I’m curious if U.N. has rights to call an emergency meeting and vote to send everything necessary to help to fight natural disaster, given that causes of rainforest extinction might be felt globally ? This is considering situation when Brazil government doesn’t ask for international help ?
The closest would probably be that the UN security council would make such a decision (=send help without being requested).
While I guess "technically" a security council meeting would be arranged by "UN", for a non-scheduled one to be called, it would require some country to bring up the urgent matter (fire) to the council. Also, I think that to consider the fire to be in their scope, would be stretching quite a bit their intended domain.
As far as I know, no other UN body could simply make a decision to send help "by force".