America’s rivers are changing color — and people are behind many of the shifts, a new study has found.
Only about 5% of U.S. river mileage is considered to be blue — a color often equated with pristine waters by the general public. But 28% of the rivers are green, which often indicates that they are choked with algae.
“If things are becoming more green, that’s a problem,” said study lead author John Gardner, a University of Pittsburgh geology and environmental sciences professor. Although some green tint to rivers can be normal, Gardener said, it’s often an indication of large algae blooms that cause oxygen loss and can produce toxins.
The study looked at more than 230,000 NASA satellite images taken over 35 years, focusing on rivers and reservoirs. It found that much of the shift to greener rivers happened in the North and West…