All coastal cities are vulnerable to climate change. For millennia, life on the coast was preferred because of the abundance of food, ease of transportation, and potential for defense against adversaries. Today at least 10 percent of the world’s population live in low-lying coastal areas. What used to be an asset is increasingly a liability. The rapid expansion of coastal cities has broken down natural barriers, destroyed resources and deteriorated water quality. As a result, swelling coastal communities are exposing more and more people to hurricanes, storms, floods, landslides, and sea level rise.
Some coastal cities are more at risk than others from sea level rise and other climate-related threats. Over the next few decades, over 570 low-lying coastal cities could experience sea level rise of at least 0.5 meters (1.6 feet). If this scenario happens, more than 800 million people could be at risk and the total economic cost could increase by $ 1 trillion. While Asian and African cities are particularly exposed, Rio de Janeiro is one of the most endangered cities in Latin America. Climatologists and the city’s planners believe that the built-up area around the city is exposed to sea level rise, flooding, increased rainfall, and heat islands, making large parts of it virtually uninhabitable.
One reason coastal cities are so exposed to climate-related threats is a combination of poor planning and rapid urbanization. Rising water levels and the increasing frequency and severity of flooding and extreme heat are only part of the problem. Another reason is that many coastal cities are built directly on coastal plains, often near estuaries and lagoons. People, including the poorest residents, are often forced to live on precarious land, including drained wetlands and swamps – or right in the lagoons like the slums of Lagos, Nigeria. This not only exposes them to flooding, but also to compaction, which leads to a sinking infrastructure. The areas most susceptible to climate stress are often the areas with the highest population density and the highest resident population at the bottom of the income ladder.
Rio de Janeiro’s current climate vulnerability is partly a legacy of its historically chaotic and uneven urban development. After Rio ceded the title of state capital to Brasília in 1960, it began to spread uncontrollably. The metropolitan area’s population tripled within five decades. Population growth exacerbated the lack of affordable housing and contributed to the steady expansion of unplanned and improvised districts to the west and north. Informal settlements or favelas increased along waterways and on slopes.
Today Rio de Janeiro has an estimated 6.7 million people. It is the second largest city in the country by the size of its economy, but it only ranks 327th in terms of GDP per capita, 71st in terms of municipal competitiveness, and belongs not only in Brazil but among the most unequal in the world. Rio is also notoriously violent: over 2,400 people were murdered in the metropolitan area in 2020, including around 1,000 people reportedly killed by police. In addition, an estimated 60 percent of the city is controlled by militias, while drug trafficking factions monitor dozens of poorer neighborhoods.
With this in mind, it is not surprising that the city is struggling to mitigate and adapt to natural disasters and climate change. A combination of turbo-urbanization and disorganized urban planning contributed to the rapid depletion of natural forest cover. Instead of protecting the city with often cheaper nature-based solutions like reforestation and wetland restoration, state and city authorities have poured funds into cement, brick and steel. The reduction in tree cover, coastal erosion and the explosion of concrete have all helped raise average temperatures there by 0.05 degrees Celsius per year.
Average global temperatures are expected to rise by 2 degrees Celsius by 2050 in a “business as usual” scenario. Warming in Rio de Janeiro is likely to result in longer, heavier, more frequent and more deadly heat waves, particularly affecting older and poorer populations. Rising temperatures could also cause sea levels to rise 0.3 to 2.15 meters by 2100 and potentially inundate much of Rio de Janeiro’s area, including residential and commercial properties, public parks, ports and power grids.
There are already signs of what is to come. The state of Rio de Janeiro has recorded hundreds of natural disasters since the early 2000s. Today researchers estimate that at least 155,000 people in over 1,300 high-risk areas are prone to landslides and flooding. One of the most devastating, a massive storm and string of landslides in 2011 that killed over 800 people, left 30,000 homeless and affected tens of thousands more with water-borne diseases such as leptospirosis. The World Bank estimated the cost of the tragedy at over $ 2 billion. In the ten years since the disaster, however, too little has been invested in rebuilding depleted infrastructures, let alone in climate protection. In 2012, the city began construction of four underground reservoirs and a bypass tunnel to improve control of light to moderate flooding. However, these are not sufficient to counteract the imminent threats.
