The Ethics of Terraforming 2

Should people one day go out and change other planets by adding living things from Earth? To do this they'd have to add water and air, and in the process change, fill or erode the planet's landscape. Additionally adding life would change the environment, so that the craters would become lakes, the valleys rivers and the depressions seas.
Mountains might slide into chasms as water lubricates billion year old faults and earth-quakes bring down giant pillars of stone as the weight of water changes the planet's crust.
But if the end result is a green and pleasant planet, is all of this just collateral damage and just something which has to be accepted?