I walked down to the beach at Eagle Landing Park, and I saw a whale.  I have been looking for whales for decades, and never seen a single one despite the occasional report of a whale in the area.  I watched excitedly as it moved closer.  It seemed as if the Orca was swimming toward me.  Before I knew it, the whale launched right up onto the beach and swallowed me whole.  I snaked down into the slimy darkness and wound up in a control room with a humanoid alien.

He said, "Sorry about the rough treatment, but I didn't want to blow our cover.  Please have a seat."

I sat down at a metal table with two large buttons on it.  The one on the left was red, and the one on the right was blue.

The alien, who wore a white suit, pointed to the red button, and said, "If you press this button, a virus will be released into the atmosphere that will wipe out every human on Earth."

I slapped the red button like a game show contestant.

The alien just looked at me with his mouth wide open.  Eventually he said, "Fortunately, the button wasn't live.  Please listen to my entire explanation before you touch anything else.  The virus released by the red button will wipe out all humans in a matter of weeks.  If that happens, nuclear reactors will eventually fail, and release huge quantities of radiation into the atmosphere.  All the cars and buildings and factories will simply rot in place.  No one would be around to undo the damage done by humans."

"You mean, you have the technology to create a space ship that looks convincingly like a killer whale, but you can't clean up the mess left by humans?"

"I only brought the one ship, and my planet is many light years away.  Please pay attention.  The blue button would release a virus that would link all humans to the planet.  A person would feel ill or well depending on the condition of the biosphere.  If the planet were harmed, a person would feel pain.  Any ecosystem that died would result in horrible pain for those people living nearby.  This virus would alter the genome of Homo sapiens so that they became the sensory nervous system of the planet.  Organelles would grow on the peripheral nervous system that linked to similar organelles within all plants and animals.  A human could not damage the planet without damaging himself."

I held my hand above the two buttons, and then brought it down decisively on the red button.

"Again, the button isn't active yet, but why choose to kill all humans?"

"You would be counting on humans to not do things that cause themselves pain.  People don't work like that.  Just yesterday, I bought a bag of Easter candy, and ate the entire bag in one day.  I knew this was bad for my health, maybe even dangerous, and I did it anyway.  You just can't rely on humans to do the right thing.  The biosphere will eventually recover from the release of radiation.  The biosphere will never recover from human destruction if we are allow to go unchecked."

"Interesting," said the alien.  "Not at all the answer I was expecting."

I awoke in my bed, next to my sleeping dogs.  I thought I detected a faint fishy smell, but I couldn't be sure.