Writer Ben Rawlence’s travels in the upper latitudes of the northern hemisphere to view firsthand the condition of the boreal forests forms the basis of this book. These forests, combined, comprise the second largest biome on Earth, surpassed only by the oceans. Their habitat, the permafrost, is melting and the trees struggle to migrate northward. The warming permafrost releases carbon dioxide and methane from the soil, an even greater stimulus to global warming than the carbon dioxide from the vast number of burning boreal trees themselves.
Unlike the tropical rainforests, which comprise the third largest biome of our planet, just a few species make up most in the boreal forest. Predominant are Scots pine in Scotland, downy birch in Norway, Dahurian larch across Russia, white and black spruce in Alaska, balsam poplar in Canada, and Greenland mountain ash. These species grow atop the melting permafrost, and weaken as it begins to melt. Rawlence also identifies a few other boreal tree species of the taiga: black alder (alders are among the few nitrogen-fixing non-legume tree species), hazel, juniper, poplars (including particularly, balsam poplar), willow species, and yews. Some species groups (genera), such as alder, willow, and, to some extent, yews, secure wet soils. Most of the conifers prefer dry soils.
The permafrost is effectively dry, as its frozen water is inaccessible to tree roots. When the permafrost melts, as increasingly happens because of climate change, and its principal species living on permafrost weaken, they become increasingly susceptible to fire. Besides the carbon released by burning forests themselves, permafrost melting releases increasing amounts of methane and other greenhouse gasses. Wide stretches of these boreal forests now burn at increasing rates.
Rawlence describes in very readable language the role of the boreal forests in planetary