Our South Louisiana
wetlands have long been heralded as the most fecund ecosystem in the United
States, but these wild places of refuge are welcoming hosts to newcomers as
well as natives. Invasive species disrupt, destabilize, and potentially threaten
the vitality of the wetlands they depend upon and call home—for "invasive"
species are, in fact, making themselves at home, wherever they go.
For example, it has been
a century since our bayous became clogged with water hyacinths, thanks to the
World Cotton Expo of 1903. The Louisiana Works Progress collection
includes an archived photo of a steamboat struggling to traverse a hyacinth-blanketed
bayou in 1920. By the 1950s, the New Orleans Department of Public Buildings and
Parks was struggling to manually remove this choking "malodorous"
overgrowth in Bayou St. John, by the truckload, and the Sewerage and
Water Board, which was losing equipment in the battle, wanted nothing more than
to bury and cover the canals.
Today, the National
Park Service has an entire page dedicated to the water hyacinth, "a
GREAT invasive species but a challenging plant to control," although some may
disagree with labelling a stinking plant that has shut down canoeing in the
Barataria Preserve as "GREAT." On the other hand, Airboat
Adventures in Lafitte, Louisiana, prefers to praise the plant's
"stunning flowers" when sharing what is "iconic" in Bayou Barataria, before
moving along with the tour.
In recent years, talk
about invasive species in Louisiana wetlands is rapidly expanding from a quiet
behind-doors mutter among government agencies to a cry of alarm by the media
about the giant applesnail—the Pomacea maculata, or island applesnail,
to be specific. The island applesnail is a native South American freshwater
mollusk, but snails have long been a favorite tank-cleaner among aquarium
keepers, which is how they were brought to the U.S. Applesnails grow to be apple-sized
and are voracious, omnivorous eaters, so they do not perform as well as some
others, such as Nerite and Ramshorn snails, in aquariums. By the 1980s,
applesnails were being dumped. Thanks to this aquarium dumping, the applesnail
invasion was first discovered by U.S.
Fish and Wildlife in 1989 in Palm Beach County, Florida.
Now, according to the U.S.
Geological Survey, applesnails have spread to 76 hydrological units,
or watersheds, along the entire Gulf Coast: from Texas to Florida, and as far
north as the Mississippi, Atchafalaya, and Red Rivers confluence. In 2006, they
were first sighted in Gretna, Louisiana, in the Verret Canal, which is
connected to the Barataria Preserve by the Intracoastal Canal. By 2008, the
applesnail was popping up in ponds and bayous along Lake Pontchartrain's
Northshore. In 2012, applesnails were infiltrating pump houses and drainage
ditches around Lake Maurepas. By 2015, they had penetrated New Orleans's City
Park, where you will now find the edges of the park's isolated bayous littered
by piles of empty applesnail shells.
Such massive unburied
graveyards of applesnails might appear to indicate a holocaust. However,
applesnails are one of the most successful animals on the planet. According to
Dr. Phil Bucolo, an aquatic biologist at Loyola University New Orleans, they
are simply "outcompeting" all of their neighbors. Besides eating anything and
everything at their trophic level, they spend their lives submerged in water,
safe from predators, only emerging at dusk and dawn to lay eggs—and they are
According to a
2017 study conducted by a coalition of Gulf coast universities, just
one applesnail clutch holds an average of 1,500 eggs. Over a lifetime of three
years, a single snail may produce 54,000 eggs. Basically, even if a mere 0.01%
(or 1 in 10,000) eggs survives, a single snail will replace herself with three
to five offspring in her lifetime—and this number is probably an underestimate
of snails' reproductive rates in the southern USA, where warm weather means a
longer breeding period. Ultimately, every applesnail shell washed ashore
represents exponentially greater numbers of them in the water—and exponentially
more problems for the creatures competing with them for life.
