Current predictions of rainfall change in the west have indicated that rainfall may decrease by as much as 40 cm in some areas. imagine a chaparral location that experiences 100 cm of average annual rainfall and an average annual temperature of 10°c. if there were a decrease in rainfall of 40 cm per year, what would you expect?

If a chaparral region experiences a decrease of rainfall by around 40 cm on annual level, this ecosystem will gradually die out.

40 cm decrease in rainfall in a chaparral means 40% decrease of rainfall in an already arid region. That will contribute to the increase of the average temperatures as well. So with an increased average temperature, and also significant decrease in rainfall, the chaparral ecosystem will gradually be replaced by a desert, as the conditions will only be suitable for the development of a desert ecosystem.