“Human excrement is a bigger problem than the oxygen bottles, torn tents, broken ladders, and cans or wrappers teams left behind. … Human waste piling up over decades … posed a health hazard to people dependent on water from rivers fed by the region’s melting glaciers.” (http://uk.reuters.com/article/2015/03/04/us-nepal-everest-idUKKBN0M00A220150304)
A bigger problem than yellow snow.
“Federal land managers were required to determine where on the country’s vast forests snow machines could travel without harming or destroying natural resources like rivers or wildlife like imperiled Canada lynx that are dependent on undisturbed winter landscapes.” (http://uk.reuters.com/article/2015/01/29/us-usa-environment-snowmobiles-idUKKBN0L207320150129)
Unfortunately the way markers were obscured by snow.