Est-ce que les plantations épargneront nos forêts naturelles?

Des mythes enveloppent encore les enjeux concernant la foresterie intensive et les plantations.  Par exemple, il y en a encore qui prétendent que les plantations n’ont aucun effet négatif sur la biodiversité parce qu’elles sont biologiquement la même chose que des forêts naturelles, et même que ces plantations réduisent les pressions sur les forêts naturelles.

Ces mythes, toutefois, ne tiennent pas compte pleinement de la complexité des écosystèmes forestiers, ni de l’évidente réalité de la consommation accélérée de notre société alimentée par son avidité et par la croissance sans limites de sa population.

Nous croyons qu’il existe des différences importantes entre une plantation d’arbres et une forêt naturelle, et plus spécialement dans notre forêt Acadienne diversifiée. Nous croyons que la promotion sans réserves des plantations forestières est irresponsable sur le plan écologique, et ne sert qu’à détourner l’attention du mouvement vers une foresterie durable.

Will Plantations Spare
Our Natural Forests?

Jamie Simpson
Peter Salonius & Judy Loo, Canadian Forest Service 
Fredericton, NB
June 2003

he view that plantations, with their faster growth of wood fiber, are necessary given our wood-hungry world and an ever-shrinking land base seems to die hard. Ample evidence of this is the Forest Products Association's demand on behalf of the forest industry to double the province's softwood harvest, and promote intensive softwood forest management on 60% of our Crown land forests.

(photo: Lowimpactforestry.com)

Myths still abound that cloud the issues surrounding intensive forestry and plantations. These myths suggest that plantations have no adverse effect on biodiversity because they are biologically the same as natural forests. Or that plantations reduce pressure on natural forests. The more plantations, the more land for parks, old growth, bird and animal habitat, and watershed protection. However, these myths do not fully recognize the complexity of our forest ecosystems, nor the reality of our society's accelerating resource consumption, driven by greed and open-ended population growth.

We believe that there are important biological differences between a plantation and a natural forest, especially in our diverse Acadian Forest. Take a walk in a maintained plantation and you see only one or maybe two tree species. Compare this to the many tree species you will see in most forests of this province - ranging from, say, four to eight. Add to these the animal and other plant species that depend on the missing tree species.

Plantations usually result in a drastic change in age and size-class structure. The natural mix of sizes and age classes is replaced with a single age class of uniformly sized trees. Plantations also lack large standing and fallen dead trees. Gone or reduced are the many species dependent on deadwood, from various fungi and insects to Pileated Woodpeckers and American Marten. Gone too, are the services provided by deadwood - water retention, nutrient storage, and soil building.

(photo: DNRE)

Think also of the genetics of plantations. In a natural stand, intense selection pressure due to competition for soil moisture and light results in only a tiny fraction of available seed surviving and becoming part of the next generation. Dynamics differ among stands resulting from different natural disturbance regimes and various genotypes have adapted to the different dynamics. A plantation, on the other hand, has a single simplified stand dynamic. Selection pressures are largely by-passed by nursery conditions, site preparation, herbicide use, and thinning, all of which reduce competition.

Further, the argument is often made that a plantation of genetically improved trees has a greater genetic diversity than the natural stand it replaces. But this is diversity of the planted species and ignores the genetic diversity among and within the species that are displaced. Also, it is wrong to think of the one plantation in isolation. A seed orchard consists of perhaps forty parents. Given that there are only forty parents populating many plantations across the landscape, genetic diversity is reduced when considered at the landscape level among different populations.

Another myth, that plantations reduce pressures on natural forests, makes sense in theory - if we can produce more wood per unit of land then we won't have to harvest from as much land. However, this argument fails to consider four facts. First, to date, softwood plantations have satisfied only a limited market - low quality softwood lumber and pulp fiber. Though rotation length is being increased in some instances, thereby increasing potential for higher quality lumber, markets for hardwood and high quality softwood lumber will likely continue to rely on natural forests.

Secondly, the myth assumes that plantations will produce high volumes of wood indefinitely. Studies in Europe, however, have found that successive plantations lead to soil acidification and nutrient leaching, thereby reducing the productivity of the site.

Thirdly, the myth assumes that increased productivity on one unit of land will necessarily alleviate pressure on another unit of land. However, for this to be true, the demand for wood would have to be static, which, of course, is not the case. Our society is addicted to a consumption and growth paradigm that creates an open-ended and constant increase in demand. That is, of course, until the resource collapses. Cod, anyone?

Finally, the myth fails to consider the use of the "allowable cut effect" in determining annual allowable cut. Increased harvesting of natural forests is justified on the forecasted fiber increases that silviculture will generate. Thus, contrary to proponents of this theory, increasing plantations can actually result in a direct increase in natural forest harvesting.

At best, plantations are a partial solution to the root problem of over-consumption by an increasing population, and, in all likelihood, will only exacerbate the degradation of our forests. They represent the long-term, continually increasing appropriation of nature in that they replace complex, stable, self-renewing ecosystems with simple, unstable wood-producing farms that require large non-renewable fossil fuel inputs - a boon to banks and big business, a blow to biodiversity.

All this said, we do not believe that all tree planting is inappropriate from an ecological perspective. Tree planting can be used to help restore the natural diversity of our forest by planting an appropriate diversity of species on abandoned agricultural land and in impoverished forests. Tree planting may also be appropriate in forests that naturally have few tree species, such as sites that are naturally black spruce or jack pine. In this way, tree planting is a part of ecosystem-based forestry, in which woodlot owners and foresters work with the forest. However, we believe that the uncritical promotion of plantation forestry is ecologically irresponsible, and serves only to sidetrack the movement toward sustainable forestry.