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Wetlands occupy a relatively small area in Pennsylvania as compared to terrestrial habitats (less than 3% of the total land area), but they have a disproportionate value for maintaining water quality and quantity and for supporting biodiversity. Careful management can protect and improve wetlands.
Wetlands occupy a relatively small area in Pennsylvania as compared to terrestrial habitats (less than 3% of the total land area), but they have a disproportionate value for maintaining water quality and quantity and for supporting biodiversity. By absorbing large amounts of precipitation, wetlands slow and regulate the volume of water entering streams during storm events. By slowly replenishing groundwater and streams, they help maintain stream flows during dry periods. Wetlands buffer streams by absorbing sediments and chemical pollutants. As important breeding areas for amphibians, aquatic insects, and birds, primary habitat for aquatic and palustrine plants, and important habitat for many of our terrestrial vertebrates, wetlands are indispensable, highly specialized places that mark a transition from land to water. Although historically maligned as wasteland, wetlands (particularly forested wetlands) have in recent times received proper recognition for the many crucial ecological and environmental benefits they provide.
Federal, state, and even local laws provide protection to wetlands. The Pennsylvania Department of Environmental Protection (DEP) is the agency that enforces wetland laws and issues permits for activities that involve wetlands. Wetlands are a protected resource in Pennsylvania Under 25 Pa. Code § 105.1. Lands that meet the U.S. EPA definition of wetlands under the Clean Water Act are subject to Pennsylvania regulation and in Pennsylvania, unlike many other states after a recent U.S. Supreme Court decision, there is no requirement that wetlands be connected to surface waters to qualify (Mandelbaum 2023).
Wetlands may be defined as areas that satisfy at least two of the following three parameters:
Wetland community types are classified by the Pennsylvania Natural Heritage Program (PNHP) according to their dominant plant species. Most wetland communities in the state fall within three broad categories: forested, shrub, and herbaceous wetlands. Sparsely vegetated wetlands, such as the unvegetated margins of lakes, beaches, and river shorelines, and unvegetated vernal pools where standing water and shade restricts the growth of dense vegetation are grouped together in a fourth category.
Because wetlands can be quite complex and multidimensional, gleaning critical hydrologic, habitat, and diversity information can be equally complex. However, describing in as much detail as possible what community type a wetland is, how it is connected or not connected with the water table and to surface flows, the characteristics of the watershed it is embedded in, how critical it is to stream base flow, and what kinds of plants and animals it supports will help to inform potential management goals.
Field inventories are used to assess a wetland’s health and identify issues. They are vital in determining management goals and actions. An effective inventory should seek to assess the above key features and identify possible issues. While inventories are important, they can be resource intensive. The categories Good, Better, and Best outline three different levels of inventories in the following sections.
The types of plant communities found in an area can tell us a lot about a site. Plant community surveys provide information about plant species presence, the structure and composition of the plant community, soil chemistry, geology, presence of wildlife habitat, and quality of the entire landscape. The PNHP provides a dichotomous key to wetland communities in Pennsylvania to help land stewards determine what type of plant community is found on a site (see Related Library Items).
The PNHP has also developed a tool to assist restoration practitioners in establishing native plant communities using species selected to thrive at a site. The user draws the location on a map and the software identifies natural communities most likely to occur there. The user can generate a list of suggested species to plant based on common species found in those natural communities (see Related Library Items).
For management and development projects, a wetland delineation is often required to obtain the requisite permits from the Pennsylvania Department of Environmental Protection. In Pennsylvania. Wetland delineation methodology is included in the Pennsylvania Code Chapter 105 regulations: Identification and Delineation of Wetlands, from the U.S. Corps of Engineers Wetland Delineation Manual (see Related Library Items).
Good—Determine whether the wetland you are working in is uniformly forested, shrub-dominated, or herbaceous plant-dominated and roughly map the extent of the wetland.
Better (in addition to Good)—Identify the dominant species in each of the cover types that make up the wetland.
Best (in addition to Good and Better)—Determine the specific community types that make up the wetland according to the Pennsylvania Terrestrial and Palustrine Community Classification (see Related Library Items). Map the boundaries and describe each plant community within the site.
