Critical Zone Observatory: NSF CZNet Guide

The Critical Zone Observatory (CZO) program was a flagship environmental research initiative established by the U.S. National Science Foundation (NSF) to investigate the complex physical, chemical, and biological interactions within Earth’s near-surface environment. Spanning from the top of the vegetation canopy down to the bottom of actively circulating groundwater, the critical zone sustains terrestrial life, regulates water resources, and governs nutrient cycles. In contemporary research administration, the initiative evolved into the Critical Zone Collaborative Network (CZNet), transitioning long-term field observations into integrated, cross-site environmental science.

For researchers and grant managers in geology, hydrology, soil science, and remote sensing, navigating critical zone funding mechanisms requires understanding how the NSF structures large-scale observatories, coordinates interdisciplinary science teams, and enforces open data compliance. Although dedicated network solicitations have transitioned into core divisional programs, the data infrastructure, collaborative protocols, and monitoring standards established under CZO and CZNet remain foundational across environmental geosciences.

What it is and who runs it

The Critical Zone Observatory program was created in 2007 by the NSF Directorate for Geosciences (GEO) through the Division of Earth Sciences (EAR). Originally funded as a collection of watershed-scale observation sites across distinct climatic and geologic terrains—such as Boulder Creek, Susquehanna Shale Hills, and Luquillo—the program provided intensive physical, chemical, and ecological monitoring infrastructure to quantify surface process dynamics over decadal timescales.

As described on the official NSF program pages on 2026-11-08, the program underwent a major strategic restructuring under NSF solicitation 19-586, transitioning from individual site observatories into the Critical Zone Collaborative Network (CZNet). CZNet organized scientific research around nine multi-site Thematic Clusters and a centralized Coordinating Hub operated in partnership with the Consortium of Universities for the Advancement of Hydrologic Science (CUAHSI). In Dear Colleague Letter NSF 24-118, the NSF Division of Earth Sciences announced that beginning in Fiscal Year 2025, CZNet is formally archived as a distinct solicitation, with future critical zone research supported through EAR core programs such as Hydrologic Sciences, Geomorphology and Land-use Dynamics, and Sedimentary Geology and Paleobiology.

Eligibility

Eligibility for NSF critical zone funding mechanisms follows standard requirements established in the NSF Proposal & Award Policies & Procedures Guide (PAPPG), as summarized on the official NSF solicitation on 2026-11-08:

Institutions of Higher Education (IHEs): Two- and four-year accredited colleges and universities situated in the United States, acting on behalf of faculty members.
Non-profit, Non-academic Organizations: Independent research laboratories, professional societies, and consortia directly associated with educational or research activities.
Consortia and Collaborative Lead Entities: Multi-institutional projects require a designated lead institution responsible for fiscal management, with partner institutions participating via subawards or collaborative proposal submissions.
Principal Investigator (PI) Restrictions: Individuals serving as lead PI or co-PI must hold primary research appointments at eligible submitting organizations; foreign organizations and federal agencies typically participate as unfunded collaborators.

What it funds or requires

Under the CZNet architecture (NSF 19-586), the NSF funded two distinct program components designed to balance field measurement with cross-network synthesis:

Thematic Clusters: Interdisciplinary research clusters focused on specific environmental gradients, including Bedrock, Big Data, Coastal, Drylands, Dust^2, Dynamic Water, GeoMicro, Urban, and the Critical Interface Network (CINet). Each cluster investigates linked watersheds across diverse land-use regimes.
Coordinating Hub: A centralized national entity responsible for standardizing data management, curating educational workshops, organizing inter-cluster working groups, and managing national outreach.

Awards under this mechanism carry strict compliance mandates regarding open access and data stewardship. Grantees are required to deposit all physical observations, sensor time-series, and geochemical analyses into recognized community repositories—such as HydroShare, EarthChem, or PANGAEA—using standardized metadata and persistent identifiers like a Crossref DOI. Datasets and analytical software must conform to open-access community standards to ensure ongoing reuse across Earth systems research.

Application or compliance steps

Securing and maintaining awards within NSF critical zone frameworks requires strict adherence to federal and program-level compliance milestones:

Program Alignment: Formulate research questions that target interconnected critical zone processes (such as deep weathering, soil moisture dynamics, and biogeochemical fluxes) rather than isolated disciplinary measurements.
Proposal Submission via Research.gov: Prepare proposals in accordance with the current NSF PAPPG, submitting through Research.gov or Grants.gov. Applications must include detailed Management Plans, Postdoctoral Mentoring Plans, and Community Outreach Strategies.
Data Management and Sharing Plan (DMP): Develop an operational DMP specifying exact public data repositories, time-series ingest cadences (typically requiring raw and QA/QC data publication within designated deadlines), and FAIR (Findable, Accessible, Interoperable, Reusable) data standards.
Cooperative Agreement Governance: Large network awards are executed as cooperative agreements, requiring active engagement with NSF program directors, participation in annual all-hands meetings, and compliance with mid-award review milestones.
Annual Reporting and Data Auditing: Submit comprehensive annual project reports documenting physical deliverables, open data releases, publications in repositories like EarthArXiv, and student training metrics.

