Environment ministry experts have responded by casting doubt on the viability of the scheme, mainly because there would not be enough room for them all.
They point out that the highly ambitious project would mean that 342,500 trees would need to be planted each day at a rate of 14,269 an hour - the Retiro park in Madrid, which occupies 120 hectares, is home to around 15,000 trees. 
The announcement came after president Zapatero pledged on the 19th January to plant one tree for every inhabitant if he is re-elected, which would mean around 45 million new trees.