Christmas is a big deal in Puerto Rico – celebrations traditionally run from November to February – but festivities are in scant supply at the end of 2017. On a hot and sweaty morning in mid-December, Pablo Méndez Lázaro and a band of volunteers are delivering not Christmas presents but essential filtration systems, food and medical supplies in the eastern interior of the island. At each house, the volunteers show residents how to purify the water they’ve collected in their backyards.

From the filter pouch, through the tubing, into the plastic bottle below. A basic act of alchemy transforms the contents of rain buckets, muddied by mosquitoes and sipped by any number of cats, into water fit to drink, clean wounds or even just wash dishes.

“Water is life,” says Méndez Lázaro, who has demonstrated this trick hundreds of times in the preceding weeks. “For a few months we can live without hospitals, without shopping centres, but, without water, no one can live.”

Water was in no short supply on 20 September 2017, when Category 4 Hurricane Maria cut like a buzz-saw across the island. The storm ditched two to three feet of rain, flooding houses and hospitals, while raging winds tore roofs off houses and electrical transmission towers from the ground, plunging the island into darkness.

Climate change may have played a role in the disaster – warmer ocean temperatures generally feed stronger storms. But even before the hurricane, exceptionally hot days, air pollution and sea-level rise – all symptoms of a changing climate – had already been taking their toll on the islanders’ health and financial stability.

The catastrophe in Puerto Rico may therefore be a worrying harbinger of a future for other countries and regions facing the effects of climate change. How the island’s recovery unfolds, and whether Puerto Ricans are able to rebuild so they might withstand future extreme events, could hold valuable lessons for the world as a whole.

Here, it is grassroots groups of volunteers who are pulling the island out of its crisis and carrying out the day-to-day fundamentals of the recovery response. The hurricane has taken its toll in a myriad of ways across Puerto Rico, but individual communities know best where their weaknesses and strengths lie and how to respond. Their example shows that, when it comes to preparing for and adapting to climate change, it might just take a village.

Hurricane Maria hit early in the morning on the south-eastern side of the island, near the harbour at Yabucoa. Winds that sometimes peaked as high as 120 miles per hour flattened some houses and tore the roofs and doors off others.

“One of the most striking effects was the sound,” says William Gould, Director of the US Department of Agriculture’s Caribbean Climate Hub, whose cement house is on the east side of the island. “It was a whistling sound, like a cat wailing or a freight train. And it was not a storm that came in gusts. It was just sustained, unrelenting.”

Gould’s house began to vibrate. Concerned about the windows blowing in, Gould and his wife put their nine-year-old son in the shower with a flashlight and toys and sat in a windowless passageway to wait out the storm.

While the winds sounded like jet engines, the storm itself travelled slowly. Over 50 miles wide, it ambled across the island like a voracious monster eating everything in its path. It spent the morning hovering over the mountainous regions, drenching them in feet of rain until the waterlogged soil began to slide down the hillsides, crushing houses and burying roads.

The fifth-strongest storm to ever hit the USA and the deadliest to pummel Puerto Rico in 80 years, Hurricane Maria decimated the electrical grid and mobile phone networks and flooded hospitals and entire neighbourhoods. The rains triggered more than 40,000 landslides and washed away roads and bridges.

When the sun set on 19 September, Puerto Rico had been a lush, verdant island with abundant forests and farms of coffee, plantains and pineapples. When Gould finally emerged from his house, it was to a different world. No longer a rich palette of many shades of green, the forests and hills appeared a sterile scene of brown and grey. “It was like every leaf had been torn from every tree,” Gould says.

In the immediate aftermath, islanders had to live with no power, no stores, limited fuel for generators and driving, and no way of communicating with the outside world. “You need food and water, and it was pretty scary that they were not available,” Gould says. “What more basic concerns do you have for yourself and your family?”

As the eye of the storm hadn’t passed over the capital, San Juan, the destruction there, although severe, was less than in other parts of the island. Quickly neighbours started helping neighbours, and volunteer groups started to sprout up.

Physician Alfredo Ayala, working with nurses from the mainland, was one of the first responders in many towns. “People were crying for water, people were crying for food and they were helpless,” he says.

The hurricane left the island’s hospitals without electricity, and they also had limited access to generators and fuel to operate lifesaving equipment like haemodialysis machines and ventilators. Many people had to fly to the mainland, if they could, to receive treatment.

