Tropical ‘alpine’ habitats: improper use of the term alpine?
The term 'alpine habitat' was initially used for habitats situated above the treeline on mountains in higher latitudes, especially in the Holarctic region. The treeline, the highest elevation that sustains tree growth, is considered as a global phenomenon. Consequently, the term 'alpine habitat' is currently in use at the global scale, including for the disjunct and intriguing habitat types located on the tropical high mountains. In this review, I will 1) present how treeline and alpine habitats are variously defined in the literature, and elaborate the factors that shape them; 2) describe how tropical ‘alpine’ habitats differ from the alpine habitats in higher latitudes in terms of climate and plant growth forms; 3) highlight why tropical ‘alpine’ habitats do not constrain growth of treeline-forming ‘trees’ and thus do not fit under the current definition of an alpine environment, and 4) reconsider the status of the tropical ‘alpine’ environments and suggest two alternative solutions: either consistently classifying alpine habitats as tropical vs. high latitude alpine ones to highlight their differences, or treating tropical ‘alpine’ habitats as a distinct non-alpine ecosystem.