Mental poverty is simply an impoverished mind. It is a way of living for some. It is a condition and state of mind where there are limited educational resources and if there are educational resources, one chooses to avoid them. It is a system that exists where the norm is ignorance and refusal. Refusal to change, to try and learn new and better ways of not only thinking but also putting thoughts into action. It is essentially a poor mind.
In today's state of environmental crisis, only someone who is afflicted with mental poverty could choose not to recycle or not to worry about the effects their choices have in regard to the sustainability of the planet.