The bottom line...
Then, to find possible routes between these areas of high habitat effectiveness, we used a Least Cost Path function that is found in Arc Info Grid. We set up the cell values so that higher values meant less suitable habitat. Arc Info, as Tom Moritz mentioned, is one of the primary mapping tools used in Geographic Information Systems or GIS. This Least Cost Path procedure finds the path between two points with the lowest overall cost. In this case, the GIS was set up so the cost would be a cost to Grizzly Bears. The path would have the best habitat with the least disturbance from humans.
This isn't entirely accurate from a biological point of view because the dispersing Grizzly Bear doesn't know where the end point is and it moves in a more random fashion. It basically wanders around from one place to another looking for food or cover and being repelled by areas of disturbance unless they learn to associate people with food. But it does have some validity in that it picks the best habitat available for a bear to travel on the shortest, safest route. So if a bear took this route, he would get to another safe haven with the least chance of interacting with humans.
You can also look at this by thinking that if you could only save a small part of the habitat and all the rest is going to be developed, this would be the best corridor to leave for bears to use if they chose to. We also looked at this in a different way. This map is what the overall area, the golden triangle (or whatever) looks like, between these three core ecosystems. These are the shortest routes through the best habitat. Actually, you can threshold these models and play around with the different levels of things. If we increased the bear's aversion to road density, they took one route, but if we decreased their aversion to road density, they went by another route. This route (second from the right) has better habitat but there's high road density up in these areas here in the Helena National Forest.
|
Narrative Index
BioForum Index
