A few years ago there was an unusual campaign to make London the world’s first national park city. London, especially south of the river, has enough green spaces to just about make that plausible. In 2019 they achieved it, though I don’t really know what difference it is making. Here’s something more impressive however: the first country to declare all of its territory a biosphere reserve.

It was announced by UNESCO recently as part of a new cohort of reserves, and São Tomé and Principe stan...