“A lot of communities didn’t suffer that much because of the hurricane,” Pablo Méndez Lázaro said shortly after the disaster. “But because of the lack of accessibility and lack of infrastructure, they are now totally vulnerable.”

Puerto Rico Ports Authority agents deliver food and water to those affected by Hurricane Maria in the mountains around Utuado, Puerto Rico. (Photo: US Department of Agriculture/Flickr)

Méndez Lázaro is a professor of environmental health at the Graduate School of Public Health in San Juan. He investigates the impacts of environmental changes on the health of Puerto Ricans.

In 2014, he wrote about the impact of natural hazards on public health systems in tropical areas, warning that government agencies and hospitals needed to prepare for both the gradual impacts of climate change and extreme events such as hurricanes or hot spells, which may become more frequent and intense in a warming climate: “If these systems deteriorate, the population’s welfare and health may be jeopardised.”

Now Méndez Lázaro is a player in his own dire predictions.

His prescience reflects a growing awareness in the scientific and medical community that climate change can have an impact on public health – and it’s already happening. In 2017, the Lancet Countdown, an international research collaboration that tracks progress on health and climate change, released a report documenting a 46 per cent increase in extreme weather events between 2000 and 2016, such as the 2003 heatwave that led to over 70,000 more deaths than expected across Western Europe.

The report also proposed that the rising temperatures associated with climate change have influenced the spread of infectious diseases. Since 1990, reported cases of dengue have doubled every decade. The greenhouse gases that cause climate change also pollute the air, contributing to increasing rates of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases.

Aside from these most obvious impacts, climate change has indirect influences on human health: droughts and floods impact food security, and rising sea levels and storm surges claim people’s homes.

“Climate change is a threat multiplier that undermines all of the basic determinants of public health, from clean air to access to safe drinking water, nutrition, shelter, and freedom from infectious disease,” says Nick Watts, Executive Director of the Lancet Countdown. “You really can’t turn your head left or right without seeing interactions between this global environmental change and public health.”

If the medical community wants a poster child for the impacts of climate change on health, they need look no further than Puerto Rico. Over the 20th century, average annual air temperatures in the Caribbean islands have gone up by more than half a degree Celsius (more than 1°F), and San Juan experiences an increasing number of extreme heat days each year. These hot spells can cause heat exhaustion or heatstroke in even the healthiest individuals, but in vulnerable people they can exacerbate cardiovascular disease, diabetes-related conditions and respiratory diseases such as asthma. Children in Puerto Rico have the highest rates of asthma in the USA.

Like islands in the South Pacific, Puerto Rico has seen the sea rise by more than 6 inches since 1880, and that could reach 22 inches by 2060. As the island is relatively flat near the ocean, rising sea levels could lead to a retreat of the coastline of up to one metre a year. Houses, roads and fields will flood; seawater will inundate the freshwater supply.

Severe storms and hurricanes have caused nearly 80 floods on the island in the last 25 years. With flooding comes an increased risk of infections carried by insects as well as contaminated food and water.

By July 2016, more than 5,500 people in Puerto Rico had tested positive for the Zika virus, which is spread by mosquitoes and causes severe birth defects in developing fetuses. The epidemic appeared to be over before Maria hit. But health officials are now concerned that pools of stagnant water that formed after the hurricane could provide a perfect breeding ground for mosquitoes and cause an uptick in Zika and dengue. Even before the disaster, Méndez Lázaro’s research had warned that warmer temperatures and higher sea levels made for more dengue transmission in San Juan.

At the beginning of 2017, Puerto Ricans were already the USA’s poorest citizens, with a child poverty rate of 58 per cent. The island carried about $74 billion of crushing debt and a tenth of the population had relocated to the mainland since 2007; in 2016, doctors were leaving at a rate of nearly two every day. By the summer of 2017, Puerto Ricans were in no position to maintain their ageing power company, and it declared bankruptcy in July. Power outages were already common.

“Maria didn’t cause everything. Maria just revealed to the world how we are living,” Méndez Lázaro says. “For us in academia, it was not surprising to see that we have a lot of people suffering and we have misery, we have poverty, disabilities and chronic disease.”

The volunteering day starts early and, in the dim dawn light, Méndez Lázaro picks me up from Plaza Colón in Old San Juan in his blue Dodge pickup, the back already laden with water bottles and filters. At the plaza’s centre stands a tall statue of Christopher Columbus, who arrived in Puerto Rico in 1493. For the next 400 years it was an overseas province of Spain before becoming a US territory with a population today of 3.3 million.

