Louisiana facing latest non-native threat
Science fiction abounds with disturbing narratives in which intentional introduction of seemingly benign or beneficial alien species to a new environment results in apocalyptic consequences.
Sadly, so does science non-fiction. A real-world example of this is playing out in Louisiana, where conservation scientists with the state’s wildlife, fisheries and agriculture agencies are scrambling to learn more about a newly arrived, nonnative organism causing significant damage to some of the most ecologically and economically important wetland habitat in the nation. They are downright frightened by the very real threat of intentional spread of the problem — a problem that easily could find its way to Texas.
It’s a situation in many ways echoing previous illconsidered introductions that have had significant negative effects on Texas’ native wildlife, fisheries, and habitat on which those resources and the people whose lives are enriched by them depend.
Earlier this year, huge swaths of phragmites in the coastal marshes of the Mississippi Delta began dying, drawing the attention of scientists as well as the area’s anglers, waterfowl hunters and others connected to the wetlands.
Phragmites, commonly called roseau cane, is a ubiquitous and crucial component of coastal wetlands. The finger-size stalks of the plant can reach more than 10 feet and often grow in almost monoculture stands that cover hundreds or thousands of acres.
Roseau cane is vital to those marshes and others along the Gulf Coast. The cane’s extensive root and rhizome systems create a latticework that holds and binds the silty marsh soil, preventing its erosion. The vegetation also traps sediment during high-water periods, accreting soil and actually building or raising land. This is hugely beneficial in coastal Louisiana, where extensive loss of wetlands has created a crisis, reducing the marshes’ ability to absorb and dampen storm surges as well as serving as the engine driving marine fisheries and providing habitat for tens of millions of resident and migratory birds and other wildlife. Without healthy marshes, coastal Louisiana faces a dire future. Thousands of acres lost
So when huge expanses of Mississippi Delta phragmites that should have been exploding with growth as spring arrived suddenly died, it triggered alarms and investigations.
What scientists found was frightening. Some areas of the Delta had suffered extensive loss of cane. On one wildlife management area in the lower Delta, 80 percent of the tract’s 110,000 acres were affected. As the expanses of cane died — and died quickly — the land beneath them almost immediately began eroding. Some areas were so severely affected that they’ve already converted to open water.
The culprit, scientists discovered, was a tiny insect. Originally termed “phragmites scale” for the scale-like crusting seen on affected plants, then “roseau cane mealy bug” for the translucent, flea-size insect creating the scale, the insect was eventually identified as Nipponaclerda biwakoensis, an insect native to China and Japan.
How the insect, which has been found nowhere else in the nation, came to find its way into the cane stands of the Mississippi Delta is unknown. What is known is that the insects are thriving and reproducing in the cane stands, boring into the stalks, and sucking the plant’s sap. The plants die quickly and en masse.
So far, the infestation and die-off is confined to areas at the far end of the Mississippi Delta. But it is spreading fast.
“The severity that the phragmites scale is having on the dominant vegetation of the Mississippi River Delta is severe. The rate at which it seems to be expanding and the severity of the impacts is alarming,” Louisiana wildlife and agriculture officials wrote in a briefing memorandum this past week. “The combination of the impacts from this new species combined with a tropical system has the potential to be devastating to the fragile wetlands and the wildlife in the lower Mississippi River Delta.”
Humans may spread bug
Louisiana and federal officials are scrambling to come up with a plan to address the infestation. While insecticides could potentially control or eliminate the insect, secondary effects of using the toxins could have equally devastating consequences, officials warned. And even if insecticides were effective against the invasive insect, the magnitude of the infestation and the expansive area involved would make it unfeasible and extremely expensive to use them.
And officials have another problem — one that potentially could become much bigger than their current issue.
Since news of the infestation has spread, officials have learned that some people — private citizens — are talking about gathering infested cane and transporting it to other areas of the state, where they plan to introduce the invasive “scale” in an effort to destroy stands of phragmites.
Why? Because phragmites can be a blessing and a curse in some coastal marshes. The cane creates thick, nearly impenetrable stands that can take over previously open areas of marsh, limiting access by waterfowlers and anglers and others who use the marshes. It doesn’t help that, in a strange twist, some of the phragmites species growing in coastal marshes are themselves non-native species considered to be a noxious invasive by many. What harm can there be in getting rid of a bothersome plant that might not even be native?
A lot. Phragmites may be a pain for some folks, but it’s a vital part of coastal marshes. Destroying it hastens destruction of the marsh in which it lives. The cane-killing insect doesn’t discriminate between native and non-native phragmites; it kills all of them. Also, Louisiana officials note they don’t know what other vegetation the roseau cane mealy bugs will attack and are begging the public to avoid intentional or unintentional spread of the invasive insect.
“Our message is very simple: Do not transport or transplant roseau cane,’’ Dr. Rodrigo Diaz, assistant professor in Louisiana State University’s Department of Entomology, said in a press release. “The scale that has invaded southern Plaquemines Parish could impact agriculture crops such as sugar cane and sorghum. It could have significant economic impacts to agriculture crops and native vegetation. So it is vital the cane not be moved.’’
If it is intentionally moved, bet on some of it being introduced to southwest Louisiana marshes, where stands of phragmites benefit and bedevil waterfowlers, anglers and landowners. The chance to be rid of roseau, consequences be damned, could well be too much for some people to resist.
If the invasive cane killer reaches southwest Louisiana, it certainly will find its way into southeast Texas marshes. The nymph stage of Nipponaclerda biwakoensis is tiny, swarms in large numbers on cane stalks, and is easily transported via wind or anything that touches infested plants, including birds, animals, boats and people.
If the roseau mealy bug invades Texas via intentional introduction and causes devastation of marsh systems, it will not be the first time humans have caused such selfinflicted wounds. Texas’ landscape has been bruised and its wildlife and fisheries diminished through a litany of such intentional introductions and spread of destructive non-natives.
The list is long. Feral hogs and feral cats. Nutria. Macartney rose, salt cedar and Chinese tallow. Water hyacinth and giant salvinia. Armored catfish and grass carp.
Best of intentions
Some of those introductions and their spread were — are — driven by avarice, some by ignorance. And some by the best of intentions. Texas inland fisheries managers in the 1970s introduced smallmouth bass to several reservoirs in the central region of the state, hoping the nonnative smallmouths would thrive and provide a recreational fishery in the rocky, clear-water lakes where native largemouth bass do poorly. The “smallies” did thrive in some waters. But they also hybridized with Guadalupe bass, the endemic black bass found only in Texas Hill Country streams. The result was that pure-strain Guadalupe bass, the official state fish of Texas, faced the very real prospect of disappearing. Texas has spent decades and millions of dollars in a continuing effort to undo the damage and secure the continued existence of Guadalupe bass.
There are consequences of introducing non-native species. Those consequences are almost invariably regretted. This makes for good science fiction. It makes for horrible reality.