J. Ecol. doi:10.1111/j.1365-2745.2009.01526.x (2009)

Average plant height peaks in the tropics and declines towards the poles, says an international team after analysing a data set of almost 6,000 species. Plants living near to the equator are 29 times taller on average than those found between 60–75 °N (in Iceland, say) and 31 times taller than those at 45–60 °S (such as on the South American archipelago of Tierra del Fuego).

Plant height drops 2.4-fold at the edge of the tropics, suggesting that temperate and tropical species pursue different ecological strategies, according to Angela Moles of the University of New South Wales in Sydney, Australia, and her colleagues. Cold or dry places support plants with a range of heights, but there are few short species in warm, wet environments. Rainfall in the wettest month of the year is the best predictor of plant height, the researchers say.