The Shore Primer, Ontario edition

HOW TO PRESERVE YOUR SHORELINE'S
TRUE NATURE

Take a good look around your property and familiarize yourself with the features of your waterfront. The natural shoreline has four components, beginning underwater and extending upland (farther than you would think). Shoreline experts call these four components the littoral zone, the shoreline, the riparian zone, and the upland zone, and each plays a critical role in keeping your lake healthy. As important as these separate zones are however, it is vital to remember that the shoreline is a natural progression - each area transforms into the next in a gradual, almost seamless transition. Altering any portion of this region affects the whole, diminishing its ability to support life on the lake.

Building a sand beach is tempting, but it can easily erode,
smothering aquatic life.

THE LITTORAL ZONE:
PERFECTLY PRODUCTIVE HABITAT

Sitting on your dock, you are perched in the littoral zone, the area from the water’s edge to roughly where sunlight no longer penetrates to the lake bottom. As much as 90 percent of the species in the lake either pass through or live in this zone. Algae floats freely in the water or attaches to twigs, stones, and plants. Microscopic water bears (freshwater invertebrates that look like tiny lumbering bears - if you ignore the two extra legs) graze on aquatic plants. Yellow perch spawn in the shallows, while northern pike lurk among the sedges. Ducks forage in the pond weeds, and turtles loaf on the trunks of fallen trees.

The water in front of the shoreline provides spawning areas, cover, nursery habitat and food for a range of species, offering foraging areas and hiding spots and a shallow, relatively protected area for young fish and amphibians to grow. Aquatic plants and downed trees are a crucial part of the system, with the plants acting as the lungs of the lake, converting sunlight into food and releasing oxygen in the process, and providing food and shelter for other creatures. Once submerged, wood becomes a major source of food for aquatic insects, crayfish, and small fish, its surface covered with tiny plants and invertebrates. Downed trees and woody debris also act as hiding spots for small fish and their predators, and are good spawning zones for yellow perch.

How we can help the littoral zone stay healthy:
The water’s edge is also a focal point for human activity. While we do not intend to, it is easy for humans to interfere with the delicate operations of the littoral zone. If you accidentally spill two-stroke fuel for example, the juvenile perch will be looking for a new home. The simplest way to keep the littoral zone vibrant and healthy is to tinker with it as little as possible:

• Use your dock as a bridge over the weedier shallows, and moor a swimming raft out in deeper water, rather than removing fish and amphibian habitat by ripping out aquatic plants to make a swimming area.
• Leave trees where they fall, unless they are a hazard to boats or swimmers. Typically, only a few trees along a kilometre of waterfront will tumble into the water during a year. When a cottager removes all of the trees lining the waterfront, habitat formed by the fallen trunks and branches that took decades to accumulate is destroyed in a single summer.
• Before the impact of creating sandy beaches on lake habitats was well understood, many cottagers liked to “improve” their swimming areas by bringing in a few truckloads of sand and dumping them on the shoreline.

So what is the harm in that? When the sand erodes, as it almost certainly will, it smothers spawning areas for smallmouth bass and other fish, buries mayflies in their burrows, and covers the vegetation where frogs and toads lay their eggs. The impact ripples through the food chain. Without frogs and tadpoles and other aquatic species to eat decaying aquatic plants and insects, more oxygen-depleting algae fills the lake and more insects swarm the shoreline. The blue heron moves on when amphibians grow scarce. While a beach may be fun for sunbathers, it is no picnic for littoral residents.

Despite these problems, sometimes a compromise is possible. You may be able to have a sandy area if, for example, it is well above the ordinary high water mark and there is little or no disruption to natural shoreline vegetation. (On a lakeshore, the ordinary high water mark is the highest point to which water customarily rises, and where the vegetation changes from mostly aquatic species to terrestrial). (For guidance, check DFO’s “Operational Statements”).

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THE SHORELINE: GLUE FOR THE WATERFRONT

Thanks to thousands of years of practice, the existence of natural shoreline vegetation provides one of the world’s most effective, least expensive erosion controls. The mix of plants, shrubs, and trees forms a complex web of roots and foliage that knits the waterfront together, holding the bank in place and fending off the impacts of wind, rain, waves, ice, and boat wake.

The barricade against erosion is the shoreline, the place where land and water meet. In its natural state, the shoreline is a profusion of stones, plants, shrubs, fallen limbs, and tree trunks. But it is also a busy intersection, with animals, insects, and birds traveling back and forth. Moose and deer pick their way down to the water to forage or drink. Mink skulk about on hunting trips. Water birds waddle from their nests to the water. Overhanging vegetation shades and cools the water, and acts as a fast-food outlet for fish by producing a rain of aphids, ants, and other insects that slip from their perches above.

How we can help keep the shoreline together:
Things start to come apart when people remove the vegetation whose roots act as the glue that holds the shoreline together. The resulting erosion sends silt and sediment into the water where it damages spawning areas. For example, the eggs of northern pike cling to vegetation in the shallows. Water circulating around the spawning bed carries oxygen to the eggs, but when silt covers them, the unhatched fish are suffocated.

A method often used to protect against shoreline erosion is to replace the natural shoreline with a breakwall made of wood, rock, concrete, or steel. In environmental terms, this converts a lively waterfront into a sterile environment. By imposing a sharp vertical drop-off on the shoreline, a breakwall limits the ability of plants to re-root up or down the bank as water levels rise and fall, typically reducing waterfront vegetation by one-half to three-quarters. The decline in the number and diversity of aquatic plants has a ripple effect, reducing habitat for fish, birds, and amphibians. As well, this kind of erosion control is almost always an expensive temporary fix. Because artificial materials lack the resilience of the natural shoreline, a homemade vertical breakwall often lasts only a decade or so before cracking and falling apart. To maintain a healthy shoreline:

• DO leave the natural vegetation on the land and in the water.
• DO NOT replace the shoreline with a hardened surface like rip rap or breakwall.
• DO NOT dump fill along your waterfront. Not only does this destroy part of the littoral zone where fish live, but it may alter water currents and increase erosion on adjacent properties.

