Un Réseau de conservation pour la forêt de feuillus des Appalaches de la Vallée de la rivière St-Jean

À mesure que la population humaine du globe continue à grandir de manière exponentielle et que l'utilisation des ressources accélère rapidement, l'importance des approches actives pour la conservation de la biodiversité devient de plus en plus claire.

Matt Betts nous parle du projet de conservation sur lequel il a travaillé.

==========
Appalachian Hardwood
Forest site:
 Forest interior
==========

(photo: Nature Trust of NB)

Saint John River 
Valley Conservation
Network

A Conservation Network
for the Appalachian Hardwood Forest
of the Saint John River Valley

Matthew Betts,
Nature Trust of New Brunswick
January 2000

ppalachian Hardwood Forest (AHF), also termed St. John River Valley Hardwood Forest (SJRHF), refers to a distinct assemblage of tree, understory vascular plant, and bryophyte species that exist in western New Brunswick and northeastern Maine. 

(photo: Nature Trust of NB)

========== Yellow Lady Slipper ==========

Appalachian Hardwood Forest is more floristically diverse than most other New Brunswick forest types and contains a number of plants that are uncommon, rare and very rare in other parts of the Maritime provinces. . These include yellow lady’s slipper (Cypripedium calceolus var. pubescens), blue cohosh (Caulophyllum thalictroides), wild ginger (Asarum canadense), Canada violet (Viola canadensis), wild leek (Allium tricoccum), and maidenhair fern (Adiantum pedatum). A number of species exist in the AHF that are found nowhere else in Atlantic Canada. These include lopseed (Phryma leptostachya), cutleaf toothwort (Cardamine concatenata), and showy orchis (Galearis spectabilis).

Agricultural development and forestry practices have resulted in widespread removal of Appalachian Hardwood Forest. With the use of the New Brunswick Department of Natural Resources’ Ecological Land Classification, it was possible to compare the historical range of this forest type to its current distribution. Amazingly, AHF covers only 0.8% of its former range! Most the remaining hardwood forest exists in small patches of less than 10 hectares. This scale of habitat removal results in decline of species which are dependent on this forest type. However, even remaining remnants are in danger of species loss. Ecological processes such as gene flow, interaction among local populations of wildlife, and fragmentation all affect the species that still survive in these fragments. Fragmentation is the process of ‘breaking apart’ the forested landscape in to small, isolated pieces. In many cases, isolated populations of plants and animals have been shown to be at much higher risk of local extinction than populations that are connected by forested lands (corridors). If biodiversity is to be conserved, research and planning must occur across whole landscapes.

In 1998, I was lucky enough to be involved with a project initiated by the Nature Trust of New Brunswick that targeted these potential conservation problems in the St. John River Valley. The goal was to determine the degree of fragmentation that exists in this region, examine the impacts to indigenous species, and to create a plan which would help maintain populations of species that depend on Appalachian Hardwood Forest. I will briefly describe the Conservation Network plan that was developed to help limit species loss due to habitat loss and fragmentation.

How do you measure the potential impacts of fragmentation and habitat loss? Because it is impossible to determine the impacts of this process on each of the thousands of New Brunswick species, I decided to select ‘indicator species’. Indicator species are organisms that depend on large tracts of old forest, and often are not very good at moving about. By focusing on the needs of these species, I hoped that species less dependent on old forest and more capable of movement would also be protected. Red backed salamander (Plethodon cenereus), red spotted newt (Notophthalmus viridescens), scarlet tanager (Piranga olivacea), northern flying squirrel (Glaucomys sabrinus), and a range of AHF plants were selected. Each of these species require a certain minimum amount of forest area for habitat. (For example scarlet tanager requires at least 10 hectares for a breeding pair). Each species has varying ability to cross open spaces. (For example many of the AHF plants are only capable of moving a few centimetres per year and will not move beyond the forest canopy).

