THREATS TO THE CARDEN PLAIN
The immediate future of Carden Plains' IBA species depends on healthy,
productive, stable, and well-managed habitats. Most grassland ecosystems
have been altered profoundly over the last 100 years, and many are
now considered North Americas' most endangered ecosystems (Vickery
et al, 2000). Effective bird conservation and management must recognize
both historical and present dynamics which shape and drive the ecological
processes of alvars and grasslands.
and habitats are subjected to threats that not only endanger their
future viability, but their very existence. Many of these threats
are of human origin, whether through direct human activities or
human-induced changes to the ecosystems. Identifying these threats
is a vital first step towards effective conservation action.
quarries are by far the most serious threat to the future integrity
of the Carden Plain IBA and its species. Recent expansion of aggregate
operations within and surrounding Carden Plain has created a high
level of concern. Quarries own approximately 13% of the Carden
Plain area and are still trying to expand. (See map of quarry
property and environmentally protected property) Yet the present
licensed reserves represents a 100-year supply and the combined
output of all the five current pits is less than 20% of licensed
limits. This suggests there is little need for more quarries yet
they continue to appear.
development and operation of limestone quarries have several effects
on habitat and species. The quarry itself, along with the associated
stockpiles, berms, and access roads, destroys natural habitats.
The practice of surface rock harvesting for large chunks of flat
limestone, which is underway in some parts of the IBA, strips
habitat of its foundation, leaving little opportunity for restoration.
Finally, the noise and dust associated with quarry operations
and truck haul routes affect nesting birds in adjacent areas.
These impacts are likely both ecological (e.g. impact on the food
web), and behavioural (e.g. impact on breeding activities such
as courtship and use of song). Some quarries may have deliberately
destroyed habitat on their property to prevent endangered or threaten
species from nesting there. While they deny this there are no
Loggerhead Shrike currently nesting on active quarry property
despite history of active nesting prior to the quarry operations.
an economic level, quarries represent a threat to tourism, probably
the most promising economic opportunity available to Carden, while
providing minimal local benefits to the economy. Despite all the
negatives, provincial policy favours quarry expansion and, in
spite of strenuous effort by environmental groups such as the
Carden Plain IBA and the municipal government, they will expand.
The Provincial Policy Aggravates Threats
is a paradox that the legislation designed to protect endangered
and threatened species actually worsens their prospects. Draconian
regulations specify the if an endangered species decides to breed
on a landowner’s property approximately a 100 acre area
surrounding the site is protected for at least five years. Some
landowners interpret this to mean that they are prohibited from
even walking on the designated land. Their solution is simple,
shoot, shovel and shut-up. In 2007, several local landowners spurred
on by the Ontario Landowners Association, created a media event
by cutting down, what they claimed were thousand of acres of hawthorn
trees. Hawthorn trees are the primary nesting sites for Eastern
Loggerhead Shrikes, a locally endangered species. The new provincial
Endangered Species Act will come into force in April 2008 replacing
the Provincial Policy Statement.. Hopefully the accompanying regulations
will focus more on positive inducements and less on punitive measures.
The Decline of Cattle Ranching
70 percent of the occupied land within the IBA is utilized for
pasture, much of it being held in lots of 400 hectares or more
(Couchiching Conservancy, 1997). Cattle grazing has been the most
common land use in Carden for over a century. There is much debate
regarding the role of grazing in maintaining grassland and alvar
sites. On one hand, many grassland birds benefit from light grazing.
It creates a mosaic of grass heights and structure, removes ground
litter, and allows the development of wildflowers and scattered
shrubs (Massachusetts Audubon Society, 2000). Disturbance caused
by grazers is one of the driving forces that maintain grassland
integrity. Grazing slows down ecological processes that eventually
lead to successional woody scrubland and forest growth, by maintaining
large, open areas (Rodger, 1998). Grasses are adapted to grazing;
since their growth points are located close to or underneath the
surface of the ground, they can easily re-grow from these points
following grazing (Rodger, 1998). A moderate amount of grazing
actually stimulates plant growth, and thus increases productivity.
A new approach to pasture management called rotational grazing
can increase productivity by 30%
this point of view, the health of grasslands for Loggerhead Shrikes
and other grassland birds is dependent on a continuation of grazing
activities. Therefore, a decline in the area of active grazing
is a threat to many grassland bird species.
the other hand, little is known about the effects of grazing on
the more pristine alvar habitats. Cattle grazing introduces weedy
species through manure and disturbance to the thin alvar soils,
and it selectively removes some alvar plants (Reschke, 1999).
Grazing has likely caused a decline in quality of some alvar communities,
and should be discouraged on these sites.
Hayfield Management and Conversion
Populations of grassland birds adapted to agricultural landscapes
are now diminishing as the result of land use changes. Over the
last part of the century there has been a general trend for fewer
farms and larger tracts of land in the IBA. A single change in
agricultural practices on one large piece of land within the IBA
poses a significant change for the birds nesting there. For example,
converting a large central hayfield to corn would not only alter
its habitat composition and make it unsuitable for many species,
but also cause a disruption to surrounding breeding birds through
agricultural practice of most concern in the IBA is the management
of hayfields. Due to the unsuitability of the predominately thin
soils for row crops, hay is the single largest crop in the Carden
area. Hayfields support a rich diversity of grasses, wildflowers,
and invertebrates that are important for breeding grassland birds
(Jones et al., 1998). Many grassland birds readily nest in hayfields,
while others nest nearby and use the fields for hunting and foraging
(Massachusetts Audubon Society, 2000). Some species, such as Bobolinks
and Eastern Meadowlarks, build nests on the ground, raise young,
and forage within the hayfields during the spring and summer months.
