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Citizen Science

Two platforms — eBird and iNaturalist — have quietly become among the largest biodiversity datasets on Earth, generated almost entirely by volunteers with smartphones.

Published May 2026 Last reviewed July 2026 Evidence level Strong Reading time 5 min

The Scale of Volunteer-Generated Data

As of September 2024, iNaturalist held more than 200 million unique species observations contributed by 3.3 million observers worldwide, making it one of the largest biodiversity datasets ever assembled — built almost entirely by members of the public using a smartphone app.

Established fact

Within the Global Biodiversity Information Facility (GBIF), eBird contributes over 75 times the number of bird observations that iNaturalist contributes — reflecting eBird's narrower, bird-specific focus and its two-decade head start, while iNaturalist is the top contributor across plants, mammals, reptiles, and amphibians combined.

Source: BioScience, Oxford Academic, 2025; GBIF contribution statistics

From Hobby Data to Formal Science

Citizen science data is increasingly cited in formal scientific and regulatory work, not just hobbyist record-keeping. A 2024 study found that use of iNaturalist data in peer-reviewed papers grew tenfold between 2020 and 2025, and that 228 of 1,355 environmental impact statements analyzed from 2012–2022 referenced or used citizen-science data.

200M+species observations on iNaturalist as of September 2024
10xgrowth in iNaturalist data use in peer-reviewed papers, 2020–2025

Goal, Method, Outcome

GoalGenerate biodiversity monitoring data at a geographic and temporal scale that professional researchers alone could never achieve, while building public engagement with conservation.
MethodSmartphone apps allowing anyone to log species sightings with photos, location, and time, which are then verified by a mix of automated identification and expert community review before entering research-grade datasets.
Measured outcomeDemonstrated, citable use in peer-reviewed research and formal environmental impact assessments — not just informal community interest, but data that meets a bar for use in professional conservation science.

Uncertainty & Evidence Gaps

Citizen science data collection is geographically uneven — concentrated in wealthier regions with high smartphone penetration and strong existing naturalist communities — meaning data-poor regions may remain data-poor even as global observation totals grow. Research also indicates data quality depends heavily on expert-led validation; projects without active expert oversight show weaker contributions to formal assessments like the IUCN Red List.