By Bianca T. Esposito, NWNL Research Intern
(Edited by Alison M. Jones, NWNL Director)
NWNL research intern Bianca T. Esposito is a senior at Syracuse University studying Biology and Economics. Her research this summer is on the nexus of biodiversity and water resources. Her earlier NWNL blogs were: Wild Salmon v Hatchery Salmon and Buffalo, Bison & Water.
My 3rd NWNL blog on biodiversity compares papyrus in Africa and phragmites in North America. I will highlight both flora’s ecological benefits, ecological threats and impacts to water, as well as solutions to prevent their uncontrollable spread.
Papyrus (Cyperus papyrus) is a tall, aquatic perennial shrub, ranging from 8 to 10 feet in height. This invasive species rooted into the ground, bearing simple brown fruit with brown/cream/green colored flowers, forms floating islands in tropical African swamps, rivers and lakes. In non-native habitats, papyrus will spread and invade the space of other native plants unless pruned. Commonly known as the “Paper Reed,” papyrus is native to Egypt and Sudan along the Nile River in North Africa, a NWNL case-study watershed. Papyrus is now also found in two other NWNL case-study watersheds: along Ethiopia’s Omo River (where damming has stabilized water levels allowing roots to take hold) and Tanzania’s Mara River Estuary.
Papyrus in Uganda (Creative Commons)
Once a well-known resource for paper making, today papyrus has potential for biofuel production. Papyrus also has many ecological benefits. Its value ranges from assimilating significant amounts of carbon dioxide from the atmosphere to providing breeding grounds for fish species, and feeding grounds for grazing herbivores.
In its native habitat, papyrus lines bodies of water, serving as a filtration system for removing sediments, sewage, and heavy metals that pollute the water. However, papyrus poses ecological threats to introduced environments, such as Italy and the United States, after being imported for ornamental use. Since it is invasive, papyrus disrupts ecosystems, threatens the growth of the native species, and impedes the flow of waterways. Papyrus will continue to expand problematically in introduced ecosystems if temperature warming continues to increase.
Papyrus blooms in the Mara River Basin, Tanzania (© Alison Jones)
Major impacts papyrus has on non-native water ecosystems include: reducing native biodiversity by altering habitat; threatening the loss of native species; altering trophic levels; modifying hydrology; modifying natural benthic communities; and negatively impacting aquaculture and fisheries.
Solutions to prevent further papyrus spread into other ecosystems are the use of physical, biological, and chemical controls. Physically, we could cut down and rake up the shrub. Biologically, we could use a novel fungal isolate that releases a phytotoxin to inhibit the growth of papyrus. And chemically, herbicides are a successful method to control papyrus spread.
Woman collecting water in the Masurua Swamp with Papyrus in the background, Tanzania (© Alison Jones)
Phragmites (Phragmites australis) is a tall perennial grass that can grow up to 15 feet or more in height, with dense clusters of purple fluffy flower heads. Referred to as the “Common Reed,” this species is native to Eurasia and Africa. Our focus is on its impact in North America. Outside of its native habitat, phragmites is “cryptic invasive,” meaning that as this non-native species spreads within another native species’ range, it will typically go unnoticed due to its misidentification for the native species. Phragmites ideal habitat is marsh communities bordering lakes, ponds and rivers. Phragmites are present in the Columbia River Basin, Mississippi River Basin, and Raritan River Basin, the three North American NWNL case-study watersheds.
Phragmites on the Raritan Bay, NJ (© Alison Jones)
The ecological benefits phragmites provide include improving habitat and water quality by filtration and nutrient removal, serving as shelter for birds and insects, as well as providing food for sparrows. Phragmites also help to stabilize soil against erosion. In light of climate change, this species is beneficial because its accretion rate keeps up with rising sea levels for protection.
Phragmites benefit marsh lands because of their ability to take up 3x more carbon than other native plants. When there is excessive carbon in the atmosphere sea level rises and allows for more frequent and intense storms, so keeping phragmites could help better protect marshes from rising sea levels and erosion. Phragmites also help build up more soil below the ground compared to native plants.
Phragmites at sunrise in Norwalk, CT (© Alison Jones)
Some ecological threats phragmites pose are as follows. Since phragmites grow in thickets by shallow water, they can displace native wetland plants, alter hydrology, and block sunlight from reaching aquatic communities. Phragmites decrease plant biodiversity, causing declines in habitat quality for fish and wildlife. This tall grass can also pose a driving hazard, as it blocks road signs and views around curves. Phragmites can also be a fire hazard when dry biomass is high during its dormant season.
The Neshanic River, a tributary of the Raritan River Basin, provides an example of the threats of non-native invasive phragmites. Here, it grows without regard to competition by suppressing regeneration of native vegetation and limiting biodiversity in the area.
Phragmites with redwings blackbirds on Long Island, NY (© Alison Jones)
Some solutions to combat the threats phragmites pose are similar to the methods used to control papyrus. Methods used include cutting or mowing the tall grass, applying herbicides (such as Glyphosate or Imazapyr), and controlling the spread of this invasive plant with molecular tools and fungal pathogens. Additional solutions would be to burn the plant, excavate the area, cover the area with plastic causing suffocation, increase plant competition in the area, increase grazing by herbivores, or use of biocontrol organisms (such as insect herbivores) to combat the spread of phragmites.
Whether in Africa or North America, we can see how detrimental non-native invasive plant species can be to the health of an ecosystem. Although papyrus and phragmites both have some positive benefits, they overwhelmingly impact aquatic habitats negatively with their spread. Thus many have concluded that the best thing to do is limit spread with the solutions suggested above, rather than attempt complete eradication. In some cases, they can become “guest invasives,” welcomed for the services they do supply, especially for wetlands and riverbank stabilization which minimizes storm damage.