Mongabay: Gum trees dot the hills and valleys of south-eastern Australia, a vivid fixture of the rolling landscape. But despite the seeming health of these iconic trees, they have earned the morbid nickname “the living dead” among ecologists, who say natural changes and human actions are threatening the next generation of gum trees. The gum trees that are scattered through the landscape are naturally dying off at a rate of one to two percent each year. With no replacement, researchers fear more …