MapBiomas data shows that out of every 100 hectares of favela, 15 were built in risk areas

Access the main highlights of Urbanized Areas from MapBiomas Collection 7

In the last 37 years, urbanized areas in the country have grown from 1.2 million hectares to 3.7 million. During this period, informal areas totaled 106,000 hectares - an expansion of approximately three times the area of the city of Belo Horizonte, in Minas Gerais. These data are from MapBiomas' most recent survey of urbanized areas, based on the analysis of satellite images taken between 1985 and 2021.

Most of the urbanized area in favelas is concentrated in the capital cities. Manaus is one of the highlights: the capital of Amazonas has the highest growth in the historical series, totaling around 10,000 soccer pitches in 2021. São Paulo (5,579 ha), Belém (5,450 ha), Rio de Janeiro (5,038 ha) and Salvador (4,793 ha) follow. All of them registered similar growth in informal areas, even though they have their own territorial characteristics.

The Amazon leads the region in the percentage of growth in informal occupations: 29.3% of urban growth in this biome was in informal areas. The northern region has 13 of the 20 cities with the highest proportion of growth, with Belém among the top five on the list.

"The growth of favelas is similar to that of urbanized areas, but in the 1990s informal areas accelerated their progress. The expansion of urbanization has an impact on the consumption of natural resources, on the quality of life and, in general, on urban sustainability, but when we talk about favelas, there is also a very high chance of an increase in the occupation of risk areas by more vulnerable populations," explains Julio Cesar Predrassoli, one of the coordinators of MapBiomas' mapping of Urbanized Areas.

Satellite images have shown that urban occupation as a whole in risk areas increased 3 times between 1985 and 2021, and in informal areas this increase was even greater: 3.4 times. Of every 100 hectares of favela, 15 were built in risk areas.

Of the 887 cities with some urbanized area in risk areas, only 20 account for 36% of all the risk area occupied in the last 37 years. Salvador (BA), Ribeirão das Neves (MG), Jaboatão dos Guararapes (PE), São Paulo (SP), Recife (PE) and Belo Horizonte (MG) are the top six on the list.

The Cerrado tops the ranking of biomes with the biggest increase in urbanized areas at risk at 382%, followed by the Caatinga at 310%, the Amazon at 303%, the Atlantic Forest at 297%, the Pampa at 193% and lastly the Pantanal at 187%. As the ranking is done by area and Petrópolis has a small urban extension, the city is not at the top of the list, but it is one of the most emblematic examples of the consequences of the occupation of risk areas that has been occurring in the region since the 19th century.

The Cerrado was also the biome that lost the most native vegetation to urban expansion. Of the more than 558,000 hectares of natural formations that were converted to urbanized areas between 1985 and 2021, 28% (156,500 hectares) were in the Cerrado. In second place is the Atlantic Forest (1,300,000 ha), followed by the Amazon (123,000 ha), the Caatinga (108,000 ha), the Pampa (40,000 ha) and the Pantanal (778 ha).

The survey also showed that the greatest expansion of urbanized areas occurred over areas of agricultural use. Between 1985 and 2021, the 2.5 million hectares that were urbanized were 67.8% agricultural use: 30.7% were pasture areas, 30.5% mosaics of use and agriculture was 6.4%.

"Although agriculture has grown by almost 70% in urban areas, it is the advance of native vegetation that draws our attention. Proportionally, some states have lost more than half of their natural cover to urbanized areas, affecting the natural ecosystems in which cities are located and contributing to a less efficient response to climate challenges," points out Mayumi Hirye, MapBiomas' Urbanized Areas mapping coordinator.

The total loss of natural formations to urban areas was 22.2% in 37 years. In Piauí, 68.4% (29,029 ha) of urbanization occurred on natural cover, with forest and savannah formations accounting for 26,421 hectares lost. In Amazonas, 59.9% (17,159 ha) of natural cover, such as forests and wetlands, was lost. Ceará lost 58.6% (53,845 ha), especially savannah formations. The loss in Mato Grosso was 51.2% (38,156 ha), with savannah, grassland and forest formations totaling more than 36,000 ha.

The states of São Paulo and Rio de Janeiro, located in the Atlantic Forest, have the two largest urbanized areas in the country and together they have lost almost 38,000 hectares of native vegetation: 26,655 ha and 10,982 ha respectively.

The Pantanal and Pampa are the biomes with the highest proportion of native vegetation in both high and low density urban areas. The Amazon saw the greatest loss of native vegetation in both density areas. "Low-density areas comprise the expansion areas of cities, where the ecosystem services of vegetation could be incorporated into new, greener and more sustainable neighborhoods," warns Hirye. The highlight is the Atlantic Forest: there are around 730,000 ha of native vegetation in low-density urban areas.

The Atlantic Forest, which concentrates more than half of the urbanized areas (53%), is also the leader in the ranking of urban occupation of marginal strips (30 m) of water bodies by biome. In 2021, the biome accounted for 67% of all urban occupation putting pressure on the banks of water bodies. In addition, 280,000 hectares of the Atlantic Forest are low-density urbanized areas.