Wetlands, especially those at the headwaters near the top of the watershed, are critically important to riparian and riverine ecosystems downstream. Understanding daily and seasonal fluctuations can give insight into the function of a wetland and establish baselines to watch for changes or to conduct management to correct impacts.
Good—Review the extent and position of the wetland on topographic maps and aerial photos to see if there are obvious surface inflows and outflows, nearby streams, or other wetlands. From this information, the footprint and recharge of the wetland can be estimated and potential impacts considered.
Better (in addition to Good)—Produce (or have a qualified individual produce) a hydrologic model of the wetland based on the above factors plus geology, soils, observation, and chemical or physical measurements taken of the wetland.
Best (in addition to Good and Better)—Directly measure surface water flows using a flow meter and measure groundwater fluctuations using monitoring wells to understand hydroperiod and inputs into the wetland.
Large, physically diverse wetlands typically support a broader range of animal and plant species than those that are smaller or simpler. Specific wetland communities provide critical habitats for specific wildlife communities and understanding the quality and condition of these communities is important for maintaining the wildlife species that depend on them. For example, the Black Spruce – Tamarack Peatland Forest supports a suite of species more common north of Pennsylvania, including several wildlife species listed as species of greatest conservation need (SGCN) in Pennsylvania’s State Wildlife Action Plan (SWAP). The Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission’s Conservation Opportunity Areas tool can be used to determine the wildlife SGCN that may occur at a site, based on the presence of particular habitats. To run this tool for a specific site, the property boundary or a specific area within a property can be drawn in the tool or imported (see Related Library Items).
Good—Given the extent and type of wetland and the amount of open water vs. vegetated wetland, determine what kinds of wildlife the wetland may support using the Conservation Opportunities Areas tool.
Better (in addition to Good)—Collect and review any information available on the wetland of interest. Consider not only natural communities but also the species that are present in the wetland. Consult local and state agencies, review community science sites, review the County Natural Heritage Inventory at PNHP’s website to read about nearby Natural Heritage Areas (NHAs) that include wetlands, and talk to local experts.
Best (in addition to Good and Better)—Perform field inventories to determine what species and habitats are present and ground-truth or enhance any information that has already been collected. Tailor the inventory to the taxa or habitats that are likely to be most valuable or rare or widespread in the wetland. These may become the central focus of any monitoring or management that will take place in the future.
Assessing the condition and viability of an ecosystem is the first step in developing a restoration and maintenance plan for a natural area. A model framework for ecological assessments (often called ecological integrity assessments, or EIAs) has been developed by NatureServe to guide the baseline assessment and later monitoring of a wetland site (see Related Library Items).
Good—Review aerial photos for signs of disturbance and encroachment, invasive species cover, and general landscape condition. Collect any data available on species presence, for example, from iNaturalist research grade observations, the Global Biodiversity Information Facility (GBIF), and members of local birding organizations. In the NatureServe EIA guidelines, this type of assessment is referred to as a Level 1 or landscape-level assessment. In Pennsylvania, landscape-level assessments may be conducted using a tool called the Pennsylvania Landscape Condition Model (LCM), which is a protocol that can be applied in GIS (see Related Library Items).
Better (in addition to Good)—Based on the information from above, further investigate through field visits possible stressors, including hydrological alterations (dams, channels, drainage ditches, drainage tile pipes, etc.), presence of invasive species, particularly if dense and widespread, any obvious disturbance (timbering, mowing, structures, trash, etc.), and nutrification. This step is referred to, by NatureServe, as a “Level 2” assessment and requires a basic understanding of ecological processes and knowledge of local flora and fauna. A trained botanist or ecologist is not necessarily required at this level. A level of severity (usually 1-3) is assigned to each stressor present. This “stressor checklist” results in a condition score for each anthropogenic (or human-caused) stressor. Note any changes and further investigate with field observation and consultation with experts.
