The Lee and Rose Warner Nature Center, a 49-year-old wilderness education site in the St. Croix Valley, will close at the end of the year, according to the center’s principal funder and landlord.

The decision by the Manitou Fund, a private foundation based in St. Paul, came as a surprise even to people who work closely with the center.

The nature center hosts thousands of schoolchildren annually at its 900-acre site in Marine on St. Croix for nature hikes, fossil hunts, canoeing on the St. Croix River and visits with its 13 captive animals.

“It is absolutely heartbreaking,” said Jim Almendinger, director of the St. Croix Watershed Research Station. “People put their heart and soul into this place.”

A statement from the nature center said the Manitou Fund chose not to renew its relationship with the Science Museum of Minnesota, which manages and staffs the site. No explanation was provided.

The Manitou Fund said it was exploring options for the land and facilities. “Any plan will continue Manitou Fund’s 50-plus years tradition of using this cherished space to positively impact the community,” a statement read.

Nature Center director Vikki Getchell was not immediately available for comment.

The center’s 11-member staff learned of the closing Thursday afternoon. The center has a $900,000 annual operating budget, according to the Science Museum.

The Science Museum called the Warner Center one of the state’s “crown jewels of environmental education.”

“The Science Museum of Minnesota is honored to be forever linked to Warner’s cherished legacy and enduring impact on learners,” said Joanne Jones-Rizzi, a Science Museum vice president, in a statement.

The nature center was created in 1970 when the Lee and Rose Warner Foundation bought land and buildings that had been used as a nature study area since 1958 by the Amherst Wilder Foundation and the Science Museum.

The center plans to continue some operations before its official closure. A monarch butterfly tagging event is scheduled for this weekend, and the Fall Color Blast open house is on for Oct. 6.