Answer:
Hermit crabs can't breathe air and they will drown in water, so the best way to maintain humidity is to provide an ideal enclosure. These include aquariums and marine terrariums that are strong enough to hold wet sand with covers that allow some ventilation and keep the crabs and humidity in.
But also it could effect climate change.
Step-by-step explanation:
(hope this helped if not I will do more research, I wasn't sure if this is what you wanted)