Climate change is going to affect agriculture across the world as rising temperatures make many dry regions even drier, hot regions hotter, and wet regions more prone to flooding. All of those changes are going to affect the way the world's food is grown.

Some regions are going to get better for growing food, but the places where most of the food is grown currently are going to see a decrease in crop yields, Bank of America Merrill Lynch's Sarjbit Nahal noted in a recent report on the future of food security and agriculture.

A change in temperature by a few degrees doesn't sound like much. But in the long-run and in the grand scheme of things, just a few degrees of temperature change can have massive implications for global agriculture.

"A world even 1.5°C [warmer] will mean more severe droughts and a global sea level rise, increasing the risk of damage from storm surges and crop loss and raising the cost of adaptation for millions of people," Nahal wrote.

"Under 3-4°C warming, large negative impacts on agricultural productivity can be expected, and there is some empirical evidence that higher atmospheric levels of CO2 could result in lowered protein and micronutrient (iron and zinc) levels of some major grain crops (e.g., wheat and rice)," he continued. "The projected impacts on subsistence and export crops production systems (e.g., soybeans, maize, wheat, and rice) would be felt at the local, national, and global levels."

Here's a map from Nahal showing how crop yields could fluctuate under a 3°C warming scenario.