Few trees are of greater ecological importance to the American northwest than the whitebark pine.  Its hardy branches and nutritionally dense seeds provide food and shelter for a host of animals including grizzlies, nutcrackers and red squirrels.  And it’s for this reason conservationists have become alarmed by its declining presence in which 90 percent of the trees have died off in recent years.  The villains are a pair of natural enemies: namely the pine beetle and a fungus called blister rust.  Fortunately biologists are fighting back by planting varieties of the trees that are resistant to the fungus and [...]