Other species, such as Savannah Sparrows, are more common in idle
hayfields than in annually mowed hayfields (Dale et al., 1997).
hayfields that were traditionally harvested late in the season
provided ideal breeding habitat. Today, remaining hayfields are
mowed earlier and often twice during the summer to provide a greater
quantity and a better quality of hay. This practice may destroy
nests and young birds, depending on the actual timing of mowing,
which is often weather-related.
Lack of fire on the Carden Plain in recent years is a potential
concern to the health of the IBA grasslands. While most people
think of fire as a destructive force, fire is often the main driving
force behind the persistence of grassland, prairie, and savannah
communities (Rodger, 1998). Grassland vegetation employs the same
strategy used in recovering from grazing - extensive stem and
root systems allow plants to regrow immediately once the above
ground biomass has been removed by fire (Rodger, 1998). The occurrence
of fire under carefully controlled conditions is desirable to
maintain a healthy grassland community (Madden et al., 1999; Rodger,
suppression allows trees and shrubs to invade the grassland community.
Re-introducing controlled burns could: enhance native grass species;
eliminate ground litter; kill trees and shrubs like juniper
There is evidence specific to the Carden Plain which suggests
that fire could be an important restoration tool in the IBA. In
1946 there was a very large and long-lived fire which burned the
7th and 8th concessions of Carden Township extensively for nearly
two months (Couchiching Conservancy, 1997). Some of the highest
quality alvar and grassland/shrubland habitats are now found in
potential of fire as a management tool for the Carden Plain IBA
has been recognized by the IBA Steering Committee Consultant advice
has suggested it is viable and preliminary discussion with City
of Kawartha Lakes officials suggest it is permissible. A pilot
burn is planned for a small portion of the Cameron Ranch in the
fall of 2008
Habitat Loss through Fragmentation
Loss of habitat is usually considered to be the major contributing
factor to species population declines, but the shape and integrity
of remaining habitat blocks is also critical. Research now shows
that many species of grassland birds require large blocks of habitat
and do not nest successfully near edges (Herkert et al., 1993).
Populations of these species generally do poorly where habitat
is broken into small, isolated patches, a process called habitat
fragmentation. Nest predators such as foxes, raccoons, coyotes,
skunks, crows, and jays are attracted to small habitat patches
as travel corridors, thus drastically increasing chances of detection
and predation. Brown-headed Cowbirds, which lay their eggs in
the nest of other species and reduce the reproductive success
of the host, also prefer habitat edges and small patches.
into smaller patches may also result in inadequate food sources
or space for social interactions for some species. Many grassland
birds are loosely colonial, and need habitat blocks large enough
to accommodate a cluster of nesting pairs. These species are genetically
programmed to breed in proximity of others of their own kind,
and isolated pairs are often not viable. For very rare species,
widely separated and fragmented habitat patches may pose difficulties
in simply finding a mate.
bird species sensitive to habitat fragmentation are generally
referred to as area-sensitive species, which includes 11 of the
30 target species in Carden.
fragmentation in the Carden Plain IBA can be attributed to a combination
of factors, including changing agricultural practices, highways,
power lines, quarrying, and related practices. Woodland succession
has been identified as an area of concern within the IBA. While
ongoing fragmentation is a serious concern, it is important to
note that the present degree of fragmentation within much of the
Carden Plain IBA is substantially lower than other areas of southern
Ontario. This character underlies much of its value to grassland
and shrubland bird species.
The presence of invasive or exotic species in alvars and grasslands
reduces the ecological value of habitat that is already globally
endangered (Couchiching Conservancy, 1997). Invasion of species
such as Viper's Bugloss (Echium vulgare) that can withstand the
harsh conditions of alvars has changed the native plant composition
in the Carden Plain IBA. Little or no research has been carried
out on how much of a threat is posed to grassland bird species
from these non-native species. Alvars at the north end of the
township are not dominated by exotic species, perhaps due to the
absence of grazing in the area (Schaefer, 1996).
comparison, many hayfields within the IBA are composed of a variety
of exotic species. Some birds will not nest in fields containing
only one species of grass. These birds depend on a variety of
height and density of grasses for nesting, foraging, and cover.
Other species such as Bobolinks and Eastern Meadowlarks are able
to take advantage of productive hayfields, as long as some vegetation
diversity still exists.
While tourism plays a vital role in IBA recognition and support,
it can also be a threat to the integrity of the habitat and presence
of certain species if not managed properly. Two threats closely
associated with tourism in the Carden Plain IBA occur through
birding and off-road vehicle recreation.
birders from many places come to view and enjoy the unique landscape
and associated species of Carden.. Visitors are encouraged through
publications (and soon signs), not to trespass, not to disturb
these birds, not to look for nests, or attempt close-up photography.
Ontario's Endangered Species Act prohibits the killing, injuring,
or interfering with endangered species or the interference with
or destruction of the habitat of the endangered species (Pittaway,
2000). The penalty is a fine of up to $50,000 and/or imprisonment
up to two years.