Anisa* was 11 years old. Leaving her war-torn country with hopes of a better life in Europe, she travelled by foot and lorry from Afghanistan to the shores of Turkey, before cramming onto a Greece-bound boat with 300 other refugees. She made it. Her parents and four siblings drowned at sea.

That was three weeks ago. Tonight the conditions on Lesbos island are even worse: steel-grey water whipped by a vicious wind. Just 6km away across the Aegean Sea, thousands of refugees are packed onto the beaches around Izmir, Turkey, anxiously waiting to travel across the water in boats and dinghies. They're assured by people-traffickers that they'll travel safely. The reality? Inflatable 'death boats' – maximum capacity, 15 – are packed with up to 70 people, a malfunctioning engine and no captain. Each £1,500 'seat' comes with three guarantees: no refunds, no returning, no second chances. Those who suggest the boat's too full or unseaworthy are beaten, raped or shot (one woman arrived from Turkey with several family members, three bullet holes and no heartbeat). Some boats manage the crossing. Many don't.

For months we've seen and read reports of refugees arriving in Greece and of the hellish journeys they've endured. But as the winter approaches, the situation at the bridgehead of Europe is getting worse. As our governments talk and argue – reluctant to provide humanitarian aid for a crisis in the non-developing world – it's the volunteers that are having to pull together to coordinate the refugee rescue effort.

They're dealing with statistics that are impossible to digest. Already this year the UN High Commissioner for Refugees (UNHCR) has declared 3,510 refugees dead or missing in the Mediterranean. I hear all the numbers, yet it's only when I'm confronted with the brutal evidence that it starts to sink in. Driving along the island's pitch-black northern coastal road, I see the silhouettes of countless capsized boats littering the shoreline, while punctured dinghies roll lifelessly in the water. Heaps of abandoned orange life jackets and children's arm bands – the kind you'd teach your toddler to swim in – scatter the side of the roads in huge, sorry piles. "Oh they're fucking everywhere, mate," says Kenny, a thirtysomething tattooed volunteer from Scotland, responding to my shock. "Fucking everywhere." He floors the accelerator of the volunteer van and necks a Red Bull in preparation for a night shift. Sleep doesn't come often, or easily, for many on this island.

While some parts of Lesbos remain largely unaffected by the refugee crisis, it's the northern towns around Molyvos Harbour that bear the brunt of the 728,910 arrivals in Greece this year. Refugees have been attempting this particular route to safety for decades, but it's one particular boat in November 2014 that Melinda McRostie, long-term resident and owner of the Captain's Table restaurant, remembers. "I gave them some dry clothes, sugary tea and food," she tells me. "That was the start of it. I'd help one boat a week for a few months. Then there were two boats. Now, on our busiest day, we've had 6,000 refugees arrive in 24 hours."

The situation has – by her own admission – fallen into her lap. Firstly, there's the location of her restaurant, right on the pretty harbour. Then there's her character: kind but fiercely passionate; she's a relentless hard-worker. Starfish, her volunteer-run organisation that's just been granted NGO status, helped 60% of the estimated 210,000 refugees who arrived on Lesbos in October.

The boats – making a profit of £300,000 per journey – will soon be sent over in perilous conditions. thousands will die

She answers my questions with a jaded smile; there's a severe emotional strain and huge amounts of responsibility grinding Melinda down. As well as coordinating around 80 volunteers, the nature of her role means she's often confronted with harrowing situations. Seeing a child fleeing from a warzone only to die on your doortstep is not a sight you can easily forget.

"We're in the process of trying to find a psychologist to man a hotline for volunteers who've witnessed particularly traumatic scenes here," Peggy Whitfield, one of the lead long-term volunteers at Starfish, tells me after describing horrific accounts of boats that didn't make it.

I'd been warned before my arrival to prepare for the inevitable – some volunteers undergo months of counselling when they arrive back home. But my timing has spared me. For the first time in weeks, strong winds mean that any boats attempting the crossing are blown straight back into the Turkish coast, and are therefore unable to start the journey over. On the one hand, it's giving volunteers time to set up logistical strategies for the harsh winter months, while on the other it's making them tense. Selling refugees tickets to Greece is a lucrative black-market business for Turkish smugglers, and greed overtakes logic. The boats – making a profit of up to £300,000 per journey – will soon be sent over in perilous conditions. Thousands more people will die.

It's a huge worry for Henrik Kjellmo Larsen, chief coordinator of Drop in the Ocean, who works closely with Starfish to help arriving refugees. At 23 years old he may be one of the younger volunteers here, but the Norwegian-born Durham University graduate has some serious clout. Driving along the 15km of coast between Eftalou and Skala, he dishes out punchy, efficient instructions to his team of 'spotters' with an endearing Norwegian-Geordie twang. At each of the four clifftop lookout zones, pairs of binocular-clad Scandinavians gaze out to sea. They'll be swapped every few hours, while there are also lookouts at night – people-trafficking is a 24-hour operation.

The economic impact

While Greece's third-biggest island works to handle the volume of refugees taking this route to Europe, there's another issue at stake here. Many locals are sympathetic, but confused and scared by the impact this is having on their tourist-dependent businesses. Already a number of flight routes to the island have been cancelled for summer 2016, and hotel bookings are virtually non-existent. "I've lost a lot of friends because of what I'm doing to help here," Melinda McRostie, founder of Starfish, told me. Along with volunteers, the island needs holidaymakers. Those who visit will experience a kind, spirited and hard-working community.

