Stemming the tide of invasive species

The second biggest threat to biodiversity in the world is human-caused biological invasions by introduced species (the first is habitat destruction in its many forms). Biological invasions represent an important facet of global environmental change, the unprecedented opportunity for accidental and deliberate human-aided dispersal of species to new environments. Untold numbers of plants, animals, fungi, and microbes that have evolved in relative geographic isolation are being introduced into new ecosystems across the globe through international trade and travel routes. Not every new species that is introduced will become invasive. Most species that escape are not successful in their new habitat, but some are well adapted to their new environment and have the bonus of having no natural enemies. Without anything the control its population, these species begin to multiply and spread rapidly, becoming invasive. In the process, invasive species take over and push out the native plants and animals that used to live (or feed, breed, etc.) there, oftentimes resulting in their extinction locally. In fact, 42% of the species on the endangered species list are there because an invasive species kicked them out of their habitat, and worldwide that number is 80%. The end result of a successful invasion is the homogenization of plant communities, often characterized by a single species exerting dominating the entire ecosystem.

It’s an expensive problem; the economic impacts of invasive species are roughly estimated to cost the US $138 billion a year, worldwide its $1.4 trillion (or 5% of the global economy). That’s spent on detection, chemical and manual control, loss of range and cropland productivity, decreased land value, increased threat from natural disasters (fire, erosion, and flooding), loss of recreational opportunities, and decreased water availability. Some are intentional introductions, plants and animals imported from other countries to be sold in the US that somehow escape captivity or disperse their offspring into the wild. Other invasions are accidental. Weed seeds, insects, fungi and bacteria can hitch a ride through nursery soil, contaminated seed or animal feed, on other plants or animals, on humans (or using our transportation), in the water or through the wind. Animals, such as the brown tree snake, can sneak onto overseas airlines. Marine invertebrates, like zebra mussels, can be released in harbors from ship ballast water. Many other animals, such as rodents, can hitch a ride on the ships themselves.

Humans have long had the habit of introducing new plants and animals whenever they traveled to new places. Humans tend to bring useful species, ones that can be cultivated or raised for food (some they like for less practical reasons), but other species can hitch a ride and arrive unnoticed, at least initially. As humans have learned to travel faster and farther, the rate of species invasions and their impact to our landscape has increased along with it. Globalization means that new species are being introduced everywhere in the world like never before. The US now has an estimated 50,000 known invasive species, and that number that is increasing rapidly. Some species become invasive quickly after being introduced to a new suitable habitat, other “sleepers” don’t become a problem until years after they’ve been introduced. Climate change models predict that global warming will allow many invasive species to expand their ranges. Because of all these factors, it’s difficult to predict which species will become pests, although scientists are creating better assessment tools for governments to use to screen imports.

What can one person do to stem the tide of invasive species? Here’s a list of some ways you can make a difference:

• Help control invasive species. Find a local community habitat restoration, land conservancy, park or watershed group that needs volunteers to pull weeds from your local creek or forest. It’s a great way to get some sunshine and exercise, and maybe learn more about nature while you’re there. You may even see a cool bird, some wildlife, or a rare wildflower, all who certainly appreciate you making more room for them.
• Be Fire and Flood Safe. Many invasive species, like Arundo and French broom increase the threat from floods and fires. Make sure your property is clear of weeds and plant appropriate alternatives, such as natives.
• Stop buying invasive species. Whenever you purchase any type of live plant or animal, find out whether it’s invasive before you bring it home. Plants in your garden can produce seeds that can travel miles and invade native ecosystems in your watershed or even beyond. Find a list of the invasive plants from your local Weed Management Area, then don’t plant them or remove any pests from your garden. Some types of beneficial insects can also be sources of invasions in some locations.
• Don’t transport invasive species. Its fun to bring back souvenirs from exotic locales, but don’t sneak stuff back that you shouldn’t, especially if it’s alive.
• Don’t dispose of stuff into waterways. Agricultural runoff, illegal dumping, and improperly disposed of aquarium water can all be sources of invasive species in our rivers, lakes, and oceans.
  
• Use your power as a consumer. Some known invasive species are still sold in the US. If you come across something you know is invasive, respectfully inform the retailer that you choose not to buy invasive species.