Corean Chronicles, book 4: Alector's Choice
L.E. Modesitt2005

Corus has been designed to become the new home of a superior race from a distant world whose very life depends on drawing sustenance from the biological life force of a planet. After changing the climate, they have grown ordinary people to tend the plants and animals, in preparation for their eventual arrival in force. Meanwhile, their plans are supervised by a staff of Alectors, who in effect rule the world. Alectors are bigger, tougher, and have both psychic talents and technology unavailable to the natives.
The time is now fast approaching for the transfer from the old world, nearly bled dry of life force. But neither the Alectors (who will be reduced in status when the real powers arrive) nor the local humans (who seem destined to become no more than cattle, though they know nothing of this) are ready.