The common belief at the time of the Buddha was that plants (and even soil) were one facultied life. Today we have ecologically green beliefs that are often equivalent — at least they seem to lead to much the same attitudes. (In Thailand, forest monks are well known as the best protectors of the jungle.)
The eleventh Confession offence concerns destroying plant life. It originated because a bhikkhu harmed one facultied life by cutting down trees. He continued to cut down a tree even when the tree deva asked him to stop, so she went and complained to the Buddha. This led to lay criticism of such behavior and a rule was set down:
"Intentionally damaging or destroying a living plant is [an offence of Confession.]"
(Summary Paac. 11; See BMC p.294)
Therefore destroying a living plant — for instance, felling a tree, uprooting a flower, burning grass — is a Confession offence; as is picking fruit from a tree, a flower from a bush, etc. It is an offence of wrong doing (dukka.ta) to damage or destroy fertile seeds or pips, or viable seedlings. (See Kappiya).
Bhikkhus who live in tropical forest monasteries constantly have to protect both the jungle and themselves. When paths are overgrown, snakes and other dangerous creepy crawlies can be trodden on — and bite back! There also may be a need for firebreaks. One way that forest monks cope with this is a daily routine of sweeping the paths. However they are not allowed to dig or clear the land.
The tenth Confession offence arose when bhikkhus dug the ground and got others to dig, and the local people criticized them because they considered the earth to be one facultied life. The rule is phrased like this:
"Should any bhikkhu dig soil or have it dug, it is [an offence of Confession.]"
(Paac. 10; BMC p.292)
Digging, breaking the surface of the earth, lighting a fire on it, pounding a stake into it are all disallowed. (If such earth is more gravel or sand than soil — and has no living creatures in it — it may then be dug.)
It is, however, allowable for monks to hint to laypeople or novices about what needs doing as long as the words or gestures fall short of a command. When bhikkhus need paths to be cleared, necessary work done on the ground, firebreaks made, etc., any lay attendant wanting to help should listen out for hints and indications: A post hole dug over there would be useful; make this ground allowable, etc. What is needed can then be clarified.
One practical and long term effect of these rules is that they have steered bhikkhus away from involvement in agriculture and land ownership. Such a development would also have isolated bhikkhus from the lay community because they would no longer have needed to depend on alms food.
Other examples of the ancient awareness of not polluting the environment and hygiene are the two Sekhiya Training rules (Sekhiya 74, 75). These prohibit a bhikkhu from defecating, urinating or spitting into water or onto green vegetation.2.
Deva is a deity or heavenly being (lit: radiant one) of which there are many levels. However, all are still subject to repeated rebirth, old age and death. A tree deva is a deity that lives in a tree.