Canada’s wild forests—how much are left, and where are they? Global Forest Watch Canada, an independent national affiliate of the World Resources Institute’s Global Forest Watch network, and Russia’s Socio-Ecological Union International recently answered these questions using more than 1,000 satellite images. The project—the most detailed assessment of its kind in Canada—demonstrated that citizen-based groups can use satellite images to perform important national and global studies.
 

A Growing Concern
Much of the world’s original forest cover has been cleared for agriculture or affected by resource-extraction activities, such as logging and mining. For example, Brazil’s government recently announced that the rate of deforestation in Brazil’s Amazon rose 2.1 percent in 2003 to its second-highest level ever as farmers encroached further on the world’s largest jungle.
 

The remaining global tracts of intact forest landscapes are becoming increasingly important as benchmarks for understanding managed forests and designing management schemes that preserve or restore significant aspects of natural forest landscapes. Intact forests are areas of opportunity and responsibility, where the best available knowledge and technology  is needed for effective and responsible decision-making.
 

The project to map Canada’s intact forest landscapes extends previous forest-assessment work in Canada and is part of a larger effort by the Global Forest Watch network to map intact forest landscapes in countries around the world. The methodology was developed by Global Forest Watch to map Russia’s intact forest landscapes, and analysts from Global Forest Watch Russia were key partners in the Canadian study.

Canada’s forests provide critical benefits to the nation, including economic contributions from the forest products industry, recreational opportunities and life-sustaining services, such as soil erosion control, watershed protection and carbon storage. Canada contains one-tenth of the world’s forests (400 million hectares), including more than one-third of the boreal forests, one-fifth of the temperate rainforests and one-fourth of the frontier forests. 
 

For the study, researchers defined an intact forest landscape as a contiguous mosaic of natural ecosystems in a forest ecozone, essentially undisturbed by human influence, including treed and naturally treeless areas. An intact forest landscape must be large enough to contain and support natural biodiversity and ecological processes, and to provide a buffer against human disturbance from surrounding areas. The study included forest tracts of 50,000 hectares or larger that are at least 10 kilometers wide.
 

The study had two objectives:
1. Increase knowledge about the extent and location of remaining intact forest landscapes in Canada.
2. Provide the data in accessible forms to government, industry and civil users to enable better decision-making about forest ecosystems and intact forest landscapes.

Satellite Imagery Analysis
The study methodology involved identifying intact forest landscapes with NASA satellite imagery. The method presumed all forest landscapes to be intact at the outset of the study. Disturbed areas would be eliminated systematically through successive efforts to detect positive evidence of human influence on the landscape. Thus, the search was for signs of human disturbance, not for intact forests, as the former are much easier to detect. This simple methodology and decision-support model is replicable, cost-effective, feasible at the continental level (at a scale of 1:1,500,000) and sufficiently detailed to support practical decision-making.
 

The analysis included four basic steps:

1.           Set study area boundaries.

2.           Eliminate disturbed areas using existing datasets.

3.           Eliminate further disturbed areas using satellite imagery and more detailed, regional datasets.

4.           Verify the results via site visits, aerial photography and a widespread review.

Several types of satellite imagery were used (Figure 1):

•           Landsat 7 ETM+—approximately 700 images (primarily from the summer season, 1998 to 2002) with 30-meter resolution.

•           Terra ASTER—approximately 200 images (primarily from the summer season, 1999 to 2000) with 15-meter resolution.

•           Landsat 5 TM—approximately 300 images (from the late 1980s to early 1990s) with 30-meter resolution.

•           Landsat 5 TM Outlooks—approximately 200 images (from the late 1980s to early 1990s) with 300-meter resolution.
 

Landsat 7 ETM+ was preferred because of its resolution and availability. Due to cost constraints and availability limitations, however, Landsat 5 TM scenes were used to fill in coverage gaps—primarily in remote areas. Most of the Landsat 5 scenes were available only as merged individual images in compressed format (resulting in some information loss), with only three spectral channels. Terra ASTER images were used to help fill the gaps in Landsat coverage and to identify additional disturbances related to energy developments in the Western Canada Sedimentary Basin, as this imagery’s 15-meter resolution is able to detect some seismic activity (Figures 2A and 2B).

Visually interpreting disturbances typically was performed at a 1:50,000–1:250,000 scale for Landsat 5 and 7 and ASTER imagery, and at 1:250,000 for degraded Landsat imagery. The range of imagery results means variable accuracy and an overall map scale of approximately 1:1,000,000–1:1,500,000. Various band combinations of the satellite images were selected and enhanced for visibility.
 

Along with the satellite images, the study used a disturbance layer created by the University of Maryland’s Global Land Cover Facility (Figures 3A, 3B and 3C). The disturbance layer was overlaid onto the study area layer to crop candidate areas.
 

Linear disturbances within individual 50,000-hectare blocks were buffered according to the nature of the disturbance before excluding them. The resulting residual areas smaller than 50,000 hectares were eliminated, resulting in a map of large intact forest landscapes.
 

Due to rectification problems, the maximum ground error was approximately 500 meters. The error was most prevalent in regions of high topographic diversity, such as the mountainous regions of British Columbia and Yukon Territory (for study results, see “Key Findings—Canada’s Large Intact Forest Landscapes,” below).

Using the Results
Large, undisturbed forest ecosystems are becoming increasingly rare at the global level, due in large part to their vulnerability to the effects of large-scale human interventions—effects that aren’t easily or quickly reversed. Hence, several companies have adopted policies that relate to intact forest ecosystems.
 

IKEA, a home furnishings company, demands that the wood it purchases in solid wood products “does not originate from intact natural forests, unless they are certified according to a standard recognized by IKEA.” Other retailers, including Home Depot, Staples and Lowe’s, have purchasing policies that relate to “endangered forests,” a concept in which elements of intact forest landscapes could be included. In addition, several Canadian governments—British Columbia, Ontario and Nova Scotia—have adopted policies that address the maintenance of large, unfragmented forest landscapes.
 

“Given the amount of intact forests left in Canada’s boreal, we have a unique opportunity to ensure the region remains a key source of clean air, clean water and abundant wildlife for all Canadians,” says Cathy Wilkinson, director of the independent Ottawa-based Canadian Boreal Initiative, a study sponsor. “Clearly, the time to plan for conserving Canada’s boreal forests is now—before this window of opportunity closes.”    
  

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