- Nearly a third of the Brazilian portion of South America’s Pampa grassland has been lost since 1985, largely to agricultural expansion and forestry plantations.
- This biome is often overlooked in comparison to the higher-profile Amazon, Pantanal and Cerrado landscapes, but has greater plant diversity than the others.
- The expansion of agriculture may also be exacerbating an age-old problem in the Pampa, which is the spread of barren, sandy patches of land.
- Efforts to reverse this process, known as arenization, often involve growing eucalyptus plantations, but experts say this commercial approach solves nothing.
The Pampa grassland of South America covers just 2% of Brazil’s territory, dwarfed to the north by the immense rainforest, wetland and savanna landscapes of the Amazon, Pantanal and Cerrado. But while global attention focuses on these latter three, the “invisible” biome of the Pampa, at Brazil’s southernmost tip, is being degraded almost unnoticed.
The Pampa covers the entirety of Uruguay and portions of several provinces in Argentina, and in Brazil covers half the state of Rio Grande do Sul, spanning some 9 million hectares (22 million acres) in 1985. By 2022, the Brazilian portion had shrunk by nearly a third, according to data from the collaborative mapping initiative MapBiomas, with much of the grassland vegetation cleared for agriculture and forestry.
During that 38-year period, MapBiomas found, agricultural land use in the Brazilian Pampa increased by 2.1 million hectares (5.2 million acres), mainly for soybean cultivation, while forestry plantations (pine and eucalyptus) expanded by more than 720,000 hectares (1.8 million acres) — growth of 1,667%.
The research also looked at the Uruguayan and Argentine portions of the Pampa (across the three countries, the biome covers a total area of 110 million hectares, or 272 million acres — nearly twice the size of France). It showed a total reduction of 20% of the grassland vegetation in the biome from 1985-2022, including 9.1 million hectares (22.5 million acres) of native grassland.
Hectare for hectare, the Brazilian Pampa has the greatest biodiversity of plant species of any of the country’s biomes, according to Tales Tiecher, an agronomist at the Federal University of Rio Grande do Sul (UFRGS). But this has suffered drastically as the native vegetation is cleared.
“Proportionally, the biome is among the most degraded in the country, ahead of the Amazon and the Cerrado,” Tiecher says.
The loss of the ecosystem is the main threat to native fauna and flora, Tiecher adds. “Around a quarter of rural birds are subject to some degree of extinction threat in at least one part of the biome, and around 30 species of mammals are at risk of disappearing forever,” he says. “In addition, several species of reptiles, amphibians and plants are also threatened.”
Juliano Ferrer dos Santos, a biologist at UFRGS, says agricultural expansion in the Pampa is taking place so rapidly that researchers are unable to monitor the real state of conservation across the biome.
“On every trip to the biome to monitor and research the annual fish, my object of study, we come across a more critical situation in relation to the known areas of occurrence and others that are suitable for their survival,” he says.
Santos cites the case of annual rivulids, or cloud fish, which inhabit small ponds that form in the grasslands during the rainy, or winter, season. “When they hatch, they grow very quickly and already reproduce, because at the end of spring their aquatic environments dry up and they die,” Santos says. “But their eggs are buried in the mud and won’t hatch until next year. When the ponds dry up, there is no indication that unique species of fish live there.”
Sand trap
The advance of agriculture and forestry plantations — and the consequent destruction of large areas of native grassland and fields — is also contributing to aggravating an old problem in the Brazilian Pampa.
These are the so-called areais, or arenization regions, dotted throughout Brazil’s south and southwest. These are patches of bare land, dating back 200 million years, when most of south-central Brazil was an immense desert. Known geologically as the Botucatu Formation, it’s an area characterized by sandy, nutrient-poor soil, caused by the gradual weathering of bedrock, a process known as arenization.
