The following map and video show the global forest structure as defined by Specht (1970) and Carnahan (1977). The classification uses the percentage foliage cover and forest height to categorise forests into structural classes. The data and outputs were described in the the following FAO report:
Mackey, B., Skinner, E., & Norman, P. (2021). A Review of Definitions, Data, and Methods
for Country-level Assessment and Reporting of Primary Forest. Griffith Climate Action
Beacon Discussion Paper, 1/2021. pp1-35. Brisbane, Australia: Griffith University.