Are planar areas adequate for the species-area relationship?

The species-area relationship (SAR) is one of the best documented patterns in macroecology and has wider applications. Measures of areas used in SARs are planar surfaces, not true surface sizes. To explain this difference I assimilated islands to cones, where the cone base is the planar area, and the cone lateral surface is the actual island area. Then, I applied the power function to 20 real-world archipelagos using both the island planar area and the lateral surface area of a cone calculated using island elevations. Although the cone model is obviously a simplistic proxy for the actual area size of islands, this simple exercise shows how a model, which increases only marginally the area sizes in SARs, may improve the fit and change the estimated parameters, suggesting the opportunity of searching for more realistic values of areas than the simple planar surface for modelling SARs.