Citizen science data validates aerial imagery to track the ‘rise and fall’ of woody vegetation through extremes of climate

Abstract

Context Ground truthing remotely sensed imagery for detecting changes in wetland vegetation can be time-consuming and costly for monitoring. Harnessing the resources of citizen scientists (CS) using mobile devices has been under utilised in Australia. Aims The project aimed to test the feasibility and practicality of using CS to collect data using mobile devices to ground truth remotely sensed imagery. Methods Using high-resolution aerial imagery, we detected the establishment of woody vegetation over a 20-year dry phase from 2000 to 2020 in Thirlmere Lakes National Park, NSW, Australia. To ground truth these woody species, we engaged with a local community group using a customised, freely available mobile device application. Key results During the dry event of 2020, CS documented well-established woody species, such as Melaleuca linariifolia (flax-leaved paperbark), amongst the Lepironia articulata grey rush. With the La Niña wet events in early 2020–22 and subsequent higher water levels, the CS documented the survival of M. linariifolia but the dieback of eucalypts, and other woody species. Conclusions Observations at higher temporal frequencies by CS using mobile devices, augmented with researchers’ observations, proved to be a valuable, quality-controlled method to ground truth high-resolution aerial imagery. Implications This case study showed that monitoring the phenology of vegetation in a peat wetland can be supplemented by the inclusion of a CS programme. This under-utilised resource can increase coverage and frequency of data observations, lower costs as well as create community awareness, capability and engagement in scientific research.