Not necessarily a question that most would ask, when considering living in a nomadic home. But one worth considering never the less. Living in a nomadic home is generally considered an alternative lifestyle by mainstream society, which often brings ill conceived prejudices with it. In these days of climate change and other environmental concerns, it is worth having at least some idea of how the environmental scales tip between living in a nomadic home and contemporary housing, with it's associated lifestyle.
There are two main aspects to consider; the first being the building itself, and the second being the general lifestyle.
If we look at the physical home itself, then I think that it would be hard to make a case against pretty much any nomadic home, as they are by their very nature, much smaller than standard housing. Which should mean less material resources are used in their construction. There are different types of materials used though, such as epoxy resins (particularly in boat construction) which are petro-chemicals. I would suspect though, that those differences would be quite easily offset just by their small size, as would be the energy costs for maintaining, heating and cooling.
On the lifestyle side of things, again, I think that living in a mobile home is likely to have less environmental impact. Sure, most land based mobile homes are going to use more fuel than the average car, but then how much distance are you actually covering on average, per day? If you are working at a site specific location, you are more likely to stay closer to it than if you are living in a house. So the house dwellers car will be clocking up plenty of miles in comparison, just getting to and from work. If the nomadic dweller is running a business from their mobile home, they won't be burning any fuel getting to and from work. More likely, they will travel a few miles here, and there, for a change in scenery, which will still usually still be less miles over a month than the contemporary house dweller.