英語聽力：自然百科 退田護河

Out of the Blue Ridge Mountains in northwest Georgia, the cold waters of the Conasauga Riverdescend toward Tennessee.

Flowing back and forth across the state line, the River's abundant wildlife and unspoiled beauty is a remnant of the past--a fading memory that Carton Petty wants to restore.

"I found out it phased out. Take care of the land and it’ll take care of you."

It break, (if) you didn't.

Petty purchased this land several years ago to grow corn and raise dairy cattle. Today, his farm covers more than 7,000 acres, 170 of them along the Conasauga. To preserve the beauty of the river and his property, Petty has built buffer zones--dedicated strips of land to stop chemicals he spreads on his crops from running into the river, and to prevent bank erosion.

"Yep, this, this is just the new buffer we put in and it just, They were sold in November. And it’ll take about a year for you to get established good. "

Buffers are an idea from the Conservation Reserve Program--a United States Department of Agriculture backed initiative that brings landowners, local alliances, and other government agencies together. Nevertheless, keeping an old river like this one healthy in a modern world is difficult.

Beneath the surface of these waters, a pollutant is killing one of its oldest residents --a rare kind of mussel(貽貝). And no one knows exactly where it is coming from.

"This animal's, probably, 20 to 30 years old... "

Paul Johnson with the Tennessee Aquarium has the task of figuring out how to preserve the mussels and help them reproduce.

"This animal’s called... Its scientific name is Cora-bean Hellene. Its common name is the Georgia Pigtail. It was believed to be extinct, then we found this species alive in the Conasauga River, and as far as we know, Conasauga is the sole river that contains this species"

It is a race against time. As long as they cannot figure out what is killing the mussels, that something poses a threat to the whole river.

While the work goes on, the Petties will keep doing their part.

"It's lucky we got something special here with the Conasauga. So, I think we all well understand and start to realize that. And we're trying to do the appropriate steps to keep it a clean and beautiful view."