A changing climate can help exotic plants escape gardens

Plants brought in by gardeners for horticultural reasons can turn invasive. Research published by an international team from the US, Europe and China finds that climate change could increase the competitiveness of non-naturalized species.

Usually, gardeners add exotic plants for aesthetic reasons, rather than ecological factors. Species that would not normally be found in a locality may need extra care and attention compared to local species that are already adapted for the climate. But what happens if the climate changes?

A gardener battling a hedge
Photo: Canva

Research by Haeuser and colleagues, published in the Journal of Ecology examines three categories of plants. Introduced garden plants, natives and alien residents. This last group are species that have been introduced, or escaped from gardens and since naturalised in their new habitat. They ran experiments in greenhouses to see how plants of these three categories reacted in simulated warmer environments. The greenhouses were set to provide an environment similar to what is expected for Konstanz, in Southern Germany, in the future.

What they found was that the most recent introductions could be worse off in the simulated climate, with flowering reduced. However, while there were problems for these plants, the two other categories did measurably worse, with the native plants slightly worse than the naturalised alien plants. The results mean that the newly introduced plants were effectively more competitive under the warmer, drier, climate than the plants already at home in Southern Germany.

Haeuser and colleagues say that their results show that it’s testing the combination of factors that makes their experiment important, as testing simply for reduced water, or higher temperatures alone can give different outcomes. They conclude that in future that it’s not just plants from climactically similar regions that could become invasive. Changes in rainfall, as well as temperature, will make the other side of the garden fence appealing to more plants.

See also this post on Emily Haeuser’s work at the Applied Ecologist’s Blog.

Reference List

Haeuser, E., Dawson, W., & van Kleunen, M. (2018). Introduced garden plants are strong competitors of native and alien residents under simulated climate change. Journal of Ecology. http://doi.org/10.1111/1365-2745.13101