An ambitious expansion of Children's Hospital, approved Thursday, is causing a stir on Beacon Hill as cost-conscience watchdogs and nature conservationists stand against the famous hospital.

Children's Hospital intends to increase the number of beds at the facility from 404 to 475 in a new 11-story tower on its campus in the Longwood Medical Area in Boston. The expansion will facilitate improvements to the hospital's neonatal intensive care unit, cardiovascular center and other pediatric operations. The $1.07 billion expansion plan assumes an estimated increase in the hospital's' annual operating expenses of around $137.5 million.

That 11-story building is slated to go up on a plot of land that is now the Prouty Garden, a much-loved spot of parkland.

"I've bought patients out there. I have brought patients out there as their last moments," said Mike McGrath, a Children's respiratory care worker at a rally Thursday outside the State House in support of preserving the garden. "That garden is a healing garden. Parents ask us, does my child have to die in the hospital, can't we go out to the garden? That garden is that important to the families."

"We support expansion as well as the garden, and we believe that we can have both of those things and we can support all of Children's Hospital's patients and not just by the building, but by maintaining the Prouty Garden there as well," said Deana Tavaras, a Prouty Garden supporter.

The project won the approval of the Public Health Council Thursday. The panel of experts regulates the medical industry in the state and needed to sign off on Children's proposal for it to get underway.

Gov. Charlie Baker is backing the expansion plan. His Department of Public Health agrees with him that a bigger Children's, one of the state's most expensive hospitals, won't add to the state's already costly health-care burden.

Baker says the nationally known hospital will attract patients from out of state and around the world. As long as local Bay Staters don't have to pay for Children's premium care, the expansion is "not going to have an impact on the local market here," according to Baker.

Baker's comments on the price expansion came after his testimony at a two-day hearing on how to control the ballooning price of health care in Massachusetts. The facilitator of that hearing, Health Policy Commission chairman Dr. Stuart Altman, issued a report in September saying expanding Children's will probably spell higher prices for the Commonwealth's medical bill payers.

Altman's report on the cost impact of the project states that "the [Health Policy Commission] concludes that the projection that Children's additional inpatient capacity will be filled entirely by non-Massachusetts discharges is unlikely based on" the project application, Children's current activities in the market and the hospital's historic trends.