Some cities in Michigan could lose half of all their trees due to disease or pests. Foresters are working to reduce the potential devastation. “So, I just wanted to show you, this is a neighborhood with old maple trees," Kerry Gray said as she led the way down a tree-lined street in Ann Arbor. She's the urban forester for the city. She’s worried about losing a lot of the city’s trees to a pest or disease. It’s happened before.