Are plants just the salt of the Earth?

Sodium is unique among abundant elemental nutrients because it is not physiologically required by most plant species, but all animals require sodium. Foliar sodium in 201 grassland species growing in experimental plots at 27 sites spanning 4 continents varied across five orders of magnitude; site-level foliar sodium increased with soil sodium and site aridity but declined with soil pH. Low sodium plants increased and high sodium plants declined in abundance with fertilization because herbivores selectively removed high-sodium plants, a ‘salted caramel ice cream’ effect. Foliar sodium is determined by interactions between soil sodium, climate, nutrient input, and herbivory rates.