Vexation is about everything that is happening on a surface level and is noticeable. It can pertain to hurricanes, floods, heat waves, and other natural disasters that occur due to human's impact on the environment.
Lamentation involves the grief for the result of those disasters represented in the first movement. This may pertain to the species going extinct, the forests dying, and the people killed due to human's poor interaction with nature.
Realization occurs when people truly realize the results of their actions. However, in this interpretation of the future, it is too late and life on the planet is in a downward spiral towards destruction.
The movement ends with the idea that, no matter how much we damage the world, the Earth will still spin on, with or without us.