Los Monegros (Ebro valley, NE Spain) is a region formed by miocenic sediments with a high gypsum content, where there are many endorheic depressions with temporary lagoons called 'saladas'. Halophilous and gypsicolous species are therefore abundant in these areas. Los Monegros is a typical example of many similar areas in the central Iberian Peninsula. This vegetation is now being threatened by a shift in agricultural methods. First, many of these 'saladas' have recently been drained in order to increase the area of arable land. Halophilous species. e.g. Riella helicophylla, R. notarissi, Riccia crustata. Pterygoneuru subsessile, Pottia pallida, which live in close relationship with the lagoons, are therefore in danger of disappearing completely. Secondly, general irrigation plans, soon to be put into practice, will affect some of the species such as Tortula brevissima, T. revolvens var. obtusata which inhabit dry calcareous and gypsocilous soils, Crossidium aberrans, Enthostodon hungaricus. © 1992.