems is incomplete; many involved sciences are new; ecological persistence is poorly understood; political, social, cultural, and economic goals complicate decisions.
  • Personal practice: base recommendations on scientific information whenever possible; even a few data points can be fundamental for conservation decisions.

• Not Easy to Cause Extinction by Hunting All Individuals

  • Elephant Seals (northern): hunted in 19th century for blubber; population rebounded after near-extinction. By late 1980s numbers grew ~9% per year, roughly doubling every 8 years, potentially reaching millions by 2070 if growth continued; current estimates exceed 120{,}000.
  • Sea Otters: hunted to near-extinction by late 19th century; protection began with 1911 international treaty; by early 21st century, world population > 100{,}000, with regional declines (southwest Alaska listed as threatened).
  • Sandhill Cranes: protected since 1916 treaty; population rose above 130,000, later reaching around 400{,}000–500{,}000 and fluctuating; current status indicates strong recovery in many regions.
  • These cases illustrate that even large populations can recover if threats are mitigated, and that extinction by hunting alone is not easily accomplished.

• A Brief History of Extinctions and Mega-Extinctions

  • Extinctions are ongoing; average rate cited as about one per year, with some sources suggesting higher rates (up to 6 per year).
  • Since multicellular life began, there have been five mega-extinctions; the Permian-Triassic (~250 million years ago) saw an estimated 80\%\text{--}90\% of species extinct.
  • Mega-extinction causes include asteroid impacts, volcanic eruptions with lava flows, and massive greenhouse gas releases; these causes are beyond human control, reinforcing limits of saving all species.
  • Since the 16th century, hundreds of species have gone extinct (>300 known cases; many more unnamed).

• Examples of recently extinct species illustrate diverse causes:

  • The Golden Toad: habitat is extremely small (≈ 1\ ext{square mile}, at elevations 900\to!1000\ ext{ft}); highly vulnerable to habitat loss, disease (chytrid fungus, Batrachochytrium dendrobatidis), and climate variation; deforestation and climate change may have contributed.
  • Po\'o-uli (Melamprosops phaeosoma): Maui, Hawaii; limited habitat (4,600–7,000 ft); disease-carrying mosquitoes and introduced predators (rats, cats, mongooses) contributed to extinction.
  • Javan Tiger: isolated on Java; habitat loss from agriculture, hunting, competition with leopards and dogs; small area too small to sustain population; status: extant only in remote areas or extinct.

• How Do We Decide a Species Is in Danger of Extinction?

  • Decisions are not purely scientific; practical examples reveal complexities.
  • The traditional 50/500 rule (second half of the 20th century):
  • If population < 50 individuals for a short time (≈ ten years), or < 500 for a long time, a species is considered endangered. This was intended to address genetic inbreeding concerns.
  • Anecdote about a scientist who provided the rule based on cattle genetics; the rule was used cautiously because it relies on assumptions about genetic variability.
  • The Isle Royale wolves example shows inbreeding concerns: population dipped below 10; only two reproductive adults remained; the pup showed vertebrate abnormalities likely due to inbreeding.
  • The IUCN uses broader criteria; some species with larger population sizes can be listed as vulnerable due to rapid declines (e.g., African lion, ~23,000–32,000 individuals in recent counts; listed as "vulnerable" due to population decline and threats like poaching).
  • Passenger Pigeons: enormous historical populations (as high as 3-4\text{ billion}; 25–40% of all birds in the U.S. at peak). Yet extinct by 1900 due to rapid, human-fueled declines once social behavior and technology (railroads, telegraphs, organized hunting) amplified predation and habitat exploitation.
  • Whooping Cranes: historical decline to ~51 individuals (1972); a population viability analysis by Mendelssohn, Miller, and the author estimated extinction risk under continued variability. They used a complete census over 30+ years to calculate the probability of extinction; their estimate for 1992 was remarkably low: around 5 ext{ in } 10^9 (5 in 1,000,000,000).
  • Caveats of 50/500-rule-like logic: the probability of extinction can be extremely low under certain conditions but not guaranteed; a single catastrophe (new disease, sharp habitat loss) could cause abrupt extinction.

• Whooping Cranes: a detailed case study

  • 1972 population in Aransas area: 51 birds; by 2015, total wild population reached 442; including captivity, total is 603 (442 + 161 in captivity).
  • The analysis suggested that, with the population history and assumptions, the chance of extinction by a future horizon (e.g., 1992 in the cited study) was extremely small, illustrating how a population can persist with steady growth and protection.
  • The calculation depended on the assumption that the past sources of variation persisted into the future and that no new catastrophes occurred; real-world risks include new diseases or catastrophic events.

• What Can We Do to Help?

  • External factors to consider for predicting extinction risk:
  • Habitat size and quality; risk of invasive disease or predator introduction.
  • The golden toad case shows how specialized, small habitats increase extinction risk.
  • Encroachment of people: focus on where human actions (including poaching) occur; observe how human pressures (e.g., hunting, habitat conversion) affect species.
  • Focus on the most vulnerable: a triage approach is advocated because saving all species is impractical.
  • Triaging three groups:
  • Likely to go extinct no matter what we do.
  • Will persist no matter what we do.
  • Might persist but only with our help.
  • Some colleagues react emotionally to triage; the author argues it is arrogant to promise to save all species and that we must be selective and evidence-based due to limited resources.
  • The practical approach: learn as much as possible about species most important from a human viewpoint; develop better technical understanding of extinction causes; study recent extinctions to inform prevention.

