Nutrient losses are the next big issue (ie desertification), that and farming practices in general. Currently we use some 1.5kJ of energy to produce 1kJ of energy in the form of food. Those numbers do not add up. Furthermore, we ignore the natural means by which nutrient and trace elements are delivered to plants through the decomposition process and bacterial activity in general. Instead we manufacture nutrients and trace elements in factories at high energy consumption and inject them directly into the soil where they only wash away since there is no biological activity to sustain them.
Arable land will run out, we (stupid as we are) will likely cut down more forests to create more land, thus accelerating the losses of topsoil through erosion, decreasing rainfall, decreasing biodiversity and so on. Arable land will be the next big ticket item.
Buy organic wherever you can, grow your own food if you can, or at least find a local farmers market and find the organic grocers. Again, costs will be higher, but this is reality. Burning 50% more energy than we can produce in the form of food is not sustainable.
I predict that this issue will hit us sooner than you think, perhaps 5-10 years from now. I accurately predicted the current water crisis some 4 years ago too

(not that it was hard to see...but people
are stupid!)