She is the co-founder of Urban Ocean Lab, a think tank for ocean-climate policy in coastal cities,[2][6] and the Roux Distinguished Scholar at Bowdoin College.

[8] In high school, she served in the Student Conservation Association, working on the Continental Divide Trail in the San Juan Mountains.

[9][10] Johnson earned a Bachelor of Arts degree in environmental science and public policy at Harvard University in 2002, where she was a friend of actress Tatyana Ali.

[11] In 2011, Johnson earned a PhD in marine biology from Scripps Institution of Oceanography at the University of California, San Diego.

[19] In 2013, she became executive director of the Waitt Institute and co-founded the Blue Halo Initiative to partner with governments and local communities in Barbuda, Montserrat, and Curaçao to enact more sustainable plans for ocean use and conservation.

With the Blue Halo Initiative, Johnson led the Caribbean's first successful ocean zoning project, providing maps, communications, policy support, and scientific assistance to the island Barbuda as it began to regulate and protect its coastal waters.

[26][27] In November 2021, Johnson organized a joint statement signed by over 100 notable figures demanding that Edelman end its work with fossil fuel companies, such as Exxon.

[44] In June 2022, Johnson was appointed a member of the US Secretary of State, Antony Blinken's Foreign Affairs Policy Board.

[49] Her conservation and policy work is frequently profiled in popular media, including The Observer,[50] Atlas of the Future,[51] Outside,[52] and Elle, which named her as one of the "27 Women Leading the Charge to Protect Our Environment".