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Prevention is worth the effort

Adaptive measures would significantly reduce the damage caused by rising sea levels in Santos by 2100

Mangrove stand in the impoverished Northwest sector of Santos...

Eduardo Amaro / Instituto EcoFaxinaMangrove stand in the impoverished Northwest sector of Santos…Eduardo Amaro / Instituto EcoFaxina

Implementing measures to adapt to climate change could considerably reduce the economic damage caused to homes in Santos, on the coast of São Paulo State, by flooding from the more intense extreme events projected to occur by the end of this century, such as rising sea levels and, on a smaller scale, heavy rainfall and high tides. If nothing is done to minimize the destruction caused by these events, and the sea level rises 45 centimeters (cm) by 2100—as projected by the most pessimistic scenario of a study on the impact of climate change on that São Paulo coastal community—the damage could come to nearly R$1.3 billion. But if the city implements a list of palliative measures, such as widening beaches, dredging silted-up areas, restoring and preserving mangrove stands, and structurally reinforcing seawalls, cumulative losses could be limited to R$200 million over the next eight decades.

“We were surprised at the magnitude of the reduction in economic damage from the use of adaptive measures based on our computer simulations,” says climatologist José Marengo, head of research at the Natural Disaster Surveillance & Early Warning Center (CEMADEN) in Cachoeira Paulista, who is coordinating the research on the effects of climate in Santos. The cost of implementing the measures would come to about R$240 million, much less than the savings that would result from damage reduction. These projections come from the Brazilian arm of Project METROPOLE, an international initiative that is studying strategies for adapting to the potential impact of climate change in three coastal locations around the globe: Santos, Brazil; Selsey, a coastal town of 11 million in southern England; and Broward County, Florida, which includes the city of Fort Lauderdale. The project is doing simulations for mid-century in addition to the scenarios for 2100.

Project METROPOLE receives funding from the Belmont Forum, the successor to the International Group of Funding Agencies for Global Change Research (IGFA), which brings together research funding agencies from around the around the world and supports studies on issues related to climate change. FAPESP funds the research conducted in Santos. Study findings were presented to public authorities and representatives of civil society in Santos, in September and December 2015. “The project integrates scientific research, discussion of public policy and participation by the local population,” says geographer Lucí Hidalgo Nunes of the Geosciences Institute at the University of Campinas (IG-Unicamp), who also contributed to the research.

... and seawall in the city’s affluent Southeast: investing in these two areas could minimize the economic damage of climate change

Luiz Fernando Menezes / Fotoarena / Folhapress… and seawall in the city’s affluent Southeast: investing in these two areas could minimize the economic damage of climate changeLuiz Fernando Menezes / Fotoarena / Folhapress

The potential economic cost of climate change in Santos can be estimated only because the METROPOLE researchers have a computational tool—the Coastal Adaptation to Sea Level Rise Tool, or COAST platform—that can simulate permanently flooded areas in accordance with the sea level and the damage caused by water that floods homes in the region. The platform, developed in the United States, has to be fed a set of data from the place to be studied, such as meteorological and topographic information, the historical sea level in the region, the pattern of land occupation, geolocation, and property values. “In the United States, there is a culture of  preparation for extreme events, such as the hurricanes that affect the country,” says engineer Eduardo Hosokawa of the Santos city department of urban development. “Here, that work is still in its infancy. But the information from Project METROPOLE was well received by the public.” Hosokawa and his local government colleague Ernesto Tabuchi supplied the data from Santos, without which COAST could not function.

Strictly speaking, the economic damage caused by rising sea levels in Santos could be higher than the project’s estimate. The area covered by the study does not encompass the entire city, and it includes only one-fourth of its population. In addition, the costs calculated in the model cover only the structural damage caused by rising water to private residences. The estimated loss is based on the market value of the real property listed on the city records, which is nearly always lower than the market price. Nor do the COAST calculations include damage to other types of private assets, such as automobiles and personal property, or equipment maintained by the government, or even the destruction of the existing infrastructure. “The damage estimates are inherently conservative,” Nunes explains.

