A stream of problems with aquatic invasive species was the topic at the Hill Country University Center last Thursday during the final Texas Water Symposium of the 2016-2017 series.
The free symposium — a partnership project of Schreiner University, Texas Tech University, Texas Public Radio and the Hill Country Alliance — considered potential costs of invasive species to native wildlife and infrastructure, approaching threats, and the most effective ways for Hill Country boaters, ranchers and landowners to protect waterways.
“Invasions of non-native plants, animals and parasites are regarded by biologists as a major threat to biological diversity and can have major impacts on water resources and economics,” said Tim Birdsong, ecosystem and assessment chief of inland fisheries of Texas Parks and Wildlife Department (TPWD) and moderator of the symposium. “They threaten the survival of native plants and animals, interfere with ecosystems and hybridize with native species.”
“They have created immediate threats to our river’s native aquatic flora and fauna, and threaten the productivity of the industrial and water supply infrastructure upon which our economy relies,” he said.
Invasive Arundo donax (giant reed or carrizo cane), Zebra Mussels and Hydrilla are among a host of aquatic plants and animals that compete with native animals and plants for food and space.
“Because introduced species lack natural enemies in waterways, they can multiply and spread at an alarming rate, interfering with boat traffic, affecting water quality and quantity and creating many other problems,” Birdsong said.
Panelists at the symposium reiterated that Arundo can spread if it’s mechanically removed.
“Arundo is one of those plants that can spread when it’s cut and can be spread with fire, so our only option is to treat it chemically,” said Rachael Ranft, director of Northern Hill Country river projects, The Nature Conservancy.
Some of the chemicals used to treat Arundo, such as imazapyr and glyphosate, can’t be done without a chemical license or permit from a trained professional.
“When you’re looking at a stream or river, chemical treatment can be really dangerous because you can harm other plant species, as well,” Ranft said. “So you have to be very careful.
Arundo doesn’t provide value to native plants, Ranft said, and it can form thick strands that reroute streams, suck water and become a fire hazard.
“It resprouts from its nodes, and there’s a node every six to 12 inches, so when you cut it, you can send fresh nodes downstream,” Ranft said.
Another way to control the invasive species is to introduce another invasive species, but that can produce a host of other problems.
“Biological control is incredibly expensive because you have to be absolutely certain that whatever organism you’re using to control your invasive plant is not going to harm something else,” said Robert Howells, fishery scientist and aquatic ecologist (ret.) for TPWD. “Imagine if the Arundo spray also attacked sugar cane or rice, that’d be a disaster. You need to know in advance if a problem would occur and that’s very time consuming and expensive to find out.”
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