Saturday, January 11, 2014

The Phragmites Invasion

Almost no matter where walk today, be it either in our yards or in a seemingly pristine state or national park, we are always constantly in the presence of invasive plant species. There is no escaping them. It’s like perpetually living in a horror movie. You spot one, try to get away by moving in the opposite direction, but no matter where or how fast you run, as soon as you turn round a bend, another one pops up, and then another, and continues this way for 3,000 miles from the east coast to the west coast. They’re as ubiquitous as the leaves on the trees. It’s quite intimidating, actually.
Despite their prevalence, many times they will go unnoticed, or if we can identify them and are aware of negative changes they deliver to an environment, we are apathetic due to their beauty, as is the case with many ornamental plants. One species that isn’t often praised for its beauty, is painfully widespread, and devours an ecosystem as readily as a swarm of locusts is a common and in a physical sense, dull reed. Phragmites australis, which undoubtedly everyone has seen at one point or another, is one of the most damaging threats to wetland and aquatic habitats today. They push out nearly all native species, both plant and animal, forming a dense and nearly impenetrable wall 10-15 feet in height that usually is measured in acres.

Where marshes or swamps were once relatively open and contained clumps of cattails, tufts of sedges just barely poking above the water that could be utilized to traverse the wetland by using them as a set of stepping stones, the occasional tree dotted here and there, and a rich array of wildflowers in all colors from the bright blue of the plebian forget-me-not to the scarlet grandeur of the aptly named cardinal flower, now in many cases these spots have been become so dense nearly everything has been eliminated. Biodiversity is wiped out and replaced by a monoculture of phragmites. Wetland species that were once rare before the invasion are declining at alarming rates as the reed continues to take a bite out of healthy habitats. The golden-winged warbler is one such species whose numbers have plummeted as a result of habitat alteration.

This reed with its prodigious biomass creation also has a tendency to rapidly fill in the areas which they inhabit. Small ponds can completely disappear and the total area of a wetland will shrink upon being colonized. After a stand has been cut down, and one walks out into the where the infestation once stood, there’s a spring to your step as you navigate a floating mat or island of dead phragmites several feet thick that has built up over the years. It’s no wonder that people of the past used reeds like these to construct rafts and thatch roofs.

It’s interesting to note that this invasive has been here for an incredibly long time (at least centuries), but no one can pinpoint exactly when or how it made it over here. It’s generally believed to be of Eurasian origin. Over the past few decades, for partially unknown reasons, the reed has been speeding up its hostile takeover.
There is also a native variety of phragmites, although its numbers have been diminishing as it is being replaced by its more aggressive cousin. Native phragmites typically is sparser and will not form stands as large as the non-native Phragmites australis.
Sites within the Hudson Valley have especially felt the effects of the invasive, having a large tidal estuary in the geographic center that is fed by many small, marshy tributaries—all prime habitat for phragmites. The Palisades Interstate Park Commission which manages large tracts of land in the region is beginning to fight back and has already begun implementing plans to remove the reed from already pre-established infestations, and perhaps more importantly, to slow its spread to other areas.

The most current project is being undertaken in the sensitive marshes of Iona Island, a part of Bear Mountain State Park in the Hudson Highlands. A couple notable species that call the mudflats home are the threatened saltmarsh aster, which has the largest population in New York at this location, and Needham’s Skimmer, a rare dragonfly that can only be found in a handful of brackish tidal marshes in the state. These species which almost entirely rely on this type of habitat feel the full force of the phragmites encroachment and are highly susceptible, as much of their preferred habitat has already been destroyed by development. Without a plan for remediation, possible extirpation is possible. For these reasons primarily, the marshes of Iona Island were the perfect candidate for remediation.

Over the years, various methods have been employed here but haven’t been especially successful. One of the most comical techniques employed has utilized a type of human “hamster wheel” to roll over and break the stalks. Machete hacking has also been used, but is an incredibly slow process that only offers a seasonal solution. Unless the roots are destroyed the plant will pop back up in full force the following spring.
In the late summer of 2013, the Park Commission turned to the use of herbicides to finally ensure a quick and complete eradication of phragmites. Using a tank-like, amphibious vehicle to gain access to the mucky environs, sprayers atop the vehicle went back and forth in long rows applying herbicide to the reeds, ultimately covering nearly 40 acres. Upon the death of the invasive the desiccated stalks have to be cut, bundled up, and removed.

Herbicide is only used as a last resort as it has the possibly to upset the delicate balance of the ecosystem. After a lengthy review process it was determined that this was the best route to protect the marsh’s biodiversity and prevent it from wholly succumbing to the influences of phragmites as the other methods weren’t working as hoped. The herbicide’s effectiveness is undeniable, however.
It is the goal of the Park Commission to each year spray a similarly sized patch, until ultimately the entire nearly 200 acre marsh has been covered. Spraying it in sections ensures the ecosystem has time to heal itself and will not undergo “shock” from a larger and more comprehensive treatment.

Another technique that may be tried in 2014 is to flood portions of the marsh by installing small flood gates on an outlet attached to a road that leads to island and bisects the marsh. A water level rise of only a few feet should be sufficient to drown the roots by keeping them perpetually submerged even at low tide.
West of the Hudson River, in the secluded interior of the Ramapo Mountains lies Sterling Forest State Park where phragmites is also a serious issue. At several scattered wetlands here the same herbicide measures are being undertaken to rid the reed. Sterling Forest is one of only a few places in southern New York that still has relatively abundant populations of the golden-winged warbler. Over the past decade numbers have been dwindling across the country and it may be designated as a “threatened” species in the near future if the trend continues.  Estimates have put the decline at around 7% annually.
These birds utilize wetlands and nearby forests for nesting sites. Surveys have shown that areas invaded by phragmites have little to no breeding pairs. Golden-winged warblers prefer sparser, natural vegetation, as do many other bird species.
The park is also home to the endangered northern cricket frog. While these frogs are confined mainly to one lake in the park, and surveys of many of the treated wetlands have not been able to document their presence, it is still possible that small remnant populations remain or that the creatures may return in the future.

Apart from the negative impacts phragmites dishes out, it does offer certain benefits. The reed’s expansive root system is helpful for controlling erosion and in low lying coastal areas the tightly packed stalks can help lessen the blow of storm surges. Furthermore, the red-winged blackbird is one of only a few species that actually thrives in the reed’s presence and utilizes the plants for nesting. It would be a grave error to stop eradicating phragmites for these few benefits, however. The negative side significantly outweighs the good. Protecting biodiversity and ensuring that ecosystems remain as natural as possible should be our number one goal.  Phragmites control gives other species, especially those that are rare, a chance of survival.

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