Rethinking Phragmites
by Judith S. Weis, PhD,
The common reed, Phragmites australis, is an invasive species in tidal marshes and is frequently removed (generally with toxic herbicides) and replaced with native Spartina alterniflora (cordgrass) during restoration projects. Most people around Accabonac and elsewhere in the US dislike Phragmites and would prefer to have it removed.
The species actually is native to the US, with the native form comprising a minor part of the high marsh. A new form—a different genetic variety—arrived some decades ago and proceeded to “take over” many brackish and freshwater marshes and reduce the diversity of plants in the marshes.
We first started paying attention to this plant in the late 1990s when a controversy was brewing in New Jersey’s Hackensack Meadowlands. A developer planned to fill in a huge area of reed marshes to build a mall, and some environmental groups opposed it. The company argued that the marshes were useless and filling them would do no ecological harm. We looked into the science that was known at that time to see if it really was “useless” and found there weren’t many studies, but they indicated that fish in the tidal creeks of Phragmites marshes in New England and Chesapeake Bay were about as abundant and diverse as in cordgrass marshes, which clearly contradicted what the developer was saying.
Aquatic Animals biodiversity and abundance
So we undertook a number of studies to look at the estuarine animals in the Meadowlands marshes and their relationship with Phragmites and Spartina. In behavioral studies in large aquaria, with one plant species on one side, the other species opposite, and a bare area between, we put various animals into the bare area and, after an hour, counted how many went to the reeds side vs. the cordgrass side. All tested species—grass shrimp, fiddler crabs, and killifish—chose both plants equally. In tanks with only one species of marsh plant, we studied whether either plant provides better protection for grass shrimp against its predator, killifish. We put grass shrimp into tanks with reeds or tanks with cordgrass. After giving them time to acclimate, we put killifish in and waited an hour to see how many shrimp got eaten—again, no difference.
These studies were in lab aquaria—which may not be the same as in the “real world”—so we did field experiments in the Meadowlands. Fortunately we found a perfect place for our studies—a tidal creek with cordgrass on one side and reeds on the other. Sampling on both sides yielded comparable numbers of animals. Other investigators have found that fish assemblages tend to be similar in Phragmitesand S. alternifloramarshes or less dense in the Phragmites. However, one small, abundant fish, Fundulus heteroclitus(killifish or mummichog) are reduced in Phragmites marshes. Adults are typically equally abundant and spawn in both, but larval and small juveniles are consistently less abundant in Phragmites. However, ribbed mussels and fiddler crabs are comparable in both types of marshes.
We also investigated invertebrates (mostly worms) living in the mud on both sides of the creek and numbers were comparable though somewhat more abundant on the reeds’ side. However, small invertebrates that live on plant stems were denser on cordgrass than on reed stems
Food value for aquatic animals
Another important ecological role of marsh plants is that their detritus (decaying dead material) is a source of food for many animals. We took decaying plant material from three types of sites: Spartina, Phragmites, and restored Spartina from the Meadowlands, and from the same types of sites in Accabonac (this was back when Pussy’s Pond had new Spartina restored). We wanted to see if there was a difference in nutritional value between different types of plants and also between Meadowlands plants (that were contaminated) and Accabonac plants (that were clean). All six types were ground up, aged, and then fed to fiddler crabs and grass shrimps. They all provided equal nutrition to support survival and growth of fiddler crabs but were uniformly inadequate for the grass shrimp, which apparently need some animal food in order to survive. All the shrimp were dead by three weeks on this diet. We concluded detritus from reeds does support certain aquatic food webs.
Terrestrial Animals and Plants
Bird use of Phragmites varies depending on bird species, geographic location, stand architecture, and other available plant species (Spartina spp. or Typha). Some birds clearly prefer Phragmites. There is little information on reptiles and mammals, with examples of both negative and positive effects of Phragmites. Phragmites-dominated habitats support diverse biota. Studies comparing the density of individuals or the numbers of species in reeds and alternate plants show variable results. Reeds apparently support fewer individuals or species of some mammals and birds, such as muskrats or three species of high salt-marsh breeding birds. It appears that extensive, dense beds of tall reeds support fewer species of breeding birds than do smaller beds—those with reeds and a mixture of other plants, sparse stands, and stands with patches of Phragmitesinterspersed with pools or clearings.
Many different organisms use Phragmites. In most cases it is not known whether these interactions are beneficial or detrimental to the species.In some cases, Phragmitesappears beneficial: roosting birds, songbirds eating seeds during migration or winter, animals taking refuge from flooding in high reed stands above the surroundings, and small mammals like cottontails hiding in reed stands. In other cases, Phragmitesappears detrimental: colonizing and shading turtle-nesting sites, and displacing short plant species in the high salt marsh
“Ecosystem Services”: Pollution
With regard to pollution, we studied the uptake and distribution of metals in Phragmites and Spartina and found that while both plants took up metals from the sediments at comparable rates into their roots, the Spartina plants sent more up into the stems and leaves from which they were excreted back into the ecosystem, while Phragmites sequestered the metals better in the roots, which kept them away from the rest of the ecosystem. Reeds are also better at sequestering a variety of other pollutants, including nitrogen and carbon dioxide. Phragmitesmarshes are capable of removing large amounts of nitrogen from surface waters and are effective in taking up nitrogen from the soil, due to the greater biomass of Phragmitesrelative to other plants, preventing the nitrogen from causing algal blooms.
