Discuss the role of evidence-based monitoring (camera traps, acoustic sensors) in judging whether eco-friendly infrastructure works. Illustrate with Indian examples.

Wildlife underpasses, overpasses and guide fencing are only "eco-friendly" if animals actually use them and fewer animals die on the road. NHAI says it has spent about ₹19,700 crore on wildlife mitigation over five years, with more than 2,150 structures built or proposed, and treats camera-trap evaluation as part of the process [1]. Monitoring turns these spending claims into results that can be checked.

Role of evidence-based monitoring

• Proof of use: camera traps record which species cross, when they cross and how often.
• Feedback on design: acoustic sensors link noise to animal behaviour. On the Delhi–Dehradun corridor, elephants and spotted deer preferred the quieter underpass segments [2]. This shows where noise barriers are needed.
• Finding hotspots: monitoring identifies collision hotspots, which NHAI then marks with speed boards and signs [1].
• Accountability: checks after construction show whether MoRTH has followed the mitigation steps prescribed by the NBWL [3].

Indian examples

• Delhi–Dehradun Economic Corridor: the NHAI–WII study "Landscapes Reconnected" ran for 40 days with 150 camera traps and 29 AudioMoth recorders. It recorded 40,444 images of 18 wild species using the underpasses [2].
• NH 715, Kaziranga: a 12-month WII–NTCA survey counted 1,176 roadkills in 2019. Reptiles were about half of them, and large mammals only 3.48% [4]. Structures designed for big mammals therefore miss most of the animals being killed.

Limits of current monitoring

• Use is not the same as survival: counting crossings does not measure deaths outside the structures, or deaths of animals too small for the cameras.
• Undercounting: on NH 715, large-mammal carcasses were removed within 12 hours [4], so many deaths go unrecorded.
• Seasons: a 40-day study can miss the worst period. At Kaziranga, hog deer and sambar deaths peaked in July–August, when floods push animals across the road [4].
• Barrier effect: hog deer avoided noisy roadside strips [4]. This loss of habitat does not show up in underpass counts.
• Counting inputs, not outcomes: the headline figures count rupees and structures, and mix completed work with plans [1].

Monitoring links the promise of green highways to what actually happens on the ground. Next steps: year-long roadkill surveys before and after construction, covering all animal groups; seasonal speed controls; and separate reporting of completed and proposed structures. These would make India's highways measurably safer for wildlife, in line with SDG 15 (Life on Land).