Invasive Species and Their Impact

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One of the biggest problems facing wildlife in South Florida, including the coastal marine ecosystems that surround it’s terrestrial ecosystems, is the presence of invasive species. Invasive species are most commonly introduced to new ecosystems thanks to human activity, both intentionally and accidentally/unknowingly, and they can be absolutely devastating to the environment. This week’s blog entry will focus on the concept of invasive species, some of the more notorious invasive species in South Florida, and what everyone can do to prevent the spread of invasive species.

What is an invasive species?
For a species to be considered invasive, it must meet two criteria (i):

1. It must be non-native or not naturally occurring in the area being discussed.
2. It must be harming or displacing one or multiple species of plants, animals, microbes, or other forms of life. This may include, but is not limited to, competition for resources, shelter, unnatural predation, and competition for a niche.

Can a species be considered non-native, but also non-invasive?
The answer is… yes! It is possible for non-native species to also be considered non-invasive, but that can change over time. A great example of a non-native species that’s also currently considered non-invasive in the Eurasian collared-dove (Streptopelia decaocto). Current studies indicate that Collared-doves aren’t displacing or pushing native mourning doves (Zenaida macroura) out of their normal ecosystems, but collared-doves have been rapidly expanding their habitat ranges for over a decade. (ii) This is probably due to the collared-doves ability to establish populations in suburban areas, and they are rarely (if ever) seen in forests. With that in mind, it will be important for ornithologists and conservationists to continue to monitor collared-dove populations, as well as the populations of similar species that they may displace in the future.

eurasian_collared_dove_1Eurasian Collard-Dove. Photo Credit: Cornell Lab of Ornithology

What kind of harm can invasive species cause?
“When we try to pick out anything by itself, we find it hitched to everything else in the Universe,” (iii) is one of the more famous quotes from iconic naturalist, John Muir. When invasive species are introduced to new ecosystems, the entire order of a system, including food webs and ecological roles of native species, can be thrown out of whack. (iii) After being introduced, invasive species lack natural predators, and unchecked populations can explode and expand rapidly. This creates a snowball effect in which the number of native species that are negatively impacted can grow very quickly. Effects of invasive species can ripple through entire ecosystems, causing native species to die off or relocate. The loss of biodiversity in an ecosystem can ultimately lead to a breakdown of the entire system. Certain invasive species can even drastically alter environmental conditions that determine what forms of life can inhabit a given ecosystem. For example, algal blooms can make bodies of water inhospitable for fish and invertebrates. (iv)


Burmese Python. Photo Credit: National Geographic

What are some well know invasive species in South Florida?

Cuban Tree frog, Osteopilus septentrionalis: These medium-sized grey-green amphibians most likely made their way to Florida as hitchhikers in storage/cargo. Cuban tree frogs threaten smaller tree frogs by competing with them for resources as well as preying upon and consuming them. (v)

Domestic Cat, Felis catus: We’ve discussed this before, but it’s important to remember that feral cat populations are continuing to grow in the United States. That means even more trouble for the birds and other native wildlife that are hunted by these super predators. It’s estimated that cats kill approximately 3.7 billion birds every year in the United States, and that number could continue to grow in the coming decades. (vi)

Burmese Python, Python molurus: The only real predators of these massive snakes are humans and alligators. This allows Burmese pythons to go unchecked while consuming native species, including endangered and threatened species. (v)

Green Iguana, Iguana iguana: Yes, we know that they’re cute. Yes, we know that they’re cool looking. But the harsh reality is that they can destroy gardens as well as consume plants that are integral to the survival of endangered insect species, such as the Miami blue butterfly. They can also steal burrows from burrowing owls. (vii)

Muscovy Duck, Cairina moschata: Muscovy ducks can transmit diseases to native water fowl populations as well as crossbreed with native duck populations. (v)


Lionfish. Photo Credit: National Geographic

What can you do to stop invasive species from spreading?
1. Before adopting an exotic pet, make sure to do your research. Many exotic animals require special care and lots of attention, especially birds.

2. Do not release exotic animal into the wild. If you have an exotic pet, but you are not able to properly care for it, then work to place the animal in a living situation that won’t negatively impact it’s quality of life.

3. Avoid providing food and other resources for invasive species. Deliberately providing food and nutrients to invasive animals can help them to outcompete native species. While you may find some of the invasive species listed above to be cool or interesting, helping them to survive negatively impacts the wildlife that is integral to the ecosystems of South Florida.

4. Stay informed on the latest ecological surveys of your local environments, and volunteer with nature conservation organizations.

5. Report sightings of invasive species to local environmental agencies such as the Florida Fish and Wildlife Conservation Commission.

6. This isn’t necessarily bird-related, but support the harvesting of lionfish! Lionfish are devastating reef communities in coastal ecosystems, but lionfish meat is now available in grocery stores. (viii)

Ian Martin, Education Coordinator, 2016


(i) United States Department of Agriculture: What is an Invasive Species?

(ii) Cool Green Science: Eurasian Collared Dove: Have You Seen This Bird?

(iii) National Wildlife Foundation: Invasive Species

(iv) Science Daily: Algal Bloom

(v) Florida Fish and Wildlife Conservation Commission: Florida’s Exotic Fish and Wildlife

(vi) American Bird Conservancy: Cats and Other Invasives

(vii) Tampa Bay Times: Florida’s iguana infestation

(viii) Sun Sentinel: Whole Foods Market selling invasive lionfish in Florida stores

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