Two leaders in sustainable investing have joined forces.

Pax World Management announced that it has entered an agreement to be acquired by the U.K.-based Impax Asset Management Group.

The transaction between Pax, which has approximately $4.5 billion in assets under management, and Impax, who has approximately $9.4 billion in AUM, will create a combined investment management firm with $13.4 billion in net consolidated AUM.

Under the terms of the transaction, Pax will be renamed Impax Investment Management (US) LLC.

Impax and Pax formed a partnership in 2007 to design and manage the Pax Global Environmental Markets Fund, which was launched in 2008 and today has more than $500 million in assets.

Pax World Management served as investment advisor to Pax World Funds — and will continue to do so post-acquisition as the U.S.-based mutual fund division of Impax’s global business.

Joe Keefe, Pax’s president and CEO, will continue to lead the renamed company and will also be named to the board of Impax Asset Management Ltd.

“This is an exciting new chapter in our decade-long partnership with Impax,” Keefe said in a statement. “We believe that combining our two firms will create a leading sustainable investment manager with business on both sides of the Atlantic. Pax World Funds’ shareholders stand to benefit in significant ways from our increased scale, research and investment capabilities as we seek to deliver a more robust investment and distribution platform for the global market.”

Keefe, together with other members of Pax’s management and senior staff, have agreed to enter new employment agreements. Keefe will report to Ian Simm, Impax’s chief executive.

The strategic rationale for the combination is supported by highly complementary areas of investment management expertise, together with strong product and geographic fit. This will allow the expanded group to offer enhanced resources and services to Pax’s and Impax’s existing and prospective shareholders and clients.

According to Simm, the acquisition will expand both firms’ investment management, global research and client service capabilities.

“Like Impax, Pax has a long track record as a pioneer in sustainable investing and a strong team of highly experienced investment management and support staff,” Simm said in a statement. “The combined group will start with closely aligned business cultures and be well placed to offer a broader service and more diversified range of products to existing and future clients.”

The acquisition is subject to approval of the investment advisory agreement by the trustees and shareholders of Pax World Funds.

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