Douglas Talmy, a University of Delaware entomologist and author of Bringing Nature Home: How to Preserve Wildlife with Native Plants and Nature’s Best Hope: A New Approach to Conservation That Starts in Your Backyard, has researched and written for years about the threat invasive species pose to native insects and wildlife habitat.
His work has shown that the transformation of native plant communities into landscapes dominated by imported species and grasslands endangers insects, especially caterpillars, as well as the birds and other animals that depend on them for their survival.
A paper he co-authored in 2020 reviewed research supporting the theory – which has had its detractors – that widespread displacement of native plant communities by non-native species is contributing to insect decline. He found that our long-standing fascination with ornamental plants over native plants degrades the local environment.
Japanese knotweed can grow 3 inches per day and reach 10 feet in height. Oriental bittersweet can climb up to 60 feet, strangling host trees. The tree of heaven can reach a height of 80 feet and reach a width of 35 to 50 feet. Glossy buckthorn can colonize undisturbed, and its dense foliage and ability to mature quickly allow it to easily outcompete native plants. Large stands of it can also produce conditions favored by deer ticks.
These four invasive species and most others have no natural predators to feed or kill them. The vast majority of native insects cannot eat or reproduce on these invaders – native plants and insects have co-evolved over thousands of years – creating a food desert for invertebrates and the birds and animals that stray from them. feed. They provide little support to pollinators.
Many of the worst invasive species strangling Rhode Island, such as bittersweet, knotweed, and glossy buckthorn, are no longer for sale, but the lack of diversity created by the state’s entire invasive species problem, including the continued sale of many intrusive plants, makes the local environment much less resilient, leaving it, for example, with fewer options to respond to the climate crisis.
The continued sale of invasive species is directly related to consumer demand, and Rhode Island’s landscape and nursery industry is meeting those needs.
Catherine Weaver, a RINLA board member and former president who owns a North Kingstown-based landscaping studio, said her clients often request miscanthus, also known as Chinese silver grass, a popular ornamental grass she called “a nuisance”. Invasive privet hedges are also in high demand by his customers. She called privet a “nasty invasive” and said she recommended using natives like pepper or viburnum instead.
“We have to prioritize environmental integrity over aesthetics,” Weaver said, “but we’re so used to using aesthetics to judge whether a plant is good. “is nice…but we have to use other criteria when making these decisions. We shouldn’t sacrifice ecosystem function for beauty. We can have both. There are so many beautiful native plants.”
Both Weaver and Brawley said the public needs to be better informed about the importance of native plants in creating more demand. They believe progress is being made on this front, albeit slowly.
“Five clients over the past year have requested mostly native plants,” Weaver said. “It had almost never happened before.”
However, not all non-native species are invasive. Invasive species are those which, reproducing outside their natural range, actively cause ecological or economic damage, depending on the Invasive Species Act 1996.
The exchange of species is natural, as there has always been drift – plants moving with the tides and seeds dispersed by birds and storms. Ecosystems change over time. Early humans brought hitchhikers with them on their migration. But comparatively, today’s invasive species levels are monstrous, due to increasing human globalization, including more than two centuries of importing ornamental plants from exotic places to show off wealth and later to track Jones.