Trees growing in our urban environments face a lot of stress from both natural and unnatural causes. While every tree is at risk from drought, insects and disease, our city trees also have unique problems that contribute to their early demise. Factors such as pollution, soil compaction, construction damage and heat radiation from pavement all play a role in the health and longevity of our neighborhood trees. Trees in the forest are constantly adding organic materials to the soil by way of dropping leaves, while all too often we sacrifice nature's process by cleaning up "leaf litter", and deplete our soil of natural nutrients. On top of that, trees in our urban forests are often competing directly with  ground covers like grass, shrubs, and other ornamentals for water and nutrients, all of which can cause a site to become depleted prematurely and no longer provide the right balance of  what it takes to support healthy trees.