Ecosystem Services: Coastal Resilience
Studies have shown that Phragmites causes a marsh to elevate more rapidly than Spartina. Therefore, many restoration projects have included removing some amount of the marsh surface after removing the reeds and before replanting cordgrass. This practice no longer makes sense in this age of sea-level rise. Phragmitesbuilds and stabilizes tidal marsh soils, and stores carbon in litter and soils more effectively than SpartinaThus, Phragmitesmay protect tidal marshes from erosion associated with sea-level rise, as well as helping to mitigate global climate change. At this time of climate change and accelerating sea-level rise, a plant that enables a marsh to increase its elevation much more rapidly should be valued, not destroyed.
Some people dislike reeds because they grow tall and dense and block their view of the water. Think about storm surge and sea-level rise: which sort of plant would you prefer to have in front of your coastal property—one that is dense and tall or one that is short and sparse?
Case in point: Piermont Marsh is up the Hudson River. New York State had set aside over $1 million to “compensate” for the environmental damage the new Tappan Zee Bridge construction would cause. The DEC proposed using most of that money to eradicate Phragmites in the Piermont Marsh. Community residents opposed the removal because they felt the dense reeds had protected their neighborhood from devastation by Hurricane Sandy. The Department of Environmental Conservation (DEC) and the Palisades Interstate Park Commission (PIP), after the outcry from Piermont residents and officials, announced that they would develop a revised “Piermont Marsh Restoration Plan” which would alter the original plan that called for the eradication of 200 acres of existing Phragmites.
Phragmites supports many plants and animals and performs valuable ecosystem services. Therefore, the general assumption that this plant degrades marshes should be re-thought by marsh managers now, when we are concerned about resilience and sustainability. We should shift our approach from attempted eradication everywhere to modification of stands to create habitat for particular species while retaining nonhabitat ecosystem services.
Because Phragmitescan provide substantial ecosystem services, as well as being an invader, it requires a management approach that is tailored to individual sites and management goals An approach that requires killing it everywhere is impractical, expensive, causes damage to sensitive species, and wastes resources.by Judith S. Weis, PhD,
The common reed, Phragmites australis, is an invasive species in tidal marshes and is frequently removed (generally with toxic herbicides) and replaced with native Spartina alterniflora (cordgrass) during restoration projects. Most people around Accabonac and elsewhere in the US dislike Phragmites and would prefer to have it removed.
The species actually is native to the US, with the native form comprising a minor part of the high marsh. A new form—a different genetic variety—arrived some decades ago and proceeded to “take over” many brackish and freshwater marshes and reduce the diversity of plants in the marshes.
We first started paying attention to this plant in the late 1990s when a controversy was brewing in New Jersey’s Hackensack Meadowlands. A developer planned to fill in a huge area of reed marshes to build a mall, and some environmental groups opposed it. The company argued that the marshes were useless and filling them would do no ecological harm. We looked into the science that was known at that time to see if it really was “useless” and found there weren’t many studies, but they indicated that fish in the tidal creeks of Phragmites marshes in New England and Chesapeake Bay were about as abundant and diverse as in cordgrass marshes, which clearly contradicted what the developer was saying.
Aquatic Animals biodiversity and abundance
So we undertook a number of studies to look at the estuarine animals in the Meadowlands marshes and their relationship with Phragmites and Spartina. In behavioral studies in large aquaria, with one plant species on one side, the other species opposite, and a bare area between, we put various animals into the bare area and, after an hour, counted how many went to the reeds side vs. the cordgrass side. All tested species—grass shrimp, fiddler crabs, and killifish—chose both plants equally. In tanks with only one species of marsh plant, we studied whether either plant provides better protection for grass shrimp against its predator, killifish. We put grass shrimp into tanks with reeds or tanks with cordgrass. After giving them time to acclimate, we put killifish in and waited an hour to see how many shrimp got eaten—again, no difference.
These studies were in lab aquaria—which may not be the same as in the “real world”—so we did field experiments in the Meadowlands. Fortunately we found a perfect place for our studies—a tidal creek with cordgrass on one side and reeds on the other. Sampling on both sides yielded comparable numbers of animals. Other investigators have found that fish assemblages tend to be similar in Phragmitesand S. alternifloramarshes or less dense in the Phragmites. However, one small, abundant fish, Fundulus heteroclitus(killifish or mummichog) are reduced in Phragmites marshes. Adults are typically equally abundant and spawn in both, but larval and small juveniles are consistently less abundant in Phragmites. However, ribbed mussels and fiddler crabs are comparable in both types of marshes.