Best (in addition to Good and Better)—Employ a trained botanist or ecologist to conduct a site visit to determine plant species composition and ecological variables that contribute to the site’s condition and viability. The plant species are extremely important in assessing the ecological quality of a site and are key indicators of conditions that can be monitored over time to see if site quality is maintained, improved, or declining. For this level of assessment, called “Level 3” by NatureServe, a full species list and quantified community composition, often assessed using fixed quadrats or other methods, is determined. A wetland delineation is often helpful. Basic steps also include review of historical aerial photos and comparison to present satellite images to determine changes in condition and extent. Water quality should be assessed to investigate possible pollution from industry, agriculture, or sewage. It is also helpful to assess the health and vigor of trees and other vegetation within the wetland. Periodic monitoring is required to determine change over time.
Whether human created or natural, wetlands face many issues. Changes in hydrology, chemistry, or temperature, loss of native species, colonization by invasive species, and loss to development are all possible, individually or in combination. Establishing long-term goals helps give context to the many management issues that may arise. Short-term goals can be more directed toward specific problems or needs.
Long-term goals may include: establishing and maintaining a buffer around the wetland; ensuring that hydrologic connections remain in place; keeping populations of desired native species healthy; maintaining and conserving important habitat connections to the landscape and other wetlands; and restoration to a previous state or conversion to a preferred state. Short-term goals include: control or elimination of certain invasive species; erecting herbivore exclosures or cages; building boardwalks; adding interpretive signage; erecting nesting boxes; and various other stewardship practices.
Broadly, the management opportunities for wetlands can fit into three categories:
Maintenance: preserving the wetland type and ecological function
Restoration: repairing the damaged wetland ecosystem and ecological functions to the way it used to be
Creation: creating a wetland ecosystem to replace a wetland that was lost or destroyed to provide a wetland function (e.g. capturing stormwater runoff and sediment) and limits wetland loss within a region.
A fourth term often associated with wetland management is Mitigation, which is the process of compensating for the loss or degradation of wetlands due to development, is also included as an opportunity here. Mitigation may relate to all three of the previous categories; the type of management undertaken will dictate many of the goals for the wetland in question.
Wetlands are dynamic and can often be successional in nature, particularly after large-scale disturbances such as beaver occupation, timbering, or extensive storm damage. But even without acute disturbances, wetlands do change slowly over time and trying to manage counter to natural change or succession can be resource intensive and unproductive. However, certain resources (e.g., rare plant populations) that require a specific wetland community type or habitat can make such efforts worthwhile.
Maintaining a natural, functional wetland is always the preferred option, regardless of the type or location. Depending upon the cover type (forest, shrubland, herbaceous), various types of management may be employed. It is important to understand how to structure planning and consequent management based upon the overall condition and context for the wetland. The assessment of condition should be done as part of the baseline inventory process.
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If a wetland has been degraded by impacts of hydrologic change, loss of canopy from tree death or timbering, alteration of an adjacent landscape, invasive species proliferation, and any number of things that have profoundly altered the wetland, restoring structure and function is likely the highest value option.
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There may be times when land managers want to create wetlands, particularly to provide habitat or for stormwater management. The health and sustainability of existing wetlands and the ecosystem services they provide can often be improved by restoration (controlling invasive species, repairing damage done inadvertently, restoring qualities that have been degraded), but using naturally occurring wetlands to manage stormwater, diverting more water into them is likely to be counterproductive, overwhelming the capacity of the wetland and resulting in losses of native plant and animal species and increases in invasive plant populations adapted to the specific natural hydrology. Instead, newly constructed wetlands carved out of upland soils, such as detention basins or retention ponds, can provide benefits without degrading or destroying natural wetlands.
The best approach is to select as the desired condition a wetland type that is most feasible to establish (similar to existing wetlands nearby), can provide the desired value and function (e.g., stormwater retention and infiltration; filtering runoff before it enters a stream or other water body; habitat for a specific species or group of species; etc.), and is stable and sustainable.
Constructed wetlands can become problematic if not properly built and managed. Where their edges are maintained as mowed turf, for example, they have little or no wildlife habitat value or aesthetic appeal and can be prone to stormwater erosion. Planting constructed areas with diverse native wetland species is essential if they are to reach their full potential in providing wetland services.
