Invasion increasing risk of Al Jawahir Wadi lentic habitats by 'Pistia stratiotes' L. (North-Central Morocco)

Résumé

Draining of wetlands and their inadequate planning contribute greatly to the decline of hygrophilous vegetation. The arrival of invasive hygrophilous species, as noted recently for Pistia stratiotes L. in Al Jawahir Wadi (North Central Morocco) could also aggravate this situation. Surveys carried out in the watershed of this river show that P. stratiotes form spontaneous communities over a river-length of 10 km, twice of that reported in 2012, in spite of measures taken to limit its spread. Plants description on the basis of vegetative and reproductive criteria ascertains the permanent presence of this species upstream of the wadi, and reveals a succession of factors causing its intermittent suffocation downstream, including hydrological and planning hazards, and water pollution. The decontamination endeavors of Al Jawahir River and the exceptional propagating power of this species would represent a real threat to local water bodies for long.