>People also talk about Europe and Asia as separate despite being a contiguous landmass on the same plate

That analogy is not useful at all. Continents are not biological organisms.

>Genetically brown and polar bears can and in reality often do interbreed producing viable offspring and exchanging genetic information between populations

And yet they are separate species. Just like the 4 separate species of giraffe the article is about, which can and do all interbreed. The concept of species is in no way reliant on an inability to produce fertile offspring.