The International Union for Conservation of Nature (IUCN) is the global authority for determining species’ vulnerability in the face of threats such as habitat loss and climate change. How widely a species can be found – its geographic range – is a key indicator used by the IUCN to assign an appropriate conservation status.
Hydrogen is the most abundant element in the universe. Estimates are that it comprises 75% of all matter. There is plenty of it here on earth too, but almost none of it is in its elemental form. It is mostly bound up in compounds like water.