Since 1998, at least 8,000 undocumented migrants have died attempting to cross the border from Mexico to the US. Their journey often involves traveling through desert areas where there’s few sources of water, steep rocky terrain, and temperatures reaching 118°F during the summer.

Extreme heat, drownings, and falls are some of the frequent causes of death for those trying to cross.

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According to Customs and Border Protection (CBP), violence, poverty, and economic insecurity are the factors “driving unprecedented levels of migration” to the US-Mexico border.

While thousands of migrants at the border apply for asylum in the United States every year, the vast majority of applications go unapproved. In 2021, 670 out of 14,361 applicants, or 4.7%, with a Mexican nationality were granted asylum.[1]

What does the US-Mexico border look like?

The US-Mexico border spans 1,951 miles. It cuts across the Sonoran Desert, which covers parts of Mexico, Arizona, and California, the Chihuahuan Desert, which covers Mexico, New Mexico, and Texas, and the Rio Grande River, which divides Texas and Mexico.

The environments that exist at the border vary widely. The San Diego CBP sector is home to residential neighborhoods and commercial areas, in addition to steep canyon walls and dense vegetation. It also contains stretches of remote desert where temperatures frequently reach 48°C (118°F) in the summer and can swing to 15°C (59°F) over the course of a day in any season.

There are 65 CBP stations on the US-Mexico border. Stations are grouped into nine sectors that stretch from southern California to southern Texas.

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What affects migrant routes through the US-Mexico border?

The routes that migrants choose to take from Mexico to the United States are informed by factors such as the terrain, the trajectory of their paths through Mexico, and their destinations within the US.

Their routes are also affected by the deterrence tactics of the CBP.

In October 1993, for instance, during the implementation of Operation Hold the Line in El Paso, Texas, CBP agents positioned themselves clearly in view along the border, leading to a 70% decrease in apprehensions of migrants in the El Paso sector.

Similarly, prior to 1994, migrants attempting to cross into California often chose to do so in the Imperial Beach area, where densely populated neighborhoods offered migrants both convenient cover and access to public transportation. After Operation Gatekeeper increased the number of CBP personnel in the area, however, Imperial Beach apprehensions decreased while apprehensions further east increased, suggesting that some migrants rerouted their journeys in response.

Finally, the Government Accountability Office (GAO) cited a study that discovered that while the total number of migrant deaths did not increase from 1993 to 1996, a period that encompassed the implementation of Operation Gatekeeper in 1994, the number of deaths in remote terrain where migrants would have traveled to avoid the CBP did.

What causes migrant deaths on the US-Mexico border?

While data on the causes of migrant deaths at the US-Mexico border remains sparse, deaths due to drowning, extreme heat, dangerous smuggling operations, fall-related injuries from the border wall, and actions from CBP officers have been recorded.

Migrants often drown in the Rio Grande River and connected bodies of water. In June of 2022, a man drowned in the American Canal in El Paso, Texas, and in August, a Guatemalan citizen drowned in the Rio Grande.[2]

Extreme heat is also a contributing factor to migrant deaths. In the worst cases, heat exposure leads to an altered mental state, dehydration, stroke, convulsions, and death. The CBP itself has described the summer heat as “severe” and the many miles of desert terrain that migrants must traverse after entering the US as “unforgiving.”

How migrants chose to travel across the border also affects their safety during their journey. Many migrants are smuggled over the border in small, enclosed spaces with few safety precautions put in place. Migrants have been found to be crammed into metal boxes with 40 other occupants, overloaded vehicles, and horse trailers.

Being confined in such spaces can be fatal during either a potential collision or a heat wave.

In June of 2022, 48 people smuggled over the border were found deceased in an abandoned tractor-trailer in southwest San Antonio, Texas. Five individuals who were rescued from the scene later died at the hospital, bringing the final death toll to 53.

Migrants’ efforts to climb over the border wall have also led to life-threatening injuries: such deaths have been documented in San Ysidro, California, Otay Mesa, California, and Tornillo, Texas.

Similarly, the actions of CBP officers also affect the number of migrant deaths. The CBP Office of Professional Responsibility reported that 151 CBP-related deaths occurred in FY 2021. This figure includes migrant deaths that occur in CBP custody as a result of use of force by a CBP officer and vehicle collisions that occur during active pursuit by the CBP, among other causes.

In June of 2022, the CBP reported a use of force incident that resulted in the death of one individual. Migrant deaths that resulted after high-speed chases by the CBP in 2022 have been documented in Arizona, New Mexico, and Texas.

These incidents are currently being investigated by Homeland Security Investigations.

How is information about migrant deaths at the border collected?

Deaths are approximated by the number of bodies or human remains discovered by CBP officers.

However, the comprehensiveness of CBP data has been scrutinized by the GAO, which stated in April of 2022 that “Border Patrol has not collected and recorded, or reported to Congress, complete data on migrant deaths, or disclosed associated data limitations.”

The GAO’s comparison of deaths recorded by the CBP Tucson sector and those from the Chief Medical Examiner for Pima County in the Arizona OpenGIS Initiative for Deceased Migrants Reported Migrant Deaths shows that the medical examiner’s numbers were frequently more than twice as high as the CBP’s.

This discrepancy points to an inconsistency in the way migrant death data is collected across CBP sectors: while the San Diego sector incorporates deaths reported by external entities such as the medical examiner’s office in their death counts, the Tucson sector does not.

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Furthermore, because some fraction of migrants die in remote areas and are not found, reports are likely to undercount the actual number of deaths.

Identification of the individual, as well as the estimation of the date and cause of death, can prove to be difficult when remains are rapidly degraded by the harsh conditions of the desert in which many of the bodies are found.

A 2019 report from the Pima County medical examiner in Tucson, Arizona, stated that of the 3,081 bodies the office had been tasked with examining from 2000 to 2019, they were able to identify 1,970 bodies, or approximately 64% of the individuals.

Over 80% of the migrants whose remains were able to be identified hailed from Mexico, while 11% were from Guatemala. Smaller numbers of migrants hailed from Honduras, Ecuador, Peru, Brazil, Costa Rica, Colombia, India, Nicaragua, and the Dominican Republic.

Of identified remains recovered between 2000 and 2019, 10.9% fell in the 13-19 age group, 35.7% fell in the 20-29 age group, and 31.9% fell in the 30-39 age group. 20.8% of identified remains were in the 40+ demographic.

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To read about COVID-19's effect on immigration at the US-Mexico border, read What was Title 42’s effect on border encounters and people seeking asylum in the US?

[1]

The number of applications includes both affirmative and defensive asylum cases.

[2]

The American Canal leads to the Rio Grande.