Here's the whole quote from Elizabeth Moon: "A tree is alive, and thus it is always more than you can see. Roots to leaves, yes-those you can, in part, see. But it is more-it is the lichens and moss and ferns that grow on its bark, the life too small to see that lives among its roots, a community we know of, but do not think on. It is every fly and bee and beetle that uses it for shelter or food, every bird that nests in its branches. Every one an individual, and yet every one part of the tree, and the tree part of every one."
Thich Nhat Hanh in his book "The Art of Living" says that we "inter-are." It's easy to see from the way we look and how we move that we are the continuation of the life of our ancestors. The latest research on viruses indicates that the over 380 trillion viruses that exist within the average human are not there to make us sick but primarily serve to assist with intercellular communication and species adaptation. Without the more than 10,000 microbial species (about 39 trillion bacteria in all) that occupy the human ecosystem, we would not be able to digest our food or produce the proteins that make up our physical form, which is home for only 30-40 trillion human cells. Think of it. Our human body is a community of bacteria, virus, and human cells. Our life continues in the lives of our children and also in the respiratory droplets that we exhale. Given some limited time, our breath can travel around the world. We are an ECOSYSTEM. Who can define the limits of an ecosystem? Viewed from this perspective, the "I" that I think of as myself does not exist; but we are everything.