More than half of US wetlands have been drained for development, farmland, and other purposes. That's 100-million acres now dried up.
The Bush Administration has continued a "no net loss" policy of any more wetlands.
So, when someone wants to drain a marsh or a swamp for, say, a new housing development, they've got to build a man-made wetland to replace it.
But a new study is finding that most of those man-made wetlands aren't doing very well.
Julie Grant reports.
