Lutte contre les bioenv-
ahissements dans un parc national : vers un processus décisionnel mieux informé dans la gestion de la flore exotique du parc national de Kouchibouguac

Les effets écologiques provenant des envahissements des plantes exotiques et l'importance des activités humaines sont de plus en plus reconnus et documentés comme étant des agents facilitateurs. Plusieurs parcs nationaux au Canada entreprennent des luttes coûteuses afin de remédier aux effets écologiques des plantes envahissantes.

Nos parcs nationaux sont en grande mesure créés afin de protéger et de mettre en valeur certains éléments de notre patrimoine naturel. Toutefois, nos parcs peuvent aussi agir comme outils de formation pour étudier les effets sur l'environnement et comme indicateurs de l'état général de nos zones naturelles. Si le parc de Kouchibouguac est un indicateur de l'état général des écosystèmes naturels de notre région, alors il est important de réaliser l'avertissement qu'il est temps de s'occuper sérieusement de la question des envahissements des plantes exotiques.

"The spread
of exotic invasive plant species into natural areas constitutes a significant problem for native biodiversity and ecosystem conservation worldwide."

The Struggle Against 
Bioinvasions in a National Park: 
Towards Better Informed Decision-making
in the Management of Kouchibouguac
National Park's Exotic Flora

David M. Mazerolle
Université de Moncton
April 2004

he spread of exotic invasive plant species into natural areas constitutes a significant problem for native biodiversity and ecosystem conservation worldwide. In recent decades, both the ecological impacts stemming from exotic plant invasions and the importance of human activity as a facilitative agent have increasingly been recognized and documented. Our protected natural areas are not immune to biological invasions. Many national parks in Canada are currently waging costly battles in attempts to mitigate their ecological impact.

Old fields are a common sight in Kouchibouguac National Park. Exotic species cover in these habitats averages over 70%.
(photo: David Mazerolle)

In recent years, Kouchibouguac National Park has shown great interest in the creation of a management strategy addressing this issue. However, important information on which to base such a strategy was lacking, and many questions had yet to be answered before management actions could be undertaken. In response to this need, a research project aiming to gather necessary information and provide decision-making tools was initiated as part of a graduate thesis under the supervision of Liette Vasseur (Université de Moncton) and Éric Tremblay (Kouchibouguac National Park).

Human intervention has considerably modified the park's landscape, where activities like agriculture and wood harvesting have clearly left a mark. At the time of its establishment in 1969, nearly 250 families resided in the area. Human-caused disturbance continues to this day through visitor use, construction of trails, campgrounds and facilities, as well as maintenance work such as the mowing of roadsides and trails.

As could be expected, a considerable number of non-native plant species have become established over the years. Previous work done in 1979 had detected the presence of at least 141 exotics. The research team had surmised that several new species had become established since then and was eager to uncover more information on the exotic vegetation in and around the park.

The study, carried out in 2001 and 2002, was comprised of two major components, the first being an assessment of exotic invasive species threatening the integrity of ecosystems in the park and its surrounding area. With the principal objectives of identifying particularly invasive species and studying their geography, areas within the park likely to contain exotics were inspected, as well as roadsides in the Zone of Influence and Cooperation*. Inside the park, this meant surveying all presently or historically disturbed sites and several relatively natural ones, such as forested areas, salt marshes, bogs, fens and riparian zones.

Invasive species were placed in four priority categories based on specific criteria: potential to invade natural undisturbed areas, potential to alter ecosystem structure and function, potential to disperse and rate of population growth, and probability of success of control efforts. Foremost in this compiled list of 28 invasives are species such as purple loosestrife, glossy buckthorn and Japanese knotweed. Following these surveys and assessments, management priorities were set according to species priority categories, significance of ecosystems threatened and proximity to the park (where species not yet established are concerned).

In recent years, the trail network has been in expansion.
Through the construction of this trail, its use and its maintenance, the establishment of non-native
species in this area will be facilitated.
(photo: David Mazerolle)

The second major component of the study consisted of a closer examination of the park's exotic flora, which was carried out in two fashions. The first was a series of visits to all disturbed areas throughout the park with the objective of updating the list of known established exotics. The second was a systematic comparison of vegetation in a variety of habitats. For this, a total of 30 sites were chosen for detailed study from six habitat categories: campgrounds, old fields, dunes, roadsides, established trails, and new trails under construction. Statistical analysis showed that these habitat types are significantly different in terms of native, exotic and exotic invasive cover, as well as in terms of biodiversity. Old fields were shown to have a much higher exotic and exotic invasive cover, followed by roadsides. A comparison between established trails and new trails under construction also yielded interesting results. The former show an exotic cover twice that of the latter, and illustrate well the role of human caused disturbance in the propagation and establishment of exotics. The highest exotic species richness was found in roadsides and campgrounds.

Further analysis also demonstrates the existence of a link between habitat type and both species composition and relative abundance of species. This same link seems to exist for exotic vegetation, suggesting it could be possible to offer general descriptions of exotic vegetation according to habitat type and human-caused disturbance regime.

Through all components of the study, 42 species were added to the park's known flora, 32 of which are not considered native to the region. Consequently, the total number of exotics was brought up to 173, representing 26% of the total flora. The highest numbers of newly established exotic species were discovered along roadsides and campgrounds.

By providing information on significant invasive species, on the geography of exotics in general, and on pathways of introduction, the results of this research project form the basis of a strategy guiding the management of the park's exotic flora.

A variety of methods and techniques are available for the eradication, suppression, containment or exclusion of invasives, yet many of these are not compatible with the guiding principles and policies of protected natural areas. Large-scale application of herbicides, for example, would be unacceptable in the context of a national park. As a general rule, the control of smaller populations is not only easier and less costly but can be achieved by methods much less harmful to natural ecosystems. The prevention of introduction, establishment and proliferation is paramount, and continued monitoring is key.

The disturbance of roadsides through frequent mowing
can contribute to the establishment and proliferation of
exotics plant species. Some park maintenance
practices may need to be modified.
(photo: David Mazerolle)

Fortunately, some of the most potentially harmful species have yet to become established in the park. This, and the fact that most of these are still distributed as horticultural species, underlines the evident need for a management strategy to look past park boundaries. Work at this level must be done not only in direct control efforts, but also in building awareness and cooperation in surrounding communities.

Our national parks were in large part created to protect and showcase certain elements of our natural heritage. However, they can also act as learning tools for studying our impacts on the environment and as indicators for the general state of natural areas. If Kouchibouguac Park is any indication of the state of natural ecosystems in our region, then let us take this as a warning that the issue of exotic invasive plants must be addressed. First and foremost, let us be aware of what grows in our backyard.

 

* The Zone of Influence and Cooperation is an area about 6500 km² surrounding Kouchibouguac National Park . It represents an ecosystem management approach, which recognizes the need to act outside the boundaries of protected areas.