Ecce and Old Earth(1991)

Jack Vance

The planet Cadwal has an ecosystem unique in the human-explored galaxy; a thousand years past it was set aside as a natural preserve, protected by law and covenant against colonization and exploitation.

But now the elite Conservator culture that has developed on Cadwal is facing a conspiracy of humans and aliens to open the planet, and its rich resources, to full commercial use. Glawen Clattuc, scion of one of the scientific houses of Cadwal, must discover who exactly is behind all the sabotage, and bring them to interplanetary justice.

But Glawen soon discovers that he is investigating his own family - there are ancient crimes to be discovered, as well as the key that will resolve the crisis that threatens Cadwal and its way of life.