Today we climbed up the most insane possible road to go to the El Rosario Monarch Butterfly Sanctuary. Every year untold millions of monarch butterflies make the migration from southern Canada all the way to here, and then they spend the winter here and mate before making the return journey.

It was incredible - the trees looked like they had bunches of leaves on them, but it was really huge clusters of monarch butterflies. And they were everywhere in the air. We just sat for a long time and watched them.

This is an area like many in the third world with a serious deforestation problem - increasing population means people cut down the forest to make open land for crops and livestock, to feed their families. But the Monarchs are severely threatened, so Mexico has set this area aside as a reserve. We can hope that they´re successful and can preserve this incredible group of migrating Monarchs.