Drifting down Sungai Pin in Sabah by boat, Borneo's majestic forests come alive with southern pig-tailed macaques frolicking along the riverbanks and proboscis monkeys lounging in the treetops.

However, the spellbinding view is broken by the sight of rope bridges connecting the forest canopy from one side of the river to the other.

At first glance, the bridges appear to be part of an obstacle course for thrill seekers.

However, these carefully crafted canopy bridges are not for people’s enjoyment. Instead, they are meant to...