女生小视频

MARINE life in the Colorado River delta has still not recovered from the
devastation caused by dam-building upstream in the 1930s. Clam populations, an
indicator of the health of the ecosystem, have plummeted from 50 per square
metre before the dams were built to just 3 per square metre today, reports
Michal Kowalewski of the Virginia Polytechnic Institute in Blacksburg (
Geology, vol 28, p 1059). Water releases over the past 20 years have helped
life along the river recover, but not marine life in the delta, says Kowalewski.
鈥淭his is consistent with the [recent World Commission on Dams] report鈥檚 finding
that efforts to counter the negative impact of dams on ecosystems usually had a
limited success,鈥� he adds.