We also investigated invertebrates (mostly worms) living in the mud on both sides of the creek and numbers were comparable though somewhat more abundant on the reeds’ side. However, small invertebrates that live on plant stems were denser on cordgrass than on reed stems
Food value for aquatic animals
Another important ecological role of marsh plants is that their detritus (decaying dead material) is a source of food for many animals. We took decaying plant material from three types of sites: Spartina, Phragmites, and restored Spartina from the Meadowlands, and from the same types of sites in Accabonac (this was back when Pussy’s Pond had new Spartina restored). We wanted to see if there was a difference in nutritional value between different types of plants and also between Meadowlands plants (that were contaminated) and Accabonac plants (that were clean). All six types were ground up, aged, and then fed to fiddler crabs and grass shrimps. They all provided equal nutrition to support survival and growth of fiddler crabs but were uniformly inadequate for the grass shrimp, which apparently need some animal food in order to survive. All the shrimp were dead by three weeks on this diet. We concluded detritus from reeds does support certain aquatic food webs.
Terrestrial Animals and Plants
Bird use of Phragmites varies depending on bird species, geographic location, stand architecture, and other available plant species (Spartina spp. or Typha). Some birds clearly prefer Phragmites. There is little information on reptiles and mammals, with examples of both negative and positive effects of Phragmites. Phragmites-dominated habitats support diverse biota. Studies comparing the density of individuals or the numbers of species in reeds and alternate plants show variable results. Reeds apparently support fewer individuals or species of some mammals and birds, such as muskrats or three species of high salt-marsh breeding birds. It appears that extensive, dense beds of tall reeds support fewer species of breeding birds than do smaller beds—those with reeds and a mixture of other plants, sparse stands, and stands with patches of Phragmitesinterspersed with pools or clearings.
Many different organisms use Phragmites. In most cases it is not known whether these interactions are beneficial or detrimental to the species.In some cases, Phragmitesappears beneficial: roosting birds, songbirds eating seeds during migration or winter, animals taking refuge from flooding in high reed stands above the surroundings, and small mammals like cottontails hiding in reed stands. In other cases, Phragmitesappears detrimental: colonizing and shading turtle-nesting sites, and displacing short plant species in the high salt marsh
“Ecosystem Services”: Pollution
With regard to pollution, we studied the uptake and distribution of metals in Phragmites and Spartina and found that while both plants took up metals from the sediments at comparable rates into their roots, the Spartina plants sent more up into the stems and leaves from which they were excreted back into the ecosystem, while Phragmites sequestered the metals better in the roots, which kept them away from the rest of the ecosystem. Reeds are also better at sequestering a variety of other pollutants, including nitrogen and carbon dioxide. Phragmitesmarshes are capable of removing large amounts of nitrogen from surface waters and are effective in taking up nitrogen from the soil, due to the greater biomass of Phragmitesrelative to other plants, preventing the nitrogen from causing algal blooms.
“Ecosystem Services”: Coastal Resilience
Studies have shown that Phragmites causes a marsh to elevate more rapidly than Spartina. Therefore, many restoration projects have included removing some amount of the marsh surface after removing the reeds and before replanting cordgrass. This practice no longer makes sense in this age of sea-level rise. Phragmitesbuilds and stabilizes tidal marsh soils, and stores carbon in litter and soils more effectively than SpartinaThus, Phragmitesmay protect tidal marshes from erosion associated with sea-level rise, as well as helping to mitigate global climate change. At this time of climate change and accelerating sea-level rise, a plant that enables a marsh to increase its elevation much more rapidly should be valued, not destroyed.
Some people dislike reeds because they grow tall and dense and block their view of the water. Think about storm surge and sea-level rise: which sort of plant would you prefer to have in front of your coastal property—one that is dense and tall or one that is short and sparse?
Case in point: Piermont Marsh is up the Hudson River. New York State had set aside over $1 million to “compensate” for the environmental damage the new Tappan Zee Bridge construction would cause. The DEC proposed using most of that money to eradicate Phragmites in the Piermont Marsh. Community residents opposed the removal because they felt the dense reeds had protected their neighborhood from devastation by Hurricane Sandy. The Department of Environmental Conservation (DEC) and the Palisades Interstate Park Commission (PIP), after the outcry from Piermont residents and officials, announced that they would develop a revised “Piermont Marsh Restoration Plan” which would alter the original plan that called for the eradication of 200 acres of existing Phragmites.
Phragmites supports many plants and animals and performs valuable ecosystem services. Therefore, the general assumption that this plant degrades marshes should be re-thought by marsh managers now, when we are concerned about resilience and sustainability. We should shift our approach from attempted eradication everywhere to modification of stands to create habitat for particular species while retaining nonhabitat ecosystem services.
Because Phragmitescan provide substantial ecosystem services, as well as being an invader, it requires a management approach that is tailored to individual sites and management goals An approach that requires killing it everywhere is impractical, expensive, causes damage to sensitive species, and wastes resources.
