The list of deaths, shipwrecks and rescues of migrants trying to cross the Atlantic Ocean from Africa's northwest coast to Spain's Canary Islands in the past weeks makes for distressing reading.

At least 51 people died on the weekend trying to cross from southern Morocco after an engine malfunction left their inflatable adrift for more than a week in the Atlantic. Emergency services found four survivors amid the wreckage. The dead included 11 women and three children.

Also on the weekend, one person died and 65 others, all men, were rescued from their boat in the south of Tenerife, the largest of the Canary Islands.

Last month, at least two died and another 35 migrants were feared drowned after their rubber dinghy capsized. The boat had originally set off from Dakhla, a city in Western Sahara under Moroccan control, en route to the Canary Islands. Of the estimated 60 people on board, Morocco's navy managed to save only 24 .

Lying barely 100 km (62 miles) from the northwest coast of Africa at their closest point, the Canary Islands have become the main route for migrants, asylum seekers and refugees trying to reach Spain by sea. In 2022, half of irregular migrants entering Spain went via the Canaries.

But some migrant advocacy organizations and Canarian locals are accusing Spanish and Moroccan authorities of failing to coordinate rescues, leading to a greater loss of lives on a voyage that is already among the most dangerous migrant routes in the world.

What is the criticism?

In the case of the boat that embarked from Dakhla, Spain's maritime rescue service, Salvamento Maritimo, said a spotter plane had located the boat in waters off the Western Sahara after an emergency call. A leaked audio recording between the plane's pilot and rescue services puts the boat in Spain's search and rescue, or SAR, zone.

Moroccan authorities, whose SAR zone overlaps with that of Spain in this area, said they would take responsibility for the rescue operation. But their patrol boat took 12 hours to arrive, by which time dozens of people had drowned.

"The inflatable had been begging for rescue in Spanish waters for more than 12 hours," criticized Helena Maleno Garzon, the founder of the Spanish migrant monitoring organization Caminando Fronteras, in a Twitter post.

Canarian journalist and migrant advocate Txema Santana is scathing in his criticism of the lack of coordination between Spain and Morocco in this case.

"Well, I can say that you rescue, or I rescue, but I stay watching until someone gets there," he told DW. "I don't leave people in the middle of the ocean in a boat with kids, with women, with a lot of people screaming and I leave. No!"

What has changed between Morocco and Spain?

Early in 2022, Spain made a political U-turn and recognized Morocco's plan for governing the contested territory of Western Sahara, resulting in a resumption of relations between Rabat and Madrid.

Since then, said Santana, Spain waits for Morocco to react when an SOS is launched. He believes, however, that the Spanish government needs to take responsibility for rescues to avert further tragedies at sea.

"Salvamento Maritimo is one of the most advanced rescue services in Europe," he said. "It rescues thousands of people every year with professional rescue ships. … It disembarks migrants in a safe port. But when Morocco rescues, it does so with military ships using people who aren't rescue professionals. And it sends people back to a country from which they are fleeing."

The migrant monitoring group Alarm Phone has also raised its concerns about Morocco extending its search and rescue zone to off the shores of Western Sahara.

"This would be particularly worrying as the Moroccan authorities have repeatedly demonstrated their unwillingness to carry out a safe and fast rescue — often at the cost of human lives," it wrote in a September 2022 report.

How popular is the Altantic route to the Canary Islands?

The route's jump in popularity started during the pandemic, although numbers have dropped this year, as Morocco extends military controls along its coastline.

So far, 5,914 migrants arrived on the Spanish archipelago until June 25, compared to 15,682 last year. The past weeks have seen a sharp uptick in landings, with an average of 100 new arrivals a day between June 15 and June 25.

The early summer months are the busiest period for attempted crossings.

"Compared to June 2022, we have noticed a considerable increase in arrivals in all the islands, especially at the end of the month," Jose Antonio Rodriguez Verona from the Red Cross told Spain's El Mundo newspaper.

The journeys that end in the Canary Islands mostly start in Morocco, Western Sahara, Mauritania and Senegal, and, less frequently, in The Gambia and Guinea.

What makes the northwest African route so dangerous?

Amid heightened controls across northern Morocco, Libya and Tunisia, migrants from northwest African nations may opt for the Canary Island route because it's easier to leave from there, said migration expert Mehdi Lahlou, a professor at Morocco's National Institute for Statistics and Applied Economy.

However, he points out, this pushes migrants into what is a more perilous sea journey compared to the more frequently used central route from northern Africa across the Mediterranean to mainland Spain or Italy. 

More than 7,500 people died or went missing at sea en route to the Canary Islands between 2020 and 2022, according to Caminando Fronteras.

The International Organization for Migration (IOM) registered fewer deaths but admits that its "figures are a minimum estimate of the true death toll." Even with the lower figures, the IOM counts the route as among the deadliest migrant voyages in the world.

The route is dangerous because of the length of the journey combined with the unseaworthiness of the boats and the treachery of the Atlantic.

The trips may take anywhere from one to ten days, and it is "common for migrants to run out of food, water and fuel after only a few days," an EU briefing on the Western African route found.

Some come in cayucos — larger wooden fishing boats commonly used in West Africa that can be packed with upwards of 100 people — while others arrive in small wooden dinghies known as pateras in Spanish. Rubber inflatables, which are far more fragile, are also increasingly being used.

These boats aren't suited for the open ocean of the Atlantic, made perilous by strong ocean currents and unpredictable winds and waves that can form locally.

"The Atlantic Sea is very dangerous in this part of Morocco,"  the migrant expert Lahlou said.

These dangers, said Canarian local Txema Santana, make professional search and rescue even more vital.

"It's not fair that thousands of people continue to die [on their way to the Canaries] and we look the other way."

Edited by: Cristina Krippahl