Smaller flooded area in Brazil’s pantanal biome has increased fires
A study by MapBiomas released on National Pantanal Day on Tuesday (Nov. 12), shows that the pantanal’s flooded area has been shrinking in recent decades. The phenomenon is believed to be caused by increasingly shorter flood seasons and longer dry spells.
The likely result is more intense fires in the world’s largest floodplain, said MapBiomas, a collaborative network of universities, NGOs, and technology companies monitoring changes in land cover and use in Brazil.
According to the survey, the biome’s flooded area totaled 3.3 million hectares in 2023—a year 38 percent drier than 2018, when the last major flood in the biome occurred, covering 5.4 million hectares. This area, however, was already 22 percent drier than that of 1988—the first major flood in MapBiomas’ time series and which covered 6.8 million hectares.
In the pantanal, the floods usually occur February through April and the droughts July through October. The study also indicates that, in 2023, the drop in the volume of water was 61 percent down from the historical average for the period monitored—from 1985 to 2023.
Permanence
The areas flooded for more than three months a year are also showing a downward trend—in other words, a smaller flooded area is accompanied by flooding with shorter permanence. This phenomenon has had an impact on the expansion of the savannah in the pantanal. Of the current savannah area—2.3 million hectares—22 percent, or 421 thousand hectares, were regions that have dried up.
According to the study, this change in the pattern of floods and droughts has an effect on the incidence of fires in the biome. From 1985 to 1990, the areas affected by fires were natural areas in the process of being converted into pastures. After the period of the last major flood analyzed, in 2018, fires recurred around the Paraguay river.
“From 2019 to 2023, the fire reached places which, at the beginning of the mapping period, from 1985 to 1990, were permanently flooded, but are now experiencing prolonged periods of drought. The total area burned from 2019 to 2023 was 5.8 million hectares, and the region most affected was precisely these areas that used to be permanently flooded around the Paraguay river,” the study reads.
Fires
The increase in the number of fires this year was confirmed by data from the BDQueimadas platform, available on the website of the National Institute for Space Research (INPE). In June, the institute reported that fire outbreaks in the Pantanal surged by over 1 thousand percent in the first half of this year compared to 2023.
INPE’s satellite detected 978 fire hotspots from the first day of the year to June 5. In the same span last year, there were 95. This year, Mato Grosso do Sul recorded 521 hotspots, and Mato Grosso 457. These are the two states in the Central-West region where the pantanal is located—the smallest and most threatened of Brazil’s six biomes.
Exotic pastures
The data also showed an expansion in exotic pastures, which is evidence of the pantanal’s deforestation, which is part of its conversion to pasture. This alters water dynamics, Eduardo Rosa, mapping coordinator for the pantanal at MapBiomas, pointed out.
“The pantanal has experienced prolonged dry periods, as in the 1960s and 1970s, but today there is another reality, one of intensive agricultural use and the replacement of natural vegetation with pasture and agricultural areas, especially on the BAP [Upper Paraguay river basin] highlands, which changes the dynamics of the water in the river basin,” he said.
Human use
The study also shows that there has been an increase in human use, especially in the BAP. This basin integrates the cerrado and Amazon biomes and plays a fundamental role in the water flow of the pantanal plain.
In 1985, human use of land in the BAP corresponded to 22 percent of the total. By 2023, this percentage had reached 42 percent. The area most affected was the BAP plateau, which saw 83 percent of all human use in the river basin from 1985 to 2023.
Made up of plateaus, mountain ranges, and depressions, the highlands gradually saw its vegetation converted to pasture and agriculture. During this period, pasture and agriculture occupied 5.4 million hectares, of which 2.4 million hectares were forests and 2.6 million were savannah formations.
“The main human use of the BAP highlands is pasture, which accounts for 77 percent of the total, or more than 11.4 million hectares, followed by agriculture and a combination of uses, which together account for 20 percent (3.1 million hectares) of human use in the BAP,” the study says.
In the lowland region, the loss of natural areas has been less intense and more recent. In total, 1.8 million hectares of natural vegetation were cleared from 1985 to 2023, including almost 859 thousand hectares of grassland and flooded fields, 600 thousand hectares of savannah, and 437 thousand hectares of forest.
