Under the terms of the new deal, United States Sugar will be able to keep farming some of the land for at least seven years. As a result, some environmental experts believe, the Everglades will be worse off in the short term.

“What you have is just another step in the category of kicking the ball down the road and chasing it,” said Alan Farago, the conservation chairman of Friends of the Everglades.

Criticism from other environmentalists, though, has been muted. Some have acknowledged concerns, but do not want to say anything that might help kill what would be the largest land purchase ever for the Everglades. With the state retaining an option to buy the rest of United States Sugar’s land, there also remains a romantic adherence in some quarters to the dream of a restored river of grass from Lake Okeechobee to Florida Bay.

“The whole concept that we are able to get additional land out of the E.A.A. — that has always been very difficult to do in the past,” said John H. Hankinson Jr., chairman of the board of directors at Audubon of Florida, referring to the Everglades Agricultural Area. “And that I think is ingrained in a lot of the consciousness of the people involved in this.”

Even if the deal goes through, it could be another generation before the Everglades gets what it needs.

Mr. Buermann said the water district was still analyzing whether it could afford to pay the $536 million and would discuss it at a two-day board meeting beginning Wednesday. Mr. Crist recently appointed two new members to the water board, both of whom support the purchase.

In an interview on Feb. 26, by phone as he traveled through the Everglades on the road known as Alligator Alley, the governor said that critics of the deal would come up with “all kinds of reasons not to do something.”

“But what are they doing to try and preserve the Everglades, other than complain about it?” he said. “What are they doing in a productive way to move forward and preserve this national treasure that exists nowhere else on the face of the earth? Nothing but complain. I rest my case.”