Wouldn't it be nice to have thousands of collaborators, collecting data and sharing observations, who didn't demand a salary at all? A nation-wide initiative called Project Budburst is enlisting the help of so-called "citizen scientists" to nip the effects of climate change in the bud. But is using the public as a data source scientifically sound?

The idea of citizen science is nothing new. Hobbyists interested in particular plants or animals have been collecting valuable data for centuries, often even corresponding with professional scientists, publishing papers, and presenting work at scientific meetings. Historically, however, amateur naturalists tended to come to the professionals when they found something interesting. Now, in large part thanks to the internet, it's the other way around.

Project Budburst is a field campaign to track the effects of global warming in the US by monitoring the seasonal activities of a variety of plant species. Volunteers from across the country are urged to watch for key "phenophases" — events such as first leafing, first flower or seed dispersal — and record their observations on the project's website. Project Budburst "allows individuals to feel they are part of a greater understanding of climate change," said project coordinator Sandra Henderson of the University Corporation for Atmospheric Research in Boulder, Colorado.

The project — which is backed by, among others, the National Science Foundation, the USDA Forest Service, and research institutions in seven states — has two main goals, Henderson told The Scientist. "First and foremost, it's an education and outreach effort. But we also hope to collect useful data that will help scientists."

A pilot project run last spring involved volunteer contributors across 26 states who recorded a total of 913 phenological events. Based on the high rates of participation in states such as Utah, Michigan, and Colorado, this year's scheme aims to be larger and more comprehensive nation-wide.

Using citizen science networks allows researchers to gather vast amounts of data and carry out large-scale studies more feasibly than would otherwise be possible, said Graham Appleton, head of publicity at the British Trust for Ornithology (BTO). He told The Scientist that the amount of time invested by volunteers in the UK each year was "equivalent to over one thousand full-time staff."

Humphrey Crick, a senior ecologist with the BTO, said the role of the scientist is "absolutely crucial" for designing citizen science projects with very clear instructions. He recognizes that collecting data in this way can introduce biases, but noted that their effects should be constant over time, so should not greatly affect the ability to reveal changes based on long-term trends. For example, the BTO's Common Birds Census suggests that the number of European starlings in the UK declined by 50% since the mid-1970s; a result that Crick said is robust even if the data — much of which was collected by non-scientists — doesn't necessarily indicate the absolute size of the bird's population. Furthermore, he said that statistical methods can be used to minimize biases and remove peculiar data.

Researchers at the Cornell Lab of Ornithology, which has been involved in large-scale, citizen science projects for over 40 years, use clearly defined protocols to "dampen out some of the variation" introduced by using many different data collectors, said Janis Dickinson, director of the citizen science program there. In their bird watching programs, they require their participants to log the time spent observing, and to record occasions even when no sightings are made.

Still, Dickinson acknowledged that some errors can creep in to the data, and though this introduces more variation, she feels that error and sample size balance each other out. "As long as the data are not biased, error is not such a huge problem when you have very large sample sizes," she said.

What do you think: Can data collected by average joes be scientifically valid and useful? Share your thoughts on citizen science, by posting a comment to this blog.