Science Fiction & Fantasy Stack Exchange is a question and answer site for science fiction and fantasy enthusiasts. It only takes a minute to sign up.
Sign up to join this community
Short story that I believe was fairly recent.
This is a long shot, but hauntingly similar to your description.
"Recording Angel" by Ian McDonald was written in 1996.
It is set in Kenya rather than the Amazon.
Earth is being transformed by space-borne nanotech that fell first in Kenya. So instead of terraforming, the story introduces the term "xenoforming".
The xenoforming "stuff" is called the Chaga. It is unstoppable by any human means, and, like the famous Body Snatcher pods, but at the nanometer level, is inexorably covering and changing the entire planet.
The story is written in the third person, but gives the strong sense of being narrated, because it primarily speaks from the thoughts and personal experiences of the woman named Gaby who is a journalist assigned to be the "recording angel" of this unstoppable process.
Mismatch: It does not match the requisite of describing a man's spine being xenoformed.
However, her main correspondent and subject, the other protagonist of the story, is determined to explore this phenomenon no matter what it does to him.
He is a hunter by the name of Prenderleith. She thinks, "He look[s] like the last of the Great White Hunters."
As they observe the advancing landscape turned into alien colored hexagons, he shows her an elephant being xenoformed, with veiny growths and limbs ending in something disturbingly like human hands.
At the end of the story, he runs into the advancing growth. His fate is no different from all other humans on earth; he is simply meeting it sooner.
I read this story in the anthology "Nanotech" edited by Jack Dann and Gardner Dozois in 2000 (which also contains "Blood Music").
I did not know that Ian McDonald had written an earlier "Chaga Saga" for Asimov's Magazine called “Towards Kilimanjaro'.
He also wrote a sequel to it called "Kirinya".
They are also set in Kenya, not the Amazon. However, now I wish to read them. I do not know if perhaps one of them describes a person being xenoformed. That is worth an exploration.
Another long shot: "The Crystal World", J G Ballard (1966). Summary from Wikipedia:
The protagonist is Edward Sanders, an English medical doctor, who arrives to the river port of Port Matarre, in Cameroon. From here he tries to reach a leprosy treatment facility where his friends, Max and Suzanne Clair, live. Soon, however, he starts to recognize that a mysterious phenomenon is crystallizing the jungle along with its living creatures. The same phenomenon is reported to be present also in the Florida everglades and in the Pripyat Marshes (Soviet Union) as well. Scientific explanations of the phenomenon are provided within the book: however, Ballard offers mostly an interior and psychological perspective about it, directly through Sanders' experiences. Several facts, furthermore, remain unexplained: for example, the ability of jewels to liquefy the crystals. The crystals also have the property to keep objects and beings in a suspended state of existence. Many passages deal with this characteristic, pointing out its capability to stop time and life.
As hinted in that summary, the internal narration is strange enough that it is not entirely clear what is happening. Supposedly the affected humans are suffering from leprosy, but one interpretation is that really it is the same crystallization process that is affecting the jungle.
Apparently Ballard took much of the setting and events of this book from his earlier short story "The Illuminated Man". I do not know whether that story would be a better match to your description.
