Tijuana, Mexico - Alfredo lives in a shelter for deportees on Tijuana Beach, a stone's throw from the border wall that bars him from the United States. That wall - not to be confused with the bigger one US President Donald Trump plans to build - has existed for decades.

Alfredo's is among the most physically emblematic of these shelters. There are many others. In fact, there are more shelters and migrants here than ever, since Trump launched his campaign to keep Mexicans and other immigrants out of the US, activists say.

The shelters are struggling to cope with what people familiar with the border-crossing industry - people-smugglers known here as "coyotes" - tell Al Jazeera is a wave of migrants and deportees coming to and from the US since Trump made calls to heighten deportations of undocumented people and signed an executive order calling to build the newer, stronger border wall.

The new wall won't do much to keep people out; many here say with confidence and often a cheeky sense of humour. Still, its imminent construction is taken as a sign that people who have acted as a driving force of the American economy - not just Mexican Americans but immigrants generally - are no longer welcome there.

"America was built with Mexican hands," Alfredo says in a low, sober voice. He emphasised to Al Jazeera that this is what he wanted to tell English-language readers around the world.

After six years as a construction worker in the southern US state of Mississippi, immigration officials rounded up Alfredo and several other undocumented American workers and deported them to Mexico. "Instead of at least treating us as humans, we are treated as animals. For them, we are animals," he says.

'We're family, we're brothers'

In a small shack crammed with around 30 deportees originally from Mexico and El Salvador, Alfredo, 54, who asked to go only by his first name out of a mistrust of authorities common among deportees, spoke to Al Jazeera in the dark, his face obscured in a lampless, unheated sleeping area. Gusts of wind burst through a broken window as he spoke, holding back a severe cough shared by his roommates.

For Alfredo, whose struggle to earn a livelihood has taken him thousands of miles from his native Mexico City, he hopes his last stop will be this dilapidated shelter - his thin mat bedding among many on a cold asphalt floor under a crumbling roof.

He won't make the dangerous, gruelling trek to the US again, he says. He's one of many migrants in Tijuana without dreams of America, but there are many more who do, in these shelters - packed with new deportees and migrants hoping to make it to the US before Trump tightens controls of what continues to be a porous border.

In the next room, Ramon, one of the co-organisers of the shelter, has fallen severely ill with a flu. He also suffers from what his roommates describe as a mysterious limpness in one leg.

His friends have prepared him a tonic - a broth with cinnamon. The warm smell perfumes the shack, the size of some walk-in closets just opposite the border.

"We are a family. We are brothers," Alfredo explains. Like many US migrant workers struggling to survive, Alfredo has no wife or children. After years of building in the US, which he says he still "respects", he says the real separation between the US and Mexico is "we have love for human beings here. It doesn't matter your colour or religion - Catholic or not. We help how we can, even though we aren't a rich country. Because we know we might be the ones suffering tomorrow."

Tijuana's people are scrambling to meet new challenges posed by Trump's plans to bolster the existing border walls with a larger wall and also to drastically ramp up deportations of undocumented Americans. Many come from across Mexico and Central America but also faraway Haiti and even Africa. They have rushed to Tijuana and other Mexican border cities, attempting to pay the coyotes thousands of dollars to smuggle them across. Activists also complain of a heightened rash of deportations since Trump's inauguration.

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Al Jazeera counted at least 30 shelters for migrants in Tijuana; some are shacks, others are spare rooms in private homes or repurposed churches. Most house migrants free of charge - some charge 20 Mexican pesos, about $1, a day to cover maintenance. Of those,19 have opened in the past seven months, according to Hugo Castro, director of Angeles de la Frontera (Border Angels), an organisation dedicated to helping deliver resources to and raising awareness of migrants attempting to enter or who have been deported from the US.

Non-migrant Tijuana residents have noticed a significant change in their city's make-up in recent months. "There are many more people suffering here than even before," said Rosario Corona, 19, at the city's signature cathedral Nuestra Senora de Guadelupe (Our Lady of Guadalupe). Corona works with a church youth group that administers aid to migrants and others in need.

Corona waits in a line at the cathedral for a priest to administer the Catholic sacrament confession, where one seeks absolution for sins. She is flanked in the pews by migrants, some of whom sit in church not only for prayer but for lack of anywhere else to go. One tells Al Jazeera that he's going to enter the confession booth not to ask the priest for forgiveness but for charity. Moments later, he leaves empty-handed - with so many in this city in need, it remains unclear whether he got what he came for.

"Unity and respect is what makes a place strong," says Liliana Vasquez, 26, one of Corona's fellow youth group workers, as their group leaves the church.

The sudden surge in the number of shelters and the influx of new migrants that prompted it, Castro says, happened amid mounting fears that Trump might win and make good on promises to build a wall and ramp up deportations.

