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.

Species 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.

Quarrying

Limestone 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.



The 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.

On 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

It 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

Approximately 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%

From 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.

On 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 habitat fragmentation.

The 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).

Historically, 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.

Fire Suppression

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, 1998).

Fire 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 this area.

The 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.

Fragmentation 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.

The bird species sensitive to habitat fragmentation are generally referred to as area-sensitive species, which includes 11 of the 30 target species in Carden.

Habitat 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.

Invasive/Exotic 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).

In 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.

Tourism

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.

Naturally, 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.