For over 40 years she has worked with her partner David B. Clark on the zoology, botany, geosciences, ecology, and climatology of the rain forests in Costa Rica.
[1] In 1978 Clark accepted a position with the Point Reyes Bird Observatory in Stinson Beach, California.
She left this position in 1979, when she and her husband became the first co-directors of the Organization for Tropical Studies's La Selva Biological Station.
In addition to rapidly expanding the scope of research carried out at La Selva, they also establish some of the long-term studies on forest dynamics that continue to this day.
[3] With funding from numerous source they implemented a 42-meter tower to measure atmospheric carbon as part a global array dedicated to studying climate change.