Climate change threatens not only to impose enormous humanitarian costs on Rio de Janeiro, but also to disrupt its main sources of income. State and city are heavily dependent on oil revenues. When oil prices fell between 2014 and 2016, the state declared a financial “calamity” just before the Summer Olympics were to be held. Oil and gas fee revenues continued to decline through 2020. With the global divestment from the hydrocarbon industry, future economic planning requires alternative sources of income.
The other major source of income for Rio de Janeiro is tourism. However, rising seas and temperatures threaten not only violence but also the value proposition. Today, Rio lags behind other Brazilian cities like São Paulo, Belo Horizonte and Porto Alegre when it comes to attracting tourist dollars. Brazil as a whole has slipped to 32nd place behind Belgium and Denmark. Still, there is enormous growth potential for Rio’s tourism industry, if only more emphasis was placed on nature-based solutions that can help remove some of its climatic uncertainties.
The first step in building climate resilience is to identify climate threats and develop strategies to mitigate and adapt to them. However, there are few current scientific studies that document the scope, extent and consequences of climate change in Rio de Janeiro. For most Brazilian cities, there are few publicly available studies on sea level rise, coastal erosion, or heat islands. Nevertheless, over 60 percent of the Brazilian population live in low-lying coastal cities: Belém, Florianópolis, Fortaleza, Paranaguá, Salvador, Recife and Vitória are particularly at risk.
A Brazilian city that has taken measures to adapt to climate change is Santos, home to Latin America’s busiest seaport. Santos processes over a hundred million tons of cargo annually. That corresponds to around 27 percent of the Brazilian trade balance. After documenting a sustained rise in sea levels, city authorities introduced tax deductions for investments in alternative energy and encouraged green roofs, reforestation, natural barriers, drainage channels and pumping stations.
Curitiba is another Brazilian city recognized worldwide for innovations in the field of climate protection. In the 1980s, the city launched a bold strategy to protect green spaces, encourage recycling, and invest in waste management. The “Green Exchange” program exchanges recycled items for food. The city’s ratio of around 600 square feet of green space per inhabitant is about four times that of São Paulo and is well above international standards. Today Curitiba is only one of two cities in Brazil with a climate adaptation plan that has been named the most sustainable city in Latin America.
These types of innovative solutions could help tackle many of Rio de Janeiro’s competing crises in terms of climate vulnerability, insecurity, inequality and economic decline. Expanding green spaces, cooling heat islands, curbing pollution and improving affordable housing can all help reduce inequality, reduce violence and increase economic opportunity. The alternative of coastal erosion, increasing flooding and scorching heat can make parts of Rio de Janeiro uninhabitable and exacerbate the crises in a financially troubled city.
Brazilian cities can strengthen their defenses against climate change by creating updated plans that focus on adaptation and containment, based on a real public consultation. Most large cities have set up some kind of council to at least discuss climate protection measures. Still, many Brazilian cities are lagging behind: 11 of the country’s 27 state capitals have outdated master plans that exceed the mandatory 10-year extension. So far, only a handful of Brazilian cities are tracking greenhouse gas emissions. Only Belo Horizonte, Curitiba, São Paulo and Rio de Janeiro have developed adaptation or mitigation strategies.
Coastal cities like Rio de Janeiro will have to experiment with different strategies to increase climate resilience. There are many ideas – including sponge cities that use a combination of repurposed built-up areas, rain gardens, ponds, and wetlands to store excess water, and ambitious environmental rehabilitation projects such as favela green roofs and green corridors. Nature-based solutions are not just an add-on. They are the key to the survival of the city and a pioneering role for sustainable economic renewal.