3: Biodiversity Threats

Section 9: Ecosystem Responses

3: Biodiversity Threats

Climate change poses a profound threat to global biodiversity—the variety of life at genetic, species, and ecosystem levels. Biodiversity underpins ecosystem resilience, providing essential services like pollination, nutrient cycling, and water purification. As global temperatures rise, biodiversity faces multifaceted pressures. Direct climate drivers include increased frequency of extreme heat events, altered precipitation patterns, and ocean acidification. These disrupt physiological processes, such as reproduction and growth, especially in ectothermic species (e.g., amphibians, insects) sensitive to thermal thresholds.

Habitat fragmentation and loss intensify these threats. Species requiring specific climatic niches (e.g., alpine or polar specialists) face compressed habitats as warming shifts optimal conditions poleward or upward in elevation. For example, Arctic species like the polar bear confront vanishing sea ice, restricting hunting grounds and triggering starvation. Similarly, low-lying coastal ecosystems (mangroves, salt marshes) are inundated by sea-level rise, reducing breeding sites for birds and fish.

Synergistic interactions with non-climate stressors exacerbate risks. Habitat destruction from urbanization or agriculture limits species’ ability to migrate toward suitable climates. Invasive species, benefiting from milder winters or disrupted predator-prey dynamics, outcompete native flora and fauna. Coral reefs illustrate this: warming-induced bleaching weakens corals, while ocean acidification impedes skeletal growth, leaving reefs vulnerable to invasive algae.

Genetic and functional diversity erosion follows population declines. Isolated subpopulations suffer from inbreeding depression, reducing adaptive capacity. Keystone species losses cascade through food webs—e.g., declines in seabird populations disrupt nutrient cycling between marine and terrestrial ecosystems. Phenological mismatches (e.g., flowers blooming before pollinators emerge) further destabilize mutualistic relationships.

Vulnerable groups include endemic species with limited ranges (e.g., cloud forest orchids) and those with slow dispersal rates (e.g., old-growth forest trees). Tropical regions, hosting high biodiversity but narrow thermal tolerances, risk disproportionate extinction rates. Climate velocity—the speed at which temperature zones move—exceeds many species’ migration capabilities, particularly in fragmented landscapes.

Ultimately, biodiversity loss diminishes ecosystem services critical to human well-being, including carbon sequestration (e.g., via deforestation-sensitive forests) and disease regulation (e.g., intact predator communities controlling vector-borne illnesses).