Abstract Recently in Biodiversity and Conservation , it was asserted that 9.64% and 5.96% of tropical dry forests (TDFs) in South America and Africa were lost between 2000 and 2020. Arriving at such results depends on how TDFs are defined and how their global distribution is mapped. A striking feature of recent maps of TDFs is the substantial overlap between them and maps of tropical grassy ecosystems (TGEs). Alarmingly, both types of maps are generally based on just two earlier maps of global terrestrial ecosystems. If extensive areas of global TGEs are being misclassified as TDFs, then there are problems because policies relevant to forests, e.g., fire suppression and ‘reforestation’ are not applicable to TGEs. Mapping of TGEs typically relies on ecologically functional criteria such as the distribution of tropical (C 4 ) graminoids and fire frequency, among others. In contrast, TDF maps typically rely on vegetation structural criteria such as height and canopy cover. Misclassification of TGEs as TDFs occurs when the definitions of ‘forest’ used to generate TDF maps are derived from the Food and Agriculture Organisation’s (FAO) biased definition of ‘forest’. The FAO definition is severely flawed because it is purely structural and ignores functional differences among ecosystems that share similar vegetation structures. A solution to this problem is to replace the historical, subjective metrics of the FAO with new, objective metrics and to include multiple environmental properties. Realising the solution requires close collaboration across numerous disciplines, such as biome ecology, biogeography, functional ecology and remote sensing.
Peter F. Scogings (Fri,) studied this question.