He became a senator, but then he decided to resign. what is the linking verb in the sentence?

Became is the linking verb.

o

one of the central themes of edward abbey's work has been his staunch opposition to the glen canyon dam on the colorado river that created lake powell, destroying stunning scenery and wildlife habitat, endangering many rare species of fish and animals, and also irreparably destroying many important archaeological sites which provided information about the early inhabitants of the united states.