NPCC News: UK Study - Riverbank physical structure that encourages native-dominated plant communities most effective for fighting invasive and noxious weeds

Native Plant Conservation Campaign News: To combat invasive non-native plants on riverbanks, create bank physical structure that supports native-dominated plant communities.

A UK study of degraded rivers confirmed that riverbanks whose structure (slope, moisture regime) favors native plant species produce landscapes that are more sustainable and resistant to harmful invasive plants.

Investigators examined characteristics of riverbanks dominated by invasive exotic plants vs. those dominated by native species. Some native-dominated sites appeared to be “immune” to colonization by invasive plants, even in areas directly adjacent to established populations of invasive non-natives. They found that riverbanks whose physical characteristics (slope, moisture content) supported native plants resisted invasion even when surrounded by populations of usually invasive non-native plants.

The authors suggest that these findings will be useful in designing more effective and sucessful restoration projects.

Mechanical (digging or pulling) or chemical (herbicides) eradication of noxious weeds and other invasive plants in aquatic systems is often not feasible or desirable because such methods are labor-intensive, and they produce erosion and/or chemical runoff into waterbodies. Also, these methods are often ineffective over the long term.

The online publication The Conversation’s report on the study notes that these findings are important because“ … there is a diverse range of freshwater habitats in the UK, which is good news not just for biodiversity but also the economy, where they are collectively valued at £39.5 billion. Rivers in particular are highly biologically diverse environments, home to a wide variety of plants, invertebrates and fish. But linked together within a river catchment, they are prone to invasion by alien species that can spread quickly between these interconnected habitats.”

Further, “Invasive alien plant species are of one of the biggest concerns to river environments. These contribute to the loss of native plants and invertebrates, as well as altering soil chemistry and impeding river flow. It costs the UK government around £1.7 billion to control invasive alien species”

The Conversation Article concludes “In 2018 Britain experienced one of its hottest, driest summers. Changing climate is likely to provide conditions which enable invasive alien plants to thrive along rivers. Hence, managing species in light of their environmental preferences is so important. Our study showed that a large abundance of dominant native plant species are more able to resist invasion ... So there has never been a better time to embrace our native species, even a river bank favourite such as the humble stinging nettle.”

This work supports the hyopthesis that rehabilitated native plant communities are more likely to resist degradation and invasions by non-native weeds if the physical conditions with which they evolved are created or restored.