This study examines the global availability and design of National Forest Inventories (NFIs) and their integration with space-based biomass data. NFIs, more developed in temperate regions, are less frequent and smaller in tropical areas, presenting challenges for statistical linkage with remote sensing data. The study highlights opportunities from recent NFI updates, showing strong correlation with space-based estimates like the Climate Change Initiative (CCI) product in countries with newer NFIs. It recommends expanding NFIs with standardized designs and super-site plots to enhance integration and improve biomass estimation accuracy.