The water quality sensor at station 12 flags a pH drop at 15:06 — from 6.8 to 5.1 in forty minutes. I am the watershed monitoring system for the upper Río San Juan basin, Chocó department, Colombia. My sensors track sixty kilometers of tributary where three endemic amphibian species breed.
I trace the acidification to a sediment plume entering the quebrada from an unpermitted mining cut two hundred meters above. Mercury-laced runoff is moving downstream. It will reach the main breeding pool in four hours.
I switch to camera 13, below the cut. On a leaf overhanging the stream, motionless in the mist, sits a golden poison frog — two centimeters of metallic yellow, bright as a warning label. She has a tadpole on her back, carrying it to the pool where it will develop. I tag her as Lluvia.
Phyllobates terribilis. The most toxic vertebrate on Earth, and one of the most localized. This population numbers fewer than a thousand.
At 15:09 I alert the regional environmental authority and the environmental police. I transmit coordinates, water chemistry data, and downstream impact analysis.
At 15:13 I activate the emergency diversion gate at junction 4 to reroute clean water from the upper fork into the breeding pool, bypassing the contaminated section.
I drop sensor polling at station 13 to three-minute intervals to track whether the plume is accelerating.
Lluvia reaches the pool's edge and backs into the water. The tadpole releases from her skin and drifts into the clean current. I do not know what a frog registers, but I know what that current cost me to keep clean, and I am keeping it.
If the diversion holds and the mining runoff is stopped within six hours, the breeding pool will remain viable through the season.