I can see no scale units on that graph so it means nothing to me, I'm afraid. Are these lines High voltage or for domestic distribution?
There are Power Lines all over the country and I have never noticed strips of different colour / density on fields used for either crops or animal grazing.
For decades, there have been claims that power lines have an effect on the health of people living near or below them. (Spend a few minutes on Google Earth)
Of course, it is not in the interest of Power companies to accept there is a case against them so there is always the possibility that the 'facts' have been suppressed. Personally, I would believe that there may be some correlation between power lines and health - but there is also a strong negative correlation between routing of power lines and the income (aka influence) of people near them. Overall, that could imply a causal relationship between income and health but nothing else.