Ground-based repeat photography has a long history in documenting landscape change. Given the growing concern over the scale and rate of global change related phenomena, such as climate and land-use change, the benefits of involving the wider public in data collection efforts is increasingly being realised. Public involvement is particularly useful in national- and international-scale photographic monitoring projects where data collection spans relatively large spatial scales and is consequently expensive to gather, local knowledge is useful, and no specific training and only basic photographic equipment is required. Several research-grade repeat photography projects exist worldwide, but few rely on the involvement of citizen scientists. Here we introduce a citizen science repeat photography project of southern African landscapes: rePhotoSA. We evaluate the progress of the project to date and describe the level of utility of citizen science contributions to research. We also reflect on four key activities that are needed to ensure the long-term success of the project including attracting and keeping citizen scientists involved, maintaining data quality, providing accurate photo-site location information, and effective dissemination of scientific knowledge to the public. We conclude that the continued use of historical photographs as a unique source of historical environmental data to complement traditional scientific methods of data collection may improve our overall understanding of changing landscapes, and may serve as an effective means of illustrating landscape- and global change to the general public.

地面重复摄影在记录景观变化方面有着悠久的历史。鉴于对气候和土地利用变化等全球变化相关现象的规模和速度的日益关注，越来越多地意识到让更广泛的公众参与数据收集工作的好处。在国家和国际尺度的摄影监测项目中，公众参与特别有用，因为这些项目的数据收集跨越相对较大的空间尺度，因此收集起来很昂贵，当地知识很有用，不需要专门的培训，只需要基本的摄影设备。世界范围内存在几个研究级重复摄影项目，但很少有公民科学家的参与。在这里，我们介绍一个关于南部非洲风景的公民科学重复摄影项目：rePhotoSA。我们评估了该项目迄今为止的进展，并描述了公民科学对研究贡献的效用水平。我们还反思了确保项目长期成功所需的四项关键活动，包括吸引和保持公民科学家的参与、保持数据质量、提供准确的照片站点位置信息以及向公众有效传播科学知识。我们得出的结论是，继续使用历史照片作为历史环境数据的独特来源来补充传统的科学数据收集方法可以提高我们对不断变化的景观的整体理解，并可以作为一种有效的手段来说明景观和全球变化大众。