(photo: Leo-Guy de Repertigny)

========== Scarlet Tanager (Piranga olivacea) ==========

With the use of a Geographic Information System (a computerized map) it was possible to determine how much habitat remained for these indicator species and how fragmentation is likely to affect populations. It did not take long to realize that very little contiguous forest exists in the St. John River Valley. Only 21 patches of scarlet tanager habitat greater than 100 hectares exist in the study region. The majority of patches are smaller than the 10 hectares that is required for breeding pair. As mentioned above, habitat for Appalachian Hardwood Forest plants is severely reduced. The distance between these patches is far greater than the ability of most of these plants to disperse (move). Such isolated populations of plants have been shown to exhibit reduced genetic diversity. This limits the ability of a species to adapt to changing environmental conditions and increases the likelihood of local extinction.

What actions could be taken to limit the effects of habitat loss and fragmentation? A number of conservation biologists in North America and Europe have suggested that a network of protected areas and corridors will serve to conserve populations of species that are dependent on large tracts of forest. In comparison to boreal-type forest which is prone to relatively recent disturbances (i.e. fires, blowdown), Appalachian Hardwood Forest is a relatively stable forest type. Craig Lorimer, an ecologist from Maine, estimated that large scale disturbances such as fire only occur in this forest about every 1000 years. This stability provides an ecological basis for corridors because in the pre-European era, the forest would have typically exhibited a high degree of connectivity.

(photo: Museum of NS)

========== Red  Eft (red spotted newt in its terrestrial stage) ==========

Based on the existing indicator species habitat that I identified during the first part of this project, I went about identifying areas that would serve as effective core areas and corridors. Core areas had to be large enough to accommodate species like the scarlet tanager. Connectivity had to be high enough to ensure the dispersal of species with poor abilities to move. Corridors were sufficiently wide to create a ‘forest interior’ condition. I only identified these areas on existing forested land due to the tremendous expense associated with restoring agricultural land. Also, I incorporated as much existing mature forest as possible. In total, after a lengthy mapping exercise, 14 core areas and 12 corridors were identified. These areas covered a total of 12% of the land base. In addition, I delineated a single large ‘core area’. This area, which exists in the Kintore Hills region east of Perth-Andover, is one of the last extensive tracts of mature tolerant hardwood forest.

Initial examination of the Conservation Network map suggests that implementation might require a costly restoration effort and extensive transformation of existing land-use practices. However, this does not need to be the case. The majority of forest which exists in the proposed Conservation Network is mature or immature (35 – 160 years old depending upon the tree species) (See graph below). Implementation would require alteration of practices in these areas so that a continuous canopy could be maintained. For example if done properly, selective cutting could occur in these areas. Particularly sensitive areas such as AHF sites should ideally be considered ‘no harvest’ zones. The 29% of the network that exists in younger age classes could be left to regenerate so that connectivity is restored. Further, many corridors tend to be associated with streams and rivers. Restoration of such areas would have the additional benefits of increasing riparian zone habitat and water quality.

(photo: Nature Trust of NB)

========== Age class structure of potential core areas and corridors. ==========

Political feasibility is clearly the biggest barrier to implementation of a Conservation Network. The St. John River Valley is primarily made up of small woodlots. Such a plan would require massive orchestration of many individual owners. However, a combination of woodlot owner education and financial incentives might provide the means through which to incrementally develop such an important biodiversity conservation measure.

As the human population of the globe continues to expand exponentially and resource use rapidly accelerates, the importance of active approaches to biodiversity conservation becomes clear. In Europe, where many native species have already been lost, large efforts are being mounted to restore degraded landscapes. In New Brunswick, we are in the lucky position of still having some ‘wild’ places that are not dominated by human influence. We must begin to consider approaches such as this Conservation Network, if we are to halt ecosystem degradation that inevitably results in species loss.

For more information on this project:
Please contact the Nature Trust of New Brunswick 
(506) 457-2398, email:  ntnb@nbnet.nb.ca  
Copies of Landscape Ecology Mapping Project:
A Landscape Approach to Conserving the Appalachian Hardwood Forest (95 pages with colour maps) can be ordered for $40.