Houston Matters

Here are 10 of the peskiest invasive species in Greater Houston

There are dozens of invasive species of plants, animals, insects, and shellfish in Texas that threaten native species and cause other environmental concerns.

Invasive Species
Images: Flickr & Wikipedia Commons
Numerous invasive species threaten the ecological systems and native species of Greater Houston and Texas.


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In Greater Houston, we’re used to people moving here from all over the country and the world for jobs and other reasons. And those newcomers can add to the demand for housing and add cars to the roads.

And while those are legitimate threats posed to the quality of life in the area, there are some other fairly recent arrivals to the region they are causing more life-and-death problems for the environment — invasive species.

Plants, animals, insects, slugs, fish, lizards, birds, mollusks, and more have come to our area from other parts of the world (either on accident or on purpose for one reason or another). But now they threaten the survival of native species by competing for resources and spreading disease.

In the audio above, Ashley Morgan-Olvera from the Texas Invasives Species Institute and Sam Houston State University talks with Craig Cohen about some of the most notable invasive species in Greater Houston and Texas.

Here Are a Few Invasive Species They Talked About:

Chinese tallow trees, an invasive species, make up about 80 percent of the tree canopy in Greater Houston, according to the Texas Invasive Species Institute.

1. Chinese Tallow – Some 80 percent of the tree canopy in Greater Houston is made up of Chinese tallow, Morgan-Olvera said. These trees are an ornamental plant brought to the United States in the 1700s. They average around 20 feet tall but can reach as high as 40 to 50 feet.

The plant is able to change the pH of the soil around it to make the ground hospitable only to it and other tallow trees. That and its deep taproot (allowing it to survive well in drought conditions) is how they’re able to quickly take over an area.

The invasive giant salvinia plant floats on the surface of water, depleting oxygen levels, killing fish, and depriving plants beneath it of sunlight.

2. Giant Salvinia – These aquatic ferns grow on the surface of the water, and Texas has no native species that floats like it. So, it can cover the surface of the water depleting it of oxygen and killing fish. It limits sunlight penetration, which kills other plants below.

The plant is originally from South America, and its Velcro-like leaves stick to things allowing it to be easily spread by boaters.

The invasive species Texans are probably most familiar with: the red imported fire ant.

3. Red Imported Fire Ant – This is probably the first invasive species that comes to mind for most Texans. They’re originally from South America and likely hitchhiked to Texas in potted plants.

This especially aggresive species is known to attack crops, lizards, birds, and, of course, humans if you disturb them. The greatest ecological concern they cause is the displacement of native ants.

Nutria are an invasive species prominent along the Gulf Coast.

4. Nutria – These large, dark-colored, semiaquatic rodents are everywhere, partly because they breed year round. They can cause great damage to rice and sugarcane crops.

In 2019, a documentary film called Rodents of Unusual Size detailed the role nutria play in the environment and culture of places like Louisiana and Texas.

MORE: Interview with filmmaker Quinn Costello

Black velvet leatherleaf slugs, originally from South America, can transmit parasites to mammals and humans if the parasite reaches the digestive tract.

5. Black Velvet Leatherleaf Slug – As the name suggests, these slugs are jet black with a matte finish. They have two black ocular tentacles on their heads and can grow up to 3.5 inches long. These natives of South America were first found in the Gulf states in the 1960s and often hitchhike to new areas in potted plants.

If you encounter one, don’t touch it. And, if you do, wash your hands thoroughly before touching your mouth. That’s becaue these slugs can transmit parasites to mammals and humans if the parasite reaches your digestive tract. However, the illness is not usually fatal to humans, but it can be bad.

Their second greatest threat is their insatiable appetite, making them a threat to many kinds of grasses and plants.

The invasive redbay ambrosia beetle can be destructive to trees, transmitting a fungus causing them to wilt and die within weeks or months, a fate known as laurel wilt.

6. Redbay Ambrosia Beetle – This dark-colored, bullet-shaped beetle is one of many wood-bourne beetles found around Greater Houston. They’re pretty small at 2 mm long when fully grown, but they can have a massive impact. They transmit a fungus to trees causing them to wilt and die within weeks or months, a fate known as laurel wilt.

The beetles threaten many kinds of trees, including avocado trees, which has a negative impact on agriculture.

They originate from Japan and southeast Asia and are often transported when people move firewood from one location to another.

7. Japanese Climbing Fern – This vine-like perennial from (you guessed it) Japan, eastern Asia and India, climbs over everything in its path and can reach around 90 feet in height. Its stems are green, orange, or black.

The greatest concern with this invasive is it can grow in dense layers as thick as 10 feet, smothering the native plants and trees beneath. And its presence can intensify fires, allowing flames to climb trees.

Asian citrus psyllids pose a serious threat to the citrus fruit industry because they transmit a bacteria that causes what's known as citrus greening disease to citrus trees.

8. Asian Citrus Psyllid – These small brownish insects are about an eighth of an inch long and can often be found feasting on the underside of leaves.

The most serious problem they cause is transmitting a bacteria that causes what’s known as citrus greening disease to citrus trees, which has caused scores of damage to the citrus industry across the country, including in the Rio Grande Valley.

The insect and the disease can be found in Harris County, which is why you might have seen notices about citrus quarantines. Once a plant has the disease it must be destroyed.

Argentine black and white tegu lizards are a growing invasive species in Texas as a result of the exotic pet trade and can grow up to 50 inches long.

9. Argentine Black-and-White Tegu Lizard – As the name suggests, this lizard is a native of South America first introduced to the United States via the exotic pet trade. They can grow up to 50 inches long and can reproduce very quickly. The area from Houston to the Piney Woods of East Texas makes a good habitat for them, and they feed on native species for their survival.

Red lionfish, originally from the western Pacific Ocean, have taken root in the Gulf of Mexico and threaten the health of coral reefs.

10. Red Lionfish – These striking red, venomous saltwater fish are originally from the western Pacific Ocean but have taken root in the Gulf of Mexico. Because of their venomous spines, they have no predators and so their numbers have taken off since being introduced in the Gulf, most likely through the aquarium trade.

Aggressive feeders, Red Lionfish can reach lengths of more than 17 inches and have threatened the health of coral reefs.

Source: Ashley Morgan-Olvera and the Texas Invasives Species Institute