Wading Right In

Discovering the Nature of Wetlands

Catherine Owen Koning, Sharon M. Ashworth, Catherine Owen Koning

• Publisher: University of Chicago Press
• Year: 2019
• Print ISBN: 9780226554358, 9780226554211
• eBook ISBN: 9780226554495
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

Where can you find mosses that change landscapes, salamanders with algae in their skin, and carnivorous plants containing whole ecosystems in their furled leaves? Where can you find swamp-trompers, wildlife watchers, marsh managers, and mud-mad scientists?  In wetlands, those complex habitats that play such vital ecological roles.

In Wading Right In, Catherine Owen Koning and Sharon M. Ashworth take us on a journey into wetlands through stories from the people who wade in the muck. Traveling alongside scientists, explorers, and kids with waders and nets, the authors uncover the inextricably entwined relationships between the water flows, natural chemistry, soils, flora, and fauna of our floodplain forests, fens, bogs, marshes, and mires. Tales of mighty efforts to protect rare orchids, restore salt marshes, and preserve sedge meadows become portals through which we visit major wetland types and discover their secrets, while also learning critical ecological lessons.

The United States still loses wetlands at a rate of 13,800 acres per year. Such loss diminishes the water quality of our rivers and lakes, depletes our capacity for flood control, reduces our ability to mitigate climate change, and further impoverishes our biodiversity. Koning and Ashworth's stories captivate the imagination and inspire the emotional and intellectual connections we need to commit to protecting these magical and mysterious places.

CHAPTER 1

At the Water’s Edge: From the Aquatic Zone to the Emergent Marsh

Magic birds were dancing in the mystic marsh. The grass swayed with them, and the shallow waters, and the earth fluttered under them. The earth was dancing with the cranes, and the low sun, and the wind and sky.

—MARJORIE KINNAN RAWLINGS, The Yearling

Daybreak crept into the marsh slowly—hardly a sunrise, more of a smudge of gray washing across the eastern horizon. Low grunts of Virginia rails echoed through the murky morning mist. The high-pitched whinnies of sora rails reverberated, accompanied by the boink-boinking of green frogs, the slow double-toned trills of swamp sparrows, and the deep boom of a bittern. Venturing into this Iowa marsh in the predawn hours, wildlife biologist Tyler Harms felt more than a little trepidation. He was a brand-new graduate student, nervous about how his first field season would go. Although he had visited this and many other marshes like it during the day, the cacophony of night sounds made his ears ring; it was a little overwhelming and a trifle spooky. “The first time I heard it, I thought, What am I getting myself into—it sounds like there are goblins out there,” Tyler recalls. But the marsh beckoned him nonetheless.

The reason for this nighttime foray was to investigate a particular group of wetland birds—the secretive marsh birds. Secretive, because they can hide in plain sight: standing motionless, their earth-toned plumages are adorned with contrasting striped feather patterns, to mimic the shadows of dark and light stripes cast by the long skinny leaves of cattails, bulrushes, and sedges. You can’t see them even when you are looking straight at them. Sneaky, too, as they move quietly and fade from view at a moment’s notice. This shy group of birds includes the rails—Virginia rail, king rail, sora rail, to name a few—which are all small chicken-like birds. Other cryptic and mysterious birds in this group are the American bittern and least bittern, the common gallinule, the American coot and the pied-billed grebe. Their secretive behavior and the dense vegetation of their habitat makes it difficult to discover the details of their lives: what kinds of wetlands they prefer, how they move through the day and the season, and how many of them are out there; but this is all important information for conservation. Thus, finding the answers presented a great challenge and a bit of an adventure for curious scientists like Tyler.

After donning chest waders and strapping on a heavy backpack of equipment, Tyler headed downslope toward the marsh. Gravity showed him the way to the low, roughly bowl-shaped depression where the marsh had formed, pulling him from the firm footing of the upland, into the squishy zone of fine-leaved, low-growing, grass-like sedges that grow in the low-water areas of the marsh. Because of the covert nature of his cryptic quarry, Tyler used a digital audio device to play the calls of the eight bird species he sought as he moved around through the different zones of the marsh, hoping that any birds out there would call right back. Standing among the sedges and bulrushes, he played one call, then listened. No response. Next, he played the recording of one of the other birds. Again, nothing but crickets—actual crickets, chirping. The third, fourth, and fifth species’ calls also elicited no callbacks from the wild. Now Tyler was really starting to worry that his whole study would fail.

