Oxy Morons

I get a kick out of things I see that seem to be contradictory, otherwise known as "Oxymora".  No, these aren't those people of low intelligence who pull down the breathing apparatuses in airplanes.  They're the things that just don't seem to make sense.  For example, why would cacti be thriving right next to a large reservoir?

Or why would a normally pale ocotillo bush be so bright green?

Then why is this man-made engineering marvel placed in a desert wilderness?

How can this little flower survive completely surrounded by concrete?

How can this huge, but fragile spider survive walking across a road traversed by hundreds of cars a day?

 How can these cacti emerge from solid rock and grow so large that they weigh several tons?

I don't know the answers to these questions, but it's always fun to notice the oxymora in nature and humanity and ponder their true meaning.