MANILA/SAN FRANCISCO (NYTIMES) - What do you do when the sea comes for your home, your school, your church? You could try to hold back the water. Or you could raise your house. Or you could just leave.
An estimated 600 million people live directly on the world's coastlines, among the most hazardous places to be in the era of climate change. According to scientific projections, oceans stand to rise by 30cm to 1.2m by the end of the century, with projections of more ferocious storms and higher tides that could upend the lives of entire communities.
Many people face the risks right now. Two sprawling metropolitan areas offer a glimpse of the future. One rich, one poor, they sit on opposite sides of the Pacific Ocean: the San Francisco Bay Area (population seven million) and metropolitan Manila (almost 14 million).
Their history, their wealth and the political and personal choices they make today will shape how they fare as the water inevitably comes to their doorsteps.
In both places, it turns out, how you face the rising sea depends mostly on the accident of your birth: whether you were born rich or poor, in a wealthy country or a struggling one; whether you have insurance or not; whether your property is worth millions or is little more than a tin roof overhead.
And in both places, climate change has magnified years of short-sighted decisions.
Manila allowed groundwater to be pumped out so fast that the land sagged and turned into a bowl just as the sea was rising. The Bay Area allowed people to build right at the water's edge, putting homes, highways and even airports at risk of catastrophic flooding.
But people tend to hold on, often ingeniously, as the water rises around them. In some cases that's because their properties are worth a lot - for now, at least - or because they have so little that they have nowhere else to go.
Now Manila and the Bay Area face tough choices. They could adapt to the rising tide, which could mean moving people out of harm's way. Or they could try to force the water to adapt to their needs by raising their defences.
For leaders, politically tough decisions lie ahead. What do they save on the water's edge, what do they forsake, and how do they reimagine their coastal cities in an age of climate disruptions?
The Bay Area and metropolitan Manila are both big and growing, with a lot of people and things to protect on the coast. How they deal with their circumstances today may offer lessons, for better or worse, for coastal cities elsewhere.
METROPOLITAN MANILA: RISING WATER, SINKING CITY
Ms Desiree Alay-ay is in the thick of trade-offs. Ms Alay-ay, 30, grew up in a low-lying, flood-prone neighbourhood on the northern fringe of Manila. It is not what she wants for her newborn baby. She wants to move and take her parents with her.
Climate change has exacerbated a long-time problem in Manila. Because of a proliferation of fish ponds and the rapid extraction of groundwater, the ground has been sinking. As a result, since the early 1990s, sea levels have risen by as much as 5cm to 7cm a year, double the global average.
Storms repeatedly sweep away spindly-legged bamboo and tin houses on the water. People flee for a while, only to come back because they have nowhere better to go. In low-lying neighbourhoods like Ms Alay-ay's, roads have been raised multiple times. Pariahan, a village just north of the city line, is now permanently underwater.
"Climate change doesn't create its own impacts. It magnifies wrong policies," said Mr Renato Redentor Constantino, executive director of the Manila-based Institute for Climate and Sustainable Cities. "This is the case with sea level rise. A large part of metropolitan Manila is facing more water-related impacts because of decades of myopic, cross-eyed land use planning."
More than 30 years ago, before Ms Alay-ay was born, her parents, migrants from the countryside, built a small house in Malabon, the only neighbourhood they could afford in Manila.
The water pooled up in the streets every rainy season. When they were children, Ms Alay-ay and her brother sneaked out and swam in the streets sometimes. Leaky sewers meant human waste sometimes floated by, which they referred to as "bazookas". Only tricycle cabs could ply through floods; when the water rose, her parents took her to school in a rented boat.
The city fought back by raising the road. So Ms Alay-ay's parents raised their house to stay above the road. They poured cement and sand on the floor four times in 30 years, as if adding layers to a wedding cake.
Everyone lived like this. One neighbour raised the floor so high that the original kitchen sink is now ankle-high. Another abandoned the house altogether; its roof is barely above street level now, and water hyacinths have taken over the rooms.
It was only after Ms Alay-ay had a baby that she set her mind to getting out of Malabon.
"I want my baby to have a good future," she said. "I don't want him to experience what I've experienced."
She wanted her parents to come, too, so they could watch the baby while she and her husband went to work. But they had other plans. Leave the baby with us, her mother, Ms Zucema Rebaldo, offered. But we're not moving. This is our home.
"This was a happy place for us," Ms Rebaldo said on a Sunday afternoon. "Even if people say one day it will be wiped out from the map. No question, I am staying."
Ms Alay-ay's dilemma is magnified manyfold in a megacity like Manila.
Millions of the city's poorest live in hazardous, low-lying areas that are already lashed by tropical storms. Climate change is projected to make those storms even more intense and more frequent.
