Citizen science connects public participation with formal research, environmental monitoring, and large-scale data collection. The figures below show the scale of that collaboration across NASA, NOAA, Zooniverse, SciStarter, iNaturalist, and the U.S. Geological Survey (USGS). Measurement periods differ, so each statistic is identified by its source and date where one is provided.
Contents
- The scale of public participation
- NASA and NOAA participation
- Zooniverse classifications and research projects
- SciStarter campaign results
- iNaturalist observations and scientific use
- USGS monitoring and mapping projects
- Research output and citation impact
The scale of public participation
Several major citizen science networks report participation in the millions. NASA Citizen Science says NASA-funded projects have engaged roughly 1.5 million volunteers, according to a NASA 2021 grant announcement. NASA also says volunteers have helped make thousands of important scientific discoveries. More than 650 volunteers have co-authored peer-reviewed research papers with project scientists, according to NASA Citizen Science highlights.
These figures describe different kinds of involvement. A volunteer count measures people engaged by projects, while co-authorship measures a smaller group whose contribution reached the level of a peer-reviewed paper. Together, the figures show that citizen science can extend from occasional public participation to direct involvement in published research.
The scale is also visible in the number of supported projects. NASA’s 2021 grant announcement reported 23 new grants in an expansion round. The same announcement said that 21 projects in NASA’s SciAct network received extensions into the next phase of the program. Those counts refer to grants and project extensions, not unique volunteers or discoveries.
Platform totals provide another view of activity:
| Organization or platform | Reported measure | Measurement period or reference |
|---|---|---|
| NASA-funded citizen science | Roughly 1.5 million volunteers | NASA 2021 grant announcement |
| NOAA citizen science | More than 570,000 participants | Fiscal year 2023 |
| NOAA citizen science | 1.2 million volunteer hours | Fiscal year 2023 |
| Zooniverse | Roughly 3 million volunteers | Reported in April 2026 and a 2025 funding post |
| iNaturalist | More than 3 million users worldwide | iNaturalist science page |
The totals should not be added together. They may use different definitions, geographic scopes, and counting methods, and people can participate in more than one organization or project.
NASA and NOAA participation
NASA’s reported roughly 1.5 million volunteers illustrate the reach of space and science projects supported by the agency. NASA Citizen Science describes thousands of important discoveries made with volunteer help. The agency also reports more than 650 volunteer co-authors on peer-reviewed research papers, connecting public participation with a formal research output.
NOAA’s fiscal year 2023 figures emphasize time as well as people. NOAA citizen science projects attracted more than 570,000 participants and contributed 1.2 million volunteer hours during that fiscal year. The hours measure reported effort, while the participant total measures people involved; neither figure indicates that every participant contributed the same amount of time.
NASA and NOAA therefore offer complementary measures. NASA’s published figures highlight the breadth of a funded project portfolio, discovery activity, and volunteer co-authorship. NOAA’s fiscal year 2023 figures quantify both participation and contributed labor. These distinctions matter when interpreting “scale”: a network may be large because it reaches many people, because it collects sustained effort, or because it supports many projects.
Zooniverse classifications and research projects
Zooniverse reported reaching 3 million volunteers in April 2026. A Daily Zooniverse report from April 2026 also recorded more than 980 million all-time classifications and more than 10 million classifications during that month. Separately, Zooniverse says volunteers contribute over 1 million classifications each week across about 80 active projects.
Zooniverse’s 2025 federal-funding post reported nearly 3 million volunteers worldwide and partnerships with more than 150 research institutions. The organization’s weekly activity figure shows why classification totals can grow quickly: many participants can make small individual contributions that become a large aggregate research dataset.
The project-level numbers show how activity can vary within the wider network. The Zooniverse project report for the South Coast Threatened Fauna Recovery Project recorded 2,696 registered volunteers. That project uploaded 40,065 subject sets of wildlife images and recorded 417,332 classifications in its first dataset.
The project figures are not a measure of the entire Zooniverse community. They describe one wildlife-image project and one first dataset. The relationship between 2,696 registered volunteers and 417,332 classifications also should not be treated as an average contribution for all Zooniverse volunteers or projects.
SciStarter campaign results
SciStarter’s Citizen Science Month results provide dated campaign snapshots. During Citizen Science Month 2025, nearly half a million volunteers from 136 countries participated. They contributed 3,039,361 Acts of Science, while 78 citizen science project teams were actively engaging during April 2025. SciStarter also said more than 1,000 projects were listed on its platform in 2025.