When wetlands are unavoidably impacted by various development activities, mitigation—replacing the impacted or destroyed wetland—is sometimes an option or a regulatory requirement. Mitigation generally refers to the Wetland Creation concept above (the creation of wetlands of a similar type in a nearby location), often of a greater acreage than the impacted wetlands. However, Maintenance and Restoration techniques can also meet mitigation requirements. Many companies are involved in wetland banking where areas are acquired or leased and used as needed to offset impacts in other locations. Mitigation banking is a complex process that serves a necessary function; however, replacing a wetland’s functions and values, particularly sustainably recreating the natural community and its species composition, is difficult and often minimally successful. That is particularly true of wetland types that require very specific conditions and processes (e.g., bogs, fens, seeps). Some wetland types can be created with more success than others but in general, mitigation requires substantial resources and long-term management. For landowners and conservation organizations, the management of wetlands created for mitigation can be a substantial undertaking and it uses resources perhaps best spent on the conservation of existing natural wetlands.
For all wetland types and conditions, there will be issues to confront. Assessing the severity of the problem and how critical it is to address it through active management is an important step before management plans are created. Setting the goals for any type of management is essential to guide ongoing management and ultimately for measuring progress and success.
According to the U.S. EPA, over 220 million acres (about twice the area of California) of wetlands have likely been lost in the lower 48 since the 1600s. This trend was much accelerated in the mid-1950s through the mid-1970s when an unprecedented number of wetlands were drained and converted to other uses. With the passage of the Clean Water Act in 1972, the rate of loss slowed dramatically. However, even with today’s regulations and oversight, wetlands are still being lost or heavily impacted, both directly and indirectly.
Changes in a wetland’s hydrology can occur even from distant activities that: affect groundwater quantity and quality; alter surface water flow and volume; change plant cover; or develop nearby land for residential, commercial, industrial, or institutional uses or public infrastructure. Development in turn can increase stressors such as edge effects, colonization by invasive species, and increased human activity.
The following management strategies are recommended as general approaches to helping managers of wetland ecosystems avoid further loss and fragmentation.
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Wetlands with abundant invasive plant species and cover, with monocultures of generalist species, or otherwise of poor quality are often the result of hydrologic modifications, such as ditching, tile pipe drainage, or other forms of hydrologic modification. Returning natural hydrology to a ditched or drained wetland is critical to recovering wetland species composition and function. Natural process-based restoration and reclamation techniques (nature-based solutions) are popular because of their low cost and high impact, as they use natural processes to restore the ecological functions and character of a wetland.
Constructed wetlands such as detention basins and retention ponds are also examples of hydrologic modification. However, these are intentionally created to serve a specific purpose such as stormwater management. As such, restoring the natural hydrology is likely not the goal. Instead land managers should take steps such as planting native species and controlling invasive plants to support constructed wetlands (see Wetland Creation above).
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Eutrophication, or input of nutrient pollution (nitrogen and phosphorus), can severely degrade wetlands. Most nutrient pollution is delivered to wetlands from diffuse sources, such as urban runoff, agricultural runoff, or septic systems leaking into groundwater. Eutrophication is one of the leading causes of impairment to wetlands.
Eutrophication of wetlands leads to changes in the composition of wetland plants, often favoring generalist species, either introduced or native. Eutrophication can be problematic for wetlands no matter where it occurs, but it is most catastrophic in our rare peatland (bog and fen) wetland ecosystems, which are by nature nutrient-poor and provide habitat for specialist species adapted to nutrient-poor conditions. Cattails—a native species (Typha latifolia), an introduced species (T. angustifolia), and a hybrid between the two—are often a symptom of eutrophication, forming dense monocultures in what were once diverse wetlands and crowding out native habitat specialists.
The following management strategies are recommended to managers of wetland ecosystems to avoid impacts from nutrient pollution.
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Just as in terrestrial ecosystems, invasive species can have dramatic impacts on wetlands—dominating and suppressing native vegetation (including rare species), compromising habitat for animals that live in or are dependent on a given wetland, and altering hydrology. Many introduced species may be present but have minimal impact; there is little need to focus on controlling or eliminating those species that exist and function in relative balance with native species.
