Canada's National Air Photo Library...Not as much 'in your face' as Google Earth, but very important to monitoring in Canada because of its up to 90 years of environmental and land use information 'knowledge' base. An important legacy started by WW-1 pilots who in their "flying canoes" created Canada's first reconnaisance resource information base across its remote regions


































Beavers played a key role in the settlement and development of Canada. Beaver pelts drove the economy and formed the "currency" for the trade between the Hudson Bay Company and the aboriginal nations in Canada.

The beaver population steeply declined under the pressures of over trapping and reached a threatened species status. Presently beavers are reclaiming much of their original habitat, at least what is left of it. In many areas this recovery is rather spectacular. This recovery is captured by comparison of old Aerial Photography with recent high resolution Google Earth imagery

The north american beaver, with its beaver dams, beaver lodges and ponds is unique in the sense that it provides a clearly visible footprint on satellite images, particularly the high resolution imagery accessible through Google Earth ( i.e. Digital Globe, SPOT et.)

Using extensive photo interpretation of Google Earth and Aerial Photo images (See the National Air Photo Library on-line site), I have identified a number of unique perspectives, superlatives related to the lengths of beaver dams, unusual high densities of beaver populations. This page report on the highest beaver concentration in Saskatchewan and possibly the world.

Pakwaw Lake Beaver Community, Saskatchewan , Canada . This high resolution Google Earth (Digital Globe) shows an unusually high concentration of the beaver dams. The highest I have observed in Canada (in the world?). Over 20 dams and lodges per Km2. The beaver lodges are clearly visible as light dots (actual size on the ground is 7-8 meters in size) in the inundated areas. It is typical to find high densities of dams in streams (10 - 25 dams per linear Km) but is is rather unusual to find them evenly spread out over a wetland like this. This image shows a portion of a large beaver community near Pakwaw Lake (see below)

Figure 1 (larger version+)


Figures 2 and 3

This NASA World Wind Pseudo Colour Landsat Image (2000) shows the broader landscape setting of this high density beaver area. The near infrared enhances the beaver ponds (small dark blue spots creating a loosely knitted landscape impression. The white square represents the approximate location of the Google Earth image above. The thin red lines outline the concentrations of beaver dams in the landscape. The Pakwaw Lake first nation's community is to the left of the square.




Figure 4

The image below is a 1990 NASA Landsat Image. There are no major differences with the Landsat 2000 image. In 1990 the water levels are higher. The dark blue bog areas have become marginally smaller in some areas (pink on the 2000 Landsat). In some areas there appear to be more beaver dams in 2000, but some of this may be the result of the slightly better resolution of the 2000 Landsat image.


Figure 5 a and b

There is a dramatic difference between the 1945 air photo (right) of the same area as the Google Earth image (left). There is certainly no larges scale presence of beaver in 1945. Tree cover at that time was probably birch and aspen with alder and willow shrubs and some open wetlands. In the surrounding area some signs of beaver activity were seen.


Figure 6

This topographic map shows the Northern Woods and Water Route which crossects this beaver landscape. The this Highway follows one of the glacial lake Agassiz beach lines, which are quite prominently on the Landsat images as a series of parallel linear landscape features, similar to the countour lines on the topographic map.