SETAC Globe - Environmental Quality Through Science
  21 July 2011
Volume 12 Issue 7

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National Critical Zone Observatory (CZO) Program: How the Critical Zone operates and evolves, including predictions of its response to future climate and land use changes

Ron Checkai, U.S. Army Edgewood Chemical Biological Center, Aberdeen Proving Ground

The Critical Zone: Where rock meets life

During a recent meeting of the National Academy of Sciences U.S. National Committee for Soil Science (NAS-USNC/SS) on 15-16 June 2011, a presentation was given on the National Critical Zone Observatory (CZO) Program, which is sponsored by National Science Foundation (NSF). The Critical Zone is earth’s porous, near-surface layer, from the tops of the trees down to the deepest groundwater. It is a living, breathing, constantly evolving boundary layer where rock, soil, water, air, and living organisms interact. These complex interactions regulate the natural habitat and determine the availability of life-sustaining resources, including our food production and water quality.

CZOs are environmental laboratories established to study the chemical, physical, and biological processes that shape the earth’s surface. Little is known about how these processes are coupled and at what temporal and spatial scales. CZO research seeks to understand these couplings through monitoring and modeling at the watershed scale. The National CZO Program is a community resource that serves the international scientific community through research, infrastructure, data, and models. One of the main questions being addressed by the program is how will the Critical Zone evolve in response to changing climate and land use.

The following summary briefly describes the basic elements (research, infrastructure, and databases) of the National CZO Program, so that the existence of this program can be conveyed to SETAC membership.


  • Supported by NSF — National Science Foundation, Geoscience Directorate, Earth Science Division
  • Interdisciplinary — hydrology, geology, soil science, biology, ecology, geochemistry, and more
  • Developing predictive ability for how the Critical Zone will respond to projected climate and land-use changes


  • Six US observatories — Puerto Rico to California
  • Community of researchers collaboratively working at same field sites
  • Existing and new resources — sensor and communication networks, eddy towers, boreholes, gages, and much more


  • Diverse datasets across disciplines, spatial and temporal scales
  • Large data volumes from in situ sensors, field instruments, remote sensing, and more
  • Integrating data across observatories and prior programs for discovery and synthesis


  • Coupled systems models that interconnect complex physical, chemical, and biological processes
  • Watershed-scale simulations — fluxes of energy, water, carbon, sediments, and other materials
  • Multi-scale and multi-process models that include landscape and ecosystems

For more information visit the National CZO Program website at

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