Key Concept

Invasive Species

Non-native plants or animals that have the tendency to spread and cause damage

Invasive species are non-native species that have the tendency to spread and cause damage to the environment, economy, or health. These species are typically introduced by humans outside of their natural distribution intentionally or by accident. As non-native (also referred to as “exotic” or “alien” species, or more conversationally as “weeds”), they may not have natural controls on their distribution, such as predators, and will gain a competitive advantage over peer species to dominate an area. When such disruptions occur, it can reduce ecosystem biodiversity, decrease ecosystem stability, and have dramatic and sometimes rapid transformative effects on landscapes. See full Wikipedia entry here.

Classic examples of invasive species include:

Spartina alterniflora: This cordgrass native to North America, was introduced to China along coastal mudflats in the 1990’s to control erosion. It out-competed local grass species almost entirely, and spread quickly over hundreds of square miles of beach and estuarine habitats.

Cane Toad: This voracious insectivore was introduced to Australia in 1935 to help control beetle populations that were damaging crops. The toads – which are poisonous to pets and other animals – have expanded into the millions throughout Australia and beyond, causing stress on the ecosystem by and reducing food sources for other insectivores.


On LandTalk, observers often note the presence of invasive species in their backyards and in recreational areas. Observers identify several impacts, including reducing human safety, disrupting or shutting down recreational activities, reducing the sense of beauty, and increasing the effort required to maintain a landscape.

Search LandTalk for invasive species.

Lake Travis, Austin, Texas, USA

Species: Hydrilla
Impact: Recreation safety

3:03 “One of the problems actually was like an invasive species and this was in lake Austin that had come in, and I’m not sure if this was directly correlated with the drought but it was happening at the exact same time. I think it was called hydrilla or duckweed and it was a problem because it would grow really big and it was really like a thick leafy, like underwater plant and it would like get caught in boat propellers and also people swimming, it would like get caught around their legs. And so it was a safety hazard.”

Lake Travis, Austin, Texas, USA: In this video, Chris Fernandez, a resident of Austin, talks about the change in water levels at Lake Travis, a beautiful, lively lake to the northwest of Austin. Chris talks about the horrible drought that affected southern Texas when he was in junior high and high school.


Lake Murray, La Mesa, California, USA

Species: Hydrilla
Impact: Recreation completely eliminated

1:35 “Well, in the late 70s, they believe someone dumped a personal aquarium into the lake, which caused the growth of a very invasive weed called Hydrilla. And the weed was so feared that they worried it would spread to all the other reservoirs and waterways in San Diego. So, they completely shut down Lake Murray, and it was shut down for all recreational activities. It was shut down as a, you know, beautiful, pristine reservoir, and it was just neglected and closed up. They closed gates for entrance. You couldn’t even jog around it anymore.”

Lake Murray, La Mesa, California, USA: Lake Murray is a lake within San Diego County. It has been shut down for years, and I got my Mom's opinion on the issue. She has been a resident of this area for 40+ years.


University Park, Maryland, USA

Species: Ornamental ivys, creepers, and bamboo
Impact: Effort to prevent spread

7:43 “Our town makes an effort to use native plants in landscaping, and they encourage people to, you know, plant trees, like they give a subsidy if your tree falls down to plant another one. So there’s a lot of beautiful, both native plants and like cultivated plants, but there’s also a lot of things like poison ivy and English ivy and Virginia creeper and bamboo, which are more invasive species that were fashionable to plant in the ’30s. And I wish they never had because I’m still yanking them up to this day.”

University Park, Maryland, USA: My mother describes how commercial development and other factors have made living in the University Park area easier. Furthermore, she discusses the influence of American and foreign students at the University of Maryland as well as of urban development and the introduction of bird diseases in the past twenty years and invasive plants in the past ninety.


Canyon Lake, California, USA

Species: Exotic plants
Impact: Presumed effect on native plants

1:41 “You know, we’ve also seen kind of a rise in home prices in the area. Change of flora in the area. As more people are moving in, spending more on their houses, they’re bringing in more exotic plants that could certainly be affecting the local surrounding landscape.”

Canyon Lake, California, USA: The audio highlighted the changes to the region, which were primarily a result of popularity and increased human population. The city became a bigger hotspot for young people wanting to get into watersports, which changed the average age and property value of living in the city. With that, changes like more people and infrastructure resulted. However, some of the main strains remained the same, such as the local small wildlife.