Systems here aren't sophisticated ("We've got a fucking radar on top of a Hertz hire car," Kenny tells me the night before), but they are effective. Communicating via WhatsApp, Henrik's team can keep in touch with other volunteer groups, lifeguards and the coastguard to try to ensure there's always someone there to meet incoming refugees. "We can't stop the war," he states, "but we can make a difference for individuals."

For successful crossings, that can be something as simple as a selfie with a boat full of young teenagers – the ubiquitous 'happy gloat' that's uploaded online when the refugees reach Wi-Fi. For those who've had particularly difficult journeys, or been rescued after hours in the water, that difference comes in the form of consolation, dry clothes and simple conversation: "They want to speak to you when they arrive, it's cathartic for them to tell their stories," Peggy says, while showing me pictures of new Facebook friends who have travelled on to Germany via Athens and the Balkans.

The coast looks so close. In the Greek sunshine, and surrounded by friendly volunteers, I'm struggling to visualise the island in rescue mode. But it's back on the beach that I'm reminded again of the severity of the situation: the sea is littered with the weather-beaten shells of three sunken boats and yet more deflated dinghies, while nearby an archetypal Greek grandma dozes underneath an orange tree. On this island, both represent a dream for photographers: "With each new boat arrival we have a douchebag test," Henrik says, explaining the volunteers' constant battle. "Are you going to help this 80-year-old lady out of this boat, or are you going to take a picture of this 80-year-old lady falling into the water?"

People of all ages are forced to make this journey. Over the last few months, entire families from Syria, Iraq, Afghanistan and more have attempted the perilous crossing, often with week-old babies and toddlers in tow – the latest UN stats show that approximately 26% of arrivals into Greece are children, and many are forced to travel unaccompanied. "I've seen so many empty-eyed kids. There's nothing there," Henrik tells me, shaking his head. "We're looking at a whole generation suffering from post-traumatic stress disorder." Alongside a boat overflowing with armbands and colourful rubber rings, a sodden teddy lies washed-up on the beach.

A lot of new arrivals land traumatised by their crossing – many of these people have never seen open water, let alone know how to swim – but coming into the winter months, volunteers are also worried about hypothermia and cholera. I meet Safwat, a softly-spoken twentysomething doctor from Palestine who has come to provide medical assistance and arrange logistics for a group of doctors who will join the volunteers in January. He tells me he felt compelled to come because he knows what it's like to live in conflict, describing his situation in Palestine as "comfortably numb". His command of Arabic, and his medic network, makes him an invaluable volunteer, although Lesbos is not in a position to be picky. "That's the one time I've felt helpless here," Henrik tells me, recalling a night he was summoned to the harbour to translate the instructions of a Norwegian defibrillator that was being used on a child who had drowned. "At that point I wish I had trained as a doctor, so I could perform CPR instead of trying to translate the instructions." Even with volunteers like Henrik and Peggy working 20-hour shifts, clearly assistance is needed.

We continue to tour the north of the island, skirting along the coastal road and stopping every few minutes to chat with volunteers and check for updates. Along with an intensely hard-working attitude, there's a powerful community spirit here. The island priest – a young Californian guy with a ponytail, who wouldn't look out of place in a surfwear ad – travels by moped, handling administrative logistics, while the coastguard – who probably dealt more with yachts and holidaymakers a few years back – now patrols the water every day. Elderly fisherman often rescue boats in distress.

Palestinian doctor Safwat felt compelled to volunteer because he knows what it's like to live in conflict

Elsewhere on the island in the car park of Oxy – a clifftop building that was a nightclub-with-a-view in a former life – volunteers are in clean-up mode. This is Starfish's transit area – the place where refugees are given blankets, shoes and shelter in UNHCR-supplied, Ilea-designed tents. Some have created a charging station for people's mobiles (letting family know they've made it is priority on arrival), while others issue bus tickets and clean toilets. Then the crowds are lined up (Syrians in one queue, other nationalities in another) to be transported by bus to the overnight camps in the south of the island.

But the worst is far from over. In the military-run Moira camp (set up for refugees from Afghanistan, Eritrea and Iraq; Syrians are transported elsewhere) the remnants of last night's campers scatter the floor – blankets dispersed with baby food, rubbish and mud. Makeshift tents have been strung up on the flood-prone slopes of an olive grove, while barbed wire lines the perimeter of the old prison, where refugees queue for hours to register in Greece, before continuing on their seemingly never-ending journey.

Most of yesterday's arrivals have already left for the ferry to Athens, determined to keep moving before temperatures fall to freezing. But there, among the olive trees, a lone 60-year-old man paces. His English is broken, and my Farsi's non-existent, but I manage to work out what he's asking for. He rubs his face and smiles, but he looks defeated and apologetic: his dishevelled appearance is clearly bothering him. He wants to borrow a razor.

"You don't lose a reality by taking a journey that labels you a refugee," Henrik had told me earlier. "They are just like us. In fact," he adds, "I prefer to use the word 'people' instead of refugees. These are people running from war and terror, after all."

I'm constantly struck by the volunteers' kindness and dedication. They tell me that it feels right being here; that it feels so much more worthwhile than any job they could do back home. "The reaction of any normal human being is to help," Peggy says again.

But more help is needed. "Life is like a supermarket," one refugee told Kenny after he lost his entire family while crossing the water from Turkey to Greece. "You come in, pick up your basket, make your choices and check out. And that's when you pay for your choices."

*The girl's name has been changed for protection. Hannah joined Starfish NGO during her time in Lesbos. The team is in need of donations and volunteers. asterias-starfish.org