Invasive Species: A Habitat Concern

By: Grace Choi

What do the common dandelion, the tall wild mustard, and the seemingly innocuous grey squirrel have in common?

You guessed it! (maybe…) 

They are all invasive species in Southern California. Often overlooked, invasive species are a staple in our surroundings, yet have tangible impacts on our native preserves and wildlife spaces. When encountering invasive plants, it is usually best to uproot and dispose of them completely, especially if you find them on your property or gardens. Animals such as the eastern grey squirrel are harder to get rid of, but there are still ways we can discourage their spread. Without further ado, let’s talk about some common invasive species here in Southern California, and what you can do to combat their colonization and proliferation.

Weeds: 

We’ve all seen these tenacious little survivors sprouting in the cracks of our sidewalks, parking lots, or any substrate with dirt or gravel. Some are immune to herbicides, and most are really, really good at growing nearly anywhere, making them hard to get rid of. Common strategies that weeds use are making their seeds “sticky” and far-reaching. This means using other vectors to transport their seeds into new places, where they can grow and outcompete native plants. Some weeds, like the burclover, use burrs that stick onto animal fur (or human clothes), while others, like the dandelions, use the wind as a vector to make their seeds go farther (maybe it's not such a good idea to blow a wish on a dandelion). 

Another strategy that weeds implement is flooding their surroundings with seeds. Weeds can produce a wide range of seeds each year, with some species producing hundreds, and others producing hundreds of thousands. To stop weeds from propagating, pulling them out by their roots is a good way to start. However, disturbing the plant could also shake free a few seeds, which is why pulling or cutting them when they are flowering is the safest way to make sure the seeds do not germinate. When passing areas with weeds, checking clothing and other materials for seeds will ensure that you do not become a vector to spread weeds to new areas. Finally, checking if plants are invasive in your area before planting them can control the spread of weeds.

Grey Squirrel:

The grey squirrel, commonly found in parks and gardens, is a California invasive species. Brought into America from the UK as gifts, grey squirrels were widely introduced to park areas across the United States, but outcompeted the native red squirrels, becoming an invasive species. To deter squirrels from your garden, you can spice up an existing bird feeder with cayenne pepper or other spicy bird seed blends. Refraining from feeding squirrels in the parks and making sure not to spill existing food, as well as sealing garbage cans, can ensure that the squirrels do not have a viable food source. 

Courtesy of New York Invasive Species

Zebra Mussel:

The zebra mussel is a lesser-known invasive species, but it has massive implications for the ecological systems it wreaks havoc on. Zebra mussels are freshwater invaders that have been brought in by ships and boats traveling through Eastern Russia and Western Europe in the 1980s. They multiply easily, consuming native zooplankton and therefore depleting the numbers of organisms higher up in the food web, as well as native mussels. Their waste can acidify and deoxygenate the water, all the while creating toxic byproducts that can render entire bodies of water uninhabitable. In fact, according to the Florida Fish and Wildlife Conservation Commission, zebra mussels are “considered one of the most impactful invasive species in the United States.” Aside from ecological concerns, zebra mussels also clog water filtration pipelines and power plants, causing millions of dollars of damage. Zebra mussel larvae are microscopic zooplankton and can be transported by boats.

Therefore, if you fish often, it is important to check your equipment and let it dry for five days before visiting another body of water. Spreading awareness about zebra mussels and the ease with which they can spread and decimate ecosystems and water systems alike can also encourage others to take measures to mitigate their harm.

There are many more invasive species in California, and learning about them can broaden our knowledge about how invasive species disrupt ecosystem functioning. There are common invasive species that we see often, like the ones we talked about today, but there are other species that are not given as much attention, such as bullfrogs, channelled apple snails, and purple loosestrife.