Crayfish and Climate: how invasive species amplify aquatic GHG emissions

Since their introduction to European waters in the 1970s, the invasive red swamp crayfish Procambarus clarkii has rapidly expanded due to traits such as rapid reproduction, high environmental tolerance, and opportunistic feeding. P. clarkii can significantly transform freshwater ecosystems, causing extensive reduction in plant coverage, predation on amphibians and other macroinvertebrates, and a decline in native crayfish species populations. In many systems, the expansion of P. clarkii has lead to a dramatic reduction in plant coverage at specific sites. While numerous studies have explored how climate change influences the spread of invasive species, little is known about the reverse relationship: how invasive species contribute to climate change.

As a country with an extensive network of freshwater ecosystems, the Netherlands provides an excellent opportunity to study the effect of invasive species on aquatic GHG emissions. More than half of the Dutch territory has already been invaded by crayfish, with detrimental effects on submerged plants. Additionally, ditches serve as significant hotspots for GHG emissions, with estimates suggesting they are responsible for approximately 10–16% of the Dutch national annual CH₄ emissions. These estimates are largely based on measurements in ditches dominated by submerged plants, which have been shown to mitigate CH₄ emissions through mechanisms such as CH₄ oxidation and reduction of CH₄ formationLoss of submerged plants can therefore lead to a considerable increase in CH₄ emissions, further exacerbating the impact of ditches on the national GHG budget.

By combining data on ditch CH₄ emissions, the area invaded by P. clarkii, and results from a controlled mesocosm experiment focusing on the cascading effects of crayfish on submerged plants and GHG emissions (particularly CH₄), we found that high crayfish densities (2 individuals/m²) increase CH₄ emissions by 2.4 times compared to systems without crayfish. This effect seems primarily driven by plant clipping and bioturbation

These findings highlight the ecological and climatic consequences of P. clarkii invasions. By enhancing CH₄ emissions, this invasive species not only disturbs local aquatic ecosystems but also contributes to global climate change. Understanding the effects of crayfish bioturbation is essential for developing targeted management strategies to mitigate their environmental impact.