← Back to Nature Notes

Nature Notes: Wetlands

Ed Robinson
April 8, 2024

“What’s the big deal, Ed?” asked Thad, “It’s just an old swamp.”

To be fair, Thad is not as thick-headed as he sounded, and I knew he was baiting me. Rather than snap at him I said quietly, “That ‘swamp’ is a salt marsh and some of the best wildlife habitat in our state.”

We were standing on the southern end of the long causeway that allows visitors to enjoy the sweep of water and vegetation that makes Scarborough Marsh a special place, one that draws people from far and wide. Over 3,000 acres in size, it is the largest tidal wetland in Maine, owned by the state and managed for wildlife habitat by the Maine Department of Inland Fisheries and Wildlife. By some measures it is the largest tidal marsh in the world, fed by four rivers and several creeks, and darned impressive by any standard. Our goal that day was to spot some of the salt marsh sparrows that call the area home, but every visit is a treat.

marsh area with trees in background

Houghton Graves Park, 4/4/2017, Ed Robinson

The word wetland is a catchall term used to describe a wide variety of habitats from Florida’s Everglades to Minnesota’s potholes, from Merrymeeting Bay to the Alaskan tundra. The common denominator, of course, is water but how that water accumulates and changes the land over time is important to understanding the many types of wetlands and the roles they play in ecosystems. Because wetlands consist of water, soil, and vegetation they can exhibit characteristics of both aquatic and terrestrial habitats.

Wetlands represent astonishing biological diversity and are known to hold more species of plants and animals than any other habitat. They are some of the most productive environments on Earth, absolutely vital to life as we know it. In some areas communities have created artificial wetlands to filter water flowing into waste treatment facilities to capture sediment and pollutants, thereby improving water quality for discharge. We should also note that wetlands change over time as siltation occurs or water levels change. Invasive plants like purple loosestrife and phragmites can have a devastating effect on marshes, crowding out native plants and limiting the amount of open water needed for waterfowl.

Living along the coast we might think first of tidal or saltwater marshes like Scarborough but there are other kinds of wetlands in our town including seeps and vernal pools. Each has unique characteristics and serves different roles in the surrounding habitat. As an example, Curtis Farm Preserve presents us with a mix of saltwater marsh, a freshwater pond, and small vernal pools. Trying to create a definitive list of wetland types is complicated because of local or vernacular names but this will get us started:

  1. Swamps – Generally these have standing water all year long except in periods of drought when surface water may be absent. They are distinguished by extensive tree and/or shrub cover, depending upon water levels.
  2. Marshes – These are located along the shores of lakes, ponds, rivers, or the oceans. The water is generally shallow but subject to periodic flooding or tidal flows. Marshes are populated by sedges, grasses, and low shrubs. In coastal areas this covers everything from small tidal pools to mudflats, beach areas and saltwater marshes where fresh water turns brackish as it flows to the sea.
  3. Wet meadows – These are low lying areas that are subject to periodic flooding due to seasonal rain and snow melt or beaver activity. Changes in the water table can also impact these areas. The soil may be damp as opposed to seeing standing water, with mostly non-woody plants.
  4. Flood plain forests – These are commonly found along the valley floor where a larger river is subject to seasonal or periodic flooding. Water is present intermittently but these areas serve as buffers against serious flood damage downstream. Trees found in these forests will be reasonably flood tolerant including cottonwoods, birches, ashes, and maples.
  5. Vernal pools – The melting of winter snow and ice, along with spring rains, forms shallow pools of water in shallow basins in forests and fields. Most of these pools will be dry by the time summer arrives but vernal pools serve a valuable role for protecting developing amphibians and invertebrates in a fish-free environment. You may refer to an earlier Nature Notes article on vernal pools.
  6. Seeps – These are commonly found at the base of steep slopes where bedrock impedes the flow of groundwater. While they may be no more than a foot or two wide, seeps are important in providing access to water during the winter and they often serve as the source of small streams.
  7. Bogs – These are particularly unique environments and quite limited in numbers. They are fed only by precipitation and characterized by spongy collections of peat, surrounding conifers and shrubs, and a thick carpet of sphagnum moss. The plants can tolerate generally acidic and low oxygen conditions.
  8. Fens – Similar in appearance to bogs, but less acidic due to the inflows of water from small streams and/or springs. Peat will be present in thick, floating mats that may allow you to walk upon the vegetation.

Thanks to Krista Spohr and Tony Colyer-Pendas for an excellent recent article in New York’s Conservationist that offered their version of this list, here augmented with other sources of information.

Look at a map of Maine and you will immediately notice a preponderance of water. A fishing buddy says that you could fish a different stream, lake or pond every day of a long life with some waters left over (you might, however, be able to hit all the Moose Ponds and Long Lakes!). All that water means that Maine is blessed with a great diversity of wetlands. Fortunately, Maine is not the kind of place where people have spent the last 200 years draining, filling, and destroying wetlands in the name of progress. The state estimates a total wetland area of 5.2 million acres, down 20 percent from historic numbers. Most of those wetlands are freshwater, with just 157,000 acres of tidal marshes.

