20-Years Cumulative Impact From Shrimp Farming on Mangroves of Northeast Brazil

Abstract

Brazilian mangroves cover about 11,100 km2 and provide a wide range of ecosystem services. Despite their importance, they are one of the most impacted ecosystems because of combined influences of climate change, pollution, and direct conversion and loss. A major driver of environmental impacts is shrimp farming and this is particularly acute in the semi-arid northeast of Brazil, where mangroves are constrained in a narrow band along ephemeral estuaries that are often impacted by multi-year droughts. Recent changes to Brazilian law, in particular the Forest Code, have weakened protection for mangroves and associated “apicum” (salt pan) ecosystems. In NE Brazil, most shrimp ponds are converted from mangrove-adjacent “apicuns” rather than the mangroves themselves with periodic hydrological connectivity through dammed channels, allowing the flushing of effluents. As a result, the main impacts on mangroves are typically indirect, because of pollution inputs from shrimp pond effluents and associated loss of ecosystem services including reductions in primary productivity, carbon storage capacity, resilience to other environmental stressors, their efficiency as estuarine filters, and biodiversity and abundance of subsistence use of marine species. Soil damage and infrastructure remaining after shrimp pond deactivation impairs mangrove recovery. This extends the duration of the damage and allows the occupation of degraded areas by other activities that can permanently impair ecosystem function. In this review, we address several aspects of the shrimp culture boom in NE Brazilian, their features and consequences, and the future of mangroves in the region considering climate change and rising poverty. Our conclusions on the practices and outcomes of shrimp farming in mangroves are likely to apply to areas with similar environmental settings, e.g., semiarid regions worldwide, and particularly in the Latin America and Caribbean region, and our findings can be taken into account to improve conservation and management of these forests at the least to a regional scale.

Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

“…AGB was also lower in São Paulo (84.2 Mg ha −1 ) and Rio de Janeiro (83.1 Mg ha −1 ), where extensive mangrove areas have been impacted by industrial activities and urban expansion (Soares, 1999;Ferreira and Lacerda, 2016;Moschetto et al, 2021). AGB values <100 Mg ha −1 were also found in Paraíba, Sergipe, Pernambuco, Ceará and Alagoas where shrimp farming has compromised the structural and functional integrity of Brazil's drier-climate mangrove forests (Lacerda et al, 2021). AGB values >100 Mg ha −1 were found in Espírito Santo and Bahia mangroves where the multidecadal stability of more than 70% of the mangrove coverage suggests that the integrity of core areas have been maintained over time (Diniz et al, 2019).…”

“…AGB values >100 Mg ha −1 were found in Espírito Santo and Bahia mangroves where the multidecadal stability of more than 70% of the mangrove coverage suggests that the integrity of core areas have been maintained over time (Diniz et al, 2019). Predicted median AGB for Rio Grande do Norte mangroves was also >100 Mg ha −1 despite mangroves developing in a semiarid climate and historical damage from shrimp farming (Lacerda et al, 2021). However, this result is likely due to the small number of observations used to constrain biomass predictions for that region (only two AGB values available for Rio Grande do Norte at the time Rovai et al, 2021b study was conducted; Supplementary Table 1).…”

Can Sustainable Development Save Mangroves?

“…Its major limitation is the relative absence of historical records of measurements; and (ii) remote sensing, which, on the other hand, is relatively expensive and requires a high level of technology, can provide historical records for the past 50 years [84]. Comparative analyses of remote sensing images can be improved greatly using vegetation indexes, such as NDVI, capable of evaluating indirect impacts on mangroves, including ecosystem's functioning, prior to losing proper plant cover [51,85,86].…”

“…However, it results in major environmental and economic losses for the local communities: degraded environment, displaced communities, loss of traditional livelihoods, and human rights violations. These are the pillars of intensive, export-led shrimp farming, which, at the global level, has also implied overfishing and depletion of the seas, due to the preferential use of fish meal in aquafeeds [51,55].…”

“…However, despite a slight reduction in forest loss rates, mainly in the Americas, Africa, and Australia [47,48], mangrove clearing and fragmentation continues, mainly in Southeast Asia [47,49,50]. Worse yet, recent research highlights widespread indirect impacts, which result in a reduction of ecosystem services, and in the resistance and resilience to environmental impacts [51]. Necessary ample reforestation programs have not been implemented, although conservation of these forests should motivate supranational efforts.…”