Lecture 11: Climate-smart conservation

Global extinction risk

• (Urban 2015)

  • estimating global extinction risk from climate change across all taxa and regions and determine how risk scales with warming

    • meta-analysis of 131 published studies comprising >5 million species projections

    • integrated predictions across multiple models, regions, and taxa

    • examined how extinction risk varies by warming scenario (1.5°C, 2°C, 2.8°C, 4°C+)

    • identified geographic hotspots of highest
      vulnerability

  • overall extinction risk is 7.9% (95% CI)

  • extinction risk high for South America (~25%), medium-high for Australia (15-20%), medium for Africa and marine (10-15%)

Causes of climate change vulnerability in Australian threatened species

• (Lee et al. 2015)

  • determine what causes climate change vulnerability in Australian threatened species, and where vulnerable
    species are concentrated geographically

    • assessed 213 Australian threatened species (mammals, birds, reptiles, amphibians, plants)

    • used NatureServe framework: exposure (temp/moisture change) + sensitivity (habitat specificity) + adaptive capacity

    • mapped what is causing vulnerability across the continent to identify conservation hotspots and priorities

  • 45% of threatened species moderately-to-highly vulnerable

    • amphibians most vulnerable

      • they have small, fragmented ranges, dependent on moisture regimes and aquatic habitats

    • plants second most vulnerable

      • low dispersal ability, specific soil types, sensitive to drought

    • birds least vulnerable

      • excellent dispersal ability, plasticity

  • Mountain Pygmy Possum most vulnerable

    • snow melt, habitat loss, ski resort development

Key traits that make some species more vulnerable

• Range size

  • small ranges mean higher vulnerability (already habitat-limited, nowhere to shift)

• Habitat specificity

  • species dependent on particular moisture regime, disturbance type, or substrate are vulnerable when those conditions shift

• Dispersal ability

  • plants (slow), amphibians (habitat-dependent), reptiles (slow in fragmented landscape), birds (excellent)

• Generation time

  • long-lived species (trees, large mammals) can't evolve fast enough

  • short-lived species (insects, small mammals) may adapt quickly

• Niche breadth

  • specialists (specific diet, temperature range)

  • generalists (can adjust to changing conditions)

• Montaine frogs have a restricted range and specific moisture habitat with poor dispersal through dry landscape

  • thus, they are extremely vulnerable

Direct physiological exposure

• Heat stress

  • exceeding physiological tolerances means mortality during extreme heat events

  • e.g. Carnaby's Black Cockatoo during 2010
    heatwave in Hopetoun, WA killed ~50% of
    population in a few days

• Mechanism

  • high ambient temperature and humidity prevent thermoregulation resulting in fatal hyperthermia

• Drought-induced stress

  • precipitation changes lead to water stress, reduced growth, or mortality

    • e.g. Amazon drought experiment (2010) where large
      tree mortality increased 4x in experimental
      drought plots

    • even old-growth forests, thought resilient, fail under extreme drought

Disrupted development

• For many reptiles sex is determined by nest incubation temperature, not genetics.

  • over 400 species including sea turtles, crocodilians etc.

• Threshold temperatures:

  • <27.7°C = males

  • >31°C = females

  • 27.7°C-31°C = mixed

• Climate warming means nearly all female offspring
  at many nesting sites globally

  • e.g. Raine Island, Australia (99% female green turtles)

  • e.g. Cyprus (97% female)

  • e.g. Dutch Caribbean (91% female Leatherbacks)

• Conservation problem:

  • few males signify reproductive failure and local extinction within decades

• Mitigation:

  • nest shading, water management, translocation to cooler sites

  • all expensive and temporary solutions

Timing Mismatch

• Phenology is the timing of life-cycle events (migration,
  flowering, emergence, breeding)

  • Climate warming advances spring at different rates across species resulting in a temporal mismatch

    • e.g. migratory birds arrive at breeding grounds, but insects haven't emerged yet resulting in food shortage for chicks and reduced fledging success

      • phenological mismatch results in a trophic cascade effect

  • Pollination mismatch where flowers bloom before
    pollinators emerge (or vice versa), leading to reproductive
    failure

  • Marine phenology

    • e.g. zooplankton peak earlier causing a mismatch with larval fish recruitment; subsequent food web collapse

• Phenological plasticity has limits if mismatch is greater than adaptive capacity

  • this means populations can decline even without habitat loss

• (Scheffers et al. 2016)

  • measure how many ecological processes are being
    impacted by climate change

    • identified 94 core ecological processes that underpin ecosystem function and human wellbeing

    • reviewed scientific literature to document observed climate change impacts on each process

    • quantified proportion of processes affected by climate change within each biological level and ecosystem type

  • 82% of biological process impacted (77/94)

    • marine (25/31)

    • freshwater (23/31)

    • terrestrial (29/32)