In this new era of citizen science, the public is playing a crucial role in tracking species and helping to conserve our natural heritage

“IS THAT A TREE SPARROW? Yeah, I think I’ve got a tree sparrow.”

“Back up in those weeds?”


“There’s at least two that I can see.”

“Oh, I’ve got a song sparrow.”

“On the mound there?”


It’s January 1. Jamie, Roger and I are standing on a quiet side road a few kilometres south of Rice Lake in south-central Ontario, spending the first morning of the new decade bundled against the cold, peering through binoculars, connected to a thread that stretches back 120 years to Christmas Day of 1900.

It was on that date that a handful of birders and amateur naturalists, led by Frank Chapman, editor of Bird-Lore, a precursor to Audubon magazine, held North America’s first Christmas Bird Count. That year, 27 people in 25 locations — including Toronto and Scotch Lake, New Brunswick — counted 18,500 birds and 89 species.

The census was conceived to promote conservation, an alternative to 19th-century Christmas Day shooting parties. Held annually since, it has evolved into something its creators and early generations of participants could never have conceived: the continent’s longest-running citizen science project. In 2018-19, 80,000 observers tallied almost 49 million birds on one-day counts in 2,616 locations over a three-week period spanning Christmas and New Year’s. For ornithologists, ecologists and other scientists, the accumulated data set is, in the words of one researcher, “indispensable for understanding changes in [winter] bird populations at scales otherwise unattainable.”

Now imagine replicating that result in all areas of ecology and natural science — not merely to count species, but to spark new discoveries, detect and track environmental hazards, measure change, support policy and action, educate and engage the public, and empower individuals to use science as a tool for environmental justice. That is the story of the recent growth and future promise of citizen science in 2020, in Canada and around the world.

Use of the term “citizen science” in this context started only in the early 1990s, yet today studies, research projects and science-based initiatives that derive in whole or in part from data generated by the public are mainstream. For a time, the term carried a stigma of not being “serious” science, but according to Leslie Ries, assistant professor of biology at Georgetown University in Washington, D.C., and a citizen science data-management specialist, that has largely passed. “Citizen science as a source of data for rigorous analysis is becoming more and more accepted,” she says.

New technologies and related trends are a huge factor, of course. Online networks, crowdsourcing, digital photography, smartphones, database software and artificial intelligence are essential parts of the citizen toolkit. But perhaps most significantly, while “citizen science” spotlights the public, the field’s current momentum is coming as much or even more so from scientists themselves. So while public interest in learning about the environment, doing one’s part for nature, and leveraging greater knowledge and involvement to have more influence on local issues and policy is key, citizen science is also now a mainstay focus of research conferences, associations and professional journals. Academics are realizing that citizen-science-based scholarship has opened the door to a new frontier of discovery.

“I’M ALWAYS REALLY CAUTIOUS when I start talking about citizen science as a thing,” says Michael Pocock, an ecologist at the U.K. Centre for Ecology and Hydrology, co-chair of the British Ecological Society’s Citizen Science Group and a board member of the U.S.-based Citizen Science Association. “It’s absolutely not a thing. It’s an incredibly diverse range of approaches, all of which are clustered under this term of convenience of citizen science.”

Several years ago, Pocock led a study that tried to categorize all the existing citizen science projects in ecology and the environment. They came up with a total of more than 500. “You could probably quadruple the dataset by now, at least,” he says.

It’s not just journals publishing more studies based on citizen science projects. In 2016, the Citizen Science Association launched Citizen Science: Theory and Practice, which reflects a growing need among practitioners for how-to material. In the U.K., the British Ecological Society just held a call for papers in a similar vein to run across its entire six-journal catalogue.

But it’s in the data that things are really taking off. Leslie Ries, whose main research focus is butterflies, agrees. “In the last three or four years, [citizen science] hit this big exponential curve,” she says. “The amount of data gain every year is in orders of magnitude!”

One of the most telling developments there — and an integral part of the citizen science story — is the growth of eBird and iNaturalist, the two largest biodiversity-focused, crowdsourced citizen science platforms. Both invite users, experts and non-experts alike, to post observations (iNaturalist requires photos, eBird does not), which are then vetted by a combination of human experts and AI technology.