Typical timeline phases

While specific calendar deadlines change across grant cycles and core programs, typical critical zone award lifecycles follow standard operational phases:

Phase 1: Opportunity Announcement and Team Assembly (Months 1–4): Release of program solicitations or core program updates by NSF EAR. Research teams form multidisciplinary consortia across universities and establish institutional subaward structures.
Phase 2: Merit Review and Panel Evaluation (Months 5–8): Submitted proposals undergo rigorous peer review, assessed against NSF’s Intellectual Merit and Broader Impacts criteria by specialized panels of earth surface scientists and hydrologists.
Phase 3: Award Negotiation and Cooperative Agreement Execution (Months 9–12): Recommended projects enter formal budget and compliance negotiations with the NSF Division of Grants and Agreements, establishing explicit reporting and data-sharing milestones.
Phase 4: Field Deployment and Network Integration (Years 1–3): Instrumentation installation, automated sensor telemetry configuration, baseline field campaigns, and active coordination with network data hubs.
Phase 5: Mid-Term Review and Synthesis (Year 3): Comprehensive performance assessment conducted via external site visits or reverse site visit presentations to determine second-half funding releases.
Phase 6: Synthesis, Long-Term Archiving, and Transition (Years 4–5): Integration of cross-site datasets, final archival validation, and transition of observational series into sustaining core program mechanisms.

Common mistakes

Siloed disciplinary scope: Proposing narrow hydrological or geochemical projects that fail to integrate biological, geological, and atmospheric coupling across the critical zone continuum.
Treating data management as an afterthought: Inadequate DMPs that omit community repository specifications or lack automated metadata pipelines, which frequently triggers severe panel critique.
Underestimating multi-institutional coordination costs: Failing to budget sufficient project management, travel, and data curation personnel needed to sustain collaborative network clusters.
Overlooking legacy data and existing facilities: Proposing redundant sensor networks rather than leveraging existing CZO, CZNet, or agency monitoring infrastructure.
Ignoring program restructuring: Submitting applications directly to archived solicitation numbers (such as NSF 19-586) rather than routing proposals through active EAR core program solicitations.

Related programs

The following table compares the Critical Zone Observatory / CZNet model with related federally funded environmental research infrastructure:

Program	Managing Agency / Division	Primary Focus	Observational Architecture
CZO / CZNet	NSF GEO / EAR	Earth surface processes from canopy to deep bedrock	Watershed observatories evolved into multi-site Thematic Clusters and Hub
LTER	NSF BIO / DEB	Long-Term Ecological Research across biological biomes	Permanent site-based ecosystem stations with continuous decadal sampling
NEON	NSF BIO	Continental-scale standardized ecological and climatic data	Standardized automated sensor towers and aquatic sites across 20 eco-climatic domains
EarthScope / SAGE / GAGE	NSF GEO / EAR	Solid Earth geophysics, seismology, and geodetic measurements	Continental geophysical instrumentation facilities and seismic sensor arrays

FAQ

What is the critical zone in environmental science?

The critical zone is the heterogeneous, near-surface layer of Earth that extends from the top of the plant canopy down to the lower limit of circulating groundwater. It encompasses the interactions between rock, soil, water, air, and living organisms that sustain terrestrial ecosystems.

Is the NSF Critical Zone Collaborative Network (CZNet) still accepting new proposals?

No. As announced in NSF Dear Colleague Letter 24-118, the dedicated CZNet solicitation is archived starting in Fiscal Year 2025. Critical zone research is now integrated and supported through existing core programs within the NSF Division of Earth Sciences (EAR).

How can researchers access legacy CZO and CZNet data?

Legacy Critical Zone Observatory data remain openly accessible through the dedicated CZO archive portal (czo-archive.criticalzone.org) and associated community repositories including HydroShare, EarthChem, and the CUAHSI data services catalog.

Which NSF core programs fund critical zone research now?

Critical zone proposals are supported by disciplinary core programs in the Division of Earth Sciences, including Hydrologic Sciences, Geomorphology and Land-use Dynamics, Geobiology and Low-Temperature Geochemistry, and Sedimentary Geology and Paleobiology.

Sources

National Science Foundation. (2019). Critical-Zone Collaborative Network (CZNet) Program Solicitation. NSF 19-586, Directorate for Geosciences, Division of Earth Sciences. https://www.nsf.gov/funding/opportunities/critical-zone-collaborative-network/505628/nsf19-586. Checked 2026-11-08.
National Science Foundation. (2024). Dear Colleague Letter: Critical-Zone Collaborative Network Retirement. NSF 24-118, Directorate for Geosciences. https://www.nsf.gov/funding/information/dcl-critical-zone-collaborative-network-retirement/nsf24-118. Checked 2026-11-08.
Critical Zone Collaborative Network / CUAHSI. (2023). About the Critical Zone Collaborative Network. https://criticalzone.org/about. Checked 2026-11-08.

Critical Zone Observatory (CZO) and CZNet Guide