Shadow and Evil in Fairy Tales she suggests that Baba Yaga is clearly Mother Nature. She talks about owning the day and the night in the story of Vasilisa the Beautiful, and as her hut is surrounded with skulls she must also be the Goddess of Death.
I've heard before that true fairies (not the cute, diminuitive fairies we find in current culture) can also be understood when thinking of them more as forces of nature as well. Fairies and other supernatural creatures have their own laws and codes of conduct, but they are not the same ones humans operate by, and a fairie's instinct is not necessarily to preserve human life. In my recent post on Baba Yaga, Helen Pilinovsky was pointing out the multiple and seemingly contradictory roles Baba Yaga plays-sometimes as a helper, yet sometimes as cruel. Nature itself also displays such opposite faces-a beautiful, breezy spring day can give way to terrible storms and result in great loss of life at times. We can love and enjoy nature, yet so often are at its mercy.