Users of eBird — which launched with coverage of the western hemisphere in 2002, then went global in 2010 — entered 140 million sightings in 2019. Managed by the Cornell Lab of Ornithology, it’s a hub for birders to track and record personal checklists linked to location, explore others’ posts, study distributions and learn about birds. Site administrators also archive the data and, once vetted, make it available for research.

iNaturalist began as a master’s project at UC Berkeley in 2008 and took off when its early developers partnered with, first, the California Academy of Sciences in 2014 and then the National Geographic Society, in 2017. In the past five years, the number of observations has roughly doubled each year, with more than 14 million new sightings submitted in 2019. The Canadian branch ( is the result of a collaboration between the CWF (along with its Hinterland Who’s Who program) and NatureServeCanada, Parks Canada and Toronto’s Royal Ontario Museum working with iNaturalist and the California Academy of Sciences. As a result, Canadians contributed more to its growth last year (15.4 per cent) than users in any country outside of the U.S.

As the names suggest, eBird is strictly for birds while iNaturalist’s scope includes all plants and animals. More than 169,000 different species were entered on the latter’s site last year. It puts identification front and centre: users post photos and their locations, and the site’s impressive AI photo recognition system returns a list of the most likely matches. For an observation to be considered research grade, the identification must also be validated by human experts on the site.

While eBird has many more observations, iNaturalist is gaining much greater traction as a source of research data. In 2019, some 219 scientific studies relied on iNaturalist data; for eBird, it was 58.

ONE OF THE MORE COMPELLING contributions iNaturalist observations are making to science is in the discovery of species new to particular areas. One such finding — the first-ever sighting in Canada of the paintedhand mudbug (Lacunicambarus polychromatus), a burrowing crayfish — was documented in the journal The Canadian Field Naturalist last fall. And it’s a story with a twist.

It began with Colin Jones, provincial arthropod zoologist at the Ontario Ministry of Natural Resources and Forestry’s Natural Heritage Information Centre, uploading to iNaturalist a photo of a crayfish found on the Ojibway Prairie Nature Reserve in Windsor, Ont. Jones identified it as a species common to the province. Several months later, however, a biologist at Ohio State University, Mael Glon, reviewed the entry and determined it was actually a paintedhand mudbug, which is common farther south. Jones and Glon did some follow-up fieldwork, found two more specimens and then published their findings.

“Had it not been for iNaturalist, [this species’] presence may have remained undetected,” they wrote, describing the site as “a platform that has greatly increased the ability of amateurs and experts to collaborate in real time.” Their paper also revealed other first-time Canadian discoveries on iNaturalist — 40 species of moths not known in Ontario, 19 of which are new to Canada, and even one new to North America. They also discuss one as a “new and potentially invasive vascular plant species” called small-flowered jewelweed (Impatiens parviflora de Candolle).

Although collaboration does go on, amateurs posting individual observations to iNaturalist don’t typically have the same involvement in the scientific process that Jones, as an expert, experienced. Usually, beyond the ID confirmation, any involvement in subsequent research linked to their data is more passive and one-way. This differs from more “traditional” purpose-built citizen science projects where the participants volunteer or enrol to do specific research.

In such cases, the citizen scientists typically have greater interaction with the professionals running the projects and sometimes with other amateur participants like themselves. And the array of projects and applications that surfaces is almost as diverse as nature itself: snorkellers in Hawaii reporting signs of coral bleaching via app to a researcher leading a real-time response team to limit reef damage; landscape ecologists in multiple locations asking drivers to submit location-linked roadkill photographs to help map dangerous “hot spots,” data that can be used to lobby for protective barriers; resources officials on Vancouver Island training the local public to collect and test water samples in small streams to monitor land use impacts on water quality; and, one that Pocock ran in the U.K., using volunteers to detect the presence and distribution of tree pests by having them collect infected leaves in plastic bags and monitoring larvae hatch rates.

This remarkable scope underscores Pocock’s view that citizen science is a “range of approaches” rather than “a thing.” It also highlights some of its other most valuable attributes in addition to the scientific findings themselves.

“For the people involved in these projects, who are contributing data, it has many, many potential benefits,” says Pocock — “learning opportunities, community-building opportunities and even behavioural change.”

The latter can be valuable when it comes to confronting issues like climate change and threats to biodiversity.

“If we’re to mitigate some of those things,” Pocock says, “surely it will require a bit of a cost from us in terms of changing behaviour as individuals. And so, one of the ways I think [citizen science] can be really beneficial is for people to be directly engaging with these things to develop that sense of care.”

Georgetown’s Ries refers to this as “the transformative power” of citizen science. “There’s actually been research showing that people who do citizen science on monarchs are then also more likely to contribute and become involved in monarch conservation.” It’s not the species, but the citizen science model, that counts, she says. “It makes people more engaged…. They’re contributing to science in a way that gives them some ownership over the data.”

