It is just over a month since the Beirut port explosion, and the footage from that day remains as shocking as it was when it first began to appear on our TV screens and social media. In fragments of video, the world saw Beirut life freeze in confusion at the unfamiliar sound of the explosion, then shatter as its impact hit. Among those bits of film we saw one scene, captured on domestic CCTV, that was replicated across the city – an African nanny instinctively scooping children up out of harm’s way, and protecting them with her body.

Many of these nannies are now sleeping on the streets of Beirut. Most are starving. Even before the explosion, an economic crisis exacerbated by the coronavirus pandemic meant that Lebanese employers could no longer pay their domestic workers. And so they made them gather their belongings, drove them to their embassies, and dumped them outside. Last June alone, more than 100 Ethiopian domestic workers were left outside their home country’s consulate. They live out of suitcases, and share mattresses. Some still try to maintain the discipline of wearing masks even as they sleep cheek by jowl on the unsanitary pavement.

Last week I spoke to Christine, a West African nanny and domestic worker who didn’t want to use her real name for fear of reprisals from her employer. A veteran of the Beirut labour market, she told me that she was trying to raise some money to help abandoned African women go back to their countries of origin. But that journey can’t be the priority. First, the women sleeping in the streets need to eat. If there is any money left over, it will be spent on shelter.

Travel from Lebanon to destinations in Africa is expensive, so the golden ticket home is reserved for the very sick who need to be with their families. She counts herself as one of the lucky ones, as her “madam” has kept her on, giving her a place to stay, and only reducing her salary by half.

The consulates, even when they are predisposed to helping, have to negotiate a labyrinth of Lebanese government bureaucracy, already infamous for its corruption and inefficiency. In order to secure the necessary paperwork for exit, hefty fees are levied by the ministry of labour, and then there are the travel costs. Ethiopian migrant workers are often told to try to return to their employers.

At the heart of this human rights crisis is a system of migrant labour that remains a stain on many countries in the Arab world. Known as kafala, or “sponsorship”, it effectively hands the fate of workers to their employers, who often withhold their passports to maintain control, and then demand that fees paid to employment agencies be repaid if workers want to leave before their contracts are up. This forces some workers to run away and become undocumented.

Anna, a nanny from the Philippines, told me how she managed to slip away from her abusive employer by layering three sets of underwear, tops and trousers on top of each other. That way she managed to bring with her a change of clothes without carrying a bag. She had lost so much weight by then, she jokes, that she could wear that much stuff without raising suspicion. She left everything else, including her passport, behind.

The cruelty of this kafala system isn’t an unfortunate outcome of bureaucracy, it is the result of a racist hierachy in which black workers find themselves at the bottom. Of all the nationalities that jostle and hustle for a living in the Middle East and the wider Arab world, dark-skinned African women are the cheapest to hire, the most desperate, and the most abused.

All migrant workers in Lebanon are struggling, Christine told me, but African women suffer the most because “we are not considered human beings, everybody ignores us. We are invisible.” Employers who can no longer pay their workers’ salaries can still house and feed them, but they choose not to, even though many maids and nannies offer to work for free.

As with any crisis, the most vulnerable are pushed off the cliff edge. Lebanon is struggling with a corrupt and incompetent political class, and now the aftermath of an explosion that would challenge the most robust infrastructure. The size of the rebuilding process that Beirut faces means that hungry African women sleeping rough on Beirut’s streets are rendered invisible twice – first by Lebanese society, which treats them as subhuman, and again by a global community that cannot see so many layers down into Lebanon’s ranking of victims.

For now, Beirut’s migrant workers are sticking together and sharing whatever meagre resources they have. They also try to warn others to stay away from the country. Christine fears they will still come in any case, because they believe they may be the lucky ones. “When you are poor you think, ‘Let me try,’ she says. “We just want to try.”

• Nesrine Malik is a Guardian columnist and the author of We Need New Stories: Challenging the Toxic Myths Behind Our Age of Discontent