9.5 Climate change and biodiversity

Climate change profoundly impacts global ecosystems and biodiversity patterns. Rising temperatures, shifting precipitation, and extreme weather events alter habitat suitability, species distributions, and ecological interactions. These changes present complex challenges for conservation efforts and ecosystem management strategies.

Biodiversity responds through species range shifts, phenological changes, and increased extinction risks. Ecosystems like coral reefs, polar regions, and tropical forests are particularly vulnerable. Adaptation strategies include assisted migration and protected area networks, while mitigation efforts focus on carbon sequestration and sustainable land management.

Impacts of climate change

• Climate change profoundly affects global ecosystems and biodiversity patterns studied in World Biogeography
• Alters fundamental environmental conditions shaping species distributions and ecological interactions
• Presents complex challenges for conservation efforts and ecosystem management strategies

Temperature and precipitation shifts

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• Global average temperatures increase due to enhanced greenhouse effect
• Precipitation patterns become more variable and extreme
  • Some regions experience increased rainfall and flooding
  • Other areas face prolonged droughts and desertification
• Shifts in temperature and rainfall alter habitat suitability for many species
• Changes in growing seasons affect plant phenology and animal migration patterns

Sea level rise effects

• Melting ice sheets and thermal expansion of oceans cause sea levels to rise
• Coastal ecosystems face inundation and erosion (mangroves, salt marshes)
• Low-lying islands and coastal communities at risk of submersion
• Saltwater intrusion into freshwater aquifers alters inland ecosystems
• Marine species distributions shift as water depths and temperatures change

Extreme weather events

• Increased frequency and intensity of hurricanes, typhoons, and cyclones
• More severe heat waves and cold snaps stress ecosystems and organisms
• Prolonged droughts lead to increased wildfire risk in many regions
• Flash floods and landslides cause rapid habitat destruction
• Extreme events can trigger ecosystem state shifts or collapses

Biodiversity responses

Species range shifts

• Organisms move to track suitable climate conditions as temperatures change
• Poleward and upslope migrations observed in numerous plant and animal species
• Range expansions for some species (invasive species, disease vectors)
• Range contractions for others, particularly endemic or specialized species
• Shifts lead to novel species assemblages and altered community dynamics

Phenological changes

• Timing of biological events alters in response to changing seasonal cues
• Earlier spring events (leaf-out, flowering, insect emergence)
• Delayed autumn events (leaf senescence, hibernation)
• Potential mismatches between interacting species (plants and pollinators)
• Changes in growing season length affect productivity and competitive interactions

Extinction risks

• Climate change increases extinction threat for many species
• Particularly vulnerable groups include (polar species, montane endemics)
• Inability to adapt or migrate quickly enough to track suitable conditions
• Synergistic effects with other stressors (habitat loss, pollution)
• Cascading extinctions possible due to loss of keystone or foundation species

Ecosystem vulnerabilities

Coral reefs vs polar regions

• Coral reefs highly vulnerable to ocean warming and acidification
  • Increased frequency of coral bleaching events
  • Reduced calcification rates in corals and other reef-building organisms
• Polar regions experience rapid warming and sea ice loss
  • Threatens ice-dependent species (polar bears, seals)
  • Alters marine productivity and food web dynamics
• Both ecosystems face potential regime shifts and loss of biodiversity

Tropical forests vs grasslands

• Tropical forests sensitive to changes in temperature and rainfall patterns
  • Risk of increased drought stress and fire frequency
  • Potential for forest dieback and conversion to savanna in some areas
• Grasslands may expand in some regions due to increased aridity
  • Woody encroachment alters grassland structure and function
  • Changes in fire regimes affect species composition and nutrient cycling
• Both ecosystems play crucial roles in global carbon and water cycles

Freshwater vs marine systems

• Freshwater ecosystems impacted by altered hydrological regimes
  • Changes in runoff patterns affect water availability and quality
  • Warming temperatures influence thermal stratification in lakes
• Marine systems face ocean acidification and deoxygenation
  • Shifts in currents and upwelling patterns alter nutrient dynamics
  • Changes in water temperature affect species distributions and phenology
• Both systems experience increased eutrophication and harmful algal blooms

Adaptation strategies

Assisted migration

• Intentional relocation of species to areas with suitable future climates
• Controversial approach due to potential ecological risks and uncertainties
• Implemented for some threatened plant species (Torreya taxifolia)
• Requires careful consideration of target species and recipient ecosystems
• May be necessary for species with limited dispersal abilities or fragmented habitats

Protected area networks

• Expansion and redesign of protected areas to account for climate change
• Incorporation of climate refugia and future suitable habitats
• Increased connectivity between protected areas to facilitate species movement
• Adaptive management approaches to address changing conservation needs
• Integration of surrounding landscapes into conservation planning

Corridor conservation

• Establishment and maintenance of habitat corridors to facilitate species movement
• Riparian corridors provide important connectivity in fragmented landscapes
• Elevational gradients allow species to track suitable climates in mountainous regions
• Stepping stone habitats support long-distance dispersal for some species
• Corridor design must consider multiple species and ecosystem functions