Ries adds that this “transformative power” cuts both ways. “It’s transformative for scientists [too], because we can ask questions at larger scales. It also changes the way we think about collecting data, about interacting with the public.”

GREG MITCHELL, A RESEARCH SCIENTIST in Environment and Climate Change Canada’s wildlife research division in Ottawa, echoes these views.

“Citizen science plays a very important role in instilling a sense of stewardship and ownership for the natural world. But it’s also a really awesome way to bring researchers together with the public to work towards a shared conservation goal. To me, it’s like the meeting point.”

Mitchell and Ries have something else in common — both published important butterfly population studies in 2019 that showcased different types of large-scale citizen science data sets and demonstrated their value for analysis.

Mitchell’s paper used 15 years of butterfly count data sourced from the Ontario Butterfly Atlas (2003–2017) and eButterfly (2012–2017), a database of butterfly observations similar to eBird, to determine what factors in the annual life cycle of the North American monarch butterfly determined the size of the annual Canadian breeding population — essentially, “what’s controlling how many monarchs we see in Canada?” says Mitchell.

The answer, it turns out, is weather conditions in the southern U.S. and their impact on milkweed growth in that area during the North American monarch’s spring migration.

To determine this, Mitchell and his collaborators, Tara Crewe, a senior scientist with Birds Canada, and Maxim Larrivée, director of the Montreal Insectarium and co-creator of eButterfly, used the observation data to estimate monarch populations and, for comparison, populations of other species of migratory and non-migratory butterflies from the data sets. Next, they factored in weather conditions and available measurements of overwintering monarch populations in Mexico, and then ran correlations until the spring weather influence was isolated.

Two critical attributes in the eButterfly data that enabled Mitchell and colleagues to calculate accurate population estimates were the lengths of the lists that observers submit and, as important, the time they spent watching butterflies to compile them. “Let’s say someone lists 15 butterflies in a day,” Mitchell explains. “What that number means changes depending how much effort was put in.”

eBird follows a similar protocol, but iNaturalist does not. “There’s still value in observations when there isn’t an effort factor,” says Mitchell, but it needs to be used in different ways.

There’s also no doubt in his mind that eButterfly and the Ontario atlas made their particular study possible. “Given the geographic range that we’re talking about, I don’t think there is any other way to monitor monarchs or milkweed in the U.S. and Canada without engaging citizen and community scientists,” he says.

Ries’s study, meanwhile, fits into the growing library of “insect apocalypse literature.” Specifically, it is one of the first works to look at drastic insect population declines outside of Europe using data gathered through long-term, systematic monitoring.

Written with lead author Tyson Wepprich, a biologist at Oregon State University, and three others, it estimated the rate of change in abundance and population trends for 81 species of butterflies in Ohio. To do this, the authors analyzed data gathered by volunteers organized and trained by the Ohio Lepidopterists in weekly butterfly surveys over 21 years (1995–2016) at 104 sites across the state. Their overall finding: “total abundance is declining at 2% per year, resulting in a cumulative 33% reduction in butterfly abundance” in the two-decade study period.

From a citizen science perspective, the survey stands out for its scale and scope and the systematic nature of the data collection. In the period studied, volunteers did an impressive 24,405 butterfly surveys following a structured protocol known as “Pollard walks.” Developed in the U.K. in the 1970s by scientist Ernie Pollard, the technique requires volunteers to do weekly walks along the same transect (a straight line through an area) at the same pace in fair weather counting every species seen within a five-metre zone around the observer.

Ries calls Pollard a “visionary” who grappled with the fact that monitoring programs for birds that existed at the time couldn’t take into account butterflies’ shorter lifespans. “Birds are vertebrates and they’re long-lived, so a lot of time we’re interested in what’s going on in the breeding season and then maybe the winter season,” she explains. “You can do one set of surveys to get a snapshot. Whereas with butterflies, if you go out and see all these butterflies, and then you go out two weeks later, you’ll be seeing all different butterflies. So, if you want to get a sense of what is going on, you have to have more repeated, structured surveys.”

Both Ries and Pocock acknowledge that Pollard walks are on the high end in terms of required commitment and level of expertise from the volunteers. “Why do people do that?” asks Pocock, rhetorically. “I think it’s something about connection to place, possibly a sense of duty that they want to help nature.”

At the other extreme is someone who merely takes note of nature around them and uploads photos to iNaturalist if they see something interesting. “I consider that citizen science as well,” says Ries.