Controlling invasive species in wetlands is also more complicated than in terrestrial systems given the hydrologic and chemical connectedness of wetlands (see Invasive Plants). Special formulations of various herbicides for wetland use exist and are normally required as part of permitting. Hand treatment is often the best option to avoid impacts to native vegetation, wildlife, and rare plants and animals. The cost for treating wetlands is often higher given the greater difficulty in access and movement of equipment.
When controlling invasive plants within a wetland area, land managers should first prioritize species that are toxic to people and animals, like poison hemlock (Conium maculatum) and giant hogweed (Heracleum mantegazzianum), to reduce risk. Next, land managers should monitor for new, and still small, infestations as it is easier to control small populations compared to large, established colonies. From there, the general rule of thumb is to control invasive plants that negatively impact priority native plant and animal populations. This includes vines growing on trees or deer-exclosure cages (e.g., mile-a-minute, Japanese hops, Oriental bittersweet, Japanese honeysuckle, porcelainberry) and invasive species that outcompete natives or disrupt food webs or other interactions between species (e.g., Japanese knotweed, phragmites, Amur honeysuckle, Morrow’s honeysuckle, Tartarian honeysuckle, multiflora rose).
Land managers should take a landscape view. Invasive plants do not respect property boundaries and can easily spread from one property to another. If land managers within a community or region take a collective approach and all work to control invasive plants, there is a greater likelihood of successful control and a lower risk of reintroduction. To further support a landscape approach, land managers can share with each other information about invasive plants, the importance of controlling them, and control methods that work best for particular species.
Good—Control invasive plants in the highest-quality areas. Control invasive plants that pose a risk to humans or animals. Prevent introduction of new invasive species.
Better (in addition to Good)—Control invasive plants in areas of moderate quality, as well as the highest quality-areas. Educate visitors about invasive plants.
Best (in addition to Good and Better)—Systematically control invasive plants throughout the entire property, following prioritization strategies. Work with nearby landowners to collectively manage invasive plants.
More information about the problems caused by invasive plants and their management is included in the main Invasive Plants section.
Wetlands are particularly vulnerable to climate change given the very specific conditions that create and maintain these systems. Due to the general lack of connectedness among wetlands across the larger landscape, species dependent upon wetland conditions have minimal opportunity for dispersal and movement if conditions change. In some cases, assisted movement or propagation for out-planting may be the only way to ensure that key plant populations, particularly of rare species, can continue. There may also be a kind of feedback between changes in conditions and changes in species composition as emerging species provide more shade or have different transpiration rates or attract animals that can significantly alter wetlands (e.g., beaver).
Numerous climate models analyzing varying emissions rates predict that Pennsylvania will get warmer and wetter. This may be particularly catastrophic for the collection of rare wetlands in Pennsylvania considered to be boreal wetlands, or wetlands with species and ecological factors that are more typically found in northern climates. Warming temperatures and changes in the amount of precipitation may greatly reduce the viability of plant species that make up these communities.
Floodplain wetlands are also considered vulnerable to climate change due to changes in the duration and severity of flooding and the amount of winter ice and freeze-thaw events. Catastrophic flooding may result in considerable change in floodplain ecosystems. Freshwater tidal wetlands along the Delaware River may see changes due to brackish water as the saltwater limit advances upstream. Catastrophic storms may increase shoreline erosion of seepage bluff wetlands along the shores of Lake Erie.
Climate change may also result in increased proliferation of invasive plants and generalist native plants, which are more tolerant of anthropogenic disturbance than native, more conservative species.
The following management strategies are recommended as general approaches to helping wetland ecosystems adapt to and survive climate change. More climate change information is included in the main Climate Change section.
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It is important not to overlook seasonal or ephemeral wetlands as they support wetland plant species and often are unique ecosystems themselves. Chapter 105 of the Pennsylvania Code recognizes seasonally wet and dry areas as wetlands if they support wetland plants or contain hydric soil indicators. Even if the soil is dry at the time of delineation, a seasonally wet site could still be identified as a wetland, although the risk is higher of failing to notice these important communities. Seasonal wetlands come in many forms ranging from ephemeral seeps fed by seasonally variable groundwater discharge to vernal pools, which have no inlet or outlet and are filled by precipitation. Vernal pools differ from most other waterbodies, filling each spring with rain and snow melt then drying up during the summer. They are crucial habitats for animals with aquatic larvae such as frogs, toads, salamanders, and many insects that survive best in environments free of predatory fish.
