You want to promote STEM learning: Citizen science is a great opportunity to provide students an immersive experience in Science, Technology, Engineering and Math (STEM). When volunteers are involved in the various aspects of a project including the development of the problem or question, data collection methods and data analysis, participants are introduced to the entire scientific process. Volunteers will also be attuned to data quality issues or concerns. When participants are able to share the results of their work, they can gain a deeper understanding of the importance of the science and how it supports decision making and resource management.
You need data across a large spatial area or for a long period of time: Citizen science can often operate at greater geographic scales and over longer periods of time than conventional science. Only with the help of volunteers would it be cost-effective to collect certain types of data in large enough areas and over long enough periods of time to be scientifically reliable. This is often the case in observations of breeding birds and in other physical and biological phenomena. The North American Breeding Bird Survey, for example, has relied on volunteers to track the abundance of bird populations across the continent. Other projects, such as Nature's Notebook, encourage volunteers and professional scientists to regularly submit observations of plant and animal occurrences, behaviors, and seasonal events such as tree flowering. Hundreds of air and water quality monitoring programs across the country depend largely on data and samples collected by citizen science volunteers. The resulting observations are used by professional scientists, government agencies, non-governmental organizations, and other decision-makers.
You need many eyes on the ground: Citizen science can speed up and improve field detection. Having many eyes on the ground can help detect environmental changes (e.g., population declines, incidences of pollution, and the introduction of an invasive species); as well as monitor the effectiveness of management practices; and increase the likelihood of a serendipitous discovery. It can also help if your project site is in a place people frequently visit.
You must analyze a large amount of data or images: When large amounts of data need to be analyzed, volunteers can speed up the process. Volunteers with proper training and guidance can accurately identify specimens at various taxonomic levels and accurately assess important population attributes, such as species abundance and distribution. Volunteers can also perform tasks difficult for computers, like analyzing digitally-collected primary data (e.g., images or audio), and by identifying and recording secondary information (e.g., presence or absence of a species and the abundance, behavior, and frequency or duration of various phenomena). In some cases, highly trained volunteers such as retired professionals may be able to contribute to higher-level data analysis.
The tasks involved can be completed online: Similarly, projects that involve sorting and analyzing large amounts of online data (for example, satellite images or photos from web cams) are often suitable for a crowdsourcing approach.
Citizen science may not be advantageous when...
The training or equipment is highly technical: Volunteers should not be expected to use sophisticated analytical instruments or participate in activities that require extensive training or certification. It would be unrealistic to ask volunteers to take measurements using equipment that is expensive or difficult to obtain, or to complete tasks that are complicated or require immense time commitments. For example, a volunteer would likely not be able to take highly detailed measurements every four hours for a long period of time. Instead, you might consider what simple tasks volunteers can do that would give trained resource specialists more time to do highly technical tasks. For example, the Four Forests Restoration Initiative works with citizen scientists to collect simple presence-absence data on hydrologic features, allowing the Forest resource specialists more time to do more complex surveys. Also, infrequent (e.g., annual) sampling might make it harder to sustain a collection of high-quality data, because participants might have to re-learn even basic protocols. A successful sampling design for volunteers lies in between, where sampling frequency is just enough to keep participants well practiced and able to gather consistent data, but not so high as to become onerous and discourage participation
Other ways to engage the public are more suited to your goals: Citizen science is one of many ways to engage the public in decision-making processes and environmental stewardship. Depending on your project, those other avenues may be a better fit for your outreach goals. Sometimes direct public outreach is more effective than citizen science projects, particularly when the connection between the science collected and management or policy decisions is not obvious. If scientific knowledge is already adequate, then additional data collected through citizen science is not needed, and resources may be better spent focusing on how to improve the communication of existing knowledge through newsletters, science cafés, public meetings, online, or through other creative sources.