Finally, he played the recording of the Virginia rail’s defense call, an ominous, loud, repetitious grunt sound. Immediately, he was rewarded: A real Virginia rail grunted right back from less than fifteen yards away. Tyler repeated the call, and the bird responded again, spot on. He was excited just to hear anything at all. Then, to his surprise, under a dawn-lightened sky, he began to see some movement in the cattails, not far from his muddy, shallow water location. As he held his breath in amazement, a chunky little bird about nine inches long ambled through the green stems and walked right up to him, stopping at his feet. Peering up at him over its long reddish bill, the rail appeared to be trying to make sense of this tall, odd-looking creature in the brown rubber suit. Lured in by a defense call, the bird was presumably expecting to meet another Virginia rail intruding on its territory. The rail tilted its head one way, then another, as if puzzling it out. Tyler stood as still as possible, holding his breath, and managed to get his camera out and take a picture—focusing straight down at the bird by his feet—without disturbing it.

Awestruck by the experience, Tyler continued to watch the dark little bird check him out. After a few minutes, the rail sauntered away, seemingly unperturbed by its alien encounter. This happened many times over the course of Tyler’s two-year study, leaving him amused and amazed each time. “Those rails are pretty brave little birds. If I moved, they’d run away a little, but they would stay, watching me, checking me out. They were defending their territory, and they stuck to it as long as I played the calls. If I stopped moving, they’d come right back. Sometimes I would get two Virginia rails, both circling around me.”

After that first encounter with the Virginia rail, Tyler was eager to continue the call-broadcast survey, so he waded in further, into deeper water, stopping to play the sequence of calls in the different zones of the marsh. Moving along, he could feel the bulrushes grazing his arms and the water sloshing around his legs, until he came to a stop in waist-deep water, cattails arching overheard. Once again, he played his bird-beckoning sequence of recordings, and once again, heard only crickets—and frogs—at first. But patience ever reaps its own rewards: despite the hordes of mosquitoes buzzing around his head, Tyler could hear the softest crackling of stems off to his left, and he could see the cattails moving. Slowly, slowly, a stumpy, brown-striped bird with long legs crunched its way into view. It was a least bittern, moving through the dense vegetation by clinging to the cattails. The bird eyeballed him for a few moments, keeping its distance, but slowly circling around as Tyler played the calls. Apparently concluding that Tyler was not another bittern after all, the bird then unhurriedly grasped its way out of sight. “Once they realize that you aren’t a threat, they go back to what they were doing,” Tyler explains. “These supposedly ‘shy’ birds, with the strange, tough-sounding calls, are literally tough creatures: when I moved, they wouldn’t just run off like you would expect; they’d stick around to defend their turf.”

Tyler spent dawn and dusk conducting this research, repeating this scenario in fifty-six wetlands across Iowa. He and his colleagues found abundant pied-billed grebes swimming in the deepwater areas beyond the cattail zones, as well as more Virginia rails, and least bitterns in wetlands with robust stands of cattails (Harms and Dinsmore 2013). It launched him into his career as a wildlife biologist for the University of Iowa. Like so many wetland researchers and managers, Tyler exemplifies a breed of scientists who are deeply devoted to the wetlands and wildlife of their home state. Proof of this dedication (er, obsession)? His ringtone is the song of the yellow-headed blackbird, and his text messages chime in with the call of the Virginia rail—two birds that find their home in the deep marsh. He’s studied dragonflies and damselflies, crawfish frogs and wading birds, songbirds and dabbling ducks, as well as wetland plants and hydrology. “I’ve always been a wetlands person,” Tyler says. “A lot of my friends call me crazy—they wonder who would want to stomp around in these habitats that are hot and buggy, wet and muddy—but I absolutely love the wetlands. They are so diverse. Everywhere you look you see something different, something new.

“After you spend enough time out in the wetland and you have these awesome experiences, you start to realize how cool these places are, and all of the difficulties of working in these habitats just fade away. You stop thinking about the one hundred million mosquitoes around your head. Instead, you focus on the damselflies and dragonflies that flush out in front of you as you walk, and on the little muskrat that swam right in front of you, heading back to its den,” Tyler says. “There is so much going on in these wetlands—it is just amazing.”

