SIR, – in the Scottish Farmer (July16) Jimmy Pierson of the Vegan Society attempted to claim some sort of moral high ground by quoting a lot of ‘scientific’ sounding figures. The main advocates in the recent referendum were rightly criticised for gross exaggerations.
Even assuming his figure of 700 litres per day of methane from an average cow is correct, this is equivalent in energy terms to about three quarters of a litre of diesel fuel.
I would really like to know where you can purchase a large 4x4 vehicle that can travel 35 miles on that amount of fuel ( that’s 209 miles per gallon ) Both methane and NO2 are chemically reactive and do not remain long in the atmosphere, so their effect is not nearly as large as CO2 ( which hangs about for more than a century ). Although it is reasonably certain that we have to wean ourselves of fossil fuels, how much they are helping or harming our climate is not a certainty.
Due to many factors, including the amount the earth’s axis changes it’s tilt and when in the year we are closer or further from the sun, over the last million years and more we have mostly been in ice ages with shorter interglacial periods lasting about 10 thousand years.
The last ice age ended about 10 thousand years ago, and but for the effects of global warming, we might be going into another one. Nobody knows for sure that another ice age could not happen anyway and the present volatility might just make it happen faster. How ice forms and melts in the arctic seems to be crucial, but a warming arctic ocean might suppress the gulf stream and it’s loss might then produce a rapid winter freeze that wasn’t balanced by a similar summer thaw.  
Bottom line – we will need all our food sources and animals that graze hillsides are still the best practical option.  

Sandy Henderson,
Faulds Farm,
Dunblane