Above: Purple loosestrife (Ohio Environmental Council), emerald ash borer (University of Maine), and zebra mussels (Texas Monthly).
By Katie Stannard
The names are hauntingly familiar, their impact devastatingly widespread: Dutch elm disease, emerald ash borer, purple loosestrife, zebra mussel.
Though winter is typically a planning time for the planting season ahead, it’s also an ideal opportunity for learning, as we turn our attention this week to the eco-implications of invasive species.
National Invasive Species Awareness Week—February 22–28—aims to shine a light on invasive species, their threats and impacts, and what can be done about them.
Asian giant hornet (University of Texas Dallas), frogbit (Lizzie Wilberforce), spotted lanternfly (City of Philadelphia).
While recent history points to the devastating impacts of the invasives noted above, there’s also concern ahead for new invaders such as frogbit, spotted lanternfly, and the Asian giant hornet (“murder hornet” in the popular imagination). Though invasives include insects, plants, pathogens, and other species, in our neck of the woods we focus largely on plant species. Join us as we pause our regular social media series this week to focus on this perennial topic.
Invasive or alien species—like the kudzu picture here—have evolved to be exceptionally adept at thriving under challenging growing conditions, spreading rampantly, and utilizing their special adaptive powers to crowd out other species or make it difficult for the native species to thrive. (Photo: United States Department of Agriculture.)
What is an invasive plant species?
The United States Forest Service (USFS) uses two key points to define an invasive species: 1) a non-native or alien species to the ecosystem under consideration and 2) whose introduction is likely to cause or does cause harm to human health or environmental health.
The thing is, invasive or alien species have evolved to be exceptionally adept at thriving under challenging growing conditions, spreading rampantly, and utilizing their special adaptive powers to crowd out other species or make it difficult for the native species to thrive.
How do invasive plants succeed? They often produce significant quantities of seed, do well in poor or disturbed sites and soils, and are spread by wind, birds, or unwitting humans. Some have tenacious root systems that may spread readily and extensively from a single plant. These roots may outcompete other plants—or may smother them or their roots. Even more intriguing—or dastardly—some invasives are allelopathic, producing chemicals which impede the growth of nearby plants.
Japanese knotweed (pictured above; Scottish Invasive Species Initiative) is a super-aggressive invasive with wildly tenacious roots.
For these invaders, their native habitats include key factors which keep them under control. Those might be soil, fungal, or other predators or ecological conditions. For example, in the northeastern United States, Japanese knotweed is a super-aggressive invasive with wildly tenacious roots. Even the tiniest bit of root fragment floating downstream can re-grow an entire colony. Yet in its native Japan, growth is held in check by soil fungi and plant diseases.
Implications of invasive plant species
Invasive plants vie with native plants for basic needs like nutrients, sunlight, soil, moisture, and growing space. They degrade ecosystems by limiting plant diversity, soils, and habitat for wildlife and insects. They can contribute to erosion, devalue agricultural fields, and impact recreation.
Importantly, invasive species affect endangered or threatened species. According to the USFS, invasives are the primary cause of decline for 18% of threatened or endangered species, while factoring in the decline of 42% of endangered and threatened species. For the whole gamut of invasive species (not just plants), invasive.org estimates yearly economic losses in the United States alone may be as high as $120 billion.
If that all sounds like a lot of doom and gloom—–it is! But, knowledge is power, and information is key to putting invasive species in their place–or getting them out of the wrong places! As the USFS notes, “Invasive plants are everyone’s problem. Spread the word, not the invasive plants!”
Some easy recommendations include the following:
Plant native species
Learn about invasive species