Mina, a valley just outside of Mecca, is one of the stops on the hajj, the annual Islamic pilgrimage established by the Prophet Mohammed. On Thursday morning, at least 717 people died there and another 805 were injured in a terrible incident.
It began with a "sudden increase and overlapping in the density of pilgrims" at an intersection in Mina, which triggered a stampede, Saudi authorities said (per to the Wall Street Journal). The hajj attracts enormous crowds — overall 2 million visitors are expected this year — making the crowded spaces potentially dangerous.
This isn't the first deadly incident during the hajj. It's not even the first this year: Earlier in September, a construction crane collapsed near Mecca's Grand Mosque, killing more than 100 people. Previous years have seen such incidents as well, with one in 1990 killing about 1,400 people.
As the world's Muslim population grows, along with the size of Muslim middle classes that can more easily afford the trip, the number of pilgrims on the hajj is growing as well.
The disturbing recent history of hajj disasters
The hajj is a religious pilgrimage to Islamic holy sites in what is today Saudi Arabia, in the area around the city of Mecca. Meant to trace the original founding moments of Islam and parts of the life of the Prophet Mohammed, the pilgrimage is a religious duty that all Muslims are in theory required to do at least once in their lives.
As the world's Muslim population has grown — it is now about 1.6 billion — more people are attending the hajj every year. The Saudi government has spent enormous amounts of resources on accommodating the groups, but incidents like Thursday's still sometimes occur.
Here's a list, compiled by journalist Brian Whitaker, of large-scale accidents at the hajj in the past few decades:
1987: More than 400 pilgrims died as a result of demonstrations.
1990: 1,400 pilgrims killed during a stampede in a pedestrian tunnel linking Mecca with Mount Arafat. The stampede is thought to have been caused by the great heat when a ventilation system in the tunnel broke down.
1994: 270 pilgrims crushed to death.
1997: 350 pilgrims killed when in a fire started by a gas cooker swept through the tents at Mina.
1998: 180 pilgrims crushed to death.
2001: 35 pilgrims crushed to death at Arafat.
2004: Some 250 pilgrims died in a stampede during the "stoning of the devil" ritual.
2006: At least 362 pilgrims died in a stampede during the "stoning of the devil" ritual; a hostel collapsed in Mecca, killing at least 76 people.
Risks such as fires and stampedes are amplified by the fact that the hajj is a physically demanding journey, and a number of the pilgrims who undergo it are elderly or otherwise at increased risk in case of an accident.
The high concentration of people makes the spread of infectious disease a real threat as well. The hajj "entails some of the world’s most important public-health and infection control problems," three researchers write in the Lancet. "The severe congestion of people means that emerging infectious diseases have the potential to quickly turn into epidemics."
Why the hajj is still dangerous
Over the past few decades, the numbers of people going on the hajj has grown rapidly, correlating with a growth in the global Muslim population as well as improving transportation infrastructure in the region and globally.
As of 1950, University of Kentucky's Sven Müller writes, fewer than 100,000 people went on the hajj annually. By 1955, that number had doubled. By 1970, half a million pilgrims attended the event. The hajj crossed the 1 million threshold in 1983, and now averages roughly 2 million people per year.
But those are just official numbers. While Saudi Arabia has imposed strict controls on the number of people allowed to attend the hajj each year, in practice it can't completely control the influx of pilgrims. Müller estimates that there are about a million non-registered pilgrims annually.
Such large numbers of people in these spaces makes stampedes, like the one Thursday morning, more likely — and more deadly.
"High-density flows are said to be a proximal cause of crushing disasters at the Hajj," scholars Hani Alnabulsi and John Drury write. "The period in which the number of pilgrims attending the Hajj doubled from 1 million to 2 million (i.e., 1982–2010) also saw a large number of major crowd disasters (1994, 1998, 2001, and 2004), which again suggests a link between crowd density and risk to crowd safety."
Drury and Alnabulsi don't think crowds are always bad for the hajj — to a certain degree, more people in a space means there are more people to help someone in need, which they're likely to do at a major shared religious event. But when crowds are packed in tightly enough, people can't do very much.
"At a certain level (>7–8 people per square meter), crowd density becomes dangerous; people lose the ability to move independently let alone to be considerate or give support to others," they write.
What is Saudi Arabia doing about it?
The Saudi government is well aware of the problem, and has invested a lot of money into infrastructure projects to accommodate more people and make the hajj safer.
"Since 1992 over £200 billion has been spent on these projects," Drury and Alnabusi write. "Crowd safety has been hugely enhanced at the Hajj since 2006 and a more scientific approach to risk assessment has developed."
But some of these developments are controversial. New infrastructure projects, as well commercial and amenity expansions, are changing the appearance and feel of some of the holy sites near Mecca, many feel adversely. "Ambitious programmes...appear to have adverse consequences for the historic and social fabric of the holy cities," Nanyang Technological University's Joan Catherine Henderson writes.
Some of these ancient sites, particularly those dating back to Islam's seventh-century founding, were simply not built with the modern-day hajj in mind. Saudi Arabia is unlikely to respond by more strictly limiting attendance. This would be unlikely both on religious grounds and for more narrow economic reasons.
"The Saudis know the oil is going to run out," Ziauddin Sardar, author of Mecca: The Sacred City, told Time. "Hajj is already their second major source of income, after oil. They look at Dubai, and Qatar, and ask ‘what are we going to do?’ And they say, ‘We have Hajj, and we’re going to exploit it to the max.'"
But if Saudi Arabia wants to prevent future incidents like this one, it will have to find a solution of some kind, whether that means more infrastructure even at the cost of the sanctity of the ancient sites, or limiting participation even further, or something else. Otherwise, this will unfortunately likely not be the last time tragedy strikes.