(backyard)

A Liquid Noah's Ark

By Tim Matson

Photo by Kathy Biggs

Jon and Sally Soest enjoy the privacy of their homemade log house in the foothills of Washington's Cascade Mountains. So when a new home popped up in the middle of their front-yard vista, they decided to dig a pond. The idea was to shift their view away from the new house. It worked. To reinforce the effect, they planted a screen of firs and pines on the pond embankment. This, too, was a success, although the jury is still out on how the trees will affect the dam. It's the Soests' first pond, and they were surprised to find out that tree roots can trigger leaks. Fortunately, the conifers have shallow roots and may not pose a threat.

A more pleasant surprise, however, has been the wildlife pilgrimage to the pond. "The first morning after the contractor left," says Sally, "we found bird footprints circling the water. It was a great blue heron."

The Soests, who belong to the North Central Washington Audubon chapter, are savvy birdwatchers, and that heron was one of many new sightings they attribute to their pond's magnetism.

In the three years since the Soests dug their boomerang-shaped, 50-foot-by-100-foot pond, they've seen signs of all sorts of new wildlife, from amphibian eggs in the shallows to ospreys diving for stocked rainbow trout. There are also western toads and green frogs, whose chorus fills the summer evening air. The crooning, however, isn't limited to frogs. "The coyotes didn't used to come so close," Sally says, "but now they're singing out by the pond trees. We've also seen more deer, and black-bear footprints."

To improve the cover for wildlife, the Soests planted native grasses around the shoreline and a corridor of trees to connect the woods behind their house to the evergreens on the pond dam. "The tree corridor invites wildlife to the pond," Sally explains. "The idea was to put some brushiness around the pond to provide cover for birds and waterfowl." It appears to be working, because the air traffic around the pond now includes Swainson's and red-tailed hawks, kingfishers, mallards, killdeer, and sandpipers. When asked if she's concerned about mosquitoes and West Nile virus, Sally says, "Not with all the resident frogs and tadpoles." Besides having amphibians to feed on mosquito larvae, the Soests installed swallow boxes to help control insects.

In addition to a small spring, the Soests' pond depends on an irrigation ditch that runs only in summer. Consequently, the water level varies throughout the year. This ebb and flow, mimicking natural seasonal water variations, fosters the growth of a variety of aquatic plants that wildlife like.

The Soests have much company in their aquatic adventure. According to the Heinz Center for Science, Economics, and the Environment in Washington, D.C., ponds currently occupy about 6 million acres in the United States, and pond acreage in this country has grown more than 100 percent since the mid-1950s, largely from the construction of small ponds. So although ponds are hardly a replacement for lost wetlands, building them can help dampen the devastating effects wetland loss has on wildlife.

Lewis Mumford, a renowned American philosopher, once described the pond as man's original "tool." Indeed, ponds have historically provided a wide array of benefits, from irrigation to fire protection to recreation to food. In the north, pond ice was once harvested for dairy and household refrigeration, although skating is more popular today.

More sophisticated pond applications have surfaced in recent years. For example, as an alternative to nonrenewable oil or gas, a geothermal pond that's connected to a heat exchanger can provide a house with summer cooling and winter heating. Detention ponds in developed areas catch and improve the water quality of runoff by reducing floodwater surges, desilting the runoff, and filtering out pollutants.

Regardless of your reason for building a pond, the costs of doing so can vary wildly, depending on size (surface area and depth), type (excavated or embankment), spillway (earth or pipe), and contractor. I've worked on half-acre ponds that cost $10,000 and ones of equal volume that cost more than 10 times that amount. Backyard water gardens, if they're professionally installed, can cost $5,000 to $6,000, maybe more, depending on how much you spend on stonework, waterfalls, plants, and fish. At the other end of the scale, a small do-it-yourself backyard water garden can be built for the price of a liner and a pump (a few hundred bucks).

Ponds are not only liquid Noah's Arks, they can be relatively inexpensive to build. As you might expect, shallow ponds cost less to dig, but they're also ideal, since shallow water promotes the growth of the aquatic vegetation waterfowl and wetland animals thrive on. Any planting you decide to do is best done with natives, which will please your local wildlife. Still, if you're patient, you might not need to shell out a nickel for plants. In fact, pond builders could take a lesson from the experiences of conservationists who are restoring wetlands on drained agricultural land by plugging ditches and pipes, and by removing drainage tiles. What they have found is that aquatics actually seed themselves quite efficiently.

Dennis Fijalkowski, executive director of the Michigan Wildlife Conservancy, explains that the seeds of wetland plants remain viable for up to 60 years. "When you bust up a tile, it doesn't happen overnight, but native aquatic plants like smartweed and beggar's-ticks come back fast. Areas that haven't been tilled will come back very fast." He even offers a wonderfully low-budget way to enhance the reestablishment of aquatic plants. "Cut mature cattail spikes," he says, "and swing them so you knock the seeds out of the spikes upwind of the pond. The seeds will blow downwind into the site."

