I encountered this interesting lecture by Guy McPherson today. It runs for about 48 minutes, so you will need some time to spare.
I feel his predictions are on the alarmist side of reality, but I am not convinced of that. My personal take is that the decline will not happen for another couple of years at least and probably more. However, the future we are headed for will look something like the picture he paints.
I found it interesting, if unsettling. Your mileage may vary.