or Greg Pauly, inspiration came in the form of roadkill.Jogging in Los Angeles, California, about ten years ago, Pauly, the curator of herpetology at the Natural History Museum of Los Angeles County, was shocked to see a Southern California legless lizard (Anniella stebbinsi) being hit by a car. "I could not believe that this particular species of lizard would be in that neighbourhood," he recalls.What else might be lurking in Los Angeles back gardens? And how could Pauly possibly find out, given that so much of the crowded county is private property, inaccessible to scientists? Then Pauly had an epiphany. "All the people are not the problem -all the people are the solution," he says.Since 2013, Pauly has been engaged in a community-science project using the natural-history app iNaturalist. His network of 9,000-plus contributors has accumulated more than 60,000 reptile sightings, allowing him to identify and eradicate an invasive species, observe rare alligator-lizard (Elgaria multicarinata) matings and publish more than a dozen papers.In community science, also called participatory science, non-professionals contribute their time, energy or expertise to research. (The term 'citizen science' is also used but can be perceived as excluding non-citizens.)Whatever name is used, the approach is more popular than ever and even has journals dedicated to it. The number of annual publications mentioning 'citizen science' went from 151 in 2015 to more than 640 in 2021, according to the Web of Science database. Researchers from physiologists to palaeontologists to astronomers are finding that harnessing the efforts of ordinary people is often the best route to the answers they seek."More and more funding organizations are actually promoting this type of participatoryand citizen-science data gathering," says Bálint Balázs, managing director of the Environmental Social Science Research Group in Budapest, a non-profit company focusing on socio-economic research for sustainability.Community science is also a great tool for outreach, and scientists often delight in interactions with amateur researchers. But it's important to remember that community science is, foremost, a research methodology like any other, with its own requirements in terms of skill and effort."To do a good project, it does require an investment in time," says Darlene Cavalier, founder of SciStarter, an online clearing house that links research-project leaders with volunteers. "It's not something where you're just going to throw up a Google form and hope for the best." Although there are occasions when scientific data are freely and easily available, other projects create significant costs.No matter what the topic or approach, people skills are crucial: researchers must identify and cultivate a volunteer community and provide regular feedback or rewards. With the right protocols and checks and balances, the quality of volunteer-gathered data often rivals or surpasses that achieved by professionals."There is a two-way learning that happens," says Tina Phillips,...