Left-leaning senators are urging the U.S. Securities and Exchange Commission to ensure its proposed climate change disclosure rule does not harm small farmers who do business with publicly traded companies, who would have to comply with the regulation.

Sens. Jon Tester, D-Montana, and Kyrsten Sinema, I-Arizona, sent a letter to the SEC expressing concern about “Scope 3″ of the proposal, which would require public businesses to disclose the greenhouse gas emissions of those in their supply chain.