bugs and beavers - Ville d`Estérel


bugs and beavers - Ville d`Estérel
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.
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.
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
*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
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
accumulates water around the shoreline
and banks, resulting in an eco-drainage
*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
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
The negative aspects
beaver’s presence are:
*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.
Agriculture and Agri-Food Canada Research Brand; A review of the environmental impacts of the microbial insecticide Bacillus
thuriensis Technical Bulletin No. 29