There is no question
about the havoc applesnails are wreaking in South Louisiana wetlands. According
to the Louisiana
State University AgCenter, their consumption of both vegetation and
the eggs of amphibians in their habitats makes inhospitable waters for ducks as
well as fish—bad news for a state nicknamed Sportman's
Paradise. In 2020, South Louisiana's extensive applesnail
colony succeeded in decimating a 50-acre field of rice and shutting
down production in crawfish farms in three parishes. According to LSU's
sugarcane entomologist Dr. Blake Wilson, even the farms and harvests that were
not completely halted suffered "revenue reductions of as much as 50 percent."
Not only Louisiana's
wetlands, but the Louisiana coast itself is embattled. The applesnail devours
plants that hold together the coastline and transforms
clear water into turbid algae-infested waterways, or water that Dr.
Bucolo warns may host the kinds of dangerous algal blooms creating dead zones
in Lake Pontchartrain and at the mouth of the Mississippi River. As was the
problem with water hyacinths, applesnails seem to have the potential to smother
all other life in their eco-communities, causing a big stink—and they seem to
be collaborating with water hyacinths in that endeavor as their colonies grow.
In 2008, the invasive
species coordinator for the Barataria-Terrebonne
National Estuary Program, Michael Massimi, noticed that applesnails
were attaching eggs to boats traveling the Intracoastal Waterway, or "hitching
a ride on the superhighway" connecting previously uninvaded wetlands across the
entire Gulf coast. Water hyacinths also traveled, conveniently, via the
Intracoastal Waterway. Dr. Bucolo has noticed that applesnails seem
to be developing a preference for depositing their eggs on water hyacinths—which
always float above the water and will therefore keep their eggs dry, increasing
their likelihood of survival—rather than the wood and plant structures they
have preferred in the past.
are highly adaptive—even smart. We need to be smarter.
More often than not, in
Louisiana, where there are water hyacinths, there are applesnails. To outdoor
recreationists, this may seem a mere nuisance, if a problem at all. However,
these colonies present a growing threat to coastal and wetland restoration
projects as well as to the Department of Environmental Quality. For example,
the Riverbend Oxidation Pond, in St. Bernard Parish, part of the Coastal
Impact Initiative, is an essential source of fresh water to the
Poydras-Verret Wetlands, with the ultimate goal being reforestation of the
cypress-tupelo swamp that once thrived there. However, the water hyacinths and
applesnails are engaged in their own growth initiative, and since 2018, the St.
Bernard Department of Environmental Quality has struggled to control the invasion
at the Riverbend Oxidation Pond.
Water hyacinths cover the
surface of the pond, disrupting the natural cycle of oxidation; applesnails
clog the channels, blocking UV lights and slowing the flow of water. Jake
Groby, the Superintendent of the Environmental Department's Water &
Sewerage Division, reports that they must regularly manually remove the water
hyacinths, but the applesnails are a more complicated problem with no obvious
solution. The result of the applesnail infestation is that for the past two and
a half years, the Riverbend Oxidation Pond has been discharging
improperly treated waste (i.e., water with excessively high levels of
coliform bacteria) into the wetlands, just on the other side of the 40 Arpent
Dr. Chris Murray, a vertebrate toxicologist at Southeastern Louisiana University, says citizens should not be terribly concerned by these exceedances, as they are unlikely to enter the human water supply. However, Dr. Bucolo argues that vast devastating disruptions may occur within eco-communities in a three-year period, and that the potential combined impacts of the water hyacinths, applesnails, and discharge of waste that fails to comply with today's relatively lax environmental regulations warrant investigation.
Groby also asserts in an
email that, in St. Bernard Parish, the applesnails "are in the drainage system
as well from end to end … All parishes seem to have them." Beyond incurring the
malfunction and failure of the Riverbend Oxidation Pond, the applesnail colony,
then, presents a farther-reaching threat to health and restoration. Discharging
treated waste material into freshwater wetland systems has become a widespread
practice, not only as a part of the Central
Wetlands Assimilation Project, but throughout South Louisiana—a
practice pioneered and promulgated by scientists such as Dr.
