# 20.1: Background

A critical human activity that is heavily impacted by changing climate is agriculture. Because what is grown in a region is determined by temperature and water availability, regional climate change alters what can and cannot be grown there. One measure of an area’s ability to sustain certain crops is thermal suitability. This metric is derived from the range of temperatures in an area, the coldest temperatures a crop can survive, and the amount of heat needed for it reach maturity. Another significant measure is irrigation demand. This is the annual unmet water requirements of a crop that must be provided by irrigation. Obviously, this demand increases whenever the climate of an area becomes warmer and/or drier.

Like Biomes$$^{1}$$ ranges migrate as regional climate changes. However, unlike the natural migration of biomes the introduction of crops into new areas requires human intervention to accomplish its purpose, which is to provide a growing human population with food. Two important questions come along with this intervention.

First, is there sufficient water available in the new areas into which crops are introduced? It is important to note that the projected suitability ranges shown in FCST are based on thermal suitability, not irrigation demand.

Second, are regional climate changes taking place slowly enough that the crops introduced into new areas can establish themselves, or will rapidly changing climate create a target that moves too quickly for farmers to adjust?

## Footnotes

$$^{1}$$Biome – A naturally community of plants and animals occupying a major habitat. E.g. a forest, grassland, or desert.