Why America’s Greatest Natural Landmark is in Danger

It’s a sad fact for the United States that not even our country’s greatest natural landmark, the Grand Canyon, is exempt from the effects of pollution.

National Geographic spoke to David Walters, lead author of a new research conducted by the U.S. Geological Survey about the pollution that has crept into the water of the Colorado River which created the canyon. Walters and his team have been studying the river and the wildlife that depend on it and were disappointed to find that high levels of mercury and selenium have been detected in its waters.

“Pristine doesn’t really exist in the world anymore. Even at the most remote reaches of the Grand Canyon,” said Walters.

The heavy metals found in the waters have a direct impact on the fish and snails that live in the river, which leads up the food chain to birds and other wildlife. Mercury is a potent neurotoxin that can alter brain development of fish, reducing their ability to escape predators and cause birth defects such as deformed eyes, mouths, and fins. The levels of mercury found in the speckled dace and fathead minnow were 30 to 40 times higher than what is considered safe for the wildlife to eat.


Pinpointing exactly where the heavy metals contaminating the canyon’s waters are coming from isn’t so easy, since it’s likely a variety of sources. “Mercury is everywhere now,” said Walters. “There’s a global pool of it in the atmosphere.” Old gold mines in the canyon’s vicinity leak it and mercury from coal-burning power plants in China drifts across the Pacific and ends up in rivers throughout the West. The canyon is also under mercury threat from power plants like the Navajo Generating Station 50 miles to the northeast and just five miles from the Colorado River. Farming operations hundred of miles away from the Grand Canyon also flood the streams with selenium-rich soil that finds its way into the Colorado River every year.

There is hope, though, that the mighty Colorado River might escape the contaminated fate that has fallen on so many of he world’s waterways. While mercury emissions in China increased 164 percent from 1992 to 2007, the nation recently adopted its own plan to cut power plant emissions, and U.S. plants have been ordered to cut mercury emissions by 70 percent under an EPA ruling.

“In the big scheme, this is one more important indicator that what we do outside of the Grand Canyon can and does adversely affect what’s living in the Canyon,” added Roger Clark, who is a Director of the Grand Canyon Trust.

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