Google Earth Community: World's Longest Beaver Dam found with Google Earth

The longest beaver dam observed with Google Earth to date (October 2 2007) is located in Northern Alberta. The dam has a length of about 850 meters (2790 ft). It has at least existed at this spot for over 15 years as it can be observed on the 1990 LandSat 7 Pseudo Color Imagery Provided by NASA World Wind. .However 1975 aerial photo's show that this dam did not exist in 1975..

.1975 Aerial photo of the dam area.:
Some minor beaver activity can be observed (green arrows) but most of the area is covered by trees and shrubs. I expect this area was burned about 20-30 years before the date photos. A evenaged stand of stand of poplar (Po) is visible on the 1970 photo, has been replaced by a wetland in 2005. Melting peat plateaus and palsas are present in the surrounding wetlands, and I suspect that permafrost melting may have played a role in this as well. The red dotted line shows the location of the beaver dam in 2007 (or rather the date of the Digital Globe image)

This image is part of flight line A24215 ( photo number 253). Date: 9 August, 1975; original scale: 1:50'000.

Aerial photos of Canada can be obtained from the National Air Photo Library (NAPL)

Comparison of the two images shows interesting elements. The dams 1 and 2 existed in 1970 but have changed very little. The beaver lodge near Dam 1, has not changed much. Dams 3 and 4 have been build since 1975. The beaver offspring of dam 4 are building two smaller dams just to the side (green arrow). Larger Image [+]

The NASA LandSat 7 images of 1990 and 2000 (accesible as part of its magnificent World Wind System,) give a simple overview of the beaver ponds and dams since 1990. It is clear that the this dam (Red Arrow) did exist in 1990 and had a similar size as in 2000 and 2007 (Digital Globe- Google Earth)

--------------------
Jean Thie
Executive Director, Canadian Institute of Geomatics
www.geostrategis.com
Google Earth - An Exceptional Ecosystem Science Tool!
Monitor Permafrost Melting with Google Earth
Fire Ecosystem Interpretations with Google Earth
Map Glacial lake Agassiz!
Find the longest beaver dam in the World with Google Earth!

Edited by jean_thie (04/11/08 05:15 PM)

Post Extras