Retailers are still struggling to recover from a difficult holiday shopping season, and things could get worse, said Jan Kniffen, a leading retail consultant and department store veteran.

"It's going to get harder," as online shopping continues to erode sales at physical stores, Kniffen told CNBC's "Squawk on the Street" on Monday.

"We're going to see more stores closures. We're going to see more bankruptcies. We're going to see more mergers," he said. "That's what happens when you go through stress in retailing."

"Fifty percent of all nonbar, nonrestaurant sales are going to be online" by 2030, compared with "about 15 percent today," said the CEO of J. Rogers Kniffen Worldwide Enterprises.

Retailers are going to have to change the way they connect with customers, he predicted, perhaps by being more socially conscious and developing a more local feel.



The downward retail store spiral is also "putting enormous pressure on what have traditionally been the full-price, brick-and-mortar space, namely the mall-based space," Kniffen said.