JOHANNESBURG, South Africa — A 3,000-mile land border running from the Atlantic seaboard to the Indian Ocean separates South Africa from five other countries, but nowhere is the traffic more intense than at Beit Bridge, the sole transit across the Limpopo River to Zimbabwe.

Despite a recent upgrade to the immigration and customs posts in both Zimbabwe and South Africa, trucks can be backed up for miles, inching their way to the gates. Cargo from as far north as Zambia and Malawi heads south to Durban or Cape Town while imports go the other way.

At Christmas, millions of migrants — many of them illegal — cross Africa’s land borders as they head home, especially out of South Africa, where the city of Johannesburg alone has a GDP greater than all the country’s neighbors combined.

Even without a passport, Beit Bridge hasn’t posed a problem for those seeking to cross the border. Touts known to the police and army charge between $40 and $120 to exit in either direction, evading security and sharing a bribe with the Department of Home Affairs responsible for immigration.

But Mother Nature has now thrown a kink in the once-familiar patterns.

Well before Christmas, the Limpopo was reduced to a series of pools and a few stretches of water as rains due September failed. In some places it has been possible to risk crocodiles sunning on the bank and simply walk across, always with a guide.

But in recent weeks, there have been fresh storms in the highlands, feeding streams that merge into the river. Within a day or two, this has the Limpopo ripping trees from the shore and discharging three times more water than the American West’s Colorado River. Drownings are common.

Then all have to use the bridge or take a circuitous route across the Kalahari Desert via Botswana.

Since the beginning of December when factories in Johannesburg began to close for the holidays, traffic has been headed out of South Africa. In the coming weeks, the flow will reverse and people-smugglers will be busy. But a shift in the political winds in Pretoria is providing even more complications.

At last May’s election, the African National Congress (ANC) — in power since 1994 when Nelson Mandela became the first democratically elected president — gained only 40% of the seats in Parliament. The long-dominant ANC was forced to cobble together a coalition of 10 parties, including its chief opponent, the Democratic Alliance (DA), which is pro-business and enjoys support among the country’s minority white population.

The DA joined the ANC in securing the tenure of President Cyril Ramaphosa, now in his second and final term under the constitution. Cabinet posts have been shared, with the key post of minister for home affairs going to the DA’s Leon Schreiber, who is of German descent and took his doctoral degree in Berlin. He has promised to clean up the department.

Immigration officers have been speaking off record to the media, complaining that the 36-year-old Mr. Schreiber has not engaged them in plans to overhaul the system, one in which they say the majority of staff work diligently and do not take bribes.

Fighting forgeries

South African citizens, by birth or naturalization, carry the country’s passport. Forged birth certificates here have led to all destinations in Europe, along with Australia, Canada and the U.S., imposing a regime of visas.

Citizens and permanent residents alike are issued with an ID document showing their date and country of birth and linked to a central computer in Pretoria.

Mr. Schreiber has reportedly demanded that on leaving or returning to South Africa, permanent residents must carry not only their ID but the original documents granting their status: even those who have lived in South Africa since the immigration boom of the 1950s and 1960s and who no longer have the papers.

Officers at Johannesburg airport complain that no public announcement was made about the new regulation, and arrivals are surprised at the request leading to heated exchanges and long processing delays.

Repeated messages sent to Mr. Schreiber’s personal WhatsApp number seeking clarity on the issue have received no reply. His spokesman, Adrian Roos, who is also a DA member of parliament, declined to answer saying he was taking time off with his family until mid-January.

Rising anger

The immigration issue is provoking rising anger in Johannesburg, where youth unemployment is high and foreigners are seen as taking jobs. For many, the informal sector offers hope: selling fruit, mending clothes, fixing flat tires. Others go door to door in Africa’s richest city offering to paint walls or work the massive gardens that are common in suburbs where the professional class of all races have their homes.

In the sprawling townships where artisans and casual workers can live four or five in a shack designed for one, pop-up shops known as “spaza” are common: cigarettes, vegetables and soft-drinks often sold through a window.

Over the past two decades, this trade has increasingly been taken over by Somalis and immigrants from Malawi, Mozambique, Zimbabwe, and even Pakistanis here on asylum visas. The local press has for years exposed the “sale” of refugee status by the Department of Home Affairs, with little action by the state. A joke runs that in South Africa even a Swiss national could claim asylum, despite that country’s famed neutrality.

In early December, ANC Secretary General Fikile Mbalula called for all foreigners running unlicensed spaza shops to be deported. The government has been trying to regulate the outlets, but across an area the size of Texas and California combined, with 60m people and mass unemployment, informal traders abound, some laying out their wares on a blanket by the roadside, others in a basket strapped to a bicycle.

Many pay no tax and critics say Mr. Mbalula’s comments merely add to xenophobia that has in the past led to campaigns of violence against foreigners. He has since suggested the running of unauthorized retail shops be reserved for South African citizens.

The flow of workers back into the country has been exacerbated by riots in Mozambique, following violence in the wake of the hotly contested October elections. Thousands have fled to neighboring states, and in December South Africa temporarily closed its main entry point to Mozambique.

From across Africa in coming weeks, as business reopens and workers return, a vast humanity will head south, finding their way in through a land border that stretches the equivalent of New York City to San Diego.

What awaits them is hard to predict. Critics fears Mr. Schreiber’s determined efforts to tighten entry processes could fan the growing disquiet about foreign workers and the steep levels of unemployment in South Africa.

Ryson Mokwena runs a mini-bus taxi between Johannesburg and Zimbabwe’s southern city of Bulawayo. He says he never carries illegals on their own. “I bring between 12 and 15 people at a time across Beit Bridge and at most I will take three who have no papers.”

He said the pattern of traffic hadn’t changed in years. “Those without documents pay double the fare, sometimes more. It is good business.”

Mr. Mokwena explained that not all illegals lack passports.

“I have passengers who entered South Africa in January 2024 with a visa allowing a stay of six weeks, but they worked until Christmas and when they left no one said anything. Now they are coming back in and officers can see by the passport they overstayed, but a few dollars and they’re through. Year after year.”

He said the Limpopo flood made his work easier. “For those crossing by foot, I drive them from Bulawayo to the bridge and take their luggage over while they do the river. I can wait hours for them on the South African side while my other clients moan about the delay. Now, when the water is high, they pay a bribe and we all leave at the same time.”

Mr. Mokwena said tighter regulations simply increased the money made by the trade, including guides, officials, food sellers, smugglers and specialists who know how to cross with children. “And I can charge more too.”

At the age of 43, he has been running the service for 18 years. “I am in and out of Zimbabwe all the time,” he said. “The place barely functions and life is terrible. Fix that problem and people will stop coming to South Africa. Now we are watching the rise of a civil war in Mozambique and the world is doing nothing, but they will howl when it’s too late and thousands are on the move.

“The police, army and Home Affairs make money out of this. Don’t blame me. I’m just a driver!”

• Geoff Hill can be reached at ghill@washingtontimes.com.