Most marshes, like the one Tyler studied, form in a low spot or along the shallows at the edge of a lake or river. This gradual topography creates a spectrum of water depths. First, near the top of the slope, comes the shallow marsh (or transition) zone, where the ground is consistently wet but has no standing water. Next, further downslope, is the emergent marsh (or deep marsh) zone, where the water may come up only to your ankles or all the way to your waist, as much as three feet deep. Finally, the deepest spots in the marsh form the aquatic zone, where the water depths measure three to six feet deep. Each set of water depths, or zones, harbors collections of plants that thrive in those conditions, and each set of plants supports a complementary group of insects, amphibians, birds, and mammals (table 1).

Table 1. Zones in a freshwater marsh

Zone	Water depth	Plant type (with examples)	Typical wildlife
Aquatic zone	3–6 feet (0.9–1.8 meters)	Submersed aquatic vegetation (pondweed, coontail); floating leaved vegetation (duckweed, water lily)	Pied-billed grebe, mallard and other dabbling ducks, coot, heron, green frog, newt, painted turtle, bluegill
Deep-marsh zone	0–3 feet (0–0.9 meters)	Emergent vegetation (cattail, reeds, bulrush, arrowhead, pickerelweed, bur-reed, grasses)	Swamp sparrow, red-winged blackbird, rail, bittern, muskrat, mink
Shallow-marsh/transition zone	Wet ground (water level just belowground)	Fine-leaved vegetation (grasses, sedges), some shrubs	Marsh wren, spotted sandpiper, meadow vole, peeper, garter snake

The murky water of the aquatic zone supports lily pads and submersed plants, such as coontail (Certaphyllum demersum) and pondweeds (Potamogeton spp.). In the deep marsh, the typical cattails (Typha spp.) and bulrushes (Schoenoplectus and Scirpus spp.) grow, edged on the deepwater side by pickerelweed (Pontederia cordata) and spike rush (Eleocharis sp.), and in the shallower spots with arrowhead (Sagittaria spp.) and arrow arum (Peltandra spp.). Grasses, sedges, and some shrubs grow in the shallow marsh zone. Of course, not every marsh has the same set of plants and animals, because it’s not just the amount of water that determines what grows, but also the type of water. Whether the water in the wetland is salty or fresh, mineral-rich groundwater, silt-laden surface runoff, or pure rainwater can make a very big difference to the plants and animals that live there (see box 1).

The resulting tableau, from lily pads to cattails to sedges, nicely matches the mental picture most often conjured in people’s minds when they hear the word wetland. It has water. It has cattails, fish, and frogs. Trees and shrubs are rare because the water is too deep (although there are some types of trees that like deep water—see chap. 5). Even if many different kinds of wetlands look nothing like this one, the “classic” marsh has much to teach us. As an aquatic resource, the freshwater marsh is one of the most valuable for living creatures—both the kinds that live in it, such as marsh wrens and mallards, and the kinds that live near it, such as black bears, bobcats, and even bankers. As a biological system, the freshwater marsh harbors awe-inspiring interactions and adaptations—all hidden, awaiting discovery by a patient observer.

Box 1. Water, Water, from Everywhere: Understanding Wetland Hydrology

One of the important features that wetland explorers need to understand is the way that water gets into and out of a wetland—its hydrology. By circumnavigating the wetland, poring over topographic maps, visiting several times during the year and installing monitoring wells, wetland scientists can determine where the water in the marsh comes from. The sources of water determine how deep the water or how wet the soil is and for how long. Water source also influences the types of natural chemicals and plant nutrients found in the wetland.

The depth of the water and its flow rate determine how much oxygen is available in the soil for plants, invertebrates and microbes to use (see box 2). When water is deep and stagnant, there isn’t much oxygen available. If the water is flowing, or if water levels drop belowground for any part of the year, then oxygen will be able to get into the soil, which allows a number of important chemical and biological processes to take place.

Fresh water can enter a wetland from precipitation, surface water (river, streams, lakes, and stormwater runoff), and ground water. Water leaves the wetland by evaporation, transpiration (release of water vapor through plant leaves), surface water, and ground water. For wetlands near the ocean, tides bring salt water in and out, too.

Casual observers can determine a wetland’s water source and learn to draw conclusions about wetland type and condition as well as the plant and animal life that lives in the wetland. All wetlands receive water from rain and snow, which bring in very few nutrients or chemicals relative to other water sources. Observers might see that the adjacent river flows up and into the marsh during high water times. Walking around the upland edge, explorers will surely see rivulets, streams, and larger channels that bring in upstream flows, or overland flood flow after a big rainfall. These sources of water tend to carry large amounts of plant nutrients most needed for growth, such as phosphorus and nitrogen.

