India, July 31 -- Before the first light reaches the forest floor, the kithul tapper is already climbing. His bamboo ladder leans against a fishtail palm that rises 40 feet above the wet earth of Ambegoda, in southern Sri Lanka. The air at this hour is cool and close, thick with the smell of damp leaf litter. At the top tree, in the blue-grey sky before dawn, he binds the tree's flower stalk with vine, makes a precise cut with a knife his father once carried, and sets a clay pot to catch what follows: a thin, milk-white sap that will begin its slow drip toward something extraordinary.

By the time the sun is ready to set, he will climb again. This is the rhythm of kithul madeema (kithul tapping)-a practice that has structured daily life i...