How does Man and the environment interact in The Grapes of Wrath?

The land is a character in this novel and an active one, although its means of pursuit might not appear to be aggressive on the surface. However, a closer look will reveal an incredibly mobile, even aggressive, landscape. Consider the opening paragraph of Chapter 3:
The concrete highway was edged with a mat of tangled, broken, dry grass, and the grass heads were heavy with oat beards to catch on a dog’s coat, and foxtails to tangle in a horse’s fetlocks, and clover burrs to fasten in sheep’s wool; sleeping life waiting to be spread and dispersed, every seed armed with an appliance of dispersal, twisting darts and parachutes for the wind, little spears and balls of tiny thorns, and all waiting for animals and for the wind, for a man’s trouser cuff or the hem of a woman’s skirt, all passive but armed with appliances of activity, still, but each possessed by the anlage of movement.
ACTIVE VERBS: catch, tangle,spread, dispersed, twisting, armed
STRONG NOUNS: darts, parachutes, spears, balls, thorns
STRONG ADJECTIVES: concrete, broken, dry, heavy, armed, twisting
There is a parallel to the Joads and the other “Okies” here as well. Although these impoverished families seem passive, at the mercy of the winds that blow them off their farms and the machinery which shoves them aggressively from one side of the country to the other, they too are armed with “appliances of activity” which will allow the people to replant and live again.
A land turtle crawls through this near war-zone-like environment:
And over the grass at the roadside a land turtle crawled, turning aside for nothing, dragging his high-domed shell over the grass: His hard legs and yellow-nailed feet threshed slowly through the grass…
It should be noted that there are parallels between the turtle and his “high domed” shell and the jalopies that traveled along Route 66 to California. These trucks were often piled so high with all of a family’s worldly possessions that the vehicles bore an uncanny resemblance to land turtles. Their movement, like the turtles, was necessarily slow due to the extreme weight the axles had to bear and the precarious arrangement of the items salvaged from homes.
There are further parallels to the turtle and the Okies. As the turtle crawls along, the head of a wild oat becomes trapped in his shell. A laborious climb up a steep hill does not dislodge the oat and finally the turtle plods across the highway as it had originally intended.
At this point, two cars come speeding down the highway. The first car is driven by a woman:
A sedan driven by a forty-year-old woman approached. She saw the turtle and swung to the right, off the highway, the wheels screamed and a cloud of dust boiled up. Two wheels lifted for a moment then settled. The car skidded back onto the road, and went on, but more slowly. The turtle had jerked into its shell, but now it hurried on, for the highway was burning hot.
The second driver is male.
[T]he driver saw the turtle and swerved to hit it. His front wheel struck the edge of the shell, flipped the turtle like a tiddly-wink, spun it like a coin, and rolled it off the highway. The truck went back to its course along the right side.
The differences between female protective action and male aggressive destruction are readily apparent. As for the turtle, he, like the many other aspects of the natural landscape, carries on:
Lying on its back, the turtle was tight in its shell for a long time. But at last its legs waved in the air, reaching for something to pull it over. Its front foot caught a piece of quartz and little by little the shell pulled over and flopped upright. The wild oat head fell out and three of the spearhead seeds stuck in the ground.
The turtle, like the Joads and many of the other travelers, eventually makes it to the other side of the road. It plants the seed where life will be renewed. The migrants must create new life in a new place, much like the turtle has done.