Tall I am born and long I will last but as a midgit I will die. What am I?

Question

I am born in the forests,
In the cities I die,
I swim all the oceans,
And wander the sky.
Though I'm numbered eighth,
I should be named first,
For without me you'd perish,
For breath you would thirst.
What am I?

Answer 1

Its a Candle