The effect of deforestation on ground surface temperatures

Abstract

Recorded ground surface temperatures (GSTs) over a period of a year at closely spaced sites in a temperate area (almost no snow or ground freezing) show that forested sites and one with a high water table have colder average temperatures relative to other terrains. At sites in southern British Columbia where trees have been logged and in the southern Yukon where they were burned down by a forest fire, the ground surface temperature increased at the time of deforestation. Borehole temperatures are used to show this since no GSTs were recorded. At these sites there has been no subsequent reforestation, and the ground surface temperature has remained nearly constant since deforestation. The times since deforestation range from 5 to 52 years, and the average increase in ground surface temperature is 1.8 K on northern Vancouver Island and 1.2 K in the southern Yukon. The heat required for transpiration in a forest is about 10% of the net radiative heat flux at the ground surface. If this amount of heat is surplus due to deforestation and if the earth is considered to radiate heat like a black body, then the expected increase in the GST is of the order of 1 K.