A group of American bishops held Mass at an unusual location on Tuesday afternoon: the U.S.-Mexico border, where they commemorated the many migrants who have died trying to cross it. The display called attention to the need for immigration reform, which is currently mired in the House of Representatives. While many aspects of the U.S. immigration system have stayed static in recent years, border security has tightened, contributing to a growing number of deaths. As a 2013 report from the University of Arizona’s Binational Migration Institute explained, “segmented border militarization has resulted in the funnel effect, or the redistribution of migratory flows into remote and dangerous areas such as southern Arizona.”

Deaths at the border have reached crisis levels: The graph below, from the Washington Office on Latin America (WOLA), shows that fatalities nearly doubled between 1998 and 2012. The only year with more deaths than 2012 was 2005. WOLA researchers Adam Isacson and Maureen Meyer explained in April 2013: “In that year, Border Patrol captured more than three times as many migrants as it did in 2012. The migrant population was far larger, but the number of deaths was similar. A much larger fraction of the migrant population is dying today.” The most recent data from the U.S. Border Patrol puts fatalities in 2013 slightly below the 2012 figure—445 deaths compared to the previous year's 477—but that still puts 2013 ahead of every other year but 2005 and 2006.

The Mass was held in Nogales, Arizona—in the state where both border crossings and deaths have become the most frequent. While overall deaths declined in 2013, loss of life in Arizona ticked upwards, from 180 fatalities in the Tucson sector in 2012, to 194 last year. Data from Arizona’s Pima County Office of the Medical Examiner (PCOME)—which investigates more migrant disappearances than any other office—was central to the Binational Migration Institute report, which demonstrated how increased border security leads to more deaths. It produced the graph below to show all the confirmed deaths that the Pima County office had labeled as “undocumented border crossers” (UBCs) at the time of the report’s release last June.

Along with Tuesday's service, the U.S. Conference of Catholic Bishops also sent a letter last week to the secretary of the Department of Homeland Security, Jeh Johnson, imploring him to make changes to the immigration enforcement policy that could decrease the loss of life. Johnson is currently under orders from President Barack Obama to review the deportations system. The Bishops asked DHS to expand its use of prosecutorial discretion, through which the government can prioritize deporting dangerous criminals; to phase out programs like “Secure Communities,” in which local law enforcement officers hunt for immigrants; and to subject more deportations to judicial review.

The letter put clear pressure on the administration to confront deportations through executive action, something immigrant advocates have demanded with increasing urgency this spring. But the public Mass—which comes after Obama and Pope Francis met for the first time last week and discussed, among other things, immigration—may also prod lawmakers from border districts, reminding them that stalling legislative reform has consequences.