Beach and dune reduction in Brazil was 15% in the last 36 years
Brazil's beaches, dunes and sands have been changing over the past 36 years. This is what MapBiomas' newest analysis of satellite images from 1985 to 2020 shows. The reduction was 15%, or about 70 thousand hectares. 36 years ago there were 451 thousand hectares; in 2020, only 382 thousand hectares. Besides dunes, beaches and sands, the study that MapBiomas presented on October 27, through YouTube, also evaluates the dynamics of mangrove areas, apicuns (salinized areas with no vegetation), and aquaculture/saliculture.
The preservation of beaches and dunes is essential to control coastal erosion and preserve the coastline and its biodiversity. The beach and the dune usually protect the mangroves from wave action. They create a calm environment where mud can be deposited and colonized by mangrove vegetation.
The reasons for the decrease in the surface area of dunes, beaches, and continental sandbanks are varied: from revegetation of the dune tops, occupation by aquaculture and salt mining enterprises, and the expansion of invasive species. The reduction of the beach and dune strips can also be explained in part by the strong real estate pressure. There is also the low protection: only 40% of this type of deposit is protected in some conservation unit. Among the cases of occupation by land uses, the advance of pine trees over dune fields in Rio Grande do Sul in areas bordering planted forests and the expansion of the aquaculture/salinization structure in the coastal region of Rio Grande do Norte call attention.
"Because of the Lençóis Maranhenses National Park and the Reentrâncias Maranhenses Environmental Protection Area, Maranhão leads in the protection of dunes/beaches and mangroves, respectively," says Pedro Walfir, general coordinator of the coastal zone theme of MapBiomas. Almost all (98% - 99 thousand hectares) of its beaches, dunes and sands, 96% (24 thousand hectares) of its apicuns and 86% (398 thousand hectares) of Maranhão's mangroves are protected by Conservation Units. "Therefore, Maranhão is the state with the largest extension of coastal environments protected by UCs in the country and one of the most conserved," explains Pedro Walfir.
From 1985 and 2020, mangrove areas in the country remained relatively stable, going from 946,000 hectares to 981,000 hectares. However, from the year 2000 to 2020 there is a 2% retraction in mangrove areas. In Brazil, more than 78% of the mangrove area is concentrated on the Amazon coast, which stretches from Amapa to Maranhao, home to the best preserved and most extensive mangroves on the continent. On the other hand, it is in the Northeast and Southeast regions, smaller in extent, where mangroves are most threatened. In both, from 2000 to 2020, direct anthropic actions were responsible for 13% of the changes in this cover.
The mangrove is the nursery for numerous marine species: 70 to 80% of the fish, crustaceans, and mollusks that the population consumes need the biome at some stage in their lives. Several economically important fish species use the mangroves as a reproduction area and then return to the sea.
In this context, the creation of Conservation Units in coastal areas protecting mangroves has been of undoubted importance. Brazil has 340 (13%) of its total 2544 protected areas in the coastal zone. Currently, 75% of the mangrove area in the country is within Conservation Units, which should contribute to the future preservation of this one of the most threatened ecosystems on the planet.
From an ecosystem point of view, apicuns are intrinsically related to mangroves that tend to grow over these hypersaline tidal flats - hence the importance of their conservation for the future of mangroves. Currently, just over half of the apicuns (56%) are also in protected areas. On the other hand, the current use of much of Brazil's apicuns for salt and shrimp production poses a risk to mangrove conservation. Because they are flat, unshaded areas, apicuns are preferred for commercial production of salt and crustaceans, especially shrimp. From 1985 to 2020, the area of aquaculture and salt culture had a 39% jump, from 36,000 hectares to 59,000 hectares. The apicuns, on the other hand, had a 12% reduction between 2000 and 2020, from 65 thousand hectares to 57 thousand hectares.
It also draws attention that 8% of the national aquaculture is found inside Conservation Units. "In these cases, it is important to check if these activities are in areas that allow commercial exploration and if they follow the Brazilian legislation to the letter," warns César Diniz, technical coordinator of the mapping of the Coastal Zone of MapBiomas. The mapping shows that the state whose aquaculture/salinization area occurs most in Conservation Units is Rio Grande do Norte (2.5%, or 1039 hectares), a state that concentrates 67% of the country's salinization/aquaculture area.