Kelp beds grow along narrow, scattered stretches of cold, rocky coastline worldwide, many of them remote or difficult to survey by boat, so no single comprehensive census exists; published global-extent estimates vary by more than an order of magnitude depending on the survey method (aerial, boat-based or satellite) and the definition of kelp forest used.
What would resolve this A standardized, repeated satellite remote-sensing survey of the world coastline, cross-validated against in-water surveys, of the kind marine ecologists have begun assembling only in the last few years for select regions.
OpenMarine ecology and remote sensingNational Oceanic and Atmospheric Administration