Scientific Evidence

Mature old forest habitat loss – impact on bird species

  • Several bird species exhibit high thresholds in habitat amount below which their occurrence falls dramatically (note: habitat is species-specific; hence, a threshold at 25% habitat within a 1-2 km radius translates into much more when considering generic mature/old forest, for ex.). (Betts et al. 2007), (Betts et al. 2006)
  • Landscape-level thresholds in habitat amount may vary geographically, but they are consistent through time at a given location. (Betts and Villard 2009)
  • The proportion of mature/old forest in the landscape is positively correlated with the survival rate of some species of forest songbirds. (Zitske et al. 2011)

Habitat fragmentation reduces species occurrence

  • Several species such as Blackburnian Warbler are sensitive not only to the loss but also to the fragmentation of remaining mature forest. Any strategy that does not consider the spatial layout of remaining habitat patches so that large patches are retained, increases the likelihood of population declines (Betts et al. 2006). Over the past 30 years, populations of species such as Blackburnian Warbler have been in decline in parts of the province that have had the most loss and fragmentation of mature forest. (Betts et al. 2007), (Betts et al. 2006)
  • Fragmenting mature forest results in decreased flying squirrel movement ability, which may reduce the viability of populations and affect critical forest ecosystem functions such as dispersal of mycorrhizal fungi that assist trees in uptake of nutrients. Ultimately, this could reduce tree growth rate. (Smith et al. 2011), (Smith et al. 2013)

Intensive silviculture of conifer trees – negative impacts on species

  • Mature conifer plantations (40-50 yrs) hosted fewer species of forest songbirds, especially woodpeckers and creepers, than naturally-regenerated conifer stands. (MacKay et al. 2014)
  • Proportion of conifer plantations within a 2 km radius of a nest had a negative effect on reproductive success in a forest songbird associated with old stands, probably as a result of locally inflated populations of red squirrels, a major nest predator. (Poulin et Villard 2011)
  • Some bird (e.g., blackburnian warbler) and mammal species (e.g., northern flying squirrels) are more frequent in mature mixedwood forest stands; hence, they are sensitive to the conversion of those stands to conifer plantations, or the removal of coniferous trees in deciduous forest. (Young et al. 2005), (Ritchie et al. 2009)
  • Some bird species (e.g. Ovenbird) are reluctant to move across spruce plantations; immigration into patches of suitable habitat may thus be impeded in landscapes with extensive plantation cover. (Villard et Haché 2012)

Intensive forestry – impacts on species

No species extinctions? Or a lack of knowledge?

“No species extinctions can be attributed to forestry practices in NB” (quote from Blake Brundsdon, JD Irving, Telegraph Journal, March 2014)

  • Construction of the Mactaquac Dam in 1965-1968, was in part necessary to provide energy for the pulp industry in New Brunswick. Construction of the Dam is believed to have been directly responsible for the local extinction of Climbing Bittersweet (Celastrus scandens), a plant known in New Brunswick only from river islands now completely flooded under the Mactaquac Headpond (Hinds, H. 1999. Flora of New Brunswick).
  • Research in NB on species diversity has focused on vascular plants, which make up 4%, and invertebrates, which make up 2% of overall species occurring in NB. (D.F. McAlpine and I.M. Smith (eds.). 2010. Assessment of Species Diversity in the Atlantic Maritime Ecozone)
  • The “Bioblitz” program, an NB Museum initiative started in 2009, aims to survey the biological diversity of New Brunswick’s 10 largest Protected Natural Areas (PNAs). In every year of the Bioblitz program, researchers have discovered species new to New Brunswick, new to Canada, new to the continent, or new to science. Most of these discoveries have been of fungi and insects, groups that play key roles in the functioning of forests.
  • From research that scientists have carried out in the PNAs and elsewhere around the province, we know that many species are dependent on old forests. We also know that such forests continue to be widely and intensively harvested before scientists are able to study their biodiversity.
  • Given the rate at which species are still being newly documented in New Brunswick, and that some old-forest species are restricted to such habitat which are already fragmented and remnant, it seems very likely that industrial forestry will indeed lead to species extinctions in the New Brunswick in the future, if it has not done so already.
  • Claims that there is no evidence of species extinctions among plants and animals resulting from past or present forestry policies and practices do not take into account these major “blind spots” in our knowledge.

More Information:

NB Naturalist – Our Forests-Nos forêts, the special edition of Nature NB’s magazine, contains a number of articles related to forest sustainability. Download the full magazine here.

Relevant articles from the magazine: