By Dr Michael Cramer

Date: Saturday 18^th April 2015

Have you ever seen and wondered at the strange vegetation rings that are found in various parts of the world?  Are they circles, or should we call them rings?

Dr Cramer in his most interesting lecture focused on the Fairy Circles in Namibia where millions of these strange formations are to be found, from Southern Angola through to Bushmanland in the south. They are only found down this western strip, up to about 100 km from the coast. Climate, especially rainfall and soil, are the most important factors influencing their presence. Fynbos soil is low in phosphates and is fairly impoverished, hence the great biodiversity of plant species. Fairy circles occur where the soil is extremely nutrient-poor.

The circle of grasses and the outer matrix feed on the inner circle, thus depleting the resource and no plants can then colonise the central area. The big question asked of the audience was: what causes the Fairy Circles? A few theories were thrown up – from aliens, lawn mowers, termites, gas emissions and chemicals. Dr Cramer spoke to each of these hypotheses.

• Gas emissions – did carbon dioxide kill off the grass? Hydrocarbons are produced normally in grasslands and gas does not necessarily cause plant death. This hypothesis does not work.

• Termites – papers have been written on this theory. Certain species were found on Fairy Circles, but fewer on the matrix. Generally, termites are rare where Fairy Circles are found. An experiment using a leaf blower exposed various foraging tunnels running throughout the landscape and not just in certain areas.

• Chemicals – the theory that certain Euphorbias were growing and left behind poisonous chemical deposits, suspected to be Euphorbia grammifera, does not extend to where all Fairy Circles occur. Fairy Circles come and go anyway, with an estimated lifespan of 40-60 years.

• The last video produced a new theory: Biological vegetation patterns where things emerge from nothing! How scientific is that? Look around you and find these patterns: cloud patterns – streaks, puffs, mackerel sky,

• Sand/wind –  shaping and smoothing edges
• Arctic stone circles
• Colorado – the stones that were pushed out in the Rocky Mountains
• Mars – 69 degrees N water freezing and thawing
• Australia – soil wets and dries forming hollows
• Animals – stripes and spots are patterns
• These are all abiotic patterns. The patterns of corrugations on a gravel road are biotic, caused by cars, wind and rain.

 

Several tests have been carried out in the sand using nutrients, termites, water, with the control site left alone, And the answer?  No proven concrete theory has come up! Perhaps it was the aliens after all!