That is a very good point, I'm not deep enough into fibres to analyze this. My approach was more from an optimization/industrialization perspective. I'm pretty sure hemp has a more vocal following for obvious reasons.

Still I think we could probably do better than cotton and trees in terms of environment.

With the exception of Ramie (which is a much less productive crop - similar yield to flax, but without the seed), none of those plants are grown in colder climates.