It takes time to drive out of San Juan – many of the traffic lights still don’t work in this city of nearly 350,000 people and almost as many cars – but when we meet up with the other volunteers the morning light is still grey. We collect outside the Caribbean Cinemas, which sounds exotic but isn’t, with its blown-out windows and boarded-up doors.

Beyond the city outskirts, signs of the hurricane become more pronounced: trees ripped from their roots, toppled electricity poles, heaps of wires, cables and debris lying by roads or on sidewalks.

The volunteers chat and introduce themselves while waiting for more to arrive. There are researchers from the School of Public Health and two medical students. And brothers Carlos and William Preston, both in the construction business, who assess the damage while volunteering and then send their crews back to do repairs. Carlos, looking slightly intimidating with his brawny build and square-cut jaw, sports a bright yellow T-shirt emblazoned with the words “Todo Saldrá Bien”: everything will be fine.

Medical student Mónica Abuela says while her role is to check people’s vitals – pulse, blood pressure, the rhythm of their hearts – sometimes it is important just to listen. “It has been so hard on everybody just changing their routine completely,” she explains. “And to talk is a basic human need.”

When the last volunteer arrives, we divide into two vehicles. Those sitting in the back of Méndez Lázaro’s truck are squeezed between supplies packed in bags with “Prevention of Zika and family planning starts with you” printed in Spanish on each one.

These volunteers have been working on relief efforts for the last three months. Today, the group is travelling to Montones, where they’ll distribute bottled water, food, insect repellent, and baby formula and diapers as needed. Nearly 100 days after the hurricane, half the island is still without power and, more importantly, access to clean water. “We need water more than we need electricity,” says Minerva Gómez, a slight and vivacious householder who is looking after three generations under one roof.

Having arrived at Montones, the group disperses: while the public health researchers demonstrate how to filter water, the Preston brothers start assessing where repairs might be needed. The medical students carry out basic health checks, clean wounds and caution residents to use bug spray and get rid of stagnant water, although it is often the only water they have.

In front of one resident’s house, Méndez Lázaro points out the many skinny cats and dogs that sniff around the rainwater buckets. Puerto Ricans love their animals – one Montones resident sat out the storm in his kitchen along with his 30 cockerels – but the close mingling of humans and their pets is yet another health hazard when it comes to storing water.

The householders appreciate the donations and attention. One woman offers each volunteer boiled confectionary from a plastic container by way of thanks. The public health researchers carefully pick out wrapped candies; the others risk a bare sticky sweet only to slip it in their pockets when the woman isn’t looking.

A couple of hours later, the volunteers regroup to drive to another part of Montones. While felled electricity poles still line the side of the road, the neighbourhood is resplendent in the bright green of new growth. Méndez Lázaro excitedly points out a mango tree starting to bear fruit. That morning he stopped his truck to buy two giant avocados from a street seller, even though they looked unlikely to ripen for months.

“The electrical system collapsed, the water system collapsed. The only system that didn’t collapse at all is the ecosystem, and you can see that right now,” he says. “So we have evidence that the ecosystem is one of the ideas that we need to follow.”

In the weeks that followed the hurricane, Méndez Lázaro was among those gathering donations of water filters from international and grassroots non-profits and going house to house. Getting information to people – especially in the mountains – proved challenging. “They are totally disconnected from reality. They have no televisions, they don’t have electric power to turn on the radio, they don’t have internet, and they don’t have access to Facebook,” Méndez Lázaro says.

The government’s strategies relied on communications and it simply wasn’t prepared for the scale of disaster it was facing, so the recovery efforts depended entirely on such grassroots efforts. “In the beginning it was all done by the communities,” says Méndez Lázaro. “When you ask the community leaders who were the first responders after the hurricane everyone will tell you the same thing.”

Another of those first responders, the physician Alfredo Ayala, founded the Rogue United Corp., fuelled by online donations, to continue his work. “Our mission is that we go where nobody goes,” he says. “Because even though there has been a hundred days after Maria, if you go to a mountain area and you make a left, then you make a right and then another left, you’re going to find people that do not have a roof, they don’t have their medicines, they’ve lost everything.”

