Editing Machair (section)

===Humans===
Human activity has played an important role in the creation of the machair. Archaeological evidence suggests that some trees were cleared for agriculture as early as 6000 BC, but there was still some woodland on the coast of [[South Uist]] as late as 1549.<ref name=glas/> Seaweed deposited by early farmers provided a protective cover and added nutrients to the soil.<ref name=glas/> The grass is kept short by [[cattle]] and [[sheep]], which also add trample and add texture to the [[Grassland|sward]], forming tussocks that favour a number of bird species.<ref name=glas/>

The [[soil]] is low in a number of key [[nutrient]]s, including trace elements such as [[copper]], [[cobalt]] and [[manganese]], requiring cattle to be fed supplements or taken to summer pastures elsewhere.<ref name=glas/> The sandy soil does not hold nutrients well, making artificial fertilisers ineffective and limiting the crops that can be grown to certain varieties of [[oats]] and [[rye]], and [[Bere (grain)|bere barley]].<ref name=glas/>