According to Dictionary.com, the definition of sanguine can be cheerfully optimistic, hopeful, or confident. The definition I am using here is hopeful. The idea behind this image is that if people do not take care of our planet properly, then it will become a desolate wasteland void of the life we can see around the planet today. There would not be enough green left to call plant life. The dead tree and sparse grassy plain symbolize what the planet may look like if we did not properly take care of it.
However, nature is a self-balancing force. When something is out of balance, nature finds a way to restore it. This is represented by the small plant in the image. The planet is beginning to heal itself, starting with that single sprout. The figure is kneeling next to it because she can see the possibility of life returning to Earth. It makes her feel hopeful for the planet’s recovery and hopeful for a better future.