It makes intuitive sense to me that heat would reduce crop yields, just by stressing many plants as they try to conserve water and limit evaporation. I hadn’t considered the way heat might affect pollen production and pollinators, but this is also an issue.

But one point is becoming alarmingly clear to scientists: heat is a pollen killer.

Even with adequate water, heat can damage pollen and prevent fertilisation in canola and many other crops, including corn, peanuts, and rice. For this reason, many farmers aim for crops to bloom before the temperature rises…

In fact, heat hinders not only tube growth but other stages of pollen development as well. The result: a pollen grain may never form, or may burst, fail to produce a tube, or produce a tube that explodes. 

BBC

It sounds like research is needed just to hold the line on the crop yields we have now, let alone achieve the increases we need to meet projected population and consumption growth. The more I think about climate change and the broad range of issues it is going to cause, the more I think food may be the most critical issue.