11.1 Climate Change Impacts on Biodiversity

Climate change is reshaping biodiversity in profound ways. From shifting species ranges to disrupting ecosystems, its impacts are far-reaching and complex. Understanding these effects is crucial for conservation efforts in a warming world.

Species are struggling to adapt to rising temperatures and extreme weather. Physiological stress, habitat loss, and altered interactions between organisms are causing population declines and extinctions. The ripple effects are transforming entire ecosystems.

Climate Change Impacts on Species

Physiological and Ecological Effects

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• Climate change directly affects species through physiological stress altering their thermal tolerances, metabolic rates, and reproductive success
  • Example: Increased temperatures lead to heat stress in cold-adapted species (polar bears)
  • Example: Changes in ocean temperature affect the timing of fish spawning (Atlantic cod)
• Rising temperatures and altered precipitation patterns lead to shifts in species' geographical ranges and habitat suitability
  • Poleward or upslope movements observed in various taxa (butterflies, birds)
  • Some species face range contractions or fragmentations due to limited suitable habitat
• Climate change impacts ecosystem processes such as nutrient cycling, primary productivity, and decomposition rates
  • Altered carbon sequestration in forests due to changes in tree growth and mortality
  • Increased soil respiration rates in warming tundra ecosystems

Extreme Events and Ocean Acidification

• Extreme weather events associated with climate change cause acute disturbances to ecosystems and populations
  • Droughts lead to increased wildfire frequency and intensity (Australian bushfires)
  • Hurricanes and storms damage coastal habitats (mangrove forests, coral reefs)
• Ocean acidification directly affects marine organisms, particularly those with calcium carbonate shells or skeletons
  • Reduced calcification rates in coral reefs and shellfish
  • Altered behavior and sensory abilities in fish species

Ecosystem Interactions and Indirect Effects

• Climate change can disrupt trophic interactions and food webs leading to cascading effects throughout ecosystems
  • Changes in plankton communities affect marine food chains
  • Altered plant-herbivore interactions due to shifts in plant chemistry
• Indirect effects of climate change on ecosystems include changes in resource availability, habitat structure, and community composition
  • Reduced snow cover affects winter survival of some species (snowshoe hares)
  • Changes in vegetation structure alter habitat suitability for many animals

Altered Species Distributions and Interactions

Range Shifts and Climate Velocity

• Species distributions shift poleward or to higher elevations as temperatures increase leading to range expansions, contractions, or fragmentations
  • Example: Northward expansion of southern European butterfly species
  • Example: Upslope movement of plant species in alpine regions
• Climate velocity influences the ability of species to track suitable climatic conditions
  • Defined as the rate and direction of climate change relative to the landscape
  • Species with limited dispersal abilities may struggle to keep pace with rapid climate shifts

Phenological Changes and Ecological Mismatches

• Phenological shifts occur as species alter the timing of life cycle events in response to changing environmental cues
  • Earlier spring flowering in many plant species
  • Changes in bird migration timing and breeding periods
• Asynchrony in phenological responses between interacting species can lead to ecological mismatches
  • Disrupts processes like pollination, predator-prey dynamics, and host-parasite relationships
  • Example: Mistiming between caterpillar emergence and bird breeding seasons

Novel Communities and Altered Interactions

• Climate change can facilitate the spread of invasive species by creating more favorable conditions in previously unsuitable areas
  • Range expansion of invasive plants into warming regions
  • Increased survival of non-native pests in areas with milder winters
• Altered competitive interactions may occur as species' ranges overlap in new ways potentially leading to novel community assemblages
  • Changes in species composition in high-latitude and high-elevation ecosystems
  • Novel predator-prey interactions in marine systems due to range shifts
• Changes in species' physiological tolerances and resource requirements can modify the nature and strength of interspecific interactions
  • Altered plant-pollinator mutualisms due to phenological mismatches
  • Shifts in competitive dominance among plant species under changing climate conditions

Case Studies of Biodiversity Loss

Arctic and Montane Ecosystems

• The case of polar bears demonstrates how sea ice loss affects habitat availability, foraging opportunities, and reproductive success of Arctic specialists
  • Reduced access to seal hunting grounds
  • Increased swimming distances and energy expenditure
• The pika in North America serves as an example of a montane species facing range contractions and local extinctions due to warming temperatures
  • Limited ability to disperse to higher elevations
  • Vulnerability to heat stress and reduced winter snowpack

Marine Ecosystems and Coral Reefs

• Coral reef bleaching events illustrate the vulnerability of marine ecosystems to increased ocean temperatures and acidification
  • Mass bleaching events in the Great Barrier Reef (2016, 2017, 2020)
  • Loss of coral cover and associated biodiversity
• Shifts in bird migration patterns highlight phenological changes in response to climate change
  • Changes in arrival and departure times of long-distance migrants
  • Potential mismatches with food availability at breeding grounds

Forests and Pest Outbreaks

• The spread of pine beetle outbreaks in North American forests exemplifies how climate change can exacerbate pest and disease pressures on ecosystems
  • Expanded range and increased survival of mountain pine beetles
  • Widespread tree mortality and altered forest composition
• Changes in plant-pollinator interactions demonstrate the potential for ecological mismatches due to differential phenological responses
  • Shifts in flowering times and pollinator activity periods
  • Reduced pollination success and potential impacts on plant reproduction

Tropical Ecosystems and Amphibians

• The case of amphibian declines in tropical montane regions illustrates the complex interactions between climate change, disease, and habitat loss
  • Increased susceptibility to chytrid fungus infections due to changing temperatures
  • Loss of suitable microclimates in cloud forests

Climate Change vs Other Stressors

Habitat Fragmentation and Connectivity

• Climate change can exacerbate the impacts of habitat fragmentation by reducing connectivity and limiting species' ability to shift their ranges
  • Increased isolation of populations in fragmented landscapes
  • Reduced gene flow and adaptive potential

Pollution and Ecosystem Degradation

• The combined effects of climate change and pollution can lead to more frequent harmful algal blooms
  • Increased water temperatures and nutrient runoff in aquatic systems
  • Impacts on water quality, aquatic life, and human health

Overexploitation and Extinction Risk

• Climate change can interact with overexploitation of species potentially accelerating population declines and increasing extinction risks
  • Reduced resilience of overfished marine populations to warming oceans
  • Cumulative impacts on endangered species with limited geographic ranges

Invasive Species and Novel Ecosystems

• The synergy between climate change and invasive species can facilitate the establishment and spread of non-native organisms in newly suitable habitats
  • Range expansion of warm-adapted invasive plants into previously cooler regions
  • Altered competitive dynamics between native and non-native species

Land-Use Change and Ecosystem Resilience

• Climate change can amplify the effects of land-use change by altering local climate patterns and ecosystem resilience
  • Increased vulnerability of fragmented forests to edge effects and drought
  • Reduced carbon sequestration potential in degraded ecosystems

Disease Dynamics and Wildlife Health

• The interaction between climate change and disease dynamics can lead to increased prevalence and severity of wildlife pathogens
  • Range expansion of vector-borne diseases (malaria, Lyme disease)
  • Altered host-pathogen interactions due to stress and immune suppression

Cumulative Impacts and Ecological Thresholds

• Evaluating the cumulative impacts of multiple stressors requires consideration of potential non-linear responses and ecological thresholds in ecosystems
  • Synergistic effects may lead to rapid and unexpected changes in ecosystem state
  • Importance of considering multiple stressors in conservation planning and management