Personally, I would take the plane; it is the lesser of many evils.
There are no real viable ecological options when it comes to traveling (other than biking or sailing or drive with an electric car)
You need to balance the cost, the time and the ecological footprint.
For example, from Paris, France which is more or less in the middle of Europe with many transportation options.
Plane is cheap and time efficient, so you will have a smaller ecological footprint.
If you decide to take the train, then it will take at least a couple of days and will have a big ecological impact (even if it is possible)
If you decide to take a ferry, you still need to travel to a port on the mediteranean (plane, bus, train... ); and boats are not really ecological; and you will loose a lot of time.
You could take a bus, but from what I can see, it takes about 60+ hours to get there, and buses are not really ecological.
couple of links decribing the itineraries and mode of transports.