Participation extended across multiple projects and events. Nearly 70% of 2025 participants joined two or more projects or events, and nearly one-third engaged in five or more projects. Close to 300,000 of the 2025 Acts of Science came from Affiliate projects.
The campaign’s public reach was measured separately from participation. More than 1,600 hashtagged posts reached over 14.1 million people and generated more than 152,000 community interactions. Within that total, #CitizenScienceMonth generated 603 posts and reached 8.7 million people. #OneMillionActsofScience generated 472 mentions and reached 1.9 million people. #SciStarter generated 104,000 interactions from 77 posts.
SciStarter’s Citizen Science Month 2026 results, measured by April 30, 2026, reported 450,918 volunteers from 140 countries. Those participants contributed 4,730,752 Acts of Science, and the campaign supported more than 950 research projects and events.
| SciStarter campaign measure | 2025 | 2026, by April 30 |
|---|---|---|
| Volunteers | Nearly 500,000 | 450,918 |
| Countries | 136 | 140 |
| Acts of Science | 3,039,361 | 4,730,752 |
| Supported projects or events | More than 1,000 listed projects; 78 active teams | More than 950 supported projects and events |
The two campaign snapshots use related but not necessarily identical measures. The 2025 result describes projects listed and teams actively engaging, while the 2026 result describes supported projects and events. They should be read as campaign-specific reports rather than a continuous annual series.
iNaturalist observations and scientific use
iNaturalist reports more than 260 million observations and more than 3 million users worldwide on its science page. The platform says scientific use of its data has grown tenfold in five years, and that its data is driving research across 128 countries. The same page lists scientific use across 638 taxonomic families and more than 6,000 peer-reviewed publications using iNaturalist data.
The iNaturalist ID Summaries page reported that, in 2024, iNaturalist data was used for 1,128 scientific studies. The platform reached 4.7 million users each month in 2024, and about 40% of its activity that year was within the United States. These are different measures from the worldwide user total and should not be substituted for it.
The 2024 summary also reported that users observed more than 300,000 species in the last year. iNaturalist says about one in four species have been documented by the community. Another iNaturalist post said nearly 300 million observations had been created by a community of 4 million people actively sharing what they find.
The distribution of observations is uneven. iNaturalist reported that the top five species had about as many observations as the bottom 243,544 species on the platform. That comparison describes concentration within the platform’s observation totals; it does not mean that the species groups contain the same number of species.
USGS monitoring and mapping projects
USGS examples show citizen science supporting long-running environmental records, coastal analysis, Indigenous-led sampling, and geographic mapping. USGS says Nature’s Notebook accumulated phenology records in more than 18,000 U.S. locations since 2009. Phenology records track seasonal biological timing, while the location count describes where records accumulated across the United States.
More than 1,200 iCoast volunteers helped improve coastal erosion predictions, according to the USGS citizen science page. The same source says more than 300 trained Indigenous citizens collect water-quality samples in the Yukon River Basin. These figures describe distinct projects and participant groups, so they should not be combined into one USGS volunteer total.
The National Map Corps provides a mapping example. A USGS news release said the project harvested more than 100,000 map points in less than two years. The map-point total measures contributed geographic data, not participants or research papers.
Across these projects, the useful comparison is between types of contribution: repeated observations over time, expert-supported prediction improvement, community-based water sampling, and mapped points. Each output has a different unit, making the project measures complementary rather than interchangeable.
Research output and citation impact
Citizen science participation can also be assessed through scholarly publication and citation measures. NASA Citizen Science reports that more than 650 volunteers have co-authored peer-reviewed research papers with project scientists. iNaturalist lists more than 6,000 peer-reviewed publications using its data, while its 2024 ID Summaries page reports 1,128 scientific studies using iNaturalist data in that year.
These iNaturalist measures cover different scopes. The more than 6,000 figure is a cumulative publication count reported on the science page. The 1,128 figure is a count of studies using the data in 2024. Neither should be interpreted as the number of new publications in 2024 unless the source explicitly defines it that way.
The Nature Index review of citizen science papers cited 143 space science and astronomy papers from 23 citizen science projects. It also found that citizen science papers had annual citation rates four times higher than the typical paper in the year 2000. The comparison is tied to the review’s cited paper set and reference point; it is not a current citation forecast or a claim about every citizen science publication.
Taken together, these measures cover volunteer authorship, data use, publication volume, and citation rates. They show several ways public participation can appear in research: people may classify or observe data, contribute to project outputs, co-author papers, or supply information later used by researchers. The exact meaning of each statistic depends on its source, unit, geography, and measurement period.