If the water sources that flow into the wetland contain lots of nutrients, there will be more plant growth. Most marshes are quite well nourished because surface waters—rivers, lakes, and runoff—commonly flow into them. Add an abundance of sunshine and the result is an explosive growth of plant life.

The marsh may also fill up with groundwater seeping in from underneath, fed by underground aquifers. This is much harder to see, although visits in very early spring can show wet, weepy spots where the plants are greening up earlier because of the input of warm groundwater. Groundwater can contain key micronutrients, such as calcium or iron, depending on the geology of the area. Some of these micronutrients, particularly calcium and magnesium, can support unusual plant communities.

Wetlands that are fed by a lot of groundwater are called fens, and may be rich in important chemical elements. Bogs, on the other hand, receive almost all their water from rain and snow, leading to a nutrient-poor situation. See chapter 4 for more about bogs and fens.

Life in the Aquatic Zone

How Plants Breathe

Perhaps you, like many outdoor adventurers, have guided a kayak or a canoe into the shallow edges of a lake or pond, and found your paddle entangled in coontails and pondweeds. These submersed plants signal the transition from the deep water of the lake to the aquatic zone at the edge of the marsh. As you look closely at this skein of green plant life adorning your paddle blade, you might notice that there are often two different kinds of leaves on the same plant. Pondweeds (Potamogeton spp.), bur-reeds (Sparganium spp.), and other aquatic plants often have aerial leaves that are wider and stouter than the underwater leaves, which are finely divided like very delicate ferns. This dual leaf shape, called heterophylly, is a response to the Big Problem that all wetland and aquatic plants face: a lack of oxygen (see box 2).

Oxygen doesn’t diffuse easily into water, and even where the water is in direct contact with the air, oxygen diffuses only a few inches into the water column. The dissolved oxygen that is present is quickly used up by bacteria and other microbes to break down organic matter (a process called microbial respiration, essential for decomposition). Oxygen is needed for respiration, the cellular process of breaking down molecules to release energy; all cells need oxygen, even plant cells. Aquatic plants have a number of adaptations that make it easier to obtain oxygen when little is present. The differently sized leaves on aquatic plants are one such adaptation. Underwater leaves are finely divided into narrow ribbons or threads only a few cells thick, to provide more surface area for the limited amount of oxygen to pass from the water directly into each cell. On the very same plant, the leaves that lay on the surface or stick out of the water will have a different outline—maybe like a paddle, an arrow, or a three-lobed clover. These surface leaves, which are in contact with the air, have far less of an oxygen problem, so they are wider in order to maximize area for photosynthesis. They also must be thicker to support themselves out of water.

Box 2. Surviving the Flood: Plant Adaptations to Standing in Water

Author Sharon writes: I water my plant until the water fills the dish below the pot and think that ought to take care of it for a while. When the water is gone from the dish, I repeat the exercise because it’s easier than sticking my finger in the dirt every day to judge moisture, and in the long run I’ll have to water the plant less frequently—I just gave it an extra supply, after all. After a few days, the plant turns yellow and wilts. Huh, the poor thing must be thirsty. So I water it again; it dies. “But I was taking care of it,” I whine to my mother. “I watered it!” Flooded it, to be precise. And maybe this is why I love wetland plants: they can handle what my poor philodendron could not.

While I’m still far too irresponsible to be trusted with all but the hardiest houseplants, I now understand why the philodendrons, the dieffenbachias, and the spider plants die. As I fill the soil pores with water, the air is pushed out and, with it, readily available oxygen. Plants don’t only produce oxygen; they consume oxygen just a...

Table of contents

• Cover
• Title Page
• Copyright Page
• Contents
• Preface
• Introduction: Sun Turtles and Superstorms
• 1  At the Water’s Edge: From the Aquatic Zone to the Emergent Marsh
• 2  Wet Meadows: Not Too Dry, Not Too Wet
• 3  Pond-Meadow-Forest, Repeat: The Beaver’s Tale
• 4  Stuck in the Muck: Bogs and Fens
• 5  Wooded Wetlands: Basin Castles and Big-River Swamps
• 6  Vernal Pools: Believing in Wetlands That Aren’t Always There
• 7  Salt Marshes: A Disappearing Act
• 8  Wetland Restoration: Changing Techniques, Changing Goals, Changing Climate
• 9  Beauty, Ethics, and Inspiration
• Acknowledgments
• References
• Index