THE RIPARIAN ZONE AND UPLAND ZONES:
THE LAKE'S BUFFER

Just like the mat laid at the cottage door that welcomes muddy feet and shoes, lakes have a similar “contaminant” barrier: the riparian and upland zones.

There are a lot of nasty things waiting to catch a lift down to the lake with rain runoff, including seepage from septic tanks, fertilizers and pesticides, deposits from family pets, and oil or gas spilled on the driveway. One of the main contaminants from cottage runoff is phosphorus, a “nutrient” that occurs both in nature, as well as in human-made products, such as fertilizer and detergent. On its own, phosphorus helps to nourish life in the lake, but when we add to that natural load, phosphorus over-feeds the lake, causing algal blooms that consume the water’s oxygen, and that results in poor water quality.

Fortunately, the jumble of trees, shrubs, and grasses along a natural shoreline forms a “buffer” that helps filter out undesirables. In the riparian zone - the section of land closest to the shoreline - the thick layer of low foliage controls erosion and sifts impurities out of surface runoff. Leaves and branches break the force of falling rain, which is further slowed by the rough surface of leaf litter, pine needles, and broken twigs.

The water is then absorbed by plant roots or the soil. As well as being a filter for the lake, the riparian zone is a refuge for wildlife: water birds nest in the tall grasses near the water; and red-winged blackbirds flit among the cattails. When the area is flooded during the high water period, even if there is only 18 cm of water, pike will thrash their way over the spring-flooded banks, scattering their eggs in the lake-edge nursery.

The higher, drier ground called the upland zone is typically forested with the kinds of trees that take advantage of better drainage, including Manitoba maple, poplar, spruce and white birch. The deep roots of the trees stabilize the slopes, while their foliage buffers the shoreline from winds. The forest canopy also cools the area by maintaining shade and boosting humidity in the summer. In winter, it shelters deer, chickadees, porcupines, grouse, and rabbits.

Together, these two zones form a buffer so effective that many experts estimate only 10 percent of the runoff actually makes it into the lake, and much of the sediment and other pollutants are filtered out before reaching the water. If the lake bottom does not drop off too quickly, then the remaining run-off will tangle with another barrier of aquatic plants in the littoral zone, where the jumble of bulrushes, arrowhead, and cattails slows the influx of runoff and consumes many of its nutrients.

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How to keep the riparian and upland zones in place:
Almost any kind of development can weaken the lake’s buffer, and some projects can ruin it altogether. Even in the upland zone, the hard surfaces of paved driveways, shingled roofs, and patios shed water, increasing runoff and heightening the danger of erosion. Sediment carried into the water is also a concern during construction when land is being cleared for a cottage, a garage, or even just a lawn. Here are a few ways you can assist the lake’s natural filtering system:

• Eliminate potential pollutants by being careful with gas and oil around the cottage, avoiding the use of fertilizers and pesticides, and maintaining your septic system with regular pump-outs. Be careful not to overload the septic system with too much water; something to consider when running the dishwasher or washing machine, or hosting a big crowd for the weekend. Working the septic system too hard shortens its life, and can send some unpleasant things seeping toward the lake.
• Maintain as much riparian and upland vegetation as possible.
• Opt for softer or more permeable surfaces (gravel or wood chips) rather than concrete and asphalt.
• Replant disturbed areas as quickly as possible, and landscape grassed swales or depressions around the cottage to catch and encourage infiltration of rainwater flowing off of the roof. Be especially careful in the riparian zone, where any soil dug up is apt to be washed straight into the lake during the next rainfall. Leave the riparian plants, shrubs and trees in place.
• Keep flower and vegetable gardens well away from the lake.

When vegetation at the water’s edge is cut down, wildlife habitat is lost
and more polluting runoff reaches the lake.

Clearing woody debris and aquatic plants from the shallows means fish
no longer come to spawn nor herons to feed.

A concrete breakwall is a sterile barrier, extinguishing shoreline vitality.

YOU CAN SAVE YOUR LAKE FROM PREMATURE AGING

Like any cottager, a lake ages in a natural process called eutrophication: the increase in nutrients due to run-off from the surrounding area and the growth and decomposition of aquatic plants over time. Eventually (thousands of years later), so much decomposing plant and animal matter builds up that the lake bottom fills in, converting it to a bog and eventually, dry land.

On the geologic time scale, this is a good and normal thing - a healthy eutrophic lake supports all sorts of warmwater fish such as largemouth bass, catfish, and pike. But when humans fast-forward the process by tearing out the shoreline buffer zone and dumping too many nutrients such as phosphorus into the lake, the water begins to change too rapidly for the life that depends upon it. The water becomes murkier as plant and algae growth explodes, the added vegetation decomposing and consuming the oxygen normally shared with other aquatic creatures. Sensitive species like trout can suffocate in the oxygen depleted environment, interrupting the food chain and causing fish with a higher tolerance of lower oxygen conditions (like carp) to flourish. The lake ages before its time.

Because eutrophication is often the result of a lot of small actions - poor septic systems, using high-phosphate soaps, removing shoreline plants - it can also be arrested by the efforts of landowners. By understanding how a natural shoreline functions and then acting collectively to preserve, not destroy, that critical balance, individuals can make a difference.

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