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What would happen if we stopped using herbicides?

Category: Vegetation Management

Without their use, it would be increasingly difficult to maintain the softwood forest needed to supply our mills and maintain broad landscape diversity of conifer, deciduous, and mixed wood forests. This affects the viability and the competitiveness of our forestry industry.

An example of natural regeneration – a white pine stump, remnant of a softwood stand that was logged years ago, sits amidst a hardwood stand that outcompeted any spruce or pine regeneration following harvest. This hardwood stand has considerably less economic value than the softwood stand that grew on the site previously. (Photo: Doug Pitt).

Because herbicides play a central role in IVM and ensuring the successful regeneration of conifers on previously conifer-dominated sites, if their use were to be curtailed or discontinued, the objectives of establishing conifers on many sites could simply not be met through affordable means and forest managers would have difficulty meeting sustainability targets and legal requirements. Ultimately, this would lead to increased deficits in the natural proportion of conifer-dominated stand types on the landscape; deficits which already exist in many areas across North America. A diminished conifer resource would have serious economic implications, through reduction of the sustainable wood supply, as well as ecological implications through loss of habitat.

For example, a detailed audit recently conducted on regeneration sites in Nova Scotia, where a decision was made not to use herbicides, provides good evidence of the probable outcomes. In this case, results showed that 87% of conifer plantations failed, with an additional 10% not meeting free-to-grow standards 6 to 8 years post-harvest (Nicholson 2007). Similar outcomes have been observed in research trials conducted in other forest ecosystems (Biring et al. 2003, Dampier et al. 2006). A 2001 decision to discontinue herbicide use on Crown lands in Quebec has resulted in plantation establishment and tending costs frequently exceeding $5,000/ha (Labbé et al. 2014), owing to the production and planting of large stock and the need for as many as 3 manual brush saw release treatments. The ultimate success of many of these plantations is currently unknown and statistics on the impacts of the herbicide restriction on conifer wood supply are not available in Quebec. Recently, the province’s Chief Forester identified appropriate monitoring of planted areas as a critical need (Bureau du forestier en chef, 2015).

Planting conifers can cost a landowner in excess of $1,000 per ha, when mechanical site preparation, seedling production, and planting costs are considered. To protect this investment, the landowner may spend approximately $200/ha for a single aerial glyphosate application, or between $1,000 and $4,000/ha for one or more manual brush saw treatments. Given the lessons learned in jurisdictions that have curtailed herbicide use, it can be very difficult to justify the higher tending costs, particularly if success is variable and uncertain. Recent wood-supply forecasts conducted by New Brunswick Department of Natural Resources staff suggest that if conifer planting were to be discontinued as result of a decision to not use herbicides, long-term total wood supply (20+ years hence) would drop by close to 20% (softwood 23% and hardwood 5%), resulting in the loss of as many as 730 direct jobs. If budgets were constrained to prevent the brush-sawing necessary to thin and tend natural regeneration, the total future available harvest could fall by nearly 60% (softwood 66% and hardwood 33%), with as many as 2400 direct jobs lost. An important aspect to emphasize is that the impact of such decisions may not be clearly evident until many years after they are made.

Biring, B.S., Comeau, P.G., Fielder, P. 2003. Long-term effects of vegetation control treatments for release of Engelmann spruce from a mixed-shrub community in Southern British Columbia. Annals of Forest Science 60(7):681-690.

Bureau du forestier en chef. 2015. Succès des plantations. Avis du Forestier en chef. FEC-AVIS-04-2015, Roberval, Québec, 22 p. + annexes.

Dampier, J.E.E., Bell, F.W., St-Armour, M., Pitt, D.G., Luckai, N. 2006. Cutting versus herbicides: Tenth-year volume and release cost-effectiveness of sub-boreal conifer plantations. Forestry Chronicle 82(4):521-528.

Labbé, F., Lainesse, M., Nadeau, F-R., Prégent, G., Savary, A. 2014. Analyse de rentabilité économique des plantations d’épinette noire et blanche et de pin gris. Bureau de mise en marché des bois, Québec (Québec). https://www.bmmb.gouv.qc.ca/analyses-economiques/.

Nicholson, J. 2007. Survey of plantations established between 1998-2000 (6-8 years of age) on eastern Crown land without herbicides. Nova Scotia Department of Natural Resources, Forest Management Planning, Forest Research Report 83, 27 p.