• Ecological Engineering and Practical Actions

  • Ecological engineering: become ecological engineers—if it’s broke, diagnose and fix it; use population monitoring and data collection to inform interventions.
  • Protect habitats and understand their size/requirements; many habitats of threatened species are not adequately protected or are being converted to other uses.
  • Acknowledges a lack of data and the need for rapid, proactive responses across society to address life-on-Earth catastrophes; contrasts with how other catastrophes (airplane crashes, train accidents) prompt immediate investigations to prevent recurrence.
  • The author foreshadows further discussion on climate change myths and other related topics in later myths.

• What Difference Does It Make If We Believe This Myth?

  • Potential consequences of believing that most species will go extinct due to human actions:
  • People may feel overwhelmed and do little to help those we could aid.
  • Insufficient monitoring of endangered populations.
  • Difficulty in performing rigorous extinction probability calculations due to data gaps.
  • Failure to identify and address root causes of extinctions (habitat fragility, overhunting, habitat loss).
  • Failure to implement triage strategies to prioritize conservation actions.
  • Without distinguishing habitats and threats, we miss opportunities to protect high-risk species and make informed decisions about where to allocate limited resources.
  • Emphasizes the need to separate endangered species by habitat fragility (small, fragile habitats) and by threat type (disease/pests with fast life cycles vs. slower threats).

• Ethical and Philosophical Implications

  • The tension between a noble goal (save all species) and practical limitations leads to a call for humility and prudent action.
  • The idea of triage raises ethical questions about which species deserve protection and how to balance ecological value with human needs and resources.
  • The discussion argues that responsible use of scientific knowledge, while not simplifying complex ecological realities, offers a pragmatic path toward reducing extinctions rather than pursuing an impossible universal preservation.

• Final Takeaways: Actions for the future

  • Treat extinctions as real but understandable given ecological and evolutionary processes; avoid hubris about universal control.
  • Adopt ecological engineering: gather more data, monitor populations, and design interventions to prevent extinctions.
  • Protect habitats and manage threats (invasive species, disease, habitat destruction).
  • Use a triage approach to allocate limited resources to species most likely to benefit from intervention.
  • Recognize that some extinctions are driven by large-scale natural events (mega-extinctions) outside human control; focus on manageable, human-driven threats where possible.

• Summary of Key Formulas, Numbers, and References (LaTeX-formatted)

  • Average extinction rate (historical): 1 species per year.
  • Mammal persistence average: 7.5\times 10^5 years. (≈ 750{,}000 years)
  • Elephant seal doubling time (observed growth): approximately every 8 years.
  • Sea otter world population (current): >100{,}000.
  • Golden toad habitat area: 1\ \text{mi}^2; elevation: 900\to!1000\ \text{ft}.
  • Po\'o-uli habitat elevation: 4{,}600\to!7{,}000\ ext{ft}.
  • Mega-extinction events: number of events = 5; Permian-Triassic extinction: 80\%\text{--}90\% species lost; time ~2.5\times 10^8 years ago.
  • Known extinctions since the 16th century: >300 species.
  • Passenger pigeon historical population: up to 3\text{–}4\times 10^9 individuals; share of birds 25–40% of U.S. bird populations.
  • Whooping crane population of concern (1972): 51 individuals; 2015 wild population: 442; captive population: 161; total = 603.
  • Probability of extinction for whooping cranes (1972→1992): 5/10^9 (five in one billion).

• Connections to foundational principles and real-world relevance

  • Aligns with the industrial/scientific approach: study causes, leverage available tools, and act on the best evidence to mitigate extinctions.
  • Highlights real-world constraints on conservation (resources, politics, economics) and the need for prioritization in policy.
  • Emphasizes ethical responsibilities to other species balanced against human needs and practical feasibility.
  • Demonstrates how historical case studies (passenger pigeons, Javan tiger, golden toad, whooping cranes) illuminate why extinctions occur and how some populations rebound when threats are mitigated.

• Quick glossary of major terms

  • Extinction: the permanent disappearance of a species.
  • Persistence: continued survival of a species over long time scales.
  • Ecological engineering: applying engineering principles to manage and restore ecological systems.
  • Triage (conservation): prioritizing limited resources to maximize conservation outcomes.
  • Inbreeding depression: loss of genetic diversity leading to reduced fitness and increased extinction risk in small populations.
  • Mega-extinction: the loss of a substantial proportion of life across broad taxa in a geologically short period.

• Note on sources and tone

  • The content reflects an argument that while human activity can influence extinctions, there are natural limits and unforeseen complexities; thus a pragmatic, data-driven approach that prioritizes high-impact actions is advocated over the notion of saving every species.

• Practical implications for study and exam prep

  • Be able to discuss why extinctions are not solely the result of human activity, and why some events are natural and beyond control.
  • Understand the 50/500 rule, its rationale, and its limitations, plus real-world examples (Isle Royale wolves, African lions).
  • Be able to explain how case studies (golden toad, Po\'o-uli, Javan tiger, passenger pigeon, whooping crane) illustrate drivers of extinction and recovery possibilities.
  • Explain the triage approach and its ethical/environmental rationale.
  • Describe how ecological engineering and habitat protection fit into a strategy to reduce extinctions.

• Overall takeaway for the exam

  • Distinguish between natural extinction processes and anthropogenic pressures; recognize the limits of saving all species; apply a pragmatic, ethical, and evidence-based triage approach to conservation; and emphasize habitat protection and monitoring as key tools in reducing extinctions.