Asian and North American trees.
I was just wondering why so many species of trees are the same in Asia and North America: the forests north of North Korea in China, below the tree-line on Mount Fuji, and in the Pacific Northwest. (Birch, fir, alder, spruce, maple, larch, etc). How did their seeds scatter across the Pacific? Perhaps, I thought, they spread between Alaska and Siberia when the climate was warmer.
Just now I came across this article, about ancient walnut forests (45 million years ago) more than a thousand miles north of what is now the tree-line in Canada:
We're going to need a lot of global warming to bring those back. Squirrels, on your marks!
Pictured: birch from Northeast China and from Fuji in Japan.