Re-Engineering Dew-Harvesting Cactus Macrostructures to Enhance Water Collection as an Adaptive Climate Change Strategy: An Experimental Comparison

The spinal structures found on Copiapoa cinerea var. haseltoniana, an efficient dew-harvesting cactus, were fabricated and evaluated both in a climate chamber and outdoors in dewy conditions. A mix of aluminium and steel was used to fabricate these surfaces, with aluminium being used for everything but the replicated spine features, which were constructed from steel. Each surface was entirely coated with a highly emissive paint containing an alumina-silicate OPUR additive. Three replica versions (stem only, spine only, and stem & spine) were compared to a flat planar reference surface. Experimental results demonstrated that all three biomimetic macro-structured surfaces significantly enhanced dew harvesting compared to the reference surface. It was established that the stem & spine replica, spine replica, and stem replica all demonstrated significantly more dew harvesting, with mean efficiency ratios in respect of the reference surface of 1.08 +/- 0.03, 1.08 +/- 0.02, and 1.02 +/- 0.01, respectively. Furthermore, the method of surface water collection was found to influence the water collection rate. The diagonal run-off flow across a flat planar surface was 34% more efficient than the parallel run-off flow on the same surface. These findings provide valuable insights for the construction and installation of biomimetic-inspired dew-harvesting devices, particularly in regions that are most challenged by decreasing dew yields as a result of climate change.