For every 100 hectares of favela that grew in the country between 1985 and 2022, 16.5 were in risk areas

Brazil has 123 thousand hectares of urban areas in regions known to be susceptible to floods, landslides, droughts and other climate disasters. This is what the most recent MapBiomas survey shows, which covers the period of 38 years between 1985 and 2022. The study found a great disparity between the national average numbers, that is, which take into account all types of urbanized areas, and the specific data on favelas. On the national average, 3% of the total urban area is in risk regions; in favelas this percentage reaches 18%. While general urbanization in risk areas increased 2.8 times in the period evaluated, in favelas this increase was 3.4 times, reaching 5.9 times in the Cerrado. For every 100 hectares of favelas that grew in the country between 1985 and 2022, 16.5 were in risk areas.

“The data shows a worrying situation, where precarious occupations and those with greater vulnerability to extreme events have grown rapidly. While urban areas in Brazil have tripled since 1985, occupation very close to riverbeds has quadrupled and occupation in areas with high slopes has increased fivefold in the same period of time”, warns Julio Pedrassoli, one of the coordinators of MapBiomas' mapping of Urbanized Areas.

>> Access highlights of urbanized areas (1985-2022)

Among the risk situations assessed are the bottoms of valleys, that is, areas that are a maximum of three meters vertically away from the nearest river. MapBiomas identified 425 thousand hectares of urban areas in a situation of potential vulnerability to flooding, but which are not yet officially recognized as risk areas. Two-thirds (68%) of this occupation occurred in the last 38 years. Of every 100 hectares of urbanization, 11.5 of them were in areas very susceptible to flooding. In the favelas, this expansion was 17.3 hectares for every 100 urbanized ones.

Another point assessed was compliance with Law 6766/79 on Land Subdivision, which prohibits occupation and subdivisions on land with a slope greater than 30%. Satellite images show that 98.8% of urbanized areas comply with legislation. However, urbanization in areas prohibited due to their high exposure to disasters has increased 5.2 times since 1985. Since 2011, urbanized areas have increased by 17.7% on land above a 30% slope.

The worsening of the climate crisis and the consequent rise in ocean levels increase the risk of flooding in coastal cities, where the expansion of urbanized areas was 2.7 times between 1985 and 2022. Last year, 10.2% of urbanized areas they were in coastal cities, with 10 of the 20 fastest growing coastal cities being capital cities.

MapBiomas researchers also measured the incidence of disasters per urbanized area: the increase was 5.2 times since 1991. Between 1985 and 2022, the increase in the incidence of disasters per 1000 ha of urbanized area was 105 times in the Caatinga, 62 times in the Cerrado and 36.5 times in the Amazon.

Every 20 years the area occupied by favelas in Brazil doubles

While urbanization in Brazil increased 3.1 times between 1985 and 2022, urbanization in favelas increased 3.9 times. During this period, 5% of all urban expansion in Brazil was in favelas – an area equivalent to the territorial limit of Feira de Santana/BA (124,000 ha) between 1985 and 2022.

Manaus gained 14 thousand hectares of favelas between 1985 and 2022. This is equivalent to the entire urbanized area of ​​Porto Velho in 2022. In Cariacica, Ananindeua, Belém and Manaus, at least half of the growth in the urban area was favelas.

Urbanized areas grew 3% per year between 1985 and 2022

Urbanized areas represent 0.4% of the Brazilian territory, occupying 3.7 million hectares in 2022. In 1985, there were 1.2 million hectares. That year, only 27 urban concentrations had an urbanized area greater than 5 thousand hectares. In 2022, that number jumped to 97.

The cities that show the highest percentage of growth between 1985 and 2022 are small ones, with less than 100 thousand inhabitants: 3.6% per year. The growth rate of large concentrations in this period, in turn, was 2.5%. The highest growth rates were recorded in the Caatinga (4.0%) and Cerrado (3.3%). In territorial extension, however, the biome that led the growth of urban areas between 1985 and 2022 was the Atlantic Forest, where there was an expansion of 1.9 million hectares – equivalent to the sum of growth in all other biomes. 

In 1985, natural areas covered 63% of urban perimeters in the Amazon; in 2022, they represent 28%.