My thoughts are specifically about climate change in general. We clearly are the cause of desertification when we practice bad farming techniques, and we deforest. This turns once fertile lands into arid deserts. We most certainly can drain millions of years old non renewable in our lifetimes aquifers. All of these little things do have an affect on our climate. When we chop the forests down, they are no longer cooling our air, or producing rain through transpiration. These are real quantifiable effects that man has on the climate. We are also in effect causing more storm energy to be released on the planet through these changes. We are most certainly acidifying our oceans, this will have drastic long term effects on our climate. You have to look deeply at the interconnected nature of the climate to get a grasp of the big picture.
We need to end commercial large scale single crop agriculture. I have several threads on the topic.