Most studies on species distributions have focused on native species and their horizontal patterns, fewer have examined diversity and distribution patterns of non-native plants at different elevations. We examined 65 major mountains worldwide including 32 on which both native and nonnative plants were surveyed.  We found that native species are mostly concentrated at mid-elevations but nonnative species are mostly at lower elevations in close association with human populations.  Due to climate change, many native and nonnative species are moving upward to higher elevations where some species are endemic, rare, or endangered and have very limited resources and space to be relocated.  With growing human populations and activities toward higher elevations, invasion prevention and early detection, and native species conservation are urgently needed.