Microclimates mitigate against hot temperatures in dryland ecosystems: termite mounds as an example, Joseph et al. 2016

This paper presents an analysis of microclimatic temperature effects of termite mounds in Zimbabwe and South Africa that provide important climatic “refuges” for other local organisms. The research compared the vegetation growing on the mounds with that on control plots in the surrounding savannah with respect to temperature differences. They found that more tall woody vegetation grows on termite mounds, compared to surrounding areas, creating shade that cools the mounds.

The authors observed that: “tall trees, being more prevalent on mounds, provide increased leafy, large-volume canopy and subcanopy vegetation, which in turn furnish more shade relative to the savanna matrix” [Joseph 2016: 7]. They found a 2°C temperature difference on the termite mounds compared to the surrounding area when the surrounding temperature was  34°C; the difference rose to 4°C at 40°C. Thus, these mound microhabitats maintained an even greater ambient temperature difference the warmer the ambient environment became.

Data were collected on 44 large termite mounds, each paired with off-mound savannah plots, in October 2015 (which was one of the hottest months on record in these areas) during the dry season. The mounds were more than 2 meters tall or more than 10 meters in diameter, and they were compared with an equivalently sized circular plot in the surrounding habitat. For each termite mound and control plot, the variables measured included: temperature, humidity, number of trees taller than 4 meters, tree canopy size, and amount of shade.

The median mean shade on mounds was 21% compared to 3% on the control plots, while the median maximum shade was 70% on mounds and only 10% on the surrounding plots, while humidity did not differ significantly. Such microclimates are likely to be important refugia for wildlife as droughts, fire events and higher ambient temperatures become more prevalent due to climate change.