I don't believe Cariuma has any better labor practices than Nike, Adidas, Lakai, or anyone else. It's extremely easy to say "we have ethical factories" and the big corporate companies do that too.
If the workers have a union then I'd believe it.
Like what was said above, the most ethical choice is second hand shoes. There is no ethical production under capitalism and our individual choices make very little difference in a global economy. Far too many shoes are produced in general, so the most ethical choice you can make as an individual is to create less demand overall and buy less shoes.
The environmental impact of making these Cariuma shoes likely far outweighs the positive impact of planting 2 tree per pair. Manufacturing with recycled materials is still horrible for the environment.