Characterization of the Traditional Activities on Salt Marshes at Patos Lagoon Estuary (RS)

Abstract

Salt marshes are predominant intertidal coastal ecosystem in 29º S and higher latitudes. At Patos Lagoonestuary (RS), 6.837 ha of salt marshes occupy margins and islands that have been used by farming and ranching since XVII century. This study aimed to characterize the use of salt marshes by economical

activities (farming and ranching) at Patos Lagoon estuary. This study was carried out in the counties ofRio Grande and São José do Norte throughout semi-structured interviews with representative of farmers,ranchers and urban residents living nearby salt marshes. Neighboring ranches have an average area of 306ha with a stocking density of 1 animal.ha-1. Cattle graze Spartina densiflora (during winter) and Scirpusolneyi (during summer), and animals can eat 4.6% to 15.3% of plant biomass production, respectively.Neighboring farms have small areas (average of 19.3 ha with 4.2 ha planted) and onion and vegetablesare the main crops. Farmers utilize 6.4% of annual biomass of S. densiflora and 20.5% of Juncus kraussiifor ground cover, manuring and construction of small sheds. Most of farmers and ranchers described theexpansion along the last 50 years of J. kraussii over grasslands, crop areas and S. densiflora salt marshes,and urban residents reported the erosion of estuarine margins during the same period. The farming andranching techniques used in the last decades at Patos Lagoon estuary allowed the social reproduction ofeconomical activity together with the conservation of salt marshes.