The central idea in this poem is that the act of killing a tree—or, on a broader scale, destroying the environment—is not confined to a single action. We cannot pretend that the slow destruction of our forests and our landscapes is a result of accident. On the contrary, it takes sustained and deliberate action, "much time," to kill a tree which will continually resist destruction; the "bleeding bark will heal" and, even after having experienced one attack, a tree can "expand again." Trees are resilient, and, moreover, trees are not simply things that grow upon the earth, but part of it: a tree spends its life "slowly consuming the earth" and "feeding upon its crust." Trees are an inherent part of the world around us, and in destroying them, humans are making a conscious choice, a determination that "the root is to be pulled out."
The poet identifies some of the many ways in which humans have destroyed trees: "scorching," "choking," "hardening," "twisting," "withering." The use of so many active verbs here underlines the poet's point, that deforestation and the destruction of the environment are a result not of human inaction, but of decisive and deliberate human attacks upon that environment. And yet, to think of the environment, and our trees, as something distinct from us is a fallacy, as the trees are part of "the anchoring earth" in which they grow, and they have been here "for years." To destroy a living thing so resilient as a tree is to wreak deliberate and forceful damage.