Earth is at the brink of an ecological catastrophe, polluted, ravaged by wars, and was abandoned by the majority of its population who left in space ships.
For generations their society relied on technologies and they developed a military style technocracy merging with the machines becoming almost cyborgs. They build their ships from an extremely durable material "diamantee" or something along those lines.
In the meanwhile a small amount of people remained on Earth. They renounced their dependence on technologies and instead cherished the abilities within themselves such as Telepathy, Telekinesis, etc - Earth managed to heal and they lived in total harmony with nature living miles apart.
At one point the departed people (technocrats) return on their ships and try to reconquer the Earth - the people with mental powers who were left resist....
Read about 2006
If anyone knows anything about the title or the author I would very much appreciate the info - I have been looking for this book about 15 years