It was the worst man-made environmental disaster in the nation’s history, but unlike other calamities of nature, this one took only 40 or 50 years to create. And once it started, it lasted a decade, claimed many lives, either through “dust pneumonia” or suicide, and taught us very little about taking the long view of our land over the opportunity for quick financial gain.

Ken Burns’ The Dust Bowl, a four-hour documentary airing in two parts Sunday and Monday, is not one of his better films by any means, but it makes its basic points and, more important, gives us an oral history from members of the aging generation who lived through the “dirty ’30s.”

Written by longtime Burns collaborator Dayton R. Duncan and narrated by Peter Coyote, it is, alas, well timed: It was only this summer that the Midwest endured a serious, extended drought.

During the 1930s, the hardest-hit areas were the Oklahoma and Texas panhandles, the southwestern corner of Kansas, northeastern corner of New Mexico and the southeastern corner of Colorado. For several years before the drought hit, farmers there enjoyed boom times. Their wheat crops were abundant, and there was a good market. The bottom fell out when the Great Depression hit, and in 1931, it stopped raining.

While the decade of drought was obviously a natural phenomenon, the Dust Bowl was caused by innovations that had enabled farmers to plow up a lot of land in a short period of time. Once the grasses of the Great Plains were replaced by crops, the stage was set. Winds sweeping down from the north and west were able to carry the topsoil away in huge “black blizzards.”

Vintage photographs and film add enormously to our understanding of the Dust Bowl, using the term coined by journalist Robert Geiger after the infamous Black Sunday dust storm of April 14, 1935. And the interviews with people who were mere children when the drought and dust hit are convincing and eloquent in their simplicity, as opposed to the windy script by Dayton and Coyote’s usual funereal intonation.

We hear an elderly man speak about the death of his precious young sister. She died from “dust pneumonia” the same time the disease claimed the family matriarch. A woman recalls her father having to club a young calf to death because there was too little milk to support both the animal and his little girl.

The end of the Dust Bowl came only when it started to rain again, but in the meantime, the federal government did what it could to help, first by teaching farmers how to minimize their land’s vulnerability to the winds by employing contour plowing, and then through New Deal relief efforts.

Like Burns’ 2011 Prohibition documentary, The Dust Bowl has implicit cautionary advice for our own times. Today, farmers in the Great Plains have some protection against drought because of an aquifer that stretches from South Dakota to north Texas and is used for irrigation. But half the water in the aquifer is already gone, and the rest could disappear in 20 years.

As a film, Dust Bowl is sadly lacking. It’s in dire need of tighter editing, most of all. The script is informative, but it’s also so full of itself that you’re even more grateful for the eyewitness interviews.

But this is how Burns makes films. When he isn’t sufficiently detached or disciplined to make needed cuts and to sharpen his focus, we get The Dust Bowl or The National Parks: America’s Best Idea, a six-part slog that made you want to fell every tree in Yellowstone.

Dust Bowl isn’t quite that bad, not just because it’s not as long, but because of the people who were there. Even all these years later, you can see and hear how fresh the memories remain, and it breaks your heart.