| The engagement management of citizen scientists | Maintaining long-term public engagement is challenging, especially for long-duration projects or those lacking sufficient incentives | 53 | Abu Ali et al. (2021), Alsina-Pagès et al. (2024), Berglund et al. (2020), Chiesa et al. (2022), Cooney and Raghavan (2022), Corburn et al. (2022), Díez et al. (2018), Dosemagen et al. (2022), Eames and Egmose (2011), Forni et al. (2019), Frögren et al. (2023), González et al. (2022), Granbom et al. (2023), Gražulevičienė et al. (2020), Grootjans et al. (2022), Haug et al. (2023), Hendricks et al. (2022), Higuera-Mendieta et al. (2023), Iwarsson et al. (2023), Kim et al. (2023b), King et al. (2020, 2021), Kumar et al. (2020, 2023), Meixner et al. (2021), Montes et al. (2022), Mueller et al. (2018), Muhamad Khair et al. (2020), Newman et al. (2020), Odeyemi et al. (2024), Okop et al. (2023), Oti et al. (2019), Pedell et al. (2021), Pedersen et al. (2022), Radicchi et al. (2021), Rickenbacker et al. (2020), Rodriguez Espinosa et al. (2023), Rosas et al. (2016), Rubio et al. (2021, 2022), Rydenstam et al. (2020), Santos-Tapia et al. (2024), Shannon et al. (2024), Sheats et al. (2017), Shim et al. (2016), Sletto et al. (2024), Soltani et al. (2023), Tuckett et al. (2018), Vanoutrive and Huyse (2023), Wannemacher et al. (2018), Wesener et al. (2022), Winter et al. (2016, 2020) |
| Citizen scientists’ lack of skills | Citizen scientists may lack the necessary skills and good training, which can affect the accuracy of the data and require adequate training and guidance | 33 | Alkhatib et al. (2023), Alsina-Pagès et al. (2024), Berglund et al. (2020), Gharaibeh et al. (2021), Granbom et al. (2023), Hendricks et al. (2022), Indrajit et al. (2019), Loh and Kim (2021), Meixner et al. (2021), Moore and Woodcraft (2019), Moran et al. (2017), Muhamad Khair et al. (2020), Newman et al. (2020), Okop et al. (2023), Oti et al. (2019), Pedersen et al. (2022), Rosas et al. (2016), Rozzi et al. (2022), Shannon et al. (2024), Sheats et al. (2017), Soltani et al. (2023), Tuckett et al. (2018), Vahidnia (2023), Vanoutrive and Huyse (2023), Wannemacher et al. (2018), Wesener et al. (2022), Winter et al. (2016, 2020), Wood et al. (2022a, b, 2023), Yaduvanshi and Park (2023), Zieff et al. (2018), Zipf et al. (2020) |
| Variability in data quality | The quality and availability of data collected by citizen scientists in citizen science projects may be limited because it affects the accuracy and reliability of the research | 19 | Abu Ali et al. (2021), Alkhatib et al. (2023), Alvarado Vazquez et al. (2024), Grazuleviciene et al. (2020), Grootjans et al. (2022), Haug et al. (2023), Kim et al. (2023a, b), King et al. (2021), Loh and Kim (2021), Meixner et al. (2021), Othman et al. (2024), Ottinger (2022), Radicchi et al. (2021), Rozzi et al. (2022), Shannon et al. (2024), Wannemacher et al. (2018), Zhou and Long (2016), Zipf et al. (2020) |
| Sample Representativeness | Participants may not represent the entire target population, leading to a lack of representativeness in the sample and affecting the generalisability of the research findings | 14 | Alvares-Sanches et al. (2021), Best et al. (2023), Díez et al. (2018), Eames and Egmose (2011), Gražulevičienė et al. (2020), Grootjans et al. (2022), Odeyemi et al. (2024), Othman et al. (2024), Pagani et al. (2023), Pedersen et al. (2022), Rozzi et al. (2022), Santos-Tapia et al. (2024), Vo et al. (2019), Zha et al. (2022) |
| Ethical and Privacy Issues | Citizen science projects may involve participants' personal data and privacy issues, requiring strict ethical review and privacy protection measures | 8 | Muhamad Khair et al. (2020), Pykett et al. (2020), Soltani et al. (2023), Tupikina et al. (2023), Vahidnia (2023), Vanoutrive and Huyse (2023), Vo et al. (2019), Wannemacher et al. (2018) |