Saving Berries for the Bears: Providing Grizzly Bear Habitat in Managed Forests

BC Environment and BC Forest Service are taking an adaptive management approach to providing grizzly bear forage in managed forests in coastal B.C.. Interim guidelines, developed using the best information currently available, will be updated and improved based on information gained from formal and informal field trials, and from descriptions of unmanipulated stands where forage is well- established.

This project illustrates how we can implement new guidelines so as to learn from them, and recognizes that actions cannot be delayed until complete information is available. Not all sites to which the guidelines are applied are part of a formal trial, and initial trials are at a small scale, which may limit the applicability of information gained. Later trials on a subset of treatments are expected to be at a larger scale. Because this project is relatively young, (guidelines were implemented in 1992 and the first field assessments will be completed in late 1995), we cannot yet evaluate its effectiveness.

Management Issue:

Current silvicultural practices in coastal valley bottoms limit the availability of forage for grizzly bears. Forage species compete with regenerating seedlings for growing space and light. Over the short term, chemical and manual control of vegetation reduce the local availability of forage. Over the long term, the resulting dense stands with closed canopies exclude important forage species. This problem is exacerbated by short rotations (80-100 years) that increase the proportion of the landscape in young, dense forest, and by concentrating harvesting at lower elevations, where prime grizzly habitat is found. Together, these factors can result in a critical shortage in grizzly forage over large areas and over an extended period.

Researchers felt that a proactive approach was necessary to maintain grizzly habitat and grizzly populations. Guidelines for promoting growth of forage species needed to be implemented as soon as possible, despite uncertainty about their effectiveness and economic impact, in order to avoid critical shortages of grizzly forage in the future.

Management Strategy:

The goal of the management strategy is to promote the growth of grizzly bear forage throughout the entire rotation, by using silvicultural methods that will create reforested stands that more closely resemble unmanaged (natural) stands. Unmanaged stands in the lower elevations of coastal valleys generally consist of clusters of mature conifers, with numerous groupings of deciduous trees, open brushy areas, and skunk cabbage swamps. They provide the diversity of vegetation vital to grizzly bears.

Together, foresters and biologists developed a set of guidelines that would apply to ecosystems important for production of grizzly bear forage. These guidelines specify reduced stocking standards for various site associations, spacing and pruning of previously reforested sites to encourage growth of forage species, and parameters for conducting and monitoring field operations.

The stocking standards are based on the best available information, but there is still uncertainty about their effectiveness and cost, how to apply them, and what additional stand tending will be required. The project therefore explicitly adopts an "adaptive management approach" where guidelines will be revised based on information gained from a combination of formal and informal field trials, and monitoring of reforested sites where forage is already well-established. All sites where guidelines are applied fall into one of these three levels of trials (i.e., formal, informal, or monitoring), based on geographical location, site conditions, and management objectives (i.e., formal trials will be done on sites scheduled for complete replanting; informal trials will be done on sites already stocked; monitoring will be done on sites where forage is already well-established.)

In the formal operational trials, the size of clusters in which seedlings are planted and the open space between clusters is varied to determine the impacts on forage production, tree growth and treatment costs. The effects of different pruning strategies and species mixtures are also being assessed. Treatments are compared to controls (i.e., operational standards), and are applied at a small scale (4-10 ha) across a range of site associations, in a number of coastal valleys. The aim is to establish 5 replicates of each treatment in each site association. These small scale trials will be used to identify the most promising treatments for testing in larger scale, longer term operational trials.

Potential benefits of adaptive management:

This is an example of a management issue where changes must be made as soon as possible - where we cannot afford to postpone changes and remedial actions until uncertainty about outcomes is eliminated. Continuing with existing practices could lead to shortages in suitable habitat that could threaten grizzly populations.

The formal trials will provide information about which treatments work best, and what the costs are, allowing managers to make more well-informed decisions. Together with the informal trials and monitoring, they may also suggest new treatments.

Information from trials will be obtained for a number of site associations. Within each site association, results from formal trials at one area can be extrapolated to other areas.

Regardless of the amount of research on which they are based, any guidelines must eventually be tested in an operational setting.

The working plan lays out a schedule of implementing and monitoring trials over a complete rotation.

Limitations of this project:

Stand level field trials provide little information about landscape level questions, such as: Will grizzly bears use managed landscapes, even if forage production at the stand level is adequate? Does increased access associated with logging outweigh any benefits of improved forage availability?

Forage availability could be affected by factors other than stocking rate (e.g., annual variations in weather). Without controls and replicated treatments, it may be difficult to determine whether the changes in stocking rate are effective.

The management strategy does not specify how and when guidelines will be updated to reflect results, nor how positive impacts on forage will be balanced against potential negative impacts on timber productivity and economics.

The design does not specify the number of replicates (spatial or temporal) necessary to detect treatment effects. Nor does it address other elements of design that will reduce the ambiguity of results. Although operational experiments will rarely conform to an "ideal" experimental design, we should nonetheless design them as rigorously as possible, given practical constraints, to avoid debate over ambiguous results.

References:

I'Anson, Bill. Saving berries for the bears. BC Environment. Pamphlet.

McLennan, D.S. and T. Johnson. 1993. An adaptive management approach for integrating grizzly bear habitat requirements and silvicultural practices in coastal B.C.: Working Plan. Oikos Ecological Consultants, Smithers, B.C. for B.C. Ministry of Environment, Wildlife Branch.

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