Yael: Hey Don . . . did you know that twenty-four billion tons of soil is lost to erosion      every year?

Don: Really, Yael? I did not know. What happens to the soil?

Y: Well, when farmers plow their fields they leave the soil bare and exposed to the      elements. So wind and rain can pretty easily sweep soil away into rivers and lakes.

D: That sounds bad.

Y: It is. Some geologists call soil erosion one of the fundamental problems of civilization.      I mean, without enough soil we can't grow food. And without food, we can't live.

D: Is there any solution?

Y: Well, there are alternative ways to farm that don't involve plowing. One is called no-      till farming. Basically, instead of plowing a field, farmers plant new crops down      through the residue left over from previous crops. The left-over stalks and cutting act      like a kind of organic blanket protecting the soil from runoff. Of course, no-till      farming also leaves more weeds, which requires farmers to use more herbicide, so      there is a tradeoff. That's why some experts say that the best way to save soil and      protect the environment is to combine no-till agriculture with organic farming.

D: Okay, but hold-on a sec . . . if plowing is so bad for soil, why have farmers been      doing it ever since farming was invented thousands of years ago?

Y: Because for the individual farmer, losing a few centimeters of soil is hardly noticeable.      So soil erosion doesn't seem like a big deal. But add those few centimeters up all      over the world and over thousands of years and you've got a truly fundamental      problem.  

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