Georgian Court University

Space Invaders: Hunting for Aliens on New Jersey’s Coastal Dunes

(Citation: Wootton, LS. 2002.  Chance Conversation Plants the Seed for NJ Sea Grant Research Project.    The Jersey Shoreline.  Winter 2002. pp. 12-14. )

Its nearly 100 degrees outside.  Heat is pulsating up from the sand, adding to that beating down from the summer sun above. To make things worse, the wind is blowing out of the west, carrying every biting fly in New Jersey to the area of dunes where my four dedicated student interns (Katy Bevaart, Audrey McGough, Jason Ondreika, Purvi Patel), the occasional student volunteer (Courtney Rella, Sheetal Patel, Anna Shipman) and I (Dr. Louise Wootton, Biology) are sitting counting plants and wondering how and why we all managed to get ourselves into this project. 

So why are four students, an occasional volunteer and one rather fraught professor traipsing over sand dunes clearly labeled “Keep off the Dunes” in the height of summer?  

The answer to that question starts with a conversation between myself and Dr. Susan Halsey, director of New Jersey’s Sea Grant program several years ago. 

“Louise.  What do you know about Carex kobomugi?” Susan asked.   “Carex what?”   I answered. “It’s commonly called Asiatic Sand Sedge” replied Susan, “and they’re talking about digging it up with a backhoe at Sandy Hook. Does that sound like a good idea?”  

As I’m always looking for good projects to get my students involved in research, I went home and started to look into what was known about the species.  It was a pretty short search, since the answer was “not much”!  I found a couple of papers describing the first observations of the species in New Jersey, speculating that it had been accidentally introduced to North America approximately a century ago when shipwrecks released plants used to pack Oriental porcelain onto New Jersey’s shores. I also found some reports from Cape May’s plant materials labs describing its dense foliage and disease- and trampling-resistance and their efforts make use of these properties by developing a strain of Carex kobomugi to be planted alongside native dune grasses to stabilize sand dunes. 

Times however have changed a great deal since then, as scientists and managers have become uncomfortably aware of the problems caused by exotic plants (think purple loose strife or Phragmites!).   This changing perception, combined with a concern that Asiatic sand sedge was expanding in New Jersey, meant that Carex kobomugi suddenly went from a species being cultivated for release on dunes, to being listed as one of New Jersey’s “top 10 most unwanted plant species” and one the State’s coastal parks were now working to eliminate.  What became clear to me, though, was that these management strategies were being implemented in the absence of much solid information on the spread rates and ecological impacts of this species. 

So it was, with the help of a grant from New Jersey Sea Grant and matching funds from Georgian Court’s faculty summer research program, that my four interns, some volunteers and I set out to map all of the Carex kobomugi beds in Island Beach State Parks, so we could compare the bed sizes with those in a survey carried out in 1985 by NJDEP.  We also set up quadrats within and outside each bed and counted the number and types of plants present to get a sense of how Carex impacts the abundance and diversity of other plants on the dunes.  Last, but not least, we set out to see how successful the management strategies currently being implemented by the parks have been. 

To avoid the peak heat we tumbled out of bed and onto the dunes at dawn and mapped and counted until heat or flies drove us home. We were blessed at both Island Beach and Sandy Hook with the help of a group of fabulous park rangers and officials.  At Island Beach the park crews grew accustomed to fielding many phone calls and complaints every day about “those people who are walking all over the dunes”.  Every morning we were greeted by the cleaning folks and other rangers with cheerful cries of “Good morning, dune people!”  Park rangers kept their eyes peeled for Carex and made sure that we found all of the beds that were there. And so it was that we slowly hiked the entire length of the park mapping, identifying and counting the plants we saw… for a total of some 23 acres of Carex beds and over 100,000 plants counted.  Then it was on to Sandy Hook and a similar number of Carex beds and plants to map, but the added luxury of park ranger, Jeanne McArthur, who was kind enough to ferry us out to some of the more distant areas of the park. 

So what did we find?  To be honest, the data hasn’t all been crunched yet.   However the data we have looked at so far tells an interesting, and somewhat alarming story.  Relative to the 1985 survey in IBSP, the number of Carex beds has increased more than 300%, and the total area covered by more than 400%. Indeed, looking at the few available data points from earlier years, it’s clear that the species is expanding exponentially within our coastal dunes.  Moreover, not only are there more acres of sedge on the dunes, but in those beds present in both our study and in 1985, stem densities of Carex have increased by 55%, implying that the plants are becoming more vigorous over time. 

What does this mean for other dune species?  To some extent Carex is colonizing back dune areas in which other dune species do not thrive.  However, numbers and diversity of other species within Carex beds were generally lower than those in comparable plots just outside those same beds, suggesting that the expansion of this species is significantly impacting the ecology and diversity of coastal dunes.  Since some of the other species within the dunes, like wormwood, and sea beach amaranth are endangered or at least “Species of Concern” in New Jersey, expansion of Carex on our coastal dunes may create serious problems in the future if allowed to continue unchecked. 

The question, then, is how to control or eradicate this species?  As mentioned at the beginning of this article, managers at Sandy Hook had initially proposed removing the sedges using a backhoe and a sifter. A small pilot project was attempted in North Gunnison, but the species rapidly returned in the treated area, probably because its roots routinely reach depths of more than1.2m, a fact that also precludes manual removal. Restrictions on chemical use within federal parks have thus meant that SHU has currently postponed further treatment of their C. kobomugi population pending future management recommendations.  

By contrast, IBSP started an eradication program for C. kobomugi in 1999, with four beds treated to date. Treatment in that case involves tightly controlled applications of Roundup® to individual C. kobomugi, hopefully sparing other species of plants.  This protects native species and leaves them in place to protect the dunes from erosion.  Counting the number and types of plants in treated and untreated beds we were able to show that this strategy does effectively spare non-target plants. The problem is that, in all cases, even repeated herbicide application failed to completely eradicate C. kobomugi. This suggests that, to actually eradicate this species from the dunes, a more aggressive application of herbicide may be needed.  Such a strategy would be likely to kill everything in the area.   Moreover, from what we’ve seen, it is likely that even such an aggressive strategy would require multiple chemical applications over time to be effective.  During that time the defoliated dunes would be vulnerable to erosion, resulting in flooding and damage to ecosystems and property currently protected by the dunes. 

The logical solution to this problem might be to change our management goals from eradication to prevention of further expansion of the species. Then, hopefully, strategies such as those currently employed at IBSP could be used to reduce and control existing stands. How effective such a strategy might be strongly depends on how Carex propagates itself. Existing literature suggests that the species grows only from runners, not from seeds.  However, another of my students, Michael Cerrato, has been working on this question for his honors thesis research.  His results suggest that this species will indeed grow from seed, if those seeds are grown at high enough temperatures.  This finding means that controlling the spread of Carex is likely to be much harder than it would have been if the seeds were indeed infertile. 

As you can see then, finding an effective management strategy for this species that won’t hurt the dunes themselves isn’t going to be simple. What’s also clear, however, is that we can’t spend too much time thinking about what to do about this species, since the longer we wait, the more of it there will be, making its removal increasingly difficult and making the removal itself increasingly damaging to the dunes and the communities that they support.