Producing plastic is not a harmful task and nor does its decomposition (mainly because i never really decomposes)
It is said that owning a plastic tree and using it for a couple of years has less "environmental impact*" then buying a new real tree every year.
This is due to the fact that real trees require a lot of heavy machinery to produce/transport. while plastic trees a light and can be packed small. (thousands of plastic trees can be packed into one container)
Also the decomposition of the real tree realises many "harmful gasses*"
*If you REALLY believe in this environmental change bull ****!