Yes, the forest lands of the Giralang Ranges are consistently described as claustrophobic, dark, threatening, silent, and as a force to be contended with. Hence the title "Force of Nature:" Nature here as wilderness is unpredictable, powerful, and a force: something to be feared and, if possible, subdued.
The author achieved this effect in two ways: First, by her own descriptions of the wilderness, and secondly, by the fearful observations of the women as they try to cope with a challenging (and threatening, at times) environment. "It was strange, Jill thought, how much the bushland started to look alike." "The thick line of trees gave him the vaguely claustrophobic sense of being under siege." Thoughts like these from the characters create this ominous feeling. Also, the characters have to deal with a lot of rain and stormy weather while hiking and camping--the bad weather adds to the sense of malaise.
i actually think that the author overdoes the ominous setting a bit. The negative descriptions started to seem relentless to me in reinforcing this theme by the time I was two-thirds through the book. (A small flaw, but not a flaw that I found in her first book, "The Dry.") On the whole, though, I thought the sense of existential dread in the novel caused both by the setting and the flaws and tensions of the characters was well done.