Large ponds must be carefully planned and constructed to avoid leaks, algae problems, erosion, and poor water quality. They often require permits from local authorities, as well as from county and state natural resource agencies.

A pond site must be carefully chosen to fulfill water and structural requirements. One or more sources of clean water (groundwater, runoff, or supplementary flow from a stream or well) and relatively nonporous soils are essential, although clay or sheet liners can sometimes be used to seal a pond bed. Depending on the terrain, building requirements may necessitate an earthen embankment and spillway piping for overflow. If you are going to stock fish in your pond, it must be dug deep enough (six to eight feet minimum) to support a fish crop through the winter. Ponds sometimes need an aeration system to control algae. Inflow and overflow channels may require the placement of some kind of fieldstone to prevent erosion.

The owners of wildlife ponds tend to equate animal size with success. After all, there is something eye-popping about watching a moose take a bath in your backyard swimming hole. And who can fail to be impressed by the Jurassic-esque image of a great blue heron touching down on a shoreline? But just as wildlife ponds don't have to be big, deep, and expensive, the dramatic wildlife they lure can be similarly small. Mere inches, in fact.

Take the case of Kathy Biggs, who presides over a 20-foot-by-24-foot pond in her Sebastopol, California, backyard. In the seven years since she and her son Jody built their pond, her favorite visitors have been the 25 species of dragonflies and damselflies she has sighted. She's also quite enamored of a gray fox that visits the pond with her kits.

Since she built the pond, Kathy has become one of the country's most knowledgeable lay dragonfly experts. She even successfully petitioned the Dragonfly Society of the Americas to change one dragonfly species' common name to clear up confusion about its territory. (Thus the Sierra damsel be-came the exclamation damsel, notable for its typographic markings.) Kathy also wrote the first guide to her state's dragonflies, Common Dragonflies of California: A Beginner's Pocket Guide.

Although she has been an Audubon member since childhood ("Some people went to the movies. We went to Audubon nature films," says Kathy, a member of Madrone Audubon in Santa Rosa), her interest in dragonflies started innocently enough. When the Biggses dismantled their above-ground swimming pool, they created a two-foot hole in the ground where the pool's deep end had been. Instead of filling it in, they decided to create a small water garden. "I was already doing habitat gardening for wildlife," Kathy says, "so I thought I'd try a wildlife pond." Retaining part of the original liner kept the pond leak-proof, and over the years the Biggses added aquatic native plants, experimented with native fish, and inoculated the pond with water nymphs. Then they watched the arrival of the wildlife: raccoons, opossums, foxes, gophers, squirrels, skunks; some 55 bird species; reptiles and amphibians; and, of course, the aerial parade of dragonflies and damselflies.

As Kathy's love affair with dragonflies grew, she began to study the insect's life cycle and was delighted to find that many were breeding in her pond. The fish she had stocked were also pleased, and they began devouring both mosquito and dragonfly nymphs. In the past she had been told fish were needed to control mosquitoes, but by now she had fallen for the dragonflies. Time for an experiment. She netted out the fish, gave them to a neighbor, and waited nervously for an explosion of mosquitoes. Instead, the dragonfly population boomed, along with the frogs, whose eggs had also been nourishing the fish.

Kathy is now waiting to see if dragonflies and frogs will be as effective at mosquito control as fish are, and she suggests that wildlife-pond owners will enjoy a greater variety of aquatic life, especially dragonflies, if they forgo the koi, goldfish, and Gambusia affinis (mosquito fish) that are commonly stocked in ponds.

Perhaps it's only natural that wildlife ponds develop so, well, wildly. Certainly the Soest and Biggs ponds evolved spontaneously. However, not all wildlife ponds are unmitigated triumphs. In fact, the more ambitious you get with your pond, the more potential there is for complications. Mixing recreational and wildlife features is often a formula for trouble. I worked on a one-acre pond in northern Vermont whose owner wanted to combine swimming, trout, and wildlife habitat. The pond was dug deep, with a constructed island designed to attract waterfowl. The pond filled up the first spring, and a pair of migrating Canada geese nested on the island. But instead of leaving with the goslings, the birds hung around. Soon they attracted more geese. In no time the pond had lost much of its charm—the shore was littered with waterfowl waste, and the water contained potentially unhealthy levels of coliform bacteria.

It has taken several years of nonlethal bird control (mostly firecrackers) to reduce the population, but the geese are still a problem. "Having all these geese doesn't quite work," the owner says. "It's a real effort to keep them away." On the other hand, the pond supports dozens of two-pound rainbow trout, and is a regular destination for herons, moose, wild turkeys, ospreys, eagles, hawks, deer, and "lots of bullfrogs." It also serves as an annual springtime classroom for local schoolkids learning pond biology. Hardly a failure, but my guess is that without the island, the project wouldn't have been such a wild-goose chase.

Tim Matson's lastest pond book is Earth Ponds A to Z: An Illustrated Encyclopedia (The Countryman Press, 2002).

© 2003  NASI

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