AS IT TURNS OUT, THERE ARE circumstances where iNaturalist is used for more than just individual entries. Specifically, one of the site’s features allows members to create projects to which multiple participants can log observations, collect additional data not typically documented on the site and communicate through posts and comments. It’s easy to imagine a school class or a naturalist club using this feature, but it turns out that even sophisticated official record keepers see its potential. A case in point is a project launched by Ontario’s Natural Heritage Information Centre. It encourages individuals to join so that their observations of provincially rare species can be considered for incorporation into Ontario’s provincial record.

“This project has become an important data source for our centre,” says Colin Jones. “Since we launched, over 500 participants have contributed nearly 40,000 observations of 1,249 species.” Not only have these records allowed the centre to update its species conservation ranks and identify locations important to the conservation of rare species, Jones adds, but in some cases, they have led to species being “removed from the list of provincially rare species because of more data.”

The iNaturalist project option has also proven to be a great tool for another prominent element in citizen science’s explosive growth: the so-called “bioblitz.” Bioblitzes are events in which participants record as many species as possible in a specific area over a set period of time, and many use iNaturalist to post and organize all the data collected. The term was first coined for an event held in 1996. As with much of citizen science, the number and popularity of bioblitzes held worldwide has surged since the early 2000s. A lot of bioblitzes today combine serious scientific data gathering with a guided public component to grow people’s awareness and interest in biodiversity in and around their local communities.

“These are exercises where we’re both showing off the scientists and doing public engagement [while also] looking to learn something through the data we collect,” says Dave Ireland, a biologist based in Dartmouth, N.S., who was a co-founder of the Ontario Bioblitz program in 2012 and a pivotal partner in creating the Canadian Wildlife Federation’s national BioBlitz Canada 150 series in 2017.

ALONG WITH MUCH OF THE GLOBAL citizen science community, Ireland says he is excited by the promise of what’s in store this April — when a wave of bioblitz-type events will be held as part of an even larger citizen science campaign coinciding with the 50th anniversary of Earth Day.

At the centre of these events is Earth Challenge 2020, “a global call to action” for the collection and integration of data for six research questions related to environmental and human health (these involve climate change, air and water quality, insect decline, plastic pollution and food security). Organized jointly by the Earth Day Network, the U.S.-based Wilson Center and the U.S. Department of State’s Eco-Capitals Forum, the event has two goals — to expand the amount of open citizen science data (new and existing) that’s available to address these six issues while providing tools and educational resources that people can use to take action in their local communities and countries.

The kickoff will feature the launch of an Earth Challenge 2020 mobile app to gather data collected at events around the world. The goal is to involve hundreds of millions of people and many more data points. Anne Bowser, director of innovation at the Wilson Center’s science and technology innovation program — whose primary role in the partnership is to ensure research integrity and data integration — says the app will enable the Earth Day Network to arm those people with “a tool for understanding the environment and then driving change.”

Bowser says working on the project’s development “has been a trip.” She recognizes that some will question the need for another new mobile app for data gathering, and says it reflects the broader challenge that comes with citizen science’s growth and maturity. “A lot of environmental problems require big data, [but they also] require interoperable data and data that’s consistent across different areas.”

Despite the event’s massive ambition, Bowser views it as a pilot project. The Earth Day launch is a starting point, not the climax. Once the excitement of the spring dies down, she says, “we’re going to take a big step back, figure out what was successful, what’s duplicative, and then figure out our long-term plan for the governance and ownership of the different resources that we’re building.”

Along with Earth Challenge, April has been designated Global Citizen Science Month by the Citizen Science Association. Another highlight will be a four-day international bioblitz program called the City Nature Challenge. Hosted on iNaturalist, the challenge began in 2016 as a bioblitz competition between San Francisco and Los Angeles but has since spread rapidly. In 2019, 159 cities took part, with a much larger number expected in 2020.

“The City Nature Challenge has brought a lot of us together,” says Ireland. “Last year Halifax did it, one of three Canadian cities. This year we’ve got about eight locations in the Maritimes registered, and there’s another 10 or more around Canada.”

In his eyes, seeing such momentum for citizen science at the beginning of 2020 marks a turning point. “I think the decade we’re entering will be a time when participatory research is fundamentally important to policy changes and natural resource management decisions. The more people are involved, the more people understand what the questions are and are actually doing work to collect the data, the more likely they’re going to be to advocate for good, sound environmental policy. Citizen science has made that opportunity available. So, I’m pretty pumped about the future.”