The last Ice Age wiped out all of the coniferous trees in Finland. After the continental ice sheet retreated, trees from elsewhere--like the Scots Pine--gradually colonized the vacant niche. On a smaller scale, the same thing happened in many high mountain ranges of the Earth's temperate regions, including the Sierra Nevada Mountains of California. We can learn a thing or two about climate change from Alpine dendrology.

Round Top Lake, at 9340 feet elevation in the Northern Sierras, is my favorite place for informal climate history research. The pine trees around the lake grow in tight clumps. Here's a link to a photo: tinyurl.com/ypjw5f

The trees in any given group are genetically identical; they reproduce asexually. A new tree trunk will sprout outward from an existing root system. The seeds that do sprout can't endure the harsh Winters.

There is a small gap between the pine trees near the lake and the ones farther down. Question: After the last Ice Age, how did the pine trees reach the lake?

Answer. At some point after the last Ice Age, the Winters in the Northern Sierras were somewhat warmer than they are now--even with Global Warming. The trees sprouted from seeds at a time when the Winters were milder.

Several years ago, I was surprised to see a knee-high seedling a short distance outside the crescent of tree clumps. However it did not survive. When I see isolated pine seedlings that grow to 6 feet in height, then I'll believe that the Northern Sierra climate is the warmest that it has been since the last Ice Age.

Round Top Lake is one of my favorite short hikes. If I can get on top of the arthritis in my hip, I'll go there next Summer. And I'll let you know if I see any solitary pine trees.