During his rescue operations, Ayala saw that many people couldn’t make the drive to healthcare facilities, assuming they were even staffed, and were running out of vital medications. With communication networks down, physicians had no means of assessing what medications people needed, or how much.

Six weeks after the hurricane, 83 of the 93 health centres on the island had reopened, but at least 60 had no power and were running with generators only. “Thank God no outbreak happened in Puerto Rico because no hospital was ready to receive something like this,” Ayala says. “There could have been a dengue outbreak, a Zika outbreak, a Giardia outbreak or an E. coli outbreak and we were not ready.”

Without power to pump water into homes, access to clean drinking water was nonexistent. Health workers became troubled that people were drinking from contaminated sources and rescue workers tried to distribute bottled water where they could. Without electricity, the ‘boil water advisory’ proved impossible to follow, and for many, even months after the hurricane, it still is.

Homes on a hillside in Puerto Rico damaged by Hurricane Maria. (Photo: Air Force Magazine/Flickr)

On my final day in Puerto Rico, I’ve arranged to meet a volunteer in Utuado, a district in the central region of the island known as La Cordillera Central. As soon as I take the winding, seemingly unmarked road into the mountainous jungle, it’s as if the hurricane happened only last week. Canopies of bowed trees stretch across the narrow, broken roads and nests of electrical cabling hang down from tilted poles.

Driving slowly to dodge the potholes and fallen wires, I have to squeeze through narrow passageways carved out of a landslide every 800 feet or so. Peering up I see a teetering mass of rocks, sand and trees looking ready to topple, and glancing down I can see where the morass has engulfed walls, sheds or cars. To top it all, it is raining. Hard.

When the hurricane hit, the rains turned the river here into a vicious torrent that wiped out the bridge connecting the town of Utuado to the rest of the municipality. The cut-off neighbourhoods went 15 days without food or water supplies and they named themselves El Campamento de los Olvidados, the Camp of the Forgotten Ones. Damage in these rural suburbs was especially severe: wind flattened houses, landslides blocked roads and many residents were isolated from the outside world for weeks.

The town itself, although savaged, fared better than its ‘forgotten’ suburbs. “Climate change is a global phenomenon that impacts individuals locally – very, very locally, on a street-by-street basis in different ways,” says the Lancet Countdown’s Nick Watts. “So when it comes to how we adapt to climate change, that depends entirely on what you and your community need.”

Echoing what he wrote in 2014, Méndez Lázaro says Puerto Rico needs to be recreated in such a way that it is resilient to stronger and more intense storms and also the slow creep of climate change: “How we address sustainability is by building for the future, not rebuilding what we had before.”

One way would be to decentralise. Replace the electricity grid with local renewable sources such as wind and solar. Design hospitals to be more resilient to flooding and with their own utilities, learning from the Texas Medical Center’s rebuilding efforts after Tropical Storm Allison in 2001. When Hurricane Harvey flooded the streets of Houston in August 2017, the medical centre stayed fully operational.

Méndez Lázaro is talking with non-profits and health organisations to bring decentralised primary health services to Puerto Rico, especially to rural areas like Utuado. His idea is to have community health workers that would know each neighbourhood, its vulnerabilities and strengths, and promote health through sharing knowledge and building required skills. “We need to learn to do things on a mini scale with the knowledge of the community,” Méndez Lázaro says.

“You need to have qualified people in the community who know how to do treatment of the water, or to maintain the quality of the water, and how to distribute the water the more efficient way,” he adds. “Let’s give them the education and the capacity to do this – that’s the way to build adaptive capacity.”

Alfredo Ayala is using a similar approach. His long-term mission for Rogue United is to create a network of independent citizens who learn to collaborate with hospitals, health clinics and non-profit foundations, with the goal that, in the future, the first response will be complete in weeks, not months. “The next time a hurricane comes here, we will already have a task force, a non-governmental, non-bureaucratic task force that has nothing to do with politics,” he says.

Puerto Rico’s key weapon in the face of climate change is its culture of community, as it has demonstrated in abundance in the recovery efforts: grassroots volunteer groups, neighbours helping neighbours, people drawing together to rebuild houses, find supplies and distribute food and water. Méndez Lázaro says that the government needs to recognise this powerful asset and work with it in building more resilience into the island: “We have the potential to recover, and that is because of the communities.”

