What can a simple jab of a knife not achieve and why?

In his poem "On Killing a Tree," Gieve Patel is expressing the idea that it is not through isolated actions that we kill trees, representative here of the wider environment. On the contrary, it is through a sustained attack upon the environment that we wreak such devastation. We cannot, having finally succeeded in destroying our environment, behave as if it was a simple accident or a single action which had such a devastating result. A "simple jab of the knife" is not enough to kill a tree, because it "takes much time," and indeed dedication, to do so.
Patel goes on to enumerate the many elements of sustained attack that are necessary in order to finally kill the tree, something which will struggle to survive, having become part of the earth. We might "hack and chop," causing the tree great pain, but even then it will heal itself. Only by pulling the tree out of the earth by its very roots, destroying it by an active and conscious onslaught, do we actually succeed in killing it. When we have killed a tree, or our environment, we know in our hearts that we have done it knowingly and deliberately.