bugs and beavers - Ville d`Estérel
Transcription
bugs and beavers - Ville d`Estérel
BUGS AND BEAVERS LIVING WITH BLACK FLIES In 2006, the City of Estérel renewed a program to eradicate mosquitoes and black flies to improve the quality of life of its residents and visitors, and protect them from the threat of the West Nile Virus. The product used in these carefully targeted applications is a microbial control agent called Bacillus thuringiensis israelensis or Bti. The public’s concern for the environmental effects associated with chemical insecticides has prompted the switch to more bio-degradable agents that are highly selective, targeting a very narrow range of pests. In this case, Bti is only toxic to the mosquito and black fly larvae and has proved safe for humans, mammals, birds, fish, all other wildlife and the environment. Black flies are small, bloodsucking insects approximately 1-3 mm long, black or grey with short legs and antennae. There are over 1800 known species. They appear in the Spring and disappear in early Summer. Black flies need water to procreate and lay eggs. The larvae attach themselves to submerged objects where they develop into adults, swim to the air above and fly to breeding site nearby. The males then seek nourishment from pollen and nectar but the females search out blood needed to produce their eggs. Female black flies track their victims by the moisture and carbon dioxide emitted during perspiration. While biting, saliva is injected into the wound, preventing blood from clotting and setting off the allergic reaction that makes the bite itch. Some suggestions to living with black flies: *Avoid the outdoors during periods of peak black fly activity. Black flies only feed during the day and rarely bite indoors or late at night. *Wear light colored clothing. It attracts less than dark. *Use eco-friendly repellents. Catnip oil or oil of lemon eucalyptus are choices in organic bug repellents and pleasant smelling alternatives to chemicals. *Eliminate all stagnant water, even the tiniest ones: saucers under plants, clogged gutters, birdbaths and rain puddles, playpens and slides. *If you have a decorative pond, stock it with mosquito and larvae-eating fish like Gambusia THE BEAVER: PROBLEM OR SOLUTION Where would we be without the beaver ? A major lure to early explorers from the late 1600’s was the fur trade of beaver pelts. In Europe, fur top-hats were the fashion rage and the export from the New World so lucrative that the powerful Hudson’s Bay Company honoured the beaver on its corporate shield. In 1833 the beaver was included in the insignia for the incorporation of the City of Montreal. Facing extinction by the mid 19th century, the beaver was saved by the whims of fashion; now silk top-hats are de rigeur and the demand for beaver pelts have declined. The adult beaver, the largest rodent in North America, can weigh as much as 35 kg, stands 30 cm tall, with a wide flat tail about 25 cm long. It is semi-aquatic, using its tail as a rudder and an emergency signal in the water. Through a life span of twenty years, it is busy as a beaver, building its habitat, cutting and felling trees, leaving a telltale signature: pyramid shaped tree trunks. For its habitat, beavers build a dam to control the flow of water surrounding their home, a lodge that is a mastery of aquatic engineering. The lodge, dome-shaped, up to 91 cm high and 1.5 m wide is built of logs, bark, sticks and mud. There are two underwater entrances for security. Interior ramps lead up to the drying off floor of the lodge and then to the living space, built above water level and covered in woodchips to deter the humidity. A vent lets in fresh air for the single beaver family in each lodge. The beaver is considered a keystone species designating it as a major influence on the surrounding ecosystem. The beaver dam and lodge induce water, temperature and chemical changes. The positive aspects of the beavers presence are: *There are less flooding problems with beavers nearby as the beaver’s landscaping raises water levels, accumulates water around the shoreline and banks, resulting in an eco-drainage system. *The raised water levels, necessary to maintain a safe habitat for the beaver, also impact the surrounding terrestrial environment. This shallow warm water, the perfect climate for wetland vegetation, revitalizes the shoreline with rich and diverse aquatic vegetation and fauna and forms a wide, swampy transition zone between water and land slowing erosion. *The beaver contributes to the purification of the surrounding water as the dam slows down the flow, functioning like a water treatment plant, filtering environment sediments and other chemical substances. Drifting to the bottom, these substances create a perfect environment for the development of aquatic vegetation. This stabilizes the waterbed and creates a further filter for incoming debris of organic substances, changing the chemistry and the hydration of the soil. The pollutants in the water can be decomposed by microorganisms supported by the new vegetation. Also, the beaver’s constant foraging for food unclogs weeds and keeps the water flowing freely. *The beaver naturally replaces its cuttings. Mature trees are lost at the shoreline due to flooding and tree loss can be recorded some distance from the water. But thinning tree volume warms the forest floor and increases the plant biomass to greater than the timber mass decrease. Aquatic plants will sprout up when the beaver abandons the lodge to build a new one, and eventually, with shrubs and other plants, the area will become a meadow. The shrubs in the meadow will provide the shade for trees to grow and the land will become woodland again. *The beaver dam increases biodiversity in the complexity of the ecosystem by creating natural shelter, food and nesting conditions for a large variety of small mammals, bird species and water invertebrates that become the food for fish, reptiles and birds. The fish attract the otter, mink, herons and storks. Moose, deer and wild hogs become frequent visitors. The negative aspects beaver’s presence are: of the *The beaver and the impact of its lifestyle are positive from an ecological stance, but in terms of forest, agricultural production, and landscaped towns, the beavers' effect on their surroundings such as felling trees and flooding crops is negative. The beaver razes our landscape with his diet of aquatic plants: pond weeds, water-lilies, and cattails and cambium, the soft tissue of hardwood trees, including birch, aspen, willow, cottonwood, and alder. *Beaver dams can cause problems. Low lying areas can be flooded, the slow flow of water can cause the build up of silt, and some species can lose their habitat. The flooding caused by the dam can upset the infrastructure involved in modern water dispersion : drained marshes, tunnels, ditches, drains and pipes controlling the direction of water, extensions of farmland and gardens. The dams change the course of streams, water flow and create ponds, streams, brooks and marshes. *Recent studies of stagnant water in the Laurentian lakes presented by the Society of Limnolog, are pointing to a new threat from the beaver population. Phosphorus, a major cause of water pollution, usually associated with the resident lifestyle, is now linked to that of the beaver. The dams that flood the forest and rot the cut trees are the culprit; producing a major source of phosphorus.Professor Richard Carignan says that the impact of the beaver is major in some lakes. “If a private business had this environmental balance sheet, they would be closed immediately”, he stated. So, is the beaver a problem or a solution? Google for interesting sites filled with facts and ongoing research about this ingenuous little mammal. . SOURCES www.gouv.qc.ca/portaiol/quebec Agriculture and Agri-Food Canada Research Brand; A review of the environmental impacts of the microbial insecticide Bacillus thuriensis Technical Bulletin No. 29 www.hww.ca www.nature.ca/notebooks/english/beaver www.members.shaw.ca/kcicl/beaver www.fishbc.com/adventure/wilderness/animals/beaver