The following management strategies are recommended as general approaches to helping to minimize and avoid impacts to ephemeral wetlands.
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If a link is broken, try searching on the keyword string preceding the link.
Climate Change Response Framework: Climate Change Projections for Individual Tree Species in Pennsylvania (forestadaptation.org/learn/resource-finder/climate-change-projections-individual-tree-species-pennsylvania, as of 2024)
Connecticut Department of Environmental Protection, Wildlife Division: Wetland Wildlife Values (portal.ct.gov/-/media/DEEP/water/wetlands/seg1wetwildpart1pdf.pdf, as of 2024)
Leibowitz, S.G., R.A. Hill, I.F. Creed, et al. 2023. National hydrologic connectivity classification links wetlands with stream water quality. Nature Water 1:370-380. doi.org/10.1038/s44221-023-00057-w (nature.com/articles/s44221-023-00057-w, as of 2024)
Mandelbaum, D.G. 2023. Wetlands regulation in Pennsylvania after ‘Sackett’ ruling. The Legal Intelligencer June 29, 2023. (gtlaw.com/-/media/files/insights/published-articles/2023/06/reprint-david-mandelbaum-june-29-legal-intelligencer.pdf?rev=f2e34d766c204fa5af60756ac57cf062, as of 2024)
NatureServe: Ecological Integrity Assessment (natureserve.org/products/ecological-integrity-assessment, as of 2024)
PennState Center for Dirt and Gravel Road Studies (dirtandgravel.psu.edu, as of 2024)
Pennsylvania Code Chapter 105 regulations: Identification and Delineation of Wetlands (pacodeandbulletin.gov/Display/pacode?file=/secure/pacode/data/025/chapter105/s105.451.html, as of 2024)
Pennsylvania Department of Environmental Protection: Wetlands Protection Program (files.dep.state.pa.us/Water/Drinking%20Water%20and%20Facility%20Regulation/WaterQualityPortalFiles/IntegratedWatersReport/2022/WETLANDS_PROTECTION_PROGRAM_DESCRIPTION.pdf, as of 2024)
Pennsylvania Natural Heritage Program: A Landscape Condition Model(LCM) for Pennsylvania (researchgate.net/publication/324569897_A_Landscape_Condition_Model_LCM_for_Pennsylvania, as of 2024)
Pennsylvania Natural Heritage Program: Palustrine Community Descriptions (https://www.naturalheritage.state.pa.us/Wetlands.aspx, as of 2024)
Pennsylvania Natural Heritage Program: Pennsylvania Community Prediction Tool for Site Restoration (https://www.naturalheritage.state.pa.us/RestorationTool.aspx, as of 2024)
Pennsylvania Wildlife Action Plan: Conservation Opportunity Area Tool (wildlifeactionmap.pa.gov, as of 2024)
U.S. Department of Agriculture, Natural Resources Conservation Service: Wetland Assessments (nrcs.usda.gov/ceap/wetlands, as of 2024)
U.S. Environmental Protection Agency: National Management Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpoint Source Pollution (epa.gov/sites/default/files/2015-10/documents/wetmeasures_guidance.pdf, as of 2024)
U.S. Environmental Protection Agency (USEPA). 2000. The Quality of Our Nation’s Waters. A Summary of the National Water Quality Inventory: 1998 Report to Congress. EPA841-5-00-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. (epa.gov/waterdata/1998-national-water-quality-inventory-report-congress, as of 2024)
Vermont Department of Environmental Conservation: Wetland Functions and Values—Wildlife Habitat (dec.vermont.gov/watershed/wetlands/functions/wildlife, as of 2024)
U.S. Department of Agriculture, Natural Resources Conservation Service: Wetland Mitigation Banking Program (nrcs.usda.gov/wetland-mitigation-banking-program, as of 2024)