15.1 Climate change and its influence on ecotoxicology

Climate change is reshaping ecosystems worldwide, altering temperatures, precipitation patterns, and ocean chemistry. These changes have far-reaching consequences for species distributions, ecosystem functioning, and the fate of pollutants in the environment.

The intersection of climate change and ecotoxicology presents complex challenges. Rising temperatures and altered environmental conditions affect how pollutants behave and impact organisms, potentially amplifying their toxic effects and disrupting ecosystems in unexpected ways.

Climate Change Effects

Rising Temperatures and Altered Precipitation Patterns

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• Global warming caused by increased greenhouse gas emissions (carbon dioxide, methane) traps heat in the atmosphere leading to rising temperatures worldwide
• Warmer temperatures alter precipitation patterns causing more frequent and intense droughts in some regions while others experience increased rainfall and flooding
• Rising temperatures lead to melting polar ice caps and glaciers contributing to sea level rise which threatens coastal ecosystems and human settlements
• Warmer temperatures expand the range of invasive species and disease vectors (mosquitoes) into new areas disrupting native ecosystems

Ocean Acidification and Marine Ecosystem Disruption

• Ocean acidification occurs as the ocean absorbs excess atmospheric carbon dioxide lowering the pH of seawater
• Acidification impairs the ability of marine organisms (coral, shellfish) to build and maintain their calcium carbonate shells and skeletons
• Coral reefs, which serve as crucial habitats for marine biodiversity, experience bleaching events and mass die-offs due to the combined stresses of acidification and warming waters
• Disruptions to marine food webs occur as acidification affects the growth and survival of plankton, the foundation of marine ecosystems, cascading up to impact fish populations and other marine life

Intensified Extreme Weather Events and Ecosystem Disturbances

• Climate change amplifies the frequency and severity of extreme weather events such as hurricanes, heatwaves, and wildfires
• More intense hurricanes cause extensive damage to coastal ecosystems (mangroves, seagrass beds) through storm surges, high winds, and heavy rainfall
• Prolonged heatwaves lead to heat stress and mortality in plants and animals, altering species composition and ecosystem functioning
• Wildfires, exacerbated by hotter and drier conditions, devastate forests and grasslands, destroying habitats and releasing stored carbon back into the atmosphere

Shifts in Species Distributions and Phenology

• As temperatures rise, species shift their geographic ranges towards cooler regions, often moving poleward or to higher elevations
• Phenological changes occur as warming alters the timing of seasonal events (flowering, migration) causing mismatches between species and their food sources or pollinators
• Range shifts and phenological changes disrupt species interactions and ecosystem dynamics, leading to novel community assemblages and potential loss of biodiversity
• Some species may be unable to keep pace with the rate of climate change, facing local extinctions if they cannot adapt or migrate to suitable habitats

Ecotoxicological Impacts

Altered Bioaccumulation and Biomagnification Patterns

• Bioaccumulation is the buildup of toxic substances (heavy metals, persistent organic pollutants) in an organism's tissues over time
• Climate change can alter bioaccumulation patterns by modifying the distribution, transport, and fate of contaminants in the environment
• Warmer temperatures and changes in precipitation can enhance the volatilization and atmospheric transport of persistent organic pollutants (PCBs, DDT) to remote regions (Arctic) where they accumulate in food webs
• Ocean acidification may increase the bioavailability of certain metals (cadmium, lead) in seawater, leading to higher uptake and accumulation in marine organisms

Modulation of Toxicity and Sensitivity to Contaminants

• Climate change factors (temperature, pH, salinity) can modulate the toxicity of contaminants and the sensitivity of organisms to their effects
• Warmer temperatures often increase the metabolic rates of organisms, potentially enhancing the uptake and toxicity of pollutants
• Ocean acidification can alter the speciation and bioavailability of metals, modifying their toxic effects on marine life
• Drought conditions concentrate pollutants in shrinking water bodies, exposing aquatic organisms to higher toxicant levels

Complex Interactions between Climate Stressors and Chemical Pollutants

• Climate change and chemical pollution interact in complex ways, often exacerbating the impacts of each other on ecosystems
• Warmer temperatures can increase the toxicity of certain pollutants (pesticides) while also enhancing their breakdown and release from environmental reservoirs (soils, sediments)
• Extreme weather events (floods, storms) can mobilize and redistribute contaminants, leading to pulse exposures and contamination of previously unaffected areas
• Multiple stressors acting simultaneously (warming, acidification, pollution) can have synergistic effects, amplifying the overall impact on organisms and ecosystems

Ecosystem Resilience and Adaptive Capacity

• Ecosystem resilience is the ability of an ecosystem to withstand and recover from disturbances, including the combined pressures of climate change and pollution
• Ecosystems with higher biodiversity and functional redundancy are generally more resilient, as they have a greater capacity to adapt and maintain essential processes
• Chronic exposure to pollutants can erode ecosystem resilience by impairing the health and reproductive success of key species, reducing their ability to cope with additional climate stressors
• Preserving and restoring ecosystem resilience through pollution reduction, habitat protection, and sustainable management practices is crucial for mitigating the impacts of climate change and safeguarding biodiversity