December 14, 2017 Deborah Perkins Essential Elements, Habitat How-To Dead and Dying Trees are Key to Life December 14, 2017 Deborah Perkins Essential Elements, Habitat How-To Dead or partially dead standing trees (snags) and cavity trees (live or partially dead trees with cavities) are important to the life cycle and habitat needs of over 40 species of birds and mammals, and countless species of insects and fungi.