He started in Mexico and kept going east until he reached journey's end in Hawaii. There he found the plastic beach I blogged about earlier and he made a good point: the plastic doesn't come from Hawaii itself. That's a rather scary thought, as it means the plastic has travelled a very, very long way, and there must be an awful lot of it out there, bobbing about in the Pacific.
Simon also dropped in on the bird sanctuary to visit some of the very few Hawaiian Crows in existence. The 'Alala as it is also known is now extinct in the wild, the only ones left are being bred in captivity. In a room containing a large mural of birds his guide went round pointing at those that are already extinct.
It was a sobering moment.
In a previous series when Simon travelled around the Tropic of Capricorn I was struck by his travels through Madagascar. 90% of the forest, he discovered, had already been cut down.
There are no easy answers for a world who's population is increasing while at the same time getting richer, and when getting richer means consuming more.
But like politicians at election time (such as here in the UK) no one likes to connect the dots and identify where the compromise is going to be. I am pretty convinced that we must use our brain power and technology. To save the planet we need to protect it's species, and that means protecting vast areas as natural parks.
That means increased efficiency in what we use, which means GM food and nuclear power, and taxation on consumption, including on CO2 generating sources of energy.
And that means a lot of angry people across the political spectrum.
Can we as a species do it? I have no idea, but we can should at least try.