A recent study, undertaken by the South African Environmental Network’s (NRF-SAEON) Arid Lands Node, provided evidence on how climate change is starting to adversely impact the fauna and flora of Namaqualand and Namib Desert.
The research project studied how climate change affected fog along the West Coast and its impact on these fog-dependent ecosystems. The vast biodiversity of these regions, in terms of the large number of endemics and high species numbers for such arid regions, could disappear along with the fog, leaving the land almost barren.
Fog as primary source of moisture
Experts say fauna and flora in an around Namaqualand and the Namib Desert rely on fog as primary source of moisture, contributing five times more moisture than rain. Fog is also associated with particulates which could contain essential nutrients for plants. The connection between fog and fauna has been a subject of interest for scientists for well over a century and had prompted numerous studies in the Namib Desert.
Scarce desert rains
According to Dr Joh Henschel, manager of the NRF-SAEON Arid Lands Node, the West Coast fog comes off the cold Benguela Current which generates low-lying stratocumulus clouds intercepting objects at ground level on the adjacent land where it deposits water droplets. Typical of deserts, rain is very scarce in this area with fog being the only continued alternative source of moisture for most of the creatures. The publication of this research project is the culmination of many years of co-operation between the University of the Witwatersrand, the Gobabeb Namib Research Institute, NRF-SAEON and the Namibian University of Science and Technology.
Fog collecting behaviours
The study also shows that at least 48 animal species and a number of plants consume fog water. Relatively few studies have examined this phenomenon. Two species of fog-basking beetles and several others construct fog-collecting trenches from which they harvest water. To achieve this, they have to develop specialised fog collecting behaviours enabling them to consume as much as a third of their body weight of water during one fog incident.
This extra-ordinary feat was first highlighted 44 years ago in scientific journals, Nature and Science. Many other species also collect fog droplets off their bodies or vegetation and spiders collect it from soaking wet silk on trapdoors. Even mammals as large as elephant and giraffe benefit by ingesting fog-wetted vegetation.
Complex fog patterns
Fog-consuming species manage to sustain active adult populations during the long intervals between rainfall periods boosting their populations. The general pattern is one of brief periods of boom, followed by long lean spells and fog is largely responsible for keeping the desert alive. According to research the long-term patterns of fog are complex, as is the underlying climatology in detail. Changes in fog could be due to changes in wind patterns and ocean temperatures or increasing elevation of warmer stratocumulus clouds reducing their interception of land. At the Gobabeb Namib Research Institute, rainfall patterns have changed during the past 30 years.
Astonishingly, according to the study, the mean annual precipitation doubled across this period due to the occurrence of more extreme events. However, the number of rainfall periods decreased by almost a third. Researchers warn that during long intervals between rainfalls when fog provides critical relief, thirsty creatures would be left wanting if fog intervals were also to lengthen. Fog is only one of several moisture sources including dew. Some small desert creatures even manage to get water from atmospheric vapour.
Global warming may affect all these moisture sources and could cause the most reliable water sources along the West Coast to disappear. This requires long-term research on land and ocean and NRF-SAEON can play a significant role in such a case study. International collaboration between SA, Namibia and Angola and the global scientific community, could be of benefit to all.