Though it may look like it, this isn’t a region undergoing desertification, the key difference being that this part of Brazil receives average annual rainfall of 1,400 millimeters (55 inches) — about the same as the U.S. state of Florida. The subtropical climate means it’s outside the zone where climate and human action are the main drivers of landscape degradation, as is the case with the Caatinga dry forests in the country’s east. Today, arenization regions in Brazil are considered areas of special attention.
Roberto Verdum, a geographer at UFRGS, says the arenization process, driven by movements of water and wind over the course of millions of years, is associated with factors such as climate, topography and vegetation cover. These, in turn, may or may not be related to agricultural activities.
Verdum says these sandy patches in the Pampa are related to the susceptibility of the region’s rocks and soils to the dynamics of torrential rains and periods of drought. “Thus, the sandy areas are constantly being reworked by climatic agents, essentially water and wind,” he says.
Agricultural activities in naturally fragile areas, coupled with a bedrock that’s highly susceptible to arenization, can, however, boost the factors that initiate and contribute to this process.
“The impacts of poor soil use and management, using technologies that are unsuitable for the fragile soils of this region, could be one of the main factors contributing to the emergence of new outbreaks of arenization in the current context,” Verdum says.
Neemias Lopes da Silva, a geographer at UFRGS, says what’s happening in the Pampa is the intensification, thanks to human activity, of erosive processes associated with arenization.
“The soils are fragile and poorly consolidated. Activities such as heavy grazing, or the weight of agricultural machinery itself, can compact the soil and help to develop furrows through which water will flow in a concentrated manner until it develops ravines and, later, gullies,” he says. According to Silva, these processes move and expand sandy sediments through the action of water and wind.
Greening the areais
Verdum says there hasn’t been a net expansion in sandy areas since monitoring carried out in the 1980s. But they could still be aggravated by agricultural production. Today, these barren spots cover 3,663 hectares (9,051 acres), spread across the municipalities of Alegrete, Cacequi, Itaqui, Maçambará, Manuel Viana, Quaraí, Rosário do Sul, São Borja, São Francisco de Assis and Unistalda, all in the state of Rio Grande do Sul.
This might be just a fraction of the total extent of the Pampa, but it’s significant for each landowner whose property is affected by the phenomenon.
One such individual is Raul Borges, a rice grower and president of the Rural Union of Itaqui and Maçambará. He owns 120 hectares (296 acres) of land, of which 46 hectares (114 acres) were sand patches when he bought the property more than 15 years ago. “It may not seem like much, but for me it was very significant, as it amounted to more than a third of my property,” he says.
That’s why he decided to restore the area. After many failed attempts, Borges achieved good results by covering the sand with rice husks or rice ash. “Today, around 25-30 hectares [62-74 acres] have been reclaimed,” he says. “In part of the area, the natural vegetation has returned.”
Borges’s success contrasts favorably with the more common method of trying to recover sandy areas here, which is through forestry. Since the 1970s, land managers, sometimes with the support of the state government of Rio Grande do Sul, have sought to green the areais by planting eucalyptus trees.
“Many of the proposals for economic activities, which see the sands only as a problem to be tackled, are responsible for interventions that decharacterize the landscape and alter the dynamics of this ecosystem,” Silva says. This is the shortcoming of the forestry approach, he says: the idea that the solution should also be commercially viable.
But it solves nothing, Silva says. “Where forestry is developed, the sand area is not recovered; it is only hidden in aerial images and all the biodiversity adapted to the region is replaced by eucalyptus and leaves on the ground,” he says. “Some plant species are endemic to sandy fields. The erosion processes don’t stop and the natural dynamics are altered, not to mention the landscape transformation, which changes the herbaceous and shrub vegetation with sandy fields into a large ‘green wall.’”
Banner image: A farm in Uruguaiana municipality, Rio Grande do Sul state, Brazil. Image by Eduardo Amorim via Flickr (CC BY-NC-SA 2.0).
This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Feb. 22, 2024.