Roamer

It wouldn't be "humans communicating with aliens" it would be "aliens using their high-frequency-brainwave-beam-device" to communicate with humans

That's like saying people should eat shit so they discuss the taste, instead of offering them a banana whose taste they can discuss without getting sick.

1) sure they thought of that, just do a google search, often a camera is attached to a helmet or put on a gun. 2) seems a bit impractical compared to just bombing the enemy, or having armored vehicles present(some of which are quite light and can be transported through air) or just dropping a barricade would also be a good idea; you don't expect soldiers to get fired on from all sides

By what measurement ? As i see it, we 've had little to no use to them, and they 're often poisonous, more harmfull then helpfull, which is enough for any negative reaction to evolve: in evolution a reaction is only "excessive" when it is disadvantageous.

Pollution can make certain systems collapse by poisoning creatures that fulfill a certain niche. EVERYTHING collapsing is nigh impossible; it's best to look at matter first, i ll try to discern 3 categories(more are possible): 1) certain matters are biologically usable; they can be made part of the bio-mass(=animals, plants) 2) other materials aren't realy usable by(/in) lifeforms (most metals) pollution would have to continue for a huuuge time before we 'd run out of matter for bio-mass 3) the third category are materials that would poison creatures; these materials could/would be consumed by creatures that cannot handle these materials, (ps:many materials are not poisonous untill taken in in large enough quantities) radio-active materials can be counted under the third category. The materials under category 2 and 3 do not necessarily increase, though they are pulled out of the earth and thrown into the atmosphere(=biosphere) (regional) eco-systems can(and have) fallen due to pollution, generally speaking the first ones to observe it happening are locals near the eco-system, not people local to the polluting factory(/car/cow/..) Humans getting poisoned until civilised systems fall/fail because of pullution ... well, i doubt even the Chinese would ever allow thát to happen.

They may be there as some kind of passage for animals, although Russia doesn't realy need those.