Slum growth in Brazil between 1985 and 2020 is equivalent to 11 Lisboas

Between 1985 and 2020, urbanized areas in the country will double, from 2.1 million hectares to 4.1 million hectares. Urban expansion in Brazil has been taking rapid steps: an annual rate of 1.97%, higher than the population growth rate of 1.45%. These data are part of the survey on urbanized areas made from satellite images captured between 1985 and 2020 that MapBiomas released this Friday, October 5, on its YouTube channel. 

Led by São Paulo, with 218,985 hectares, the 20 largest population agglomerations in the country concentrate 30% of the urbanized areas. Rio de Janeiro (174,534 ha), Brasília (89,243 ha), Belo Horizonte (87,121) and Curitiba (74,239 ha) complete the top five in area.  

In the whole country, informal areas grew by the equivalent of 95,000 soccer fields between 1985 and 2020.  This growth is equivalent to three times the area of Salvador or 11 times the area of Lisbon, in Portugal.  In all, 4.66% of the growth of urbanized areas between 1985 and 2020 have characteristics of informality. The temporal analysis of the areas occupied informally throughout the country shows that they are more sensitive to economic and social policies, growing more in periods of GDP retraction.

The Amazon leads the percentage of growth of informal occupations in the territory: 18.2% of the urban growth in this biome was in informal areas. The states of this biome also lead when the total area is analyzed. In the state of Amazonas, informality accounts for 45% of the urbanized area; in Amapá, 22%; in Pará, 14%; and in Acre, 12.6%.  Only Espírito Santo, with 21.5%, has a greater participation of informality in the total urbanized area of its territory than the states of the Amazon. 

When analyzing how much of the total urbanized area is occupied informally, Manaus, Belém and Salvador stand out. In the two large capitals of the northern region, informality has been the rule for the last 36 years, since, in both cases, the percentages remain above 50%.  Belém has 51% of its urbanized area occupied by informality, while in Manaus this percentage is 48%.  When we include the boundaries of the Special Social Interest Zones (ZEIS) defined in the city's master plan, Salvador comes close to this pattern, with 42%.

The satellite images also allowed us to identify the occupations in areas with a slope greater than 30%, i.e., which are more prone to landslides.  They are predominantly located in Minas Gerais, Rio de Janeiro, Santa Catarina, Espírito Santo and São Paulo. However, they are already beginning to occur in Amazonas, Paraná, Rio Grande do Sul, Alagoas, Pernambuco and Bahia. In all, the growth of urban occupation in areas with high slope was of the order of 40 thousand ha - that is, 1 in every 100 ha is already in slope risk areas. 

"The combination of these two data should turn on a yellow light for public managers because they create the perfect conditions for urban disasters," explains Julio Cesar Pedrassoli, one of MapBiomas' urban infrastructure mapping coordinators. "On the one hand, we have large areas without adequate public services; on the other, accident risk potentiated by the increasing occurrence of extreme weather events. Looking at informal occupations from the angle of adaptation to climate change is fundamental to avoid tragedies", he alerts. 

Although the Atlantic Forest still concentrates more than half of the urbanized areas in Brazil (54.7%), the largest growth recorded in the last three decades took place in the Amazon, Caatinga and Cerrado - all with annual growth rates above the national average: 2.5% p.a., 2.53% p.a. and 2.08% p.a., respectively.  

The survey showed that of the areas urbanized in 2020, a little more than a third (34%) were areas of pasture and areas of mixed use of agriculture and pasture, and 13% were native vegetation in 1985. The areas used for urban expansion reflect the predominant land use in each region. In the North, for example, 32% of the expansion took place in native vegetation - almost three times the national average. In the South, almost 10% of the urbanized areas in 2020 were dedicated to agriculture in 1985, while in the Brazilian average, this percentage is only 4%. 

The Cerrado, which already holds one fifth of the country's urbanized areas, was the biome that lost the most native vegetation to urban expansion. Of the more than 388 thousand hectares of native vegetation that were converted to urbanized areas year-on-year, 33% (127 thousand hectares) were in the Cerrado. In second place comes the Amazon (almost 92 thousand hectares). In percentage terms, the biome that lost the most forests was the Atlantic Forest: 58.3% of the native vegetation converted to urban areas in this biome was forest. In the Amazon, this percentage was 44.1%. 

Subnormal Agglomerations are urban areas occupied by residential use in places without land tenure by the occupants. They have an irregular urban pattern, lack essential public services (regular water, sewage and garbage collection, for example) and are sometimes located in areas with restrictions on occupation (areas at risk of landslides, flooding or inundation, for example).  Official definition at: https://www.ibge.gov.br/geociencias/organizacao-do-territorio/tipologias-do-territorio/15788-aglomerados-subnormais.html?=&t=o-que-e 

The Special Social Interest Zones (ZEIS) or Special Social Interest Areas (AEIS) are urbanistic instruments that define areas of the city destined for popular housing construction: https://www.capacidades.gov.br/dicionario/index/letra/z

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