1

The jungle is of inorganic but growing substance

2

The jungle covers a formerly-urban area

3

The natives have extremely high-tech resources

4

The jungle is holy to a violent sect

5

Humans can't survive the jungle atmosphere for too long

6

Multiple groups are fighting for control of the jungle

7

High-tech weapons are dangerous to use in the jungle

8

The jungle is semi-sentient and malevolent