Greenery
The melting of the polar ice caps cause widespread climate change turning portions of the earth that were formerly temperate zones into tropical jungle. Understandably, descriptions of greenery, whether in the form of lush jungle growth or patches of moss and lichens growing over ruined architecture, abound in the novel.
Ruins
The Drowned World is one of the first examples of the post-apocalyptic sub-genre of science fiction so it is only natural that there are many descriptions of ruined cities, most notably, London. It is interesting though to see various descriptions of structural ruin brought about by climate change and the overgrowth of plants rather than destruction brought about by the ravages of war.
Moisture
There is widespread flooding as a result of the solar flares melting the polar ice caps and the earth is changed into a massive brackish swampland cum rainforest. Moisture is a constant either in the form of ever-present lagoons and murky swamps or the humid, saturated, sweltering air that is all around the characters.
Animal/Anatomical Analogies
It is interesting to read that the characters in the novel depict the environmental conditions and the terrain as if it were a living organism or being with its own consciousness and will. Dr. Kierans describes the waters of the lagoon as "amniotic" alluding to a womb-like, life-giving quality to it. A buildup of sludge he sees as "humped backs" and the hills covered in giant bamboo he describes as being covered as if with fur. Even the molds and fungus that encrust the ruins of the Ritz are described as having become living components of the lavish furnishings. The attribution of living characteristics to the environment is deliberate as the environment is, in a manner of speaking, treated almost as an antagonist working to defeat humanity and whatever is left of the world he used to dominate.