Mitigation efforts

Carbon sequestration in ecosystems

• Enhancement of natural carbon sinks to remove atmospheric CO2
• Forest conservation and restoration (tropical rainforests, mangroves)
• Soil carbon management in agricultural and grassland systems
• Blue carbon ecosystems (seagrass beds, salt marshes) store significant amounts of carbon
• Potential trade-offs between carbon sequestration and other ecosystem services

Reforestation and afforestation

• Reforestation restores forest cover on previously forested land
• Afforestation establishes new forests in areas not recently forested
• Both approaches increase carbon storage and provide habitat for biodiversity
• Consideration of native species composition and local ecological conditions crucial
• Potential for negative impacts if poorly implemented (monoculture plantations)

Sustainable land management

• Adoption of practices that maintain ecosystem health and productivity
• Agroforestry systems combine trees with crops or livestock
• Conservation agriculture minimizes soil disturbance and enhances soil carbon
• Improved grazing management in rangelands to reduce degradation
• Integrated landscape approaches that balance multiple land uses and stakeholder needs

Biodiversity hotspots

Identification of vulnerable areas

• Regions with high species richness and endemism at risk from climate change
• Tropical Andes, Madagascar, and Caribbean Islands face multiple threats
• Mediterranean-type ecosystems highly vulnerable to increased aridity
• Quantification of exposure, sensitivity, and adaptive capacity of species and ecosystems
• Use of climate velocity metrics to identify areas of rapid change

Conservation priorities

• Focus on areas with high irreplaceability and vulnerability
• Protection of climate refugia and areas of high genetic diversity
• Consideration of ecosystem services and human well-being in priority setting
• Adaptive conservation planning to account for changing conditions
• Integration of traditional ecological knowledge in conservation strategies

Resilience factors

• Identification of ecosystem characteristics that confer climate resilience
• Genetic diversity within populations enhances adaptive potential
• Functional redundancy in ecosystems provides insurance against species losses
• Landscape heterogeneity offers microclimatic refugia
• Connectivity facilitates species movement and gene flow

Climate change indicators

Bioindicator species

• Organisms sensitive to environmental changes used to monitor climate impacts
• Amphibians serve as indicators of ecosystem health and climate stress
• Coral reefs provide early warning signs of ocean warming and acidification
• Migratory birds reflect changes in phenology and habitat suitability
• Selection of appropriate indicator species for different ecosystems and regions

Ecosystem health metrics

• Measures of ecosystem structure, function, and resilience
• Net primary productivity tracks changes in ecosystem carbon dynamics
• Species diversity indices reflect community composition shifts
• Trophic level biomass ratios indicate food web alterations
• Ecosystem service provision (water quality, pollination) as functional indicators

Long-term monitoring programs

• Sustained observations of ecological variables over decades
• Global Observation Research Initiative in Alpine Environments (GLORIA) tracks mountain plant diversity
• Long Term Ecological Research (LTER) network provides insights into ecosystem responses
• Citizen science projects engage public in biodiversity monitoring (eBird, iNaturalist)
• Integration of remote sensing data with ground-based observations

Policy and management

International agreements

• United Nations Framework Convention on Climate Change (UNFCCC) addresses global climate action
• Convention on Biological Diversity (CBD) sets targets for biodiversity conservation
• Ramsar Convention focuses on wetland conservation and wise use
• Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) assesses global biodiversity status
• Challenges in implementing and enforcing international commitments

National biodiversity strategies

• Country-specific plans to conserve and sustainably use biological diversity
• Integration of climate change considerations into biodiversity policies
• Development of national adaptation plans for ecosystems and species
• Establishment of protected area systems and ecological networks
• Promotion of nature-based solutions for climate change mitigation and adaptation

Local conservation initiatives

• Community-based conservation projects engage local stakeholders
• Indigenous and community conserved areas (ICCAs) protect traditional landscapes
• Urban biodiversity initiatives create green spaces and wildlife corridors in cities
• Watershed management approaches address ecosystem health at landscape scales
• Importance of local knowledge and practices in conservation efforts

Future scenarios

Climate models and projections

• General Circulation Models (GCMs) simulate global climate systems
• Downscaling techniques provide finer-scale projections for ecological applications
• Representative Concentration Pathways (RCPs) represent different emission scenarios
• Ensemble modeling approaches account for uncertainty in climate projections
• Challenges in representing biological complexity and species interactions in models

Biodiversity forecasting

• Species distribution models predict future ranges under climate change
• Mechanistic models incorporate physiological and demographic processes
• Community-level models project changes in species assemblages and interactions
• Ecosystem models simulate shifts in biomes and ecosystem functions
• Incorporation of evolutionary responses and adaptive capacity in forecasts

Tipping points and thresholds

• Critical levels of change beyond which ecosystems undergo rapid transformations
• Amazon rainforest dieback potential under severe drought conditions
• Coral reef ecosystems at risk of collapse due to repeated bleaching events
• Arctic sea ice loss accelerates warming and affects global climate patterns
• Importance of identifying early warning signals for ecosystem state shifts