I think this is the third year of Show the Love - the Green Hearts campaign which encourages people to make and wear green hearts on Valentines Day to show their love for nature.
The campaign is lead by the Climate Coalition, which is made up of a number of environmental charities including Woodland Trust.
I still wear the heart sent to me two years ago by World Wildlife Fund, it was made by Annette in Guildford, who loves 'the planet'. It's now permanently pinned to my coat....
Climate change threatens to disrupt our seasons (and we already see signs of this in some plants blooming earlier than they used to and some birds nesting earlier). If seasons get out of alignment then some birds won't be able to breed at all - if for example caterpillars start coming out earlier but migrating birds are unable to change their arrival dates to benefit from this change and instead find themselves facing a food shortage.