“According to the Woodland Trust, recycling just one Christmas card saves enough electricity to allow five people to watch the [UK] Queen’s Christmas day message.” in …Turn old cards into gift tags. “Last year more than 93 million cards were collected by the Woodland Trust – enough to enable the charity to plant 22,000 trees – or a forest the size of 44 football pitches.”

That is a lot of tree cut down for the cards, not to mention all other related activities (turning trees into paper cards, delivering cards to stores, buying the cards, mailing the cards, etc.). The best way to save the environment is to reduce consumption.