Gary Shaffer, a wetlands ecologist at Southeastern Louisiana
When asked about how the
applesnail is impacting similar
operations with which he is involved in the Central Wetlands, Lake
Maurepas, Hammond, and Ponchatoula—all places identified as infiltrated by
applesnails—and what measures they are taking to control their populations and
protect these restoration initiatives, he was unavailable for comment. The
Louisiana Department of Environmental Quality was also unavailable for comment.
Groby believes that "the state has been caught off guard" by the applesnails
and the infrastructural problems they are causing. And no one has yet to examine
whether applesnails' clogging New Orleans's drainage system (along with the
water hyacinths) is related to pump failures and the noticeable increase in
flooding that started in 2017.
We need to be smarter.
Dr. Bucolo posed a
provocative question: How can we consider established populations invasive?
Without a doubt, these colonies are here to stay. Killing their massive
populations might prove to be even more deadly, just as one of Dr. Bucolo's
recent (yet-to-be-published) studies showed that chemically killing water
hyacinths rapidly depleted oxygen in the water and created a dead zone. Killing
is a solution that, simply put, only leads to more death—a literally bigger
stink—never mind that blanketing applesnails with salt or copper means adding
those elements to our freshwater environments, which may also add to the death
Every creature represents
a vital link in the great rhizome of life—most obviously, as a part of the food
web. But the applesnail has evaded natural predators such as the snail kite by
migrating to the Louisiana coast and wetlands. Many humans do find snails
appetizing, and applesnails are landing
on tables throughout the world, particularly in Asia, or in Cajun
homes—in cultures that are accustomed to living closely with and off the land.
Unfortunately, because of what applesnails are eating in our drainage systems
(rat feces), their populations in the Gulf of Mexico region carry rat lungworm,
a potentially fatal parasite. Fully cooking the snails before consumption kills
this parasite, but eating them, unless necessary for survival, is ill-advised.
As of now, our best
course of action is to suppress their reproduction before they fatally tip the
natural balance of the eco-communities that applesnails call home. Dr. Bucolo
encourages people to manually scrape applesnail eggs into the water, where they
are much less likely to hatch, whenever and wherever we find them: the
shorelines, piers, and boats in backyards and parks under their care. Farmers
may protect their crops by removing plants and structures that
applesnails might use to lay eggs from the perimeters of their fields. Local
governments may aggressively manually remove and reduce water hyacinth colonies
as a strategic defense.
In the meantime, some
people have even decided to profit from the invasion by collecting, cleaning,
polishing, and embellishing empty applesnail shells, for sale on Etsy. A local
poet collects them while kayaking in City Park and converts them into fun
little poetry-filled fortune cookies.
We certainly need to be
smarter, but nature may still prove to be smartest over time.
In Asia, carnivorous
ducks have been introduced to agricultural practice, thereby
reducing the applesnail population in those areas by 95 percent. However, such
artificial human introduction of new plants and animals to ecosystems often
means transforming creatures of beauty into "invasive species" when they
suddenly disrupt the intricate balance of local eco-communities. Fortunately,
other animals may adapt more quickly than we: The limpkin,
one of two avian applesnail predators, arrived and began breeding in Terrebonne
Parish, at Lake Houma, in 2018. And like the bright purple spring of the
hyacinth's bloom and the algorithmic appeal of applesnail shells, the limpkin
is an absolute cutie—an invisible tug on heartstrings—especially when spotted
passing, beak to beak, a feast of applesnails among friends.
Cover photo:The shells of dead applesnails litter the old bayou circumnavigating the interior of City Park in New Orleans, and their bubble-gum-colored clutches dot the water foliage, cypress knees, and decked overlooks in the park's Couterie Forest, where this photo was taken in October 2020. Photo by Michelle Nicholson.