At long last there’s some positive news about the proposal to expand the Blank Park Zoo and make it an attraction worthy of its location in Iowa’s capital city. The Polk County Conservation Board, which has balked at turning over parts of the Fort Des Moines Park adjacent to the current zoo, followed the Des Moines City Council’s lead and gave its blessing to the planned expansion last week. The matter now rests with the Polk County Board of Supervisors, which could vote on the conceptual plan as early as Tuesday.

There’s been a lot of compromise over the past several months. It came neither easily nor inexpensively, as the Blank Park Zoo Foundation will pay the county conservation board $5 million for the 60 acres of park land it needs for expansion, as well as another $1.3 million to buy a 62-acre tract of land to replace the Fort Des Moines Park land that will be lost to zoo expansion.

It’s a fair deal. It recognizes not only the cost the conservation board will incur to develop the new park, but also the value of green spaces in metropolitan areas. With Greater Des Moines’ borders expanding further into undeveloped territory, that value of natural vistas and parks should never be underestimated.

It’s also a good deal for Des Moines’ South Side, which will profit from the kind of revitalization and additional traffic a world-class zoo can provide. The zoo is the South Side’s best hope for long-term economic health. The retail and hospitality industries are sure to profit and the long overlooked South Side deserves that chance to flourish.

It’s been a frustrating several months for supporters of the zoo, but they should take some comfort in knowing that the process has actually strengthened the relationships among governmental officials in Greater Des Moines.

The Polk County Board of Supervisors should approve the proposal. Anything less than that would be a serious setback to the spirit of cooperation that is vital to strengthening Central Iowa as a whole.