Massive cuts that cost some 440,000 jobs globally at energy companies in the last two years have left veteran workers and skilled job-candidates without a clear future in oil and gas, according to recent surveys.

Unable to find work in their chosen field, some oil and gas professionals have turned their sights to technology or other industries.

The outflow of experienced workers and a lack of hiring as oil companies drive to become more efficient could put future production growth in jeopardy should a nascent upturn in the industry accelerate, say experts. In western Canada, companies resuming production of crude oil are struggling to rehire rig crews following job and pay cuts.

A University of Houston global survey of laid off oil workers found that 25 percent had already moved to another industry and another 55 percent were considering it, according to Reuters. Only 13 percent of those polled in late 2016 had found energy jobs.

“A good number of people are ‘lost’ to other industries,” Christiane Spitzmueller, the study’s principal investigator, told Reuters. “This will translate into high recruitment and training costs for new hires.”

In western Canada, where many more rigs are working this year than last, drillers say a lack of experienced employees could slow their work later this year – or force them to pay higher salaries to lure workers back.

Dan Block, chief executive of Edmonton-based Jomax Drilling (1988) Ltd, told Reuters that contractors he once employed took jobs in other industries, including construction.

“We are scrambling to bring people back,” Block said.

Halliburton, an oil services firm that had about 50,000 employees at the end of 2016, down from more than 80,000 two years earlier, is now holding job fairs in regions where there is an uptick in drilling activity, such as Colorado, Texas, New Mexico, Oklahoma, and Ohio, the company said.

The U.S. oil and gas industry will need to fill 1.9 million new jobs through 2035, according to experts, with many in the Permian Basin – one of the hottest drilling areas in the United States due to its favorable economics.

But filling those jobs could prove a challenge. A study last year by KCA, Pink Petro and Glexnet, which polled 1,000 laid off and working energy professionals, found that 45 percent of executives or board members said they were ready to seek other job options, retire or are unsure what they will do post-downturn.

If experienced workers are less inclined to stay through another economic cycle, younger workers may already be placing bets on other careers, Reuters found. Before oil prices crashed, the University of Texas placed more than 90 percent of students who majored in petroleum engineering into oil and gas jobs. In 2015 and 2016, that number fell by around a quarter.

LSU said its May 2016 engineering graduates reported fewer than 50 percent had found jobs, down from around 63 percent in 2013.

Despite a potential shortage of engineers, companies could still grow their businesses using existing staff augmented with newer technology and contract labor, said KCA.