Trees on the move

 kw: book reviews, nonfiction, forestry, biology, trees, climate change

The lighter green area in this figure shows the Canadian range of the Great Horned Owl, Bubo virginianus, an iconic North American owl.

The northern boundary of the owls' range is close to the northern tree line, for these birds need trees. It illustrates the American range of the subject of The Treeline: The Last Forest and the Future of Life on Earth by Ben Rawlence.

The tree line (or sometimes treeline) in the north circles the Arctic, passing through nearly every circumpolar country, although Greenland is nearly all to its north, and Iceland is wholly south of it, being warmed by the ocean currents that produce an equable climate in the British Isles and southern Norway. The tree line is the northern boundary of the boreal forests of Canada, Alaska, Siberia and northern Europe. To its north we find tundra, which is consumed where the trees advance, and itself advances anywhere the trees might retreat (just about nowhere, in living memory). This forest, primarily its northern portions, is the subject of the book.

The six primary sections of the book weave their stories around six species of hardy tree, each being the primary tree species in one or another section of the northern boreal forest. From the Scots Pine in Scotland (in America it is called Scotch Pine, which is probably a solecism), around the circumference of the Arctic to the Greenland Mountain Ash of southern Greenland and eastern Canada, these trees respond quickly (in tree terms) to climatic trends. Their varied methods of seed dispersal either facilitate or limit the rapidity with which they can spread northward as the land warms over years and decades. But all are on the move to the North.

The core story of Treeline is that in the North, the warming trend of recent decades is in no way subtle. Most of us live in areas of temperate weather. For us, a difference of a degree or two F (half to one degree C) is hardly noticeable. Year-to-year variations swamp the signal. But in Alaska, for instance, the people have noticed dramatic changes for at least 30-40 years, in the kinds of plants that have been spreading across the landscape, sightings of birds not seen before but that are becoming common, and the instability of the landscape itself wherever permafrost is melting and in some places washing away entirely.

Throughout, the author describes the dependence upon trees seen in all the life around them. This is not just species that feed on their substance, nor birds that nest in them, but such things as the many beneficial substances emitted by pine trees as their leaves and cones grow: the "fresh pine smell" is actually medicinal, which may be what is behind the practice in Japan of "forest bathing". A walk in the forest is healthier than a walk in the absence of trees, for both physiological and psychological reasons. Trees' roots host fungi that help them extract water and minerals from the soil, and the fungi in turn are fed by the trees in one of the oldest synergistic relationships. Materials shed by the trees and their fungi make their way into nearby waters, where—in ways we have not yet determined—they greatly increase the fertility of the waters. Forest pools and streams are very rich in species of fish and other vertebrates and in insects and other small invertebrates, as compared to bodies of water in meadows and other areas far from forests (though those can be rather prolific in their own right).

The author sums up the matter in this marvelous sentence: 

"If how the treeline made our world habitable in the first place, if how forests create rain, drive winds, manage water, seed the oceans, provide the foundations of much modern medicine, cleanse the air of man-made pollution and disinfect the atmosphere were more widely taught and understood, it would be much harder to cut them down." (p 266)

Clearing forested areas does more harm than we ever imagined. If somehow everyone on Earth could be made to know the true value of the forests, everyone would nurture them as priceless treasures, rather than exploit them for a dollar today and leanness of soul tomorrow.

I thoroughly enjoyed this book, as bittersweet as it is. I am glad to live near a forested area that is intended to remain so. When our son was growing up, he and I sometimes "rock hopped" our way down a little stream, sometimes for as much as a mile. Just breathing feels different in a forest, even a little one.

I have a nit or two to pick, so if you don't care to see the errata, feel free to stop reading here.

• On page 93 the Russian Bios-3 experiment was described. It was stated as having an internal volume of 1,111 cubic feet. That is slightly bigger than a 10-foot cube. I looked it up. The volume is 1,700 cubic meters, which comes to a bit over 60,000 cubic feet.
• On page 185 it is stated, "Sunlight activates their [plants'] chloroplastic structures, and they use the photons from the sun's gamma rays to split carbon from the oxygen in carbon dioxide." Solar gamma rays do not make it through the atmosphere; if they did, we would soon be consumed with cancers, if we did not first die of radiation poisoning. Leaves are green because chlorophyll uses the red and blue photons to do the splitting. They have sufficient energy, while a gamma ray typically has a million times as much energy as a visible photon.
• On page 222 beluga whales are called baleen whales. They are not. They are toothed whales, as are all dolphins.
• In the same paragraph but on page 223, plus in the last paragraph on the page, the whales are described as attracted to oxygenated water. They breathe air from the atmosphere, as do all mammals, and the oxygen content of the water is irrelevant to them. They are not fish!
• This is more of an anomaly. Each place the author visited is prefaced with a name and a latitude, but the latitude is expressed thus: 64° 50' 37' N. In only one place did I find the correct notation, for Huslia, Koyukuk, Alaska: 65° 42' 7" N (p 160). The subtle difference between using " and using ' for seconds of latitude is easy for a reader to compensate for, but it is a bit jarring on first sight.