When I say all governments on the surface of the earth will be gone from the surface by 2050:

 I'm maybe not saying what you think.

What I'm actually saying is that people in governments on earth can no longer survive above ground without being targeted and killed by 2050 so they have to live and work underground to stay safe enough to live without being killed by the drones of the Air or the land everywhere on earth.

Are there plants and trees and animals still on earth?

I hope there is but I'm not seeing which was this goes or not.

For example, if Land, Air, Sea and Space drones were programmed ONLY to kill humans then there might be animals still alive on earth.

Otherwise, if it is programmed to kill anything that moves it would be literal to the programming of that robot or robots and it would kill all animals and birds in addition to human beings too.

So, it would all depend upon the programming of the Land, Air, Sea or Space Drone to begin with.

There are some science fiction series and movies about all this. 

A friend of mine likes the one called "Silo" but it makes me to claustrophobic to watch myself so I watched and episode or two before it creeped me out.

Can robots of Land, Air, Sea and Space be stopped from killing humans?

This is possible if you build other robots faster and stronger to kill the ones that kill humans that aren't programmed to kill humans but only bad robots.

So, the only way governments survive all this is if these governments make sure the bad robots are either not manufactured or that they are all killed or disposed of in some way.

Which could take the human race (this has happened many times before on earth) where a few humans destroy ALL technology so that some humans can survive and we go back to where Native Americans were when our ancestors arrived from Europe.

Like I said this has happened periodically for millions of years here on earth by the way, especially during Ice Ages where all technology was lost by humans or humanoids living here on earth.

So, what may happen has happened many times before now here on earth to humans and humanoids.