It is rare that any individual can shepherd in a new field of study, but that is exactly what Dr. Barrera did in her role as program officer at the National Science Foundation (NSF). In 2002, through encouragement and support from Dr. Barrera, a nascent idea of seeking funding for the study of water-rock interactions and weathering eventually blossomed into embracing the broader concept of the critical zone: the reactive skin of the terrestrial Earth, extending from the top of the vegetation through the soil and down to fresh bedrock and the bottom of actively cycling groundwater. It is an entity composed of a co-evolving landscape of bedrock weathering, soil formation, vegetation growth, water and carbon cycling and water runoff to streams, and it is where we live.

The early meetings Dr. Barrera supported were charged with the excitement of this concept and the realization of how little was known (especially below the base of the soil) and that to tackle this thing, it would take intensive fieldwork, theory development and collaborations across a broad spectrum of sciences. Essentially, a new field of science was needed. She supported the formation of the Critical Zone Exploration Network and then the establishment of critical zone observatories (CZOs). Here again her leadership led not just to the pragmatic securing of funds but also to the realization that a field observatory is the ideal structure to bring together the full range of disciplines at a single location for a sufficient observational period that fundamental new understanding about the functioning and evolution of the critical zone could be discovered.

She called on the CZO community to hold annual meetings, to share findings and ideas, and to identify common questions and methods. Dr. Barrera encouraged researchers to think big and creatively. She welcomed new ideas and new investigators and actively worked to build a community of critical zone scientists. She built international connections, which contributed to the development of 45 CZOs worldwide. By 2018 there were 40 assistant professors who had worked in a CZO. Though the U.S. observatories were terminated, critical zone science remains an active program at NSF. It is not an exaggeration that this simply wouldn’t have happened without the tenacious, inclusive and insightful leadership by Dr. Barrera fostering critical zone science.

— William Dietrich
University of California, Berkeley
Berkeley, California