Doing the scientific research is the step that you left out in your "therefore" statement. That is the important step. Quantifying the effect rather than saying "yep, CO2 is up, the world is coming to an end and my corns are hurting" is what I'm trying to clarify.

And the jury is still out about global warming. The margin of error is higher than the claimed rise in temperature.

Maybe the poison ivy grows better when surrounded by certain other plants - or maybe somebody was trying to get a bigger crop and spilled some of the fertilizer.