What ecological roles do mosses, liverworts,and hornworts play in the environment?

Answer 1

A lot of these are colonizers. They go in on bare ground after a major disturbance event, like a forest fire, and live in the poor soil that is left over. Moss can grow on rocks, and break them down. This releases more nutrients so that other plants can come in after them and take hold.
There's a traditional cycle after a major disturbance event that is something like: mosses, grasses, brush, forests. It's a lot more complex than that in reality, but that is the basics...one step creates the conditions for the following step to be able to occur.

Answer 2

Well!!!!!!!!1 Human Race is the only race in which majority of the generation never care about their offspring... Humans want to live the very moment. They are not interested much on future generations... Hence, they disturb the ecological balances and destroy the environment for their own benefit!!