Invasive species are a big problem

What do these things have in common: Bermuda grass, feral hogs, red imported fire ants, common clover, and feral cats and dogs? They are invasive species.

Invasive species are species that have been introduced into the ecosystem, either on purpose or accidentally, whose spread changes the ecosystem in such as way that wildlife, plants, and even people can be adversely affected. Also, not all introduced species are considered invasive.

About 7,000 invasive species inhabit the U.S. In Texas, we have seventy-nine plants, ten mammals, four birds, seven fish, eleven insect, and eleven mollusk and crustacean species considered invasive. I got out my calculator and did the math. That’s 122 invasive species in our state. As the second most biologically diverse state in the U.S. (Who beat us?), with 340 species found no place but Texas, invasive species can definitely pose a threat to our ecosystem.

The exact cost to the state has not been calculated, although the U.S. spends $137 billion annually combating invasive species.

Introduced species become a problem when they begin to populate outside their intended range due to a love of their new environment, lack of predators and diseases. While native species are busy staying in balance with their neighbors, these new species go wild, literally. This can affect the biodiversity of the region, jeopardizing the survival of native species, as well as changing the environment itself. Salt Cedar, for example, was introduced in West Texas as a wind break and stream bank stabilizer. It worked, but they have overtaken native plants, as they are water hogs and can recover from fire quickly. They provide little food for native wildlife.

We can place blame everywhere for the rise of invasive species. Point to agriculture for the introduction of plants for forage. Point to science for bringing in predators of invasive species that, in turn, became invasive themselves. Point to ourselves. Has anyone ever dumped a dog or cat onto the side of the road? How about dumping an aquarium?

The Eurasian water milfoil was originally an aquarium plant dumped into the water, and has since become an obnoxious weed that chokes out natives. Using nonnatives in landscapes has brought many invasives into the country. Consider these: Chinese Wisteria, introduced from Asia in the early 1800s, overtakes just about everything, including homes. Believe it or not, we have an American wisteria that we should grow instead.

Elephant Ears are a taro plant eaten in Asia that were brought here in 1910 as a substitute crop for potatoes. They found fame as an ornamental. They have invaded wetlands and lakes. (please don’t eat your Elephant Ears.)

English Ivy grows up the side of many a home. It came from Europe way back in colonial times. It can climb 90 feet, engulfing trees and anything else in its path. It also harbors Bacterial Leaf Scorch, which is harmful to elms, oaks, maples and other native plants.

Other invasive ornamentals include Heavenly bamboo (Nandina domestica). Safer versions of this species are firepower nandina, harbor dwarf nandina, and Gulf Stream nandina; and Pampas grass, used as an ornamental and wind barrier, forms dense stands that become fire hazards.

One of my favorite trees, the Chinaberry tree, is invasive. It came from Asia around the mid-1800s. These are fast growing trees with dark green, lacy, fern-like leaves. Their leaves can alter the soil pH. Their yellow berries are poisonous.

To help combat the spread of invasive species:

• Buy native plants, and wildflower seed mixes from a reputable native seed dealer.

• Clean your boat after leaving the water.

• Don’t dump fish bait.

TPWD is focused on two major invaders:

• Chinese Tallow tree–introduced in 1970 as a landscape plant has overtaken 30,000 acres of Galveston County.

• Giant Salvinia–the top aquatic invasive plant management priority of TPWD is capable of doubling its population in as little as two to eight days.

Our own resident master naturalist, Rusty Thomas, is the Milam County representative for Texas He has documented several invasive species growing along our roadsides.

Good websites to check out are:, texasinvasives. org,

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2010-08-26 digital edition

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