Biomass

What are the effects of biomass harvesting on biodiversity?

New Brunswick needs to consider the impacts on biodiversity caused by forest biomass extraction. The Conservation Council of New Brunswick is alarmed that the province of New Brunswick is moving ahead biomass extraction from Crown forests without a strategy to halt biodiversity loss in place first.

While biomass extraction could be a greener energy source, we are concerned that its removal will lead to further degradation of our Acadian forest and the extirpation of species that depend on woody debris.

Downed woody material is important for wildlife.  The Forest Guild in their Forest Biomass Retention and Harvesting Guidelines for the Northeast (2010) recommends leaving and protecting litter, forest floor, roots, stumps, large downed woody material, live cavity trees, den trees, other live decaying trees and snags (dead standing trees >10″) to retain forest structures needed for wildlife and biodiversity.

At least one-quarter of wildlife species in our Acadian forest depend on woody debris (Elliot, 1999) while studies done in the spruce-fir stands of Maine show that downed woody material, snags and cavity trees are important habitat for 58 % of reptile species, 50 % of mammal species, 44 % of amphibian species and 20 % of bird species (Flatebo et al., 1999). De Graaf et al (1992) found that at least 40 species rely on dead woody material in the northeastern U.S. For example, red-backed voles are negatively affected by low densities of highly decayed logs (Bowman et al. 2000) while spotted salamanders populations were increased in sites of downed woody retention in a Maine study (Patrick et al. 2006). The removal of woody debris in Sweden has been correlated with a rapid decline in biodiversity. Species across Europe that depend on deadwood are the largest single group of threatened species. Downed woody material is also key in maintaining habitat for saproxylic insects – those insects that are dependent, during some part of their life cycle, on dead or dying wood (Evans and Kelty, May 2010).

Dead logs are sites of seedbeds for trees and plants. Researchers from Sweden (Astrom et al (2005) studied the effects of slash harvest on bryophytes and vascular plants in southern boreal forest clear-cuts and found that “slash harvesting from forests to provide bioenergy reduces the amount of woody debris in the managed forest landscape and changes the physical and chemical environments in clear-cuts.” The researchers noted that “slash harvest reduces shelter and woody substrates, which changes species composition and reduces species richness of liverworts and mosses in clear-cuts.” The researchers recommend “leaving more tree clusters, and creating and protecting large woody debris.” Fungi, mosses and liverworts depend on dead wood for nutrients and moisture while many trees rely on the fungi.

The Forest Guild Biomass Working (May 2010) also recommends leaving and protecting existing woody material in streams, ponds and lakes. “Downed woody material in riparian systems provides sites for vegetation colonization, forest island growth and coalescence, and forest floodplain development.” Downed woody material in aquatic habitats provide important refuge from predation, aerate streams and store sediments.

New Brunswick needs to first finalize its biodiversity strategy and make sure that it will meet Canada’s commitment to the U.N. Convention on Biological Diversity that requires a halt to biodiversity loss by 2010. The provincial government must ensure that biomass removal is firmly regulated so as not to harm the health of our forest. The State of Maine has the Biodiversity in the Forests of Maine report that recommends guidelines for maintaining biodiversity in the forests of Maine.  The State of Maine has guidelines for retaining a certain amount of snags per acre while the province of Newfoundland and Labrador requires a certain amount of snags be retained per acre. The amount of snags retained per acre depends on the forest type. Retention of standing dead trees, existing coarse woody material, coarse woody material generated by a harvest, fine woody material, and forest floor and litter layer should be part of biomass harvesting guidelines. For an overview of biomass guidelines and policies in Canada and the U.S., visit the Forest Guild’s Revised Assessment of Biomass Harvesting and Retention Guidelines.

The government has only looked at suitable sites for biomass extraction in terms of soil nutrient composition and depth of water table. There are many other concerns with forest biomass extraction that the government needs to consider like habitat and biodiversity loss and carbon storage.

New Brunswick’s new biomass policy does not allow for whole-tree harvesting. This is a picture of such an operation at Northern Pulp’s “SFI-certified” license in Nova Scotia. Photo: Jamie Simpson.

Biomass and carbon

Different forest practices have different impacts on the accumulation of atmospheric carbon. While using woody slash for energy may be part of a strategy to reduce atmospheric carbon, retaining some slash after harvesting may also be important for maintaining forest productivity. Silviculture that encourages structural complexity in forest stands stores more carbon than even-aged management. Check out the Forest Guild’s Forest Biomass Retention and Harvesting Guidelines for the Northeast for more information on determining the carbon impact of biomass harvesting and guidelines for carbon storage.

A recent report commissioned by the Massachusetts Department of Energy Resources entitled Biomass Sustainability and Carbon Policy Study found that biomass electricity generation could increase greenhouse gas emissions in the short term. In response to the study, the State Secretary of Energy and Environmental Affairs Commissioner recommended that biomass projects be required to prove “significant near-term greenhouse gas dividends” before qualifying as a source of renewable energy.

The Manomet Center, commissioned in part by the State of Massachusetts, released a study on the carbon emissions of forest biomass in June 2010. The study found that the greenhouse gas impacts on the atmosphere of using woody biomass are a function of the lifecycle of the biomass being used, the biomass energy technology and the fossil fuel technology it replaces, and the way landowners choose to manage their forests.

New Brunswick’s public forest should not be opened to biomass removal until we have a clear and comprehensive bioenergy strategy for the province. Though using biomass to produce energy can be considered to be a low carbon method of energy production, this is only the case when forests are properly managed, and feed stock is used in efficient, low-emission generators such as those that convert biomass to biogas.

Sound science and public participation

Biomass harvesting guidelines should be based on sound science and include public participation in the development of guidelines.

Related reading:

Astrom, M Dynesius, M, Hylander, K and Nilsson, C. 2005. Effects of slash harvest on bryophytes and vascular plants in southern boreal forest clear-cuts. Journal of Applied Ecology 42, 1194 – 1202.

Forest Guild Biomass Working Group. May 2010. Forest Biomass Retention and Harvesting Guidelines for the Northeast. Forest Guild.

Hesselink, T.P. 2010 Increasing pressures to use forest biomass: A conservation viewpoint The Forestry Chronicle 86, No. 1.