Heath is a globally distributed shrubland habitat type occurring on every continent except Antarctica (Australia, southern Africa, Texas, New Caledonia, Chile, Mediterranean shores and elsewhere), not one bounded place, and this atlas's own cited Wikipedia article gives no single combined global area figure for it anywhere in the text, only qualitative statements that it is widespread and that many of its European stands are vanishing.
What would resolve this A single authoritative global inventory of heath habitat extent across every continent where it occurs, using one consistent definition of what counts as heath as opposed to moorland or other shrubland.
OpenPhysical geography / vegetation ecologyHeath (Wikipedia)