Final answer:
Michael Pollan's specific start year for his research is not provided, but his significant published work by 2006 indicates an established research career by that time.
Step-by-step explanation:
The specific year when Michael Pollan began his research is not explicitly mentioned; however, we can infer from his bibliography that his significant contributions to discussions about food, agriculture, and sustainability were well formulated and published by 2006, with the release of his book The Omnivore's Dilemma: A Natural History of Four Meals. Pollan's work has included various aspects of food systems, the environmental impact of agriculture, and the ethical considerations of our eating habits. His subsequent work, In Defense of Food: An Eater's Manifesto, which was published in 2008, suggests that his research career had been established before these dates.