Scientists studying a dead mangrove forest, Marsassoum, Senegal. Mangroves are salt-tolerant plants (halophytes) that contain a complex salt filtration system and complex root system to cope with salt water immersion and wave action. Droughts in Senegal in the 1970s and 80s caused much of the water in mangrove swamps to evaporate, greatly increasing the salinity of the remaining water. This increase was too much even for these adapted plants to survive and Senegal lost around 40 per cent of its mangrove forests.