In February, Austin residents were treated to the smell of foul, fishy water emanating from their taps. For close to a week, Austin Water customers, many in the most urban of skyscraper and concrete settings, were directly impacted by an invasive species. The stinky water was caused by an infestation of zebra mussels inside a water treatment plant pipe that had been turned off for a couple of weeks where, in brief, the non-native mollusks perished and rotted. Described as striped and fingernail-sized, it’s hard to imagine such tiny things could wreak such big havoc on a major city’s water supply, but the funky smell and taste they created, that took more than a week to flush out of the city’s water system, did just that.
In a study from the University College of London published March 3, 2019, researchers reported that “alien species” (non-natives) are the “main driver of recent extinctions in both animals and plants,” finding that “of 953 global extinctions, 300 happened in some part because of alien species, and of those 300, 42% had alien species alone listed as the cause of their demise.” In addition to non-native mammalian culprits, the scientists noted the many intentionally introduced plants, such as ornamental plants for gardens that, once in place “start to spread and threaten the native flora and fauna around them.” Per the study: “alien plants are several times more likely than natives to achieve a maximum cover of at least 80%.”
From a fingernail-sized mussel to bright yellow roadside flowers to a 200-pound feral hog, invasive, non-native species in Texas run the gamut, as do the problems they cause. The following takes a look at just a few of the “alien species” that impact our state’s wildlife.
Bastard Cabbage
With its ethereal spray of delicate yellow blooms festooning Texas roadsides, it might be difficult to find offense in the roguishly named “bastard cabbage” but Rapistrum rugosum is nothing short of a villain when it comes to our native Texas wildflowers. Bastard cabbage grows from one to five feet, looming over bluebonnets and paintbrushes, basketflowers and winecups. As described by Lady Bird Johnson Wildlflower Center in their “How to Eradicate Bastard Cabbage“ article: “This invasive plant outcompetes our native wildflowers by blocking sun with its broad leaves, leaving some fields a complete monoculture of bastard cabbage.” While it is uncertain how bastard cabbage arrived in the U.S., it appears to be spread through contaminated grass seed mixes or mulching materials, according to TexasInvasives.org.
Zebra Mussels
As described by KUT, zebra mussels, originally from the Caspian Sea, “hitched a ride to North America in the ballast water of ships back in the ’80s and have been spreading through the continent ever since.” By attaching themselves to boats and other watercraft, zebra mussels have now “fully infested” fifteen Texas lakes, per Texas Parks and Wildlife Department (TPWD), in addition to the lakes that are “positive”, “suspect”, and “likely” for the presences of zebra mussels. The first infestation was found in Lake Texoma in 2009. While the Austin Water scenario is a showy, news-making impact of their invasion, the more common reality is they rob other small creatures in Texas waterways of food, depleting their populations, leaving the creatures that eat those other small creatures likewise starved. While the non-native invaders are powerful water filters, which may make for sparking clear water, it also means sunlight is now reaching deeper into lakes which could encourage plant growth (including invasive plant growth) and, in short, disrupt the entire ecosystem. For the latest zebra mussel updates, TPWD maintains an online “Zebra Mussel Threat”
European Starlings
The history of European Starlings in the U.S. began a poetic one. As part of a “plan” to introduce all birds mentioned in Shakespearian works to the country, about 100 were released in Central Park in New York City in 1890 and 1891. As described by the Texas Bird Atlas Breeding Bird Atlas, this “triggered an explosive expansion to an estimated population of 200 million birds spread across North America. The first starling was found in Texas in 1924, suggesting an almost exponential range and population expansion.” What’s the problem with these birds whose wings give them “a star-like appearance” and who, in summer, turn “iridescent purplish-green with yellow beaks.”? They pose a serious ecological threat. As described by the Texas Invasive Species Institute: “This recent and extremely successful arrival to North America is a fierce competitor with blue birds, purple martins, woodpeckers, and other cavity nesting birds. European Starlings often take over the nests of native birds, expelling the occupants. With so many starlings around, this causes some concern about their effect on native bird populations.”
Feral Hogs
Feral hogs have been on the tear thanks to early Spanish explorers over 300 years ago who brought them for sustenance. In the 1930s, “Russian boars” that were imported for sport hunting escaped Texas game ranches and began breeding with feral hogs.
According to TPWD’s feral hog data, “there is currently an estimated population in excess of 1.5 million feral hogs in Texas.” Feral hogs that wreak economic, environmental, and agricultural havoc. Per a CNBC report: “The U.S. Department of Agriculture estimates feral swine costs about $1.5 billion in damage annually, although experts at the University of Georgia suggest the cost maybe closer to between $2 billion to $2.5 billion. The damage to agriculture is estimated at just under $1 billion annually.”
In addition to their legendary fecundity, feral hog populations continue to grow thanks to their strength, smarts, and comfort with eating their young when the pantry’s bare. The solution to getting this porcine genie back in the bottle remains elusive. Feral hogs are hunted by land and by air, and we have previously written about a feral hog trap app but, thanks to their sometimes monstrous size, almost armor-like skin, and remarkable wiliness, guns and traps are often rendered useless. Attempts at a feral hog poison have generally proved too dangerous for other wildlife and the food chain.
If only the feral hogs would eat the bastard cabbage, zebra mussels, and starlings.
Photo of bastard cabbage, above, growing along Ranch Road 12 in Driftwood, Texas.
