Halophytic Life in Brazilian Salt Flats: Biodiversity, Uses and Threats

Abstract

Brazil has over 8000 km of coastline and 1,085,187 km 2 of drought-affected areas where natural processes and land-use changes originated extensive salt flats. Brazilian coastal salt flats are found as transition zones of mangrove forests or salt marshes and dry upland areas, and they are located above the mean level of the spring tides, either in semiarid or in seasonally dry coasts. The salt flats' distributions are irregular, covering 1-24.4 % of the studied intertidal areas. Their sandy soils show salt contents near the seawater values and can increase to 150 ppt during the dry season. Dominant plants are widespread species more frequently found in tropical parts of South America. Halophytic forbs and grasses cover the mid-littoral and hypersaline gaps of the mangrove, whereas mixed stands with sedges occur when seasonal superficial fresh water drainages alleviate soil salinity. Although there are very few records of halophyte utilisation, intertidal crabs are important for the estuarine food web and exploited by indigenous peoples and fishermen for human consumption. Salt pans and shrimp farming are the most common anthropogenic activities that occur within salt flat areas. Inland salt flats are common in low annual rainfall (500-800 mm) areas of the northeast region of Brazil. The stony soils with sodium character promote natural formation of salt flats. Low rainfall, a high water deficit and careless irrigation management can establish very quickly secondary salinisation in these soils. Surface soil saturate extract of natural and man made salt flats can average 8-40 dS m(-1) CE values during the drought season. The dominant cover of inland salt flats includes few native halophytic forbs and exotic shrubs and grasses, introduced in NE Brazil for forage and fodder for domestic animals. Native Malvaceae species are common and also used for animal fodder. Several plants are traditionally used to treat influenza, urinary-renal problems and ulcers, as well as they shown anti-inflammatory and antioxidant properties. Coastal (Sarcocornia ambigua) and inland halophytes (Atriplex nummularia) has been cultivated in integrated multitrophic aquaculture systems and in salt flats resulting from secondary salinisation, as cash crops and phytoextraction techniques, removing salt from soil and waste nutrients from saline effluent.