Monitoring the critically endangered Clanwilliam cedar with freely available Google Earth imagery

Monitoring of species and populations is essential for biodiversity observation and reporting at local, national and global scales, but can be an exceedingly difficult task for many, if not most, species. We tested the viability of using Google Earth™ imagery to manually map and monitor all individuals of the critically endangered Clanwilliam cedar, Widdringtonia wallichii Endl. ex Carrière, across its global native distribution; the remote and rugged Cederberg mountains. Comparison with sampling from field surveys reveals this to be a highly efficient and effective method for mapping healthy adult tree localities, but it fails to detect small or unhealthy individuals with green canopies <4 m², or discern the number of individuals in clumps. This approach is clearly viable as a monitoring tool for this species and, with the rapid progress being made in machine learning approaches and satellite technology, will only become easier and more feasible for a greater number of species in the near future. Sadly, our field surveys revealed that the number of trees that have recently died (dead leaves still present) outnumbered live trees by a ratio of 2:1.