Mr. Merwin’s ardor for the natural world took frequent root in his poetry. But while for many poets nature begets odes, for him it was far more likely to inspire elegies. In “For a Coming Extinction,” part of his acclaimed 1967 verse collection, “The Lice,” he wrote:

Gray whale

Now that we are sending you to The End

That great god

Tell him

That we who follow you invented forgiveness

And forgive nothing

I write as though you could understand

And I could say it

One must always pretend something

Among the dying

When you have left the seas nodding on their stalks

Empty of you

Tell him that we were made

On another day

Stylistically, Mr. Merwin’s mature work was known for metrical promiscuity; stark, sometimes epigrammatic language; and the frequent use of enjambment — the poetic device in which a phrase breaks over two consecutive lines, without intervening punctuation.

“It is as though the voice filters up to the reader like echoes from a very deep well, and yet it strikes his ear with a raw energy,” the poet and critic Laurence Lieberman wrote, discussing “The Lice,” a collection whose bitter contents were widely understood as a denunciation of the Vietnam War. He added:

“The poems must be read very slowly, since most of their uncanny power is hidden in overtones that must be listened for in silences between lines, and still stranger silences within lines.”

The themes that preoccupied Mr. Merwin most keenly were those that haunt nearly every poet: the earth, the sea and their myriad creatures; the cycle of the seasons; myth and spirituality (he was a practicing Buddhist); personal history and memory; and, above all, life and its damnable evanescence.

Yet there was about his work an intensity of purpose — heightened by a formal style not quite like anyone else’s — that, his champions maintained, gave it a fervor often described as oracular. A “post-Presbyterian Zen poet and channeler of ancient paradoxes,” The Los Angeles Times called him in 2007.

In “Leviathan,” from his 1956 collection, “Green With Beasts,” Mr. Merwin evokes the epic verse of old through his strategic use of alliteration, the central organizing principle of Anglo-Saxon and Old Norse poetry:

The hulk of him is like hills heaving

Dark, yet as crags of drift-ice, crowns cracking in thunder,

Like land’s self by night black-looming, surf churning and trailing

Along his shores’ rushing, shoal-water boding

About the dark of his jaws; and who should moor at his edge

And fare on afoot would find gates of no gardens,

But the hill of dark underfoot diving,

Closing overhead, the cold deep, and drowning.

Some critics indicted Mr. Merwin’s later work for trafficking in a level of abstraction bordering on the obscure. It was rendered even less accessible, they complained, by the fact that by the late 1960s he had jettisoned punctuation almost entirely. (Mr. Merwin had his reasons, which spoke to the very heart of his lifelong poetic program.)