All changes impact nature, only questions of how much, what’s impact, etc — and my guess in the impact of tunnels is poorly understood. While not tunnels, hydra

All changes impact nature, only questions of how much, what’s impact, etc — and my guess in the impact of tunnels is poorly understood. While not tunnels, hydraulic fracturing ("fracking") to known to increase earthquakes. Another likely impact would be any vibrations that reach any organisms able to sense them, which might in turn change the behavior on organisms above the ground.