“Climate change probably represents the biggest threat to human health over the next 10 or 20 years,” says Ashish Jha, Director of the Harvard Global Health Institute. Although national efforts will be key to coordinating our responses, Jha predicts more community-based approaches to public health will emerge. “Ultimately, you’re going to need to see local municipalities and cities and towns really take ownership of health,” he says. “That’s going to be much better for a variety of reasons, not the least of which is that it’s going to help countries and places be much more resilient when challenges strike.”

To an onlooker, the current situation in Puerto Rico might appear unique. And it is. Before the hurricane the country was in economic decline, and the fact that it’s an island means that it faces specific challenges in recovering from the disaster and rebuilding in preparation for future storms. But many similarities exist between the situation in Puerto Rico and other regions of the USA, still the richest nation in the world and, in theory, the most able to cope.

Less affluent countries also face sea-level rise, air pollution and extreme weather events while grappling with ageing infrastructures and diminishing access to clean drinking water. “I know that this is not a uniquely American problem and that we’re going to see other countries’ health systems struggle when you have extreme weather events,” Jha says. “We’re going to see a lot more of this. We just have to get prepared.”

The path to resilience in Puerto Rico will undoubtedly be expensive. But preparing for climate change will be much less expensive than dealing directly with its aftermath. It is estimated that Hurricane Maria will cost the economies of Puerto Rico and other US territories nearly $48bn in gross domestic product. According to the World Health Organization, the direct global health costs of climate change could be as high as $4bn per year by 2030, and the indirect costs, related to impacts on water and food supplies, are likely to be much higher.

The costs to human health from climate change could also be high, but the good news is that taking action on public health and climate change are mutually beneficial goals. Air pollution, including the effects of greenhouse gases, caused 3.7m deaths worldwide in 2012. If governments promote greener transportation systems and encourage more cycling and walking, they could reduce air pollution and improve public health at the same time.

“Much of what we want to do to respond to climate change is just common sense public health,” Watts says. “That’s the real positive there, and that helps us shift this narrative away from, ‘The response to climate change is expensive’. These are win–win choices.”

It’s late afternoon and I am still driving through Utuado, unable to find or call my contact. I feel like I am caught in an Escher drawing, forever destined to be going up one hill, taking a sharp right and down another, only to find myself back on the same potholed road as before. Then, as I turn yet another hairpin bend, I stumble across the tropical equivalent of an oasis in the desert: a nativity scene with a Father Christmas and a snowman built out of used car tyres.

Miraculously, the rain stops for a few short moments and I get out to puzzle at a broad-leaved, strangely decorous evergreen tree, hung not with electric lights but with 30-odd Coca-Cola cans. Around the tree stand an array of figurines – brightly painted slats of wood – many of which bear signs. The centrepiece, a wooden Puerto Rico flag, reads: #FuerzaPuertoRico. Created by a San Juan newspaper, this hashtag calls for “Strength, Puerto Rico”.

The rain starts again and I get back to my tortuous journey, wondering if I will get out of this warren before sundown. As the daylight fades it’ll become impossible to navigate the treacherous roads, and I could be spending the night in my car. But, for now, my heart is a little more fortified.

When I make it back to San Juan later that night, I find a message from Méndez Lázaro, checking I’d survived the mountain mayhem. I feel touched and grateful for the care and concern of the volunteers, who had been really worried about me driving there alone.

What has happened in Puerto Rico is nothing short of a cataclysmic tragedy for the island, its economy, its people and their health. The aftermath of Hurricane Maria shows how the impacts of our developing environment are quickly moving from abstract scenarios to grim reality. It is a call to action for every country, every community, to start preparing for the metaphoric storms that are already on their way.

But the actions of Puerto Ricans send a message of inspiration to others struggling to survive in a changing world. The people of this small island have come together heroically to help their communities survive and recover. “We created such a team effort that now we know that we are safe whatever comes,” says Ayala. “As human beings, as brothers and sisters, we can do so much.”

He draws my attention to the new growth of trees and plants. Foliage is back in force, enveloping the island in luminescent green. “It is so beautiful,” he says. “And it makes me think that everything is going to be all right.”

One species held particularly strong during the hurricane – the tabonuco tree that grows in the rugged mountains of Utuado. The roots of these trees knit together and, when the high-speed winds hit, they clung to the ridge tops, holding each other up. Certainly a few tabonucos were damaged. But through the complex labyrinth that connects them, their neighbours sent them nutrients, reviving them. They’ll survive.

This article first appeared on Mosaic.