Southern Atlantic Coastal forests

• Category: Forest Biomes.
• Geographic Location: South America.
• Summary: An extensive biome extending along the Brazilian coast and reaching into inner plains and even mountain areas, this high-diversity biome is also a highly threatened biodiversity hot spot.

The southern region of the Atlantic coastal forests was originally one of the largest rainforests of the Americas, extending over 580,000 square miles (150 million hectares) and covering greatly heterogeneous environmental conditions, which contributed to its exceptionally high biodiversity. With a latitudinal span of 38 degrees, it extended into tropical and subtropical regions of South America, north to south along today's Brazilian Atlantic coast. Its wide longitudinal range, extending inland toward plains and mountains—with altitudes ranging from sea level to over 9,500 feet (2,900 meters) reaching modern-day Argentina and Paraguay, also contributed to its high biodiversity, together with a variety of soil types and variation in rain patterns: Areas closer to the coast receive up to 160 inches (400 centimeters) of rain annually, while inland areas get in the range of 40 inches (100 centimeters).

These diverse environmental conditions have resulted in very different formations within the biome, comprising both coastal rainforests and seasonal mixed coniferous-deciduous forests farther inland. Mixed Araucaria pine forests and distinct Lauraceae-dominated forests are found in the south; deciduous and semi-deciduous forests are located inland. A number of associated formations include mangroves, restingas (coastal forest and scrub on sandy soils), high-elevation grasslands (campo rupestre), and brejos (humid forests resulting from orographic rainfall in otherwise semi-desert scrub in the northeast of Brazil).

Unique Species

The rich biodiversity of this biome has made it one of the twenty-five recognized biodiversity hot spots of the world, which together account for over 60 percent of all terrestrial species. As with other biodiversity hot spots, the Southern Atlantic coastal forest has experienced significant environmental loss. It is considered one of the most devastated and highly threatened biomes of the planet—between 85 and 95 percent of its original cover has disappeared. Overall, the recognized biodiversity hotspots have lost three-fourths of their original landscapes.

Although only a small portion of the original Southern Atlantic coastal forest is intact, it still hosts thousands of common and endemic species (native and unique to a biome), including over 20,000 plant species (40 percent endemic), 2,000 vertebrates (30 percent endemic), nearly 300 mammals (90 endemic), over 1,000 bird species (200 endemic), 475 amphibians (285 endemic), and over 300 reptiles (94 endemic). Additionally, 80 percent of the twenty-four monkey species of these forests are endemic. Surprisingly, most of the original species thought to integrate the original biome can still be found, although most often in small areas and highly fragmented landscapes. Many flora and fauna species are endangered, threatened, or vulnerable in the Atlantic Forest, including the wooly spider monkey, the golden lion tamarin, the maned three-toed sloth, the red-tailed parrot, and thousands of tree species.

Agriculture and Other Stresses

The drivers of biodiversity loss in this forest are extremely complex, as they stem from the varying socioeconomic conditions of the different regions it comprises, north to south and east to west, today and dynamically back through history. Since the colonization by the Portuguese and the Spanish, the biome has experienced severe transformations, mostly related to intensive land use related to the production of commodities, from brazilwood to sugarcane, coffee, and cocoa plantations, and cattle ranching, and the expansion of soy fields and pine and eucalyptus plantations.

High urbanization rates in the early twenty-first century are also related to environmental loss in the biome. The population in areas of the Southern Atlantic Coastal Forests biome has kept increasing sharply in the three countries over which the biome extends—Brazil, Paraguay, and Argentina. Three of the largest cities of South America, including its biggest urban center, São Paulo, are located within the area originally occupied by the biome. Over 20 percent of the Brazilian population live in São Paulo.

Yet human influences in these woodlands started millennia ago. Records of human presence indicate that the first humans inhabited the biome 11,000 years ago, with evidence of agricultural activity dating to 3,900 years ago. This implies previous ecological transformations, especially from the introduction of slash-and-burn agriculture, which uses fire to manage plant succession and has a reductive effect on the complexity and biomass of the forest.

