Brand actually has a point. There is no richer fertilizer on the planet than volcanic ash mixed with soil. The eruptions are deadly, but once over, plant life will quickly take over the ashfall areas and begin to grow again.
And he does know his volcano dragons.
But they never truly answered the question of WHAT ELSE WOULD BE RELEASED? Her mother might not have stolen everything in that eyestone. She might have won some of it in battle....
