The key importance of nature in the novel The Pearl lies in that nature is unique, unpredictable, and surprising. No matter how much we try to understand nature, it continues to baffle us with new manifestations of its beauty in its constant changes, in its evolution, and it in its capacity to produce rarities.
One of such rarities is the Pearl of the World that so many fishermen covet in the novel. Imagine the chances that, within the depths of the entire world's oceans, a treasure of unique traits and qualities just lays dormant, awaiting for fate to decide when to allow it to surface. That Kino, a man in desperate need, is the one who accidentally stumbles upon such piece of natural wonder is, indeed, a situation worthy of analysis; is this fate manifesting itself, or is it an accident of a morbid origin?
It is clear that Steinbeck is focused on showing how a rare event can intensely shape the everyday life of an everyday individual. Yet, the nature of the individual is what will determine whether this rare event will bless or curse him; whether the individual will allow a great thing to dictate the mandates of his conscience.
In the end, the gorgeous rarity of the pearl does nothing to better the lives of Kino, nor the other fishermen. Allegorically, it means that our human nature is too wicked to understand the rarities of a natural blessing. The men's prejudices, biases, and hunger for riches got in the way of praising and properly admiring the pearl for what it actually is: a fanciful, rare, and beautiful occurrence of nature. Instead, human nature took over, exalting in the men the greed, viciousness, and wickedness of which we seem to only be capable of, even Kino. Although Kino is essentially a good man, Steinbeck is clear in that even a good man can be negatively impacted when greed and ambition get in the way of something meant to be given to him for a good cause.