The machines are shown to be heartless while the farmers are connected with the land. He who tills the land with his blood and sweat is the rightful owner of the land - not some large corporation. Steinbeck pretty much proposes that we stop the march of modernization. Go against the natural scheme of things in a way.
However, the Dust Bowl of the 1920s was a human tragedy caused by overpopulation.The implications on human life were tragic, but fact remains that we ended up over populating an area which couldn't sustain the human density. Natural balance had to occur. Maybe I appear radical because most droughts or famines could then be explained away as 'natural corrections'. What about the eyes of helplessness, the starving children, etc? As an answer, I think we just need to expand our lens a bit.
We as a species have taken over forests and converted them into farmlands. Sent several species into extinction in the process. There could have been a similar impassioned appeal by nature against man. But the fact is, it was in the natural course of things. About 20,000 years ago, we became at last the one species in the history of the earth which could
Grasslands are by definition areas where denser vegetation is unable to survive (due to difficult climate). Instead, they sustain a delicate ecosystem comprising grasses, birds, small rodents, etc. However we humans have time and again converted grasslands into farms. The result? These farms may run fine for 10 or 20 years, and then boom, one day nature catches up via a large drought. Steinbeck himself talks about this sequence of events (rampant agricultural-ization of Oklahoma wildlands) as the precursor to the dustbowl events of the 1920s. So when the drought did hit, population was bound to rebalance. Then why blame the machines?
I believe that the same issue holds true for semi-arid areas of the Indian subcontinent. Parts of Vidarbha, Telangana, perhaps Orissa...they probably can't sustain the level of farming we have today (where every square inch of non-hilly terrain is under farms). Absolute recipe for disaster. Agricultural advances in the 60s (Green Revolution) mean that at least the farmers in these regions wont die for lack of food, but it becomes difficult for them to sustain anything but the most basic, haphazard lives. Perhaps that is the reason why tragic farmer suicides are so common here. But while this human tragedy has been unfolding over the last few decades, an equally tragic consequence has been the extermination of grassland species. The Great Indian Bustard is of course the poster-boy of grassland species. Nearly extinct. So too are dozens of other, smaller species. How is one to say which is the greater tragedy?