Nevertheless, the study of this São Paulo coastal community, the first of its kind in Brazil, is proving to be an important planning tool for the future of the coastal cities most vulnerable to rising sea levels—one of the principal effects attributed to climate change. The two areas of Santos that were analyzed in the research—the affluent Southeast area and the impoverished Northwest sector—are the parts of the city that will suffer the most impact from climate change. They create a portrait of contrasts and disparate vulnerabilities. Although Santos encompasses a total of 381 square kilometers (km2), nearly all of its population of 420,000 lives in a small insular area. Over 99% of the population lives on the 39.4 km2 of the island of São Vicente that lie within the city limits; the rest of the island belongs to the neighboring city of São Vicente. The two areas chosen for the study total 12 km2 and are home to 117,000 residents (10 km2 and 83,000 residents in the Northwest and 2 km2 and 34,000 residents in the Southeast).

Santos’ Northwest (in green) and Southeast (blue) sectors

Google Earth / Project METROPOLE Santos’ Northwest (in green) and Southeast (blue) sectorsGoogle Earth / Project METROPOLE

These two areas are quite distinct from one another. The impoverished Northwest is a flood invasion area that contains modest homes, favelas and stilt houses built on 20,000 tax parcels. Under a climate change scenario, its principal vulnerability is the summer floods caused by storms and high tides. The Southeast includes middle-class high-rise neighborhoods that include 1,400 parcels, stretching from Canal 3 to the Ponta da Praia neighborhood and the port, and is home to the city’s beaches. The area has suffered coastal erosion for decades, and its sandy strip is shrinking. According to the COAST simulations, the economic damage from climate change in the Southeast will be three to four times greater than that in the Northwest. The difference arises mainly from the higher property values along the beaches.

The compensatory adaptive changes that the model calculated for the Southeast—widening the beaches and reinforcing the seawalls—would cost about R$36 million, nearly six times lower than the cost of the measures simulated for the Northwest—dredging silted-up areas, restoration and preservation of the mangrove stands, and building flood barriers and water-drainage systems. “The simulations show that it is worthwhile to invest in these measures,” Marengo says. “The costs of implementation are much less than the savings such measures would generate from damage reduction in the region.”

The choice of Santos as the focus of the study was not an arbitrary decision. It was determined on the basis of two objective factors. The city holds enormous economic importance for Brazil. One-quarter of the country’s imports and exports pass through its port, an area that will clearly be affected if sea levels rise too much in the next few decades. A second consideration, perhaps more important than the first, was the existence of a historical series of records of the sea level from the 1940s to the present. That kind of information was vital input that enabled the researchers to run scenarios that take into consideration the economic losses potentially incurred if the Atlantic rose by different levels.

The maps below show areas that would be flooded (green) under different rising-sea-level scenarios

Google Earth / Project METROPOLE The maps show areas that would be flooded (green) under different rising-sea-level scenariosGoogle Earth / Project METROPOLE

Marigraph and satellite
Professor Joseph Harari of the Oceanographic Institute at the University of São Paulo (IO – USP), an expert in the study of ocean dynamics, integrated the historical data on sea levels along the Santos coast. The data from 1945 to 1990 were provided by a marigraph, or tide gauge—an instrument that measures the level of the ocean’s surface at a specific point on the coast—that was installed on a pier at the port. “From 1993 to the present, we’ve used satellite altimetry data,” Harari says. These two types of measurement employ different methodologies, but the researchers processed the data in such a way that they could be compared.

If the recent past is a reference for the future, the residents of Santos have cause for concern. From 1945 until the early 1990s, the sea level rose an average of 1.3 millimeters (mm) each year in Santos. From 1993 to 2014, that figure doubled to 2.7 mm per year. In the 2003 to 2013 period alone, the number is even higher, at 3.6 mm per year—similar to the global average calculated by the Intergovernmental Panel on Climate Change (IPCC) and the average ocean level along the entire coast of Brazil. If that pace continues to 2050, the Atlantic will have risen 18 cm in Santos in the first half of this century. And if it remains unchanged by 2100, the city will see a cumulative sea level rise of 36 cm by the end of the 21st century. Under this scenario—which the Project METROPOLE researchers regard as more realistic than the general, global projections of the IPCC—the economic damage in Santos would be slightly higher than R$1 billion over the course of the 21st century. “As for the average rise in sea level, there is nothing to discuss,” says Harari. “Measurements don’t lie. The scenarios and consequences in the next few decades will depend on what measures governments put into place.”

Project
An integrated framework to analyze local decision-making and adaptive capacity to large-scale environmental change: community case studies in Brasil, the UK and the US – FAPESP-Belmont Forum Agreement (nº 2012/51876-0); Grant Mechanism Thematic Project; Principal Investigator José Marengo (CEMADEN); Investment R$328,168.00.

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