I think the message of this video is the importance of nature (especially plants).
In the video, new varmints suddenly come up and build a huge, concrete city.
The nature disappeared, except for the twig the main character saved.
In the end, the city dies, probably because of air pollution.
Ironically, the city varmints who killed the nature were saved by the only plant the main character had saved.
This pretty much shows the importance of nature, and how we should save plants on Earth.
