Plants and invertebrate animals require a certain amount of heat energy to grow. For example, spinach can grow when average daily temperatures are as low as 2.2°C, while corn requires daily temperatures of at least 10°C. The availability of heat energy is related to the average daily air temperature and is thus sensitive to changes in climate. This indicator measures changes in the amount of heat energy available for plant or animal growth from 1900 to 2013. Results are provided for British Columbia and each of the nine terrestrial ecoprovinces.

• Average available heat energy has increased in British Columbia from 1900 to 2013. On average there are 190 more Growing Degree Days (hereafter GDD) in British Columbia than at the beginning of the 20th century.
• The greatest increase in available heat energy is occurring in coastal British Columbia. The Coast and Mountains and Georgia Depression ecoprovinces are both experiencing an increase in energy available for plant growth of 220 GDD per century.
• Annual average heat energy is increasing by 160 to 190 GDD per century in northern parts of British Columbia. The Central Interior ecoprovince has an increase of 160 GDD per century. The annual trend in both the Southern Interior and Southern Interior Mountains ecoprovinces is an increase of 120 GDD per century.
• The availability of heat energy is related to the average daily air temperature. The temperate climate in coastal regions of B.C. means that increased temperatures, even in winter, will contribute to an increase in available heat energy for plant and invertebrate animal growth. In the northern part of the province however, where observed air temperatures have increased the most over the past century, winter temperatures generally remain below the 5°C threshold and so there is less increase in overall GDD.