READ MORE - Voices from the border: Opposing Trump\'s wall

'... Some I assume are good people'

It began in June 2015, when Trump launched his presidential election campaign with a speech that bewildered many across the US-Mexico border and around the world: "When Mexico sends its people, they're not sending their best," he said.

"They're sending people that have lots of problems, and they're bringing those problems with us. They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people."

For many in Tijuana, these words hit a nerve. Susan Smith, 61, is a non-Latina US-born social justice and anti-nuclear-proliferation activist, born on the US border with Mexico in the state of New Mexico. She identifies as Mexican, not by birth or ethnicity, but by life experience and family. Her husband, child and grandchild are ethnically Mexican, and she lives in Tijuana's Playas or Beach neighbourhood - not far from Alfredo's shelter.

For her, Trump's words about Mexicans are "slightly moderated hate speech, designed to turn a whole swath of humanity into caricatures from a Clint Eastwood movie, isn't it? All about the drama and soundbite, poisonous metaphors - messages of mass destruction."

In July 2015, Trump made a brief visit to a US border town with Mexico - Laredo, Texas - where he reiterated promises to crack down on migrants.

READ MORE: Massive anti-Trump rallies staged across nation

In mid-2016, Castro says, migrants began to realise that Trump might beat his Democratic opponent, Hillary Clinton. The migrants flocked to border towns, particularly Tijuana.

On January 25, the freshly inaugurated president finally signed the executive order allowing for the creation of the wall - who will pay for the wall remains uncertain, despite Trump's insistence that Mexico will.

Mexican officials have scoffed at that assertion. And then in early February, the Los Angeles Times newspaper reported, citing calculations of presidential directives, that Trump would deport as many as eight million undocumented Americans.

Trump has that said he "wasn't kidding" about the border, telling the press that it was "being designed".

But just hours earlier, across the US border in San Diego, a US Customs and Border Patrol (CBP) officer, who spoke without offering his name or being recorded because the officer was not authorised to speak to the press, joked that there was already a wall and said that the new one "will change nothing".

CBP declined to respond to a request for comment on the wall and deportations - specifically criticism of the project's efficacy and potential impact on the communities it affects, saying that such questions are "speculative".

The CBP press team also directed Al Jazeera to the Trump administration for further comment as well as the original executive order signed in January for more information.

Trump's press team did not respond to an interview request from Al Jazeera. The Trump administration has repeatedly expressed disdain for media coverage that it complains is unflattering, provoking the ire of free press and US constitutional rights advocates.

'It's a war against international migrants'

Among the criticisms of the wall and deportations are signs that they may actually hurt the US economy. Undocumented Americans contribute $11.64bn to the US economy in taxes annually, according to a February 2016 study from US think-tank the Institute on Taxation and Economic Policy. But with Trump's promises to expel them, the burden is also strongly felt beyond the US border, in Mexico.

"Trump is creating a humanitarian crisis" in Tijuana, Castro said.

"He's a war criminal of a war that hasn't been declared. It's not a war against a country. It's a war against international migrants from Somalia, Mexico, Central America, Iraq, from all the world. The migrants are suffering, the risk of dying [in transit] has increased."

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Castro visits about five shelters a day with donations of food and cash, he says. A dual citizen with the US, he often visits universities there to explain the issues faced by migrants. He raises funds on Border Angels' website. But with so many newcomers to feed, he says resources are drying up faster than ever. "Money just evaporates," Castro said.

With the new pressure put on Tijuana's city infrastructure and a network of philanthropists rushing to house a surge in workers from around the country and world, Alfredo "thanks God" he lives in his overcrowded shelter, which in recent weeks has had new arrivals - freshly deported from the US, where their families - in one case a newborn baby - are left behind without a father.

Some migrants don't have shelter at all, Alfredo says. Many migrants are crowding the streets - particularly in Tijuana's Zona Norte (Northern Zone) - infamous for rampant drug trafficking and other crimes. There, the migrants are in a vulnerable position, Castro says; one shelter has in recent months devolved into a crack house, as desperation and disillusionment abound.

At the beach, just outside of Alfredo's shelter, a man sits on a bench before what appears to be a door at the wall that remains locked. The door is referred to by locals as the "gate of hell". The man sits before the "gate" much as one waits for a bus. Like many of the migrants wandering the city, he has an overstuffed backpack and a listless expression on his face. From there, beyond the grating and another series of small walls, the man looks at San Diego kilometres away, as dusk turns to night and lights turn on in the cookie-cutter high-rise buildings that differentiate the US from this place.

This is the first story in a five-part series looking at the US-Mexico wall and the people who live along side it. If you want to follow this story, please enter your email here