Invasive species & climate change

Invasive species and climate change are considered the two largest threats to biodiversity, ecosystem function and human health. These two complex issues are interrelated and form a self-reinforcing “feedback loop” where each factor accelerates the other.

Climate change creates habitat for invasive species to spread, while these species disrupt ecosystem functions that would otherwise help mitigate global warming.

How Invasive Species Exacerbate Climate Change

Invasive species can directly increase atmospheric carbon dioxide and reduce the natural resilience of ecosystems.

• Reduced Carbon Storage – Invasive pests like the emerald ash borer (EAB), beech leaf disease and hemlock woolly adelgid (HWA) kill millions of trees, which are critical for long-term storage of carbon in ecosystems. Salt marsh carbon dynamics are affected by invasive plants and invertebrate species. Expanding populations of invasive green crabs undermine salt marsh stability and lead to carbon loss.
• Altered Fire Regimes – Some invasive plants, such as stiltgrass and phragmites, create dense, highly flammable monocultures. These result in more frequent and intense wildfires that release massive amounts of stored carbon into the atmosphere.
• Ecosystem Degradation – Invasive plants prevent or reduce tree regeneration, which can reduce carbon sequestration. Jumping (Amynthas) worms consume leaf litter, releasing carbon that would otherwise be stored in plants or soils, and can destroy native animal and plant habitats.
• Lowered Ecosystem Resilience – Invasives can reduce a habitat’s ability to withstand climate impacts. For instance, they may deplete water in drought-stricken areas or destroy lake, river or stream cover that provides essential shade to keep water temperatures cool.
• Increased Urban Heat – Invasive insects like the EAB have destroyed millions of urban ash trees that have provided essential shade for homes, parks, and roadways, exacerbating heat wave effects.

How Climate Change Facilitates Invasive Species

Climate change acts as a “threat multiplier,” making it easier for non-native species to establish and dominate.

• Range Expansion – Warmer temperatures allow species limited by cold winters – such as the HWA or burning bush – to move northward and into higher elevations, while native plants and animals are not able to compete as well or find new suitable habitats.
• New Introduction Pathways – The melting of Arctic sea ice is opening new shipping routes, providing direct conduits for aquatic and terrestrial invaders to hitchhike into previously isolated regions.
• Competitive Advantage – Many invasive species are “generalists” that adapt more quickly to shifting conditions (like earlier springs) than more specialized native species. High CO2 levels also favor the rapid growth of most plants, yet certain invasive plants are often better equipped to utilize the additional CO2.
• Weakened Native Resistance – Extreme weather events (floods, hurricanes, droughts) create disturbances that displace native plants, leaving “empty niches” that fast-spreading invaders like barberry or Himalayan balsam quickly fill.
• Reduced Control Efficacy – Climate change can make management tools less effective. For example, drought-stressed plants may absorb less herbicide, and warming can disrupt the life cycles of biological control agents (such as beneficial fungi or parasitoid insects) that normally keep invaders like the brown-tail moth or winter moth in check.

Featured image: Major interactions between non-native invasive species and climate change. Courtesy of the Northeast Regional Invasive Species & Climate Change Network.