(CBS) — A retired astronaut and a horticulturist had some sobering prediction as the Chicago Botanic Garden marked World Environment Day Saturday.

Four-time Space Shuttle astronaut and physician Dr. David Hillmers likened the planet Earth to a lifeboat. Asked if man is punching holes in the bottom, he said, “If we don’t take care of it, I fear it’s going to sink – and that’s literally what’s going on right now, I think.”

Today, Hillmers practices medicine in far-flung corners of the world, focusing much of his practice on underserved populations.

The retired Marine Corps colonel said that what he sees is a mixed bag. He said he is encouraged by efforts to restore rainforests in Brazil. But he said actions such as Saddam Hussein’s decision to drain the Mesopotamian marshes and all but destroy one of the cradles of civilization to root out Iraqi insurgents don’t bode well.

Botanic Gardens horticulturist Patti Vitt said that, even with reasonable efforts to control global warming, Chicago could be nearly 7 to 19 degrees warmer in winter by 2080 and even hotter during the summer, with changed rain patterns concentrating rain in the winter and spring and spawning fewer flowers and eternally brown lawns each summer.

She said the resulting climate would be far more like that of east-central Texas today.

“Maybe we’d get the beautiful Texas bluebells,” she quipped.

Hillmers said that if left unchecked, eventually moving man to the moon or Mars may not be movie fantasy but a must, an undertaking that he said would be enormously expensive.

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