Since 2008, over 400,000 Irish people have emigrated; testing the waters and starting new lives in the UK, the US, Canada, Australia and far beyond.

Each journey – be it for a year-long J-1 visa or the next 50 years – will change the person who takes it, and the collective fact – whether we talk about it in terms of 1,000 people a week, ten people an hour, or just a significant piece of an entire generation – will change Ireland itself.

Dublin photographer David Monahan has made it his mission to document and commemorate as much of this change and as many of these journeys as he can.

It started in 2010 with the “Leaving Dublin” series. Emigration was rapidly increasing, and having seen his own family members and friends move abroad, Monahan understood the difficulty of the decision, the bravery involved.

He decided to shoot portraits that zeroed in on that liminal moment between deciding to leave and actually leaving. Posting a call for participants online, he wrote that he wanted to create images that were "monumental," and to "show those depicted in a true heroic spirit."

The responses resulted in a photographic series both visually stunning and emotionally resonant.

Between March 2010 and July 2013, Monahan created 84 individual portraits and met with over 120 individuals, couples and families who were on the brink of emigrating. The locations around Dublin – some quickly recognizable, others less so – were selected by the sitters, based on their personal significance. All of the photos were shot at night, and all included a tattered suitcase that had traveled between Ireland and the UK with Monahan’s relatives.

Leaving Dublin” gained national and international acclaim, covered by CBS News, the New York Times, all the Irish news outlets, and more. Monahan was invited to stage a solo exhibition at the Museum of Immigration in Melbourne, Australia, which ran for 10 months and drew 109,000 visitors. It was a resounding success.

But just as life often begins rather than ends when you leave home, Monahan knew he was just getting started.

In the summer of 2012 he was in London and decided to pay a visit to Conor McMahon, one of the people he had photographed for “Leaving Dublin.” As they were riding the train to McMahon’s neighborhood, Monahan snapped a few spontaneous photos of him, and suddenly everything clicked together.

On and off over the past year he’s been traveling the world on a shoe-string budget, checking in with the people he photographed for “Leaving Dublin” and taking snapshots of how their lives are continuing abroad. For Monahan, this series of photos, “Visitation,” is not a new project so much as it is a continuation of the work he started in 2010.

The most recent leg of Monahan’s journey took him to New York for a few days, where we talked about “Visitation” and about his ultimate goal, which is to collect all of his immigration photos in one volume, titled “On Leaving.”

The collection (which is wrapping up its crowd-funding campaign in seven days) stands to be one of the most – if not the most – comprehensive and intimate explorations of contemporary Irish immigration.

It will include all 84 images from Leaving Dublin, a selection of photographs Monahan took of the locations in daylight and empty of any people, and the portraits he's been taking throughout his visits. An exhibition featuring work from each of these three strands ran for a month last fall at Siamsa Tire in Co. Kerry, and a collaboration with Solas Nua in Washington D.C. is on the horizon.

Thus far, Monahan has reconnected with immigrants who settled in the UK, France, Australia and New Zealand and Brazil. Prior to New York, he stopped in Washington and from there he journeyed to Vancouver, San Francisco, Berkley, Los Angeles, and Mexico City. After New York, he pressed on to Chicago; Akron, Ohio; Reading, PA and back again to D.C. before returning home.

The portraits he’s shooting now contrast starkly with the images from “Leaving Dublin.” While those were in rich color, carefully posed, and shot at a distance, the photographs of “Visitation” are black-and-white close ups that seem to have been captured spontaneously during a chat.

“It’s intimate; it’s close up; we’re having a conversation,” Monahan says of the new style. It also reflects the development of a genuine friendship between Monahan and many of his subjects, whose journeys he has come to know quite well over the last few years.

Going through the photos, he volunteered a little information about each one. “His daughter had just been born.” “She was in the US on the J1 [visa], but she’s back in Dublin now working for Microsoft.” “He’s a truck driver, but you can tell he could have been a great entertainer.” “She’s in a long distance relationship with an American runner and she's doing ultra-marathons.” “He said it was hard at first, but things are better now.” “It took moving to Australia for him to become friends with Cork people.”

The switch to black and white, he said, has also had the effect of making location secondary. “There are no color references for you to latch on to so you’re really looking at the person.”

That seems at first like a contradictory thing to strive for in a photo series shot in different countries around the world, but Monahan’s primary focus has always been the people and their feelings about leaving Ireland for somewhere else.

Of the 120 people he first photographed, Monahan said 20 of them had returned to Ireland. “Who knows what that number will be in 10 years?” he wondered.

The one pattern he said he’d noticed was that the "possibility of people returning diminishes with time and diminishes with their involvement with their new location.

“Most people, when they were leaving, viewed it as a temporary thing. But now a lot of people I’ve talked to – not so much people who are a part of the series but other immigrants I met while traveling – they all say they meant to stay for a few months or a few years and now it’s been ten years or 18 years and they have families, they set down roots.

“Looking back into my own family past, this is also the case,” he added.

In Central Park, under a sky threatening rain, he reunited with Naoise McGee, a 26-year-old from Killiney, Co Dublin who posed for the "Leaving Dublin" series in early 2012 before emigrating to New York.

Her past two years here, during which she was hired by FSG Books, got married and settled in Brooklyn, are a strong testament to how quickly everything can change. Learning to drive on the other side of the road, however, will take a bit more time, she said.

To see more photos from the "Leaving Dublin" and "Visitation" series, click here.

For more information about "On Leaving," to pre-order a copy or to make a donation, visit Monahan's page.

* Originally published in May 2014.