our trees are dying. how can i help?

tl;dr

tree roots need support from a healthy ecosystem, above and below ground. even in small spaces, this is possible with easy modifications:

1. plant natives around trees
2. remove turf grass and add untreated mulch while natives establish
3. do not use stones, gravel, landscape fabric, or other inorganic/synthetic coverings around trees
4. leave sticks, leaves, and other debris at the base of the tree
5. top dress with compost in unhealthy sites
6. eliminate use of synthetic, store-bought pesticides, herbicides, and fertilizers

you don't need to do all of this at once. pick one and stick to it.