Like other coastal cities, Santos, at the shore of São Paulo State, Brazil, is experiencing a situation reminiscent of Aesop’s fable of the ant and the grasshopper. Sea levels are expected to continue rising in the years ahead, and the city faces the dilemma of adapting or having to pay the high price of increasingly frequent storm surges and floods.

Adapting to climate change involves public works that place a costly burden on the budget of any city. A wide-ranging study has concluded that adaptive construction projects in the Ponta da Praia area of Santos and the northwest of the city would cost at least R$300 million. On the other hand, failure to adapt to climate change would cost at least R$1.5 billion, in addition to the suffering it would cause the population.

“However, the cost could be underestimated at R$1.5 billion because the model only considers physical buildings and other structures, and the calculations are based on their imputed or taxable values. If we included losses in other areas, such as health and education, for example, the value would easily reach R$3 billion,” said José Marengo, head of research and development at the Natural Disaster Surveillance & Early Warning Center (CEMADEN) and coordinator of Project Metropolis, in an interview given to Agência FAPESP.

These calculations are part of the final results of the project, which was supported by FAPESP and the Belmont Forum, an international initiative that studies strategies for adapting to the impacts of climate change in three coastal locations: Santos, Selsey (UK) and Broward County (Florida, USA).

During the project, which has ended after four years of studies, scientists from CEMADEN, the National Space Research Institute (INPE), the Geology Institute (IG), the University of São Paulo (USP) and the University of Campinas (UNICAMP) developed three lines of research: estimating economic losses and adaptive capacities; extreme weather modeling; and health impacts. Their scenarios considered projections for 2050 and 2100.

The analysis of health impacts shows how climate change will affect all sectors of society. Investigating the link between rising temperatures and the incidence of dengue, the researchers concluded that expenditure on patient hospitalizations and treatments in Santos would rise by at least R$720,000 as a result of this connection.

“Health is a key factor that directly affects people’s lives, and so, it’s important to have these data to justify the need for adaptive measures. We estimated some of the impacts on health, but if all diseases linked to rising temperatures and flooding are factored in, we can see the real impact of this problem in the area of health,” said Luiz Eduardo Oliveira e Cruz de Aragão, a researcher at INPE and a member of the project team.

Risk analysis and the investigation of adaptive strategies, according to Aragão, identified a connection between El Niño and the rising number of dengue cases in the summers of 2010 and 2015.

“It’s well-known that El Niño causes higher temperatures, and we have now found a correlation between this anomalous temperature rise and the proliferation of dengue cases,” he said. “This link is important because it helps us understand weather patterns and their consequences so that we can quantify the impact on the city.”

Science, government and participation

Sea levels in Santos have risen at different rates since the 1940s. “Based on time series, we identified two possible scenarios for the city. One is more realistic, with sea levels rising by 0.36 cm per year. The other is the worst-case scenario, with sea levels rising by 0.45 cm per year. The conclusion was that sea levels could rise between 18 cm and 23 cm by 2050, and between 36 cm-45 cm by 2100,” said Celia Regina de Gouveia Souza, a researcher at IG and a member of the project team.

The model also considers the occurrence of extreme events, such as meteorological tides and storm surges, which are increasingly frequent because of climate change and result in rapid rises in sea level.

According to Gouveia Souza, who maintains a database of the occurrences of extreme events in the Baixada Santista area (1928-2016), the frequency of storm surges has increased significantly, as has the number of consecutive years with storm surges, since the late 1990s.

“The Santos tide gauge data tables show that the peak rise during one of these extreme events in the 2000s was 146 cm,” she said. “According to our projections, it could reach 160 cm in 2050 and 166 cm in 2100. This means that the city will be even more vulnerable to coastal floods and erosion, which will migrate toward Bairro do Embaré [Canal 4 sorroundings].”

Having produced the coastal flooding scenarios for 2050 and 2100 and having calculated the potential damages to buildings, the researchers shared their findings with the population of Santos and the local government to discuss appropriate adaptive measures.

“Options for adaptation were brought up at these town hall meetings,” Marengo said. “One option is fortification using revetments, seawalls and structural enhancements. In other cases, it’s possible to opt for beach replenishment. Another strategy we see as necessary for Santos is mangrove rehabilitation, which can be classified as an ecosystem-based adaptation.”

“The measures chosen by the public were quite adequate. We hope the project will continue under the aegis of the local authorities with ongoing popular participation. If so, the worst-case scenario is much less likely to materialize,” said Luci Hidalgo Nunes, a researcher at UNICAMP and a project team member.

The city of Santos, where Latin America’s largest port is located, was chosen by the Project Metropolis team not just for its economic importance but also because its tidal, rainfall, temperature and storm surge data time series are the best among Brazil’s coastal cities.

“Although scientists and decision makers must discuss adaptations, it has to be public policy. It must come from the government,” Marengo said. “It’s an action that cannot stop and obviously there must be investment. Santos has achieved a high level of awareness, with a broad dialogue involving the public, decision makers and academia. The construction projects must be implemented. The worst thing that could happen would be if it all stayed on the drawing-board.”

Source: Agência FAPESP