A new study published in the Proceedings of the Royal Society B (Biological Sciences) adds weight to the idea that an animal’s origin is less important than behavior and function in an ecosystem.
The study compared the effects of native white-tailed deer and “alien” wild pigs on forests in the eastern United States. Researchers examined forest inventory data along with large-scale camera-trap monitoring and found that the presence of deer resulted in reduced abundance of native tree seedlings and an increase in invasive plants. In contrast, wild pigs did not have a significant effect on the number of native plants but– in a result that surprised researchers– pigs in a forest reduced the number and variety of invasive plants.
The researchers believe that the different effects are due to the animal’s feeding behaviors. Deer are selective feeders; they prefer to eat native plants and avoid (often invasive) plants that are less appetizing. Wild pigs, on the other hand, eat a wide variety of native and nonnative plants. The study mentioned Japanese stiltgrass and Chinese tallow, two invasive plants that deer avoid but wild pigs either eat or disturb when they root in the soil for food.
(The study noted that the effects are context dependent, and vary with temperature, precipitation, the presence of humans, etc.)
Jens-Christian Svenning, one of the study authors, summarized the findings: “This study shows that we need a more nuanced discussion about biodiversity and ecosystem management. A species’ impact on ecosystems does not mainly depend on whether it is native or non-native, but on what it actually does in nature.”