RiskMetrics, the largest of the shareholder voting advisers, has acquired a specialist research firm that analyses companies' environmental records, in an indication that issues like climate change are becoming mainstream for some investors.

RiskMetrics, which advises about 2,300 investors worldwide on how to vote their shares, has purchased New York-based Innovest Strategic Value Advisors for $16m (€13m), with the transaction expected to close on March 2.