And it's glass, no? So not going to environmentally degrade over time.
Considering the fighting is mostly over agricultural fields, what are the long term consequences of years of war?
Even if you had 100 drones starting from the same exact place and going to the exact same place you would find 24g of glass per meter. A single leftover beer bottle would be at least 6 times that amount.
When you worry about stuff it is useful to do the work.
And unlike landmines, how do you detect and remove kilometers of cable?
What happens when someone uses agricultural machinery on a field littered with cable, both to machinery and people? What are the consequences of consuming broken bits of cable that may mingle into produce?
And most critically, if the above are issues, how do you then remove cable from fields at scale? It would seem maddening to try to detect and gather kilometers of tangled glass.