Indigenous populations dispersed cultivated plants, which ultimately affected natural selection and the hybridization of wild species. Yet, Indigenous groups here maintained low levels of trade, which resulted in a low-intensity land use pattern, as opposed to the agricultural intensification that followed European colonization. This factor helped prevent the Southern Atlantic coastal forests from becoming an entirely secondary formation.

Indigenous groups in the region gathered more than 100 forest fruit species and hunted deer, marmosets, turtles, crocodiles, monkeys, sloths, peccaries, agoutis, armadillos, capybaras, tapirs, and otters among larger animals. Coastal groups intensively used various fish and shellfish species, including mullet and twenty-three other species of saltwater fish, eight species of freshwater fish, as well as crabs, cockles, shrimp, and manatee. Biocultural diversity has been eroded among the descendants of these ethnic precursor groups. Only a fraction of the people belonging to some of the original Indigenous groups continue living there in the twenty-first century.

However, efforts to restore indigenous peoples' rights to their land made significant progress in the 2010s and 2020s. Because Indigenous peoples living in the Atlantic Coastal Forest depend on the forest's ecosystem for sustenance and income generation, they care for and protect the land. In a study that analyzed data from 1985 to 2019 concerning 129 Indigenous lands, researchers found that reforestation and sustainable land management improved the forest in areas that were returned to the Indigenous peoples. In those lands that were not returned, deforestation and pollution continued. Indigenous peoples are an essential element of reforestation efforts and maintaining these forests.

Modern Developments

Global climate change will be a factor in the sustainability of the remnants of the Southern Atlantic coastal forests. The challenges include increased saltwater intrusion, altered precipitation patterns, invasive species expansion, and rapidly changing nutrition and mineral availability to plants and animals due to the combined effects of all of these factors.

Against these negative vectors, the activities of human populations can have mitigating effects if they are applied with intelligence and determination. The Southern Atlantic Coastal Forests biome has become a top-priority hotspot for biodiversity conservation at the local, regional, national, and international scale. Around twenty-five protected areas have been created in the Atlantic Forest South-East Reserves, which have been named a UNESCO World Heritage Site. Still, only roughly 10 percent of the forest is under firm protection measures. Increasing environmental awareness regarding the value of forest resources among the general public, together with the involvement of conservationist groups, the academic community, farmers, private businesses, and governments, has resulted in numerous high-quality studies, conservation measures, enforcement practices, and sustainable development initiatives.

Bibliography

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Galindo Leal, Carlos, and Ibsen de Gusmão Câmara, editors. The Atlantic Forest of South America: Biodiversity Status, Threats, and Outlook. Island Press, 2003.

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Surma, Katie. "Study Documents a Halt to Deforestation in Brazil’s Atlantic Forest after Indigenous Communities Gain Title to Their Territories." Inside Climate News, 6 Feb. 2023, insideclimatenews.org/news/06022023/brazil-atlantic-forest-indigenous-communities-deforestation. Accessed 16 Dec. 2024.

Tabarelli, Marcelo, et al. “Challenges and Opportunities for Biodiversity Conservation in the Brazilian Atlantic Forest.” Conservation Biology, vol. 19, no. 3, 2005, pp. 695–700.

Vancine, Maurício Humberto, et al. “The Atlantic Forest of South America: Spatiotemporal Dynamics of the Vegetation and Implications for Conservation.” Biological Conservation, vol. 291, 2024, doi.org/10.1016/j.biocon.2024.110499. Accessed 16 Dec. 2024.

Wilson, Oliver J., et.al. "Floristic Change in Brazil's Southern Atlantic Forest Biodiversity Hotspot: From the Last Glacial Maximum to the Late 21st Century." Quaternary Science Reviews, vol. 265, 15 July 2021, doi.org/10.1016/j.quascirev.2021.107005. Accessed 16 Dec. 2024.