But leaving those areas can mean being even farther from where you make a living. Or losing the neighbourhood health clinic you've been going to for years. Or being marooned in a neighbourhood where there are no tricycle cabs, let alone public transportation.
Forcing people to move away from the coast is not enough, said Ms Antonia Yulo-Loyzaga, a member of the board of directors of the Manila Observatory, a research organisation. They need to be able to find work nearby or have an efficient public transportation system to get there. That doesn't exist now; average commutes are two hours or more each way.
"You need some sort of rational, organised retreat from the coast," she said. "There's no option unless you want people to live in constant fear."
SAN FRANCISCO BAY AREA: A POLITICAL LIGHTING ROD
A rising sea underscores the missteps of the past in the Bay Area, too.
The Pacific has risen 10cm to 20cm along the Northern California shore over the last century - and so, too, the San Francisco Bay, the ocean's largest estuary in the Americas.
Depending on the growth of greenhouse gas emissions, the Pacific could rise 70cm to 1m by 2100, which is why the California Coastal Commission has encouraged city governments to start planning for the future - by fortifying their flood defences, restoring wetlands or, in some instances, making people move.
That is as difficult in the Bay Area as it is in Manila.
"People's properties and investments are at risk," Mr Jack Ainsworth, head of the commission, said in an interview. "It becomes very political and very emotional."
Unlike Manila, Bay Area municipalities are wealthy. And many of them are already paying handsomely to fortify high-value coastal infrastructure at risk.
Voters in San Francisco have approved a US$425 million (S$590 million) bond measure to start fortifying a sea wall along the bay-front road, the Embarcadero. Along the road sits some of the city's most expensive real estate; below it sits a subway line, a light rail tunnel and part of the city's sewage infrastructure.
Meanwhile, the builders of a new real estate development in a former industrial area called Mission Creek are raising the old roads and warehouses by as much as 3m. And the San Francisco airport, which sits on tidal marshlands, is getting a US$587 million makeover to raise its sea wall.
Farther south, a suburban community called Foster City, built on steadily subsiding landfill, has raised property taxes to increase the height of a levee that protects the area from storm surges. Nearby, county officials have rebuilt another levee to protect a golf course along with a low-income community called East Palo Alto.
And on San Francisco's rugged Pacific shore, on Ocean Beach, a caravan of dump trucks is shifting sand to control erosion, while a portion of the adjacent coastal road known as the Great Highway is being moved inland.
"We basically built everything just about at the high-tide line," said Ms Laura Tam, a policy director at Spur, a Bay Area urban planning and research group. "Nothing was built thinking of future changes in tides. We didn't think about sea level rise."
Nowhere is the danger more starkly on display as it is in Pacifica, a suburb south of the city, where coastal bluffs are so swiftly eroding that city officials have already demolished some properties before they could fall into the water.
The soft, sandy bluffs have been eroding for thousands of years. Climate change is accelerating that process, though, said Mr Charles Lester, a former Coastal Commission official who now directs the Ocean and Coastal Policy Centre at the University of California, Santa Barbara. The tides are higher, and the waves are more frequently coming up to the foot of the bluffs.
On a gray Monday morning, Mr Lester stood at the edge of the bluff on the north end of town on a walking path that ribbons around an apartment complex called OceanAire. He pulled up on his phone a picture taken in the 1970s, when the complex was built: A wide grassy lawn lay in front. That's gone.
Even when he first came here 10 years ago, the bluff was 27m wider. The bluff has stepped back since then. Today, at its narrowest point, a few steps separate an apartment balcony from the cliff's edge.
A sea wall had to be built - and then rebuilt after it failed. A pile of boulders sits at the bottom of the wall to stave off damage from the waves.
"I see the challenge that the entire state and many states are facing: how to manage development along an inherently hazardous shoreline that is going to be increasingly hazardous under sea level rise and climate change," Mr Lester said.
All that armoring, as it's known, has saved the apartment complex. But it has come with a public cost: The beach has narrowed. In some parts, there is no beach left.
That is the problem facing many Bay Area communities: How much do you armour the coast, what do you choose to save, and who will have to move? Managed retreat, as it's called, has become a political lightning rod.
Money complicates matters in other ways: Property taxes are a key source of revenue. Forcing people to move away would punch holes in city budgets. And anyway, who would pay to buy out homeowners? Pacifica, for instance, can't. Some single-family houses on the bluff are worth upward of US$1 million.
Already, there's been unmanaged retreat in Pacifica. Some sea walls crumbled, at one point endangering a row of apartments. The 52 tenants were entitled to zero compensation. They just had to move - in one of the most expensive counties in the state. The city spent US$620,000 on demolition.