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Keeping our beaches healthy By Geoff Peach, Dune grassland systems on the Great Lakes are one of the most vulnerable ecosystems in the nation. They can also be considered rare coastal features, amounting to only 1.5 percent of Ontario’s Great Lakes coastline. Yet these ecosystems with their high quality beaches are the most attractive locations for beach goers. It’s important to understand the ecological significance of these features, and what impacts we can have on them. Minimizing our impacts can mean leaving behind some of the old practices that have led to dune degradation. Conserving these ecosystems can ensure that we continue to have high quality beaches to enjoy. Sand dunes act as a long-term sand store to build sand bars during major erosion events. Large waves make ‘withdrawals’ from the dune sand bank to build offshore, protective sand bars, and then small waves return this sand back to the beach. The general pattern is one of swift erosion during storms, and a gradual return to the beach of the eroded material during quiet, gentle wave periods. Native dune vegetation significantly influences the size and stability of dune areas. Dune grasses, like Marram, Great Lakes Wheat Grass and Long Leaved Reed Grass are examples of some of Lake Huron’s most important dune stabilizers. All of these plants are rare species. Some dune plants, like Pitcher’s Thistle, is not only rare, but is an endangered Species at Risk. Landowners should encourage the development of a ”buffer”, in the form of stabilized, undisturbed, vegetated sand dune system. Stabilized and vegetated sand dunes help to increase the volume of sand available to build sand bars during erosion events, thus protecting the properties behind The long, deep and expansive root systems of native dune plants help to minimize sand losses from frontal dune areas caused by wave attack during severe erosion events, and from wind erosion, particularly during the storm season in fall and winter.. The varying of height and density of native dune species provides an good buffer to minimize wind effects. Native dune vegetation can withstand burial by wind-blown sand, a common occurrence in active foredune areas. Dune vegetation provides habitat and corridors for a wide range of insects, birds and other wildlife. It also enhances the natural appearance, overall character and environmental quality of the beach and dune areas. Non-native invasive species can be a real problem in dune areas. They can often displace native dune vegetation due to their ability to grow aggressively, smother native dune species, and compete for available nutrients. Beach and dune areas where native vegetation has been disturbed provide the conditions that are ideal for invasive plants to colonize. Invasive plants can alter the entire ecology of the dunes. Invasive exotic plants that inhabit areas close to the shoreline can be spread along the coastline by currents and become invasive in other areas, or they can move in from properties where they ‘escape’ from gardens and lawns. Some examples of invasive beach plants include, Spotted Knapweed, White Sweet Clover and Common Reed. Turf grass, or lawn grass, is another type of non-native invasive, and can pose a real problem in coastal areas. It can also escape from properties and invade natural shoreline ecology. Turf grass does not have the ability to trap wind-blown sand traveling just above the ground level. The absence of sand-trapping vegetation causes sand to be lost from the beach system. The natural, dynamic cycle of sand movement is broken. The establishment of turf and the mowing of herbaceous vegetation stunts the growth of the sand dunes (both height and width), and inhibits their capacity to act as long-term sand reserves. The result of stunted dune growth is a degraded beach system. In areas where native dune species have been encouraged, the replenishment of sand has resulted in well-formed dunes. In areas where native dune species have not been encouraged, the dunes are poorly developed and contain small reserves of sand to replenish the beach and provide protection from wave attack. Recent research on Lake Huron has concluded that degraded dune areas can actually create the conditions that lead to elevated bacterial pollution of the nearshore. The change in the structure of the beach and dune, reducing the volume of sand retained, has shown a positive correlation with higher incidences in E. coli bacteria. Turf grass is also implicated in the increased occurrences of E. coli because turf grass attracts waterfowl, like Canada Geese, which leave large amounts of their waste behind. These birds, on the other hand, are not attracted to native dune vegetation. Turf is not capable of withstanding sand burial. Buried turf is most likely to die off, leaving the dune area without vegetative stabilization in erosion events. Mown turf should not encroach into active foredune areas. The acceptance of environmentally inappropriate turf grass, or exotic species within the dune environment can reduce the natural heritage values of lakefront land, be detrimental to the sustainability of the dune environment, degrade the environmental quality of the beach and have a negative impact on the aesthetic value of our coast. Maintaining the quality of our beaches and dunes is up to each one of us. Let’s keep Lake Huron a great lake. (for more information on dune conservation, or information on the conference "Caring for Our Beaches" in Midland on July 13, 2007, contact the Lake Huron Centre for Coastal Conservation – (519) 523-4478 - www.lakehuron.on.ca) |
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