INVASIVE SPECIES AND THE SALISH SEA

Welcome to the Homogocene, Issue 16, Summer 2022

European Green Crabs. photo courtesy of Washington Department of Fish & Wildlife

INVASIVE SPECIES AND THE SALISH SEA:

Welcome to the Homogocene?

Issue 16, Summer 2022

Deb Rudnick, Ph.D., Guest Managing Editor

Table of Contents is below this intro

“What’s in a name?” a famous bard once asked. Invasive species is a complicated ecological term and can also be a confusing one. I’m not sure we’ll undo the complication in this issue of Salish Magazine — but we’ll dive into it in this issue, and hopefully resolve some of what can be confusing.

For ecologists and resource managers, invasive species are those organisms which are introduced into a new habitat, survive and thrive in that new habitat, and go on to have measurable impacts on wildlife, ecological processes, human health, or some or all these things. As we will explore in this issue of Salish Magazine, there is even more to the concept of invasive species. Let’s start by unpacking that definition a bit further.

If you want a weird and interesting connection between Shakespeare and invasive species, check out the effort to introduce all the birds mentioned in Shakespeare’s writings to the US!

Purple varnish clam. photo courtesy of WDFW

When we talk about invasive species, we are typically describing a species that has ended up somewhere else because it’s been helped to get there by people. But organisms move all the time! How is humans moving other species around any different from other natural process, like a storm that blows new seeds onto an Island, or a parasite that travels on a bird to find a new host? The difference is not so much the mechanism; whether it’s people who are the vector, or other species or climate events, it is helping things move from one place to another. Other species hitchhike rides in our cars or boats or planes or bodies, and people can also intentionally spread plants as in the lore of “Johnny Appleseed”.

What is very different about human-facilitated movement of other species is the rate at which we move species around the world, and the ways in which we can help species overcome barriers of space and time that otherwise would make them much less likely to end up in that new place. For example, crab larvae sucked into ships’ ballast water in an estuary in Europe, can be rapidly moved across an entire ocean and deposited in a North American estuary with a similar salinity and temperature so that those larvae survive their trans-Atlantic trip. Or snakes on a plane (not just a bad movie!) can end up on an Island formerly devoid of snakes. Or, to reuse an earlier example, Johnny Appleseed was spreading apple varieties far and wide in North America. People are incredibly good at intentionally and unintentionally moving species around. We are so good at it that we are introducing species globally at rates orders of magnitude higher, and at far greater distances, than many of nature’s other processes can accomplish.

photo courtesy of Pexels

It’s the pace and frequency of those processes that lead to what some ecologists have dubbed “ecological roulette” — keep throwing new species at an ecosystem, and not everything is going to survive, but some will. And some of those will thrive. And some of those will thrive by being able to eat a lot of the things that are in their new ecosystem, or by growing faster than the plants that are already there, or because the other organisms that would have eaten or infected them in their home ranges don’t live in their new environments.

Complicating matters still further, habitat fragmentation, climate change, stormwater impacts, and many other human impacts can create new conditions that can be favored by pioneering invasive species. And, in creating and sustaining many of these impacts, it can certainly be argued that humans themselves behave as an invasive species in our ecosystems. Arguably — and I think our authors would say, hopefully — the difference lies in our ability to recognize, repair, and shift this role in our relationship with the other members of our ecological community to be less invasive and more collaborative and caring of the other species with which we share the Salish Sea.

If invasive species repeatedly outcompete, consume, and cause declines of native species, will this lead us to what some scientists have referred to as “the homogocene”: the global mixing of species facilitated by human actions that contributes, along with other stressors, to a decline in biodiversity throughout many ecosystems, including the Salish Sea? It can feel as though we are in the midst of large-scale ecological experiments of seeing what happens when we add new species to ecosystems, and puts us in the middle of many complex choices about how to prevent, control, and manage invasive species with limited resources.

European green crab. photo by by Jonathon Hallenbeck

Invasive knotweed. photo courtesy of Washington Invasive Species Council

English Ivy on Cedar. photo by John F. Williams

The eight articles in this issue address many of these different ways of viewing invasive species. The Table of Contents below links to each article.

There are many examples of invasive species which have measurable impacts on our Salish Sea ecosystems, as Chase Gunnell and Leah Robinson describe for European green crab, and Justin Bush and Tara Galuska investigate in terms of impacts all the way up the food chain to Southern Resident Killer Whales. But we do ourselves a disservice if we simply label introduced species as bad, and unquestioningly target all introduced species for control. Humility in the face of complex ecosystems should keep us asking if a new species is measurably problematic, and even if so, whether the cure might be worse than the disease, as Melissa Fleming investigates with the arrival of the green frog in Kitsap County. We are also facing new challenges in defining invasive species as climate change drives new shifts in species’ distributions—and even making us question whether humans might need to directly intervene and help species at risk through methods like assisted migration, as Paul Heimowitz explores.

Invasive species can also be looked at through a lens as being another species in the world trying to get by. While we recognize the harm that many of these species can do to upend established relationships in an ecosystem, they’re also doing what life does, in persisting and adapting in new environments. We can hold these thoughts simultaneously, and even find the humor and the beauty in invasive species’ persistence, as Diane Moser and Lauren Clark illustrate in their poetry.

As Skye Pelliccia points out, taking the long view of respecting the history that many of our native Salish ecosystem species have together, managing and reducing the impacts of invasive species in the Salish Sea ecosystem can be an act of stewardship, and even reparation. As Sarah Lorse describes, we can each make choices that support healthy relationships and minimize impacts of invasive plants, even in our own yards. And we can bring entire communities together in a common goal, as Douglas Crist shows us on Bainbridge Island with the formation of a Cooperative Weed Management Area that has multiple community groups and organizations collaborating to steward and restore the ecological health of their open spaces.

Join us as we apply many different lenses to looking at the complicated role of invasive species in the Salish Sea ecosystem.

Issue 16, Table of Contents

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