Non-native species: enemies or victims?

In recent years, the push has been vigorous in favor of native species.  The thinking is that they thrive better that introduced species and are more beneficial for the insects, birds and other wildlife that have evolved and adapted in the same geographic area.

Now, in the prestigious journal, Nature, 19 ecologists are contending we've dissed non-natives unfairly.

"Scientists who malign introduced plants and animals for thriving under favorable conditions seem to be disregarding basic ecological and evolutionary principles," say Matthew Chew, an ecologist and historian of invasion biology, and Julie Stromberg, a plant ecologist, with Arizona State University. Both are quoted in a press release. "Evaluating whether a species 'belongs' in a particular place is more complicated than just finding out how and when it arrived."

So maybe the non-native mock orange that served as a bird condo in winter wasn't so bad after all.

Although non-natives are often referred to as aliens and hitchhikers, the ecologists wonder if they shouldn't be called "abductees" instead, given the human factor in their transport.  The emerald ash borer from Asia didn't just pick up and decide to move to Detroit, where it was first detected in this country. Someone brought it.

The authors note that that assumptions that "introduced species" offer only deleterious impacts are misguided and "that human-induced impacts, such as climate change, nitrogen eutrophication, urbanization and land use change are making the native-versus-alien species dichotomy in conservation increasingly meaningless," the press release says.

In the end, the difference will surely hinge on whether a non-native species is simply co-habitating with other species and performing a service, or whether it has transgressed into the "invasive" arena, knocking out other native species and providing little benefit.

More from the press release:

Chew and Stromberg have studied the impact of the non-native species in riparian ecosystems, most particularly tamarisk trees in the Southwest United States. Introduced to control erosion, Chew and Stromberg consider its continued perception as a pest species, water consumer and invader overplayed, while research shows its ecological role and ecosystem services have been undervalued. They point to outmoded perspectives and continued deference to outdated science as playing strong roles in negative perceptions of the species and intensive investment in eradication efforts. Recent discoveries have found that tamarisk in fact provides nesting habitat for birds, including the endangered Southwestern willow flycatcher, and that regional water management and climate change increasingly favor tamarisk over once-common cottonwoods and willows.

While the introduction of non-native species was noted as early as the 1620s, by Sir Francis Bacon, the field of invasion biology arose as an ecological approach as recently as the 1980s and 90s, inspired by Charles Elton's 1958 The Ecology of Invasions by Animals and Plants. More recent appraisals of Elton's research and publications by prominent ecologists now prompt a call for a change, these authors believe: "Invasion implies so many values. We need to consider the impact of these terms and approaches and how they affect scientific perception, public perception, and in turn, decision-making in conservation and restoration management."