“Fasten your horticultural seatbelts.” That was the gist of what Dr. Bethany Bradley told me when I interviewed her for my podcast last month. Dr. Bradley is an invasion ecologist at the University of Massachusetts Amherst. She studies how ecosystems react to human-driven changes, in particular the interaction of invasive species (primarily plants) and climate change. Her point was that as serious as the impact of invasive plants have been on our natural areas to date, climate change is likely to bring far more profound problems.
That shouldn’t be surprising. Invasive cheatgrass has already increased the violence and frequency of wildfires in the American West; flourishing during wet seasons, it produces lots of biomass which dries to serve as fuel during droughts. Japanese stiltgrass could theoretically have a similar sort of effect in the East.
Another too-common woodland invasive, Japanese barberry, still sold in Connecticut nurseries (By Opioła Jerzy (Poland) – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=791935)
Climate change enhances the impact of existing invasive plants by disrupting ecosystems that may already be struggling. A warming climate can impair the growth of cold-adapted native plants, opening opportunities for further infiltration by the current crop of invasives. What’s more, according to Dr. Bradley, it may also help to transform exotic plants that have been non-invasive up to this point into more aggressive spreaders. That’s because a large proportion of the foreign plants introduced into northern gardens come from warmer regions where the species diversity is greater and so the plant hunting is richer. Such southerners may have been held in check by a cooler climate when introduced into northern regions of North America. As the climate warms, however, that brake will be released.
Gardeners, who are responsible for introducing a disproportionate share of invasive plants, can, according to Dr. Bradley, play a role in ameliorating this situation. If we began to cultivate native plant species from our own southern regions, we could assist in what is likely to become a natural process, the migration of the southern native flora northward. Essentially, we would be spreading the seeds of a healthier ecosystem adaptation. Our focus on such southern species could also cause local nurseries in the north to stock such plants. That could lead even ecologically unconcerned gardeners to take them home and unwittingly do their part.
Yes, there is a growing understanding of the need to accommodate the inevitable change in vegetation that results from climate change. In this recent article in Yale Environment 360, even dedicated invasion biologists such as Daniel Simberloff and Doug Tallamy are ready to accept to such changes in vegetation. https://e360.yale.edu/features/native-species-or-invasive-the-distinction-blurs-as-the-world-warms?fbclid=IwAR1xdM5dEfHSEStY3tff4fh6rUUruvpVudpCSDcXrDY0SPSS35mi2Ibj8OU
“Other experts question whether climate-displaced species should be characterized as unwanted intruders at all. University of Tennessee biologist Daniel Simberloff and University of Delaware entomologist Doug Tallamy, for example, point out that species on the move under their own steam will likely be readily distinguishable from the disruptive alien species introduced into new habitats through global trade and travel.”
Garden Rant can play an important role in getting this information into the hands of home gardeners because that’s its audience. Many members of the general public still believe that 1491 is the standard for where plants “belong.” Here in the San Francisco Bay Area, Monterey pines are being destroyed that are native less than 150 miles down the road, despite the fact that there is fossil evidence they lived in the Bay Area in the distant past.
All is panic for the present, but ecosystems have been changing since the first archaebacteria appeared in the new seas. If they were sentient, would they have despaired at the first lowly blue-green algae to evolve? Yes, its a crisis, but bare ground demands growth and life and some new things will triumph.