Since 1972 wetlands have been protected by the federal Clean Water Act and some states passed similar legislation. The primary author of the Clean Water Act was Maine’s own U.S. Senator Edmund Muskie. The law gives states the authority to prevent or control any discharges or damage to wetlands through a rigorous permitting process. Legal battles still rage across the country where private landowners and developers chafe at such restrictions but the law has had a significant positive impact on clean water and wetlands across the country. Public opinion is solidly in favor of wetlands protection and in recent years wetland restoration is gaining momentum and funding.

snowy marsh at edge of coastal preserve

Stover’s Point Preserve, Ed Robinson photo

At the beginning of this article, I noted that wetlands are critical habitat for wildlife. For instance, wetlands serve as fertile nurseries for most fish and shellfish harvested for sport or commercial use. A host of other creatures large and minute make use of wetlands wholly or partly during their life cycles. This includes waterfowl, insects, amphibians, reptiles, songbirds, and myriad plant species. A notation in Wikipedia states that nearly 40 percent of threatened or endangered species in our country are completely dependent upon wetlands for survival.

At a time when we are all concerned with rising sea levels and the protection of critical fresh water supplies in Harpswell, wetlands play a vital role. Coastal marshes serve as buffers along our shorelines, reducing erosion and assisting with flood control. It is well established that wetlands help to absorb and sequester excess nutrients, sediments, and other pollutants from agricultural, industrial, and residential sources. In the face of threats to the limited aquifers under Harpswell’s islands, wetlands serve as giant filters and water storage facilities to gradually put clean water back in the ground to sustain our wells. As construction of new housing and impermeable roads or driveways continues, our wetlands become even more valuable.

Given the above factors it is no surprise that the priority areas for land conservation in Harpswell are heavily influenced by the presence of wetlands. Two recent additions to HHLT’s list of preserves are Little Ponds and Otter Brook. Look at a detailed map or better yet, walk the trails at these lovely preserves to see the prevalence of water and wetlands, critical to the lands around them. Other protected places with notable wetland areas include Hackett and Minot, Long Reach, Houghton Graves, and Widgeon Cove. Thanks to conservation-minded landowners and continued fundraising efforts there is a focus for the town and HHLT to protect even more of these special places.

It would be negligent to write about wetlands while ignoring their recreational value. Forgiving Thad for his unenlightened view of ‘old swamps,’ there is something for everyone who takes the time to observe and understand wetland areas. In coming weeks places like Little Ponds Preserve will come alive with the high and low chorus of wood frogs and spring peepers, bolstered by the occasional trilling of a toad. Ornithologist Nat Wheelwright will lead two bird watching tours at Otter Brook to delight participants with a wide variety of migrating warblers and other songsters. Larger wetlands allow you to enjoy travel by boat or canoe, fishing, and hunting.

Wetlands may be appreciated throughout the year. These sensitive and ever-changing ecosystems demonstrate seasonal dynamics that influence their plant communities, wildlife populations, and hydrologic functions. Spring is a time of renewal when an inflow of new water and the departure of ice sees the wetland species coming to life. Spawning, nesting, and foraging are the activities most visible to us then.

Summer sees wetlands in full flower, a boom time for insects and the creatures that depend upon them for a ready source of nutrition. I love few things more than soaking in the sights and sounds of a healthy wetland at first light. Your binoculars or camera will find any number of attractive subjects around the waters. The hot days of late summer raise water temperatures and lower water levels, with oxygen levels also dropping.

red moss grows in bog

The bog at Long Reach, 10/23/2021, Priscilla Seimer

Autumn means the vibrant greens of spring and summer yield to the golds, oranges, reds, and browns of fall. This is a time of southward migration for hundreds of species with wetlands serving as important layover stops for rest and refueling. I particularly enjoy a walk at Long Reach, both for the birds around the salt marsh and the bright colors of the small bog in the center.

Winter is the time for rest, when most wetland functions go dormant. Plant matter slowly breaks down, returning carbon to the bottom. Frogs and turtles lie in the mud, their metabolisms slowed to the minimum necessary to sustain life while preserving stored energy. Beavers and muskrats go about their business under the ice, making use of brush piles and cattail roots for sustenance. Water is slowly returned to the aquifer while the wetland stores rain and snow for the drier months ahead.

Surely you get the point: protecting our wetland areas is one of the highest priorities for conservation efforts. The benefits of wetlands extend to every living creature and wetlands repay our efforts many times over. In coming weeks please take the time to visit a local wetland to enjoy the sights, sounds, and smells while counting the blessings of these vital habitats. In the future, I will be writing about some of the more interesting types of wetlands and offering your detailed descriptions of the life in and around them.

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.