The colonization of a coastal lagoon by a mangrove ecosystem: Benefit or threat to the lagoon?

Abstract

• We studied the structure of a natural and planted emerging mangroves. • The colonizing mangroves areas increased 12 and 95 times in 15 years. • Despite distinct ages, the studied mangroves present similar richness and abundance. • Local carbon sequestering is equivalent to 3% of the Brazilian industrial emissions in 2016. A planted and a natural stand that started colonizing a coastal lagoon after an artificial channel permanently connected it to the sea were studied in Brazil’s Southwestern Atlantic coast to assess the ecological role of emerging mangrove forests and the ecological changes of the supporting ecosystems (i.e., coastal lagoon). In 15 years, the natural mangrove stand area increased 12 times, and the planted stand 95 times in 6 years, covering 25 and 1.9 ha, respectively. Although the natural and planted stands have different ages (approximately 42 and 6 years, respectively), their species richness and relative abundance are similar but differ in tree size. Consequently, above-ground and roots biomasses were higher in the natural stand. Compared to other mangroves from the Neotropical region, the studied mangroves’ biomass and carbon stock were lower. Nevertheless, since 2003 it sequestered 4,063.1 ± 894 Mg of carbon dioxide (CO 2 ) from the atmosphere, only considering the forest biomass, which is equivalent to 0.03‰ of the Brazilian industrial emissions in 2016. The colonization of the lagoon by mangroves resulted in changes in the ecosystem state. This ecological change imposes an understanding of the new environment’s function and dynamic to support management practices and prevent and solve conflicts among local players.