Bye bye fishies! That's right folks, by 2048 (which is 42 years from now by the way) there will be very few fish in the ocean that we can eat. What shall I do for sushi then?

Let me point out that there have been about 7 (the number can be debated, since there have been a lot of little extinctions and drawing the line between mass extinctions and crappy times is hard to pin down) mass extinction in the history of life on the planet Earth. Here's what usually causes the giant die offs.
1) A change in the global weather patterns or average temperatures.
2) The changing of the ocean to being slightly anoxic (this means the ocean has less oxygen in it, thus it's harder to support life).
3) A trend toward less species more reliant on a specific environment.

Other things can help wipe out life, such as a big meteor strike or massive volcanism. So let's look at what's happening to the globe right now.
Global warming? Check.
Change in weather patterns? Check?
Less species in more specific environments? Check?
Oceans becoming less habitable? Check.

Well, congrats to you! Looks like you're the next contestant on MASS EXTINCTION!!!
It's been a good run, homo sapien, but really you've just overstayed your welcome. As far as I know, you're the only species to actually produce a mass extinction event just be being assholes. Oh well. The average life span for most species is about 2 million years, and we've been here for 3 million or so. Really, it surprises me that homo sapiens ever did anything better than average.