PHOENIX (AP) — A project that maps the bodies of border-crossers recovered from Arizona’s inhospitable deserts, valleys and mountains said it documented 227 deaths in 2020, the highest in a decade after the hottest, driest summer in state history.

The previous annual high mapped by the Pima County Medical Examiner’s Office in Tucson and the nonprofit Humane Borders was 224 migrant deaths in 2010.

Enforcement efforts in California and Texas over the years have pushed migrants into dangerous terrain in Arizona without easy access to food and water. Humanitarian groups like No More Deaths leave water jugs and other provisions in remote parts of southern Arizona in hopes of saving lives in a region where nearly 3,400 migrant deaths have been documented since 2004.

Despite the increase in deaths, U.S. Border Patrol apprehension figures suggest that the number of migrants crossing the U.S.-Mexico border illegally in Arizona has actually fallen by almost 50% over 10 years.

There were 131,759 migrants apprehended between Oct. 1, 2018, and Sept. 30, 2019, in the Border Patrol’s Yuma and Tucson sectors, which cover the entire Arizona border, compared with more than 248,624 in the same 12 months from 2008 to 2009.

Immigration scholars say they expect a wave of people from Guatemala, Honduras and El Salvador to try to cross the U.S.-Mexico border this year following a pair of disastrous hurricanes in Central America and with a Joe Biden administration after four years of hardline policies under President Donald Trump.

“Heading north will continue to be seen as an option,” Andrew Selee, president of the nonpartisan Migration Policy Institute, wrote in November in Americas Quarterly magazine. “President-elect Joe Biden has promised to do things differently, treating migrants and asylum-seekers with dignity.”

Selee warned that sudden policy changes could encourage would-be border-crossers to flood north.

Dr. Greg Hess, Pima County’s medical examiner, and Michael Kreyche, mapping project coordinator with Humane Borders, have said they believe the summer’s record heat and dry weather were the main causes of the unprecedented number of deaths in 2020.

The National Weather Service in Phoenix says the average high temperature was nearly 110 degrees (43 degrees Celsius) in July and nearly 111 in August, helping make it the hottest summer in history. Phoenix’s highs tend to be similar to those in Arizona’s Sonoran Desert north of Mexico, forecasters say.

The weather service said July and August also were the state’s driest summer months on record.

While many remains recovered last year were weathered, partial skeletons that indicated older deaths, there were considerably more recent deaths in 2020 than in previous years, said Dr. Bruce Anderson, forensic anthropologist with the Pima County medical examiner’s office.

Some officials and activists working near the Arizona border, including recently retired Santa Cruz County Sheriff Tony Estrada, have said they believe border wall construction also pushed migrants into riskier places to avoid workers.

The Border Patrol keeps its own border death statistics, counting the remains of suspected migrants it learns about in the course of its duties, according to its parent agency, Customs and Border Protection.

From January to September 2020, the Border Patrol listed 43 deaths in the Arizona border area. The mapping project tracked 181 deaths over the same nine-month period.

The Border Patrol, which operates on a federal fiscal calendar that ends Sept. 30, has not yet released figures for the last quarter of the 2020 calendar year.

Arizona is not the only place with fluctuations in border deaths over the years.

While migrant deaths are now down in South Texas, eight years ago, the mass graves of border-crossers were being discovered after people began trekking through isolated ranches to avoid the official checkpoint by the small town of Falfurrias.

The Brooks County sheriff’s office said this week that migrant deaths in its jurisdiction fell to 34 last year from 45 in 2019.

In Arizona, a passer-by discovered the last migrant remains of 2020 in the remote southeast corner of the state near New Mexico.

Hess, the medical examiner, said nothing is known so far about the person, whose skeleton was discovered in the uninhabited area east of Douglas, a few miles from Guadalupe Canyon. Work crews there are rushing to complete as much of Trump’s signature border wall as possible before he leaves office.

Hess said autopsy results aren’t expected for several weeks but that the person probably won’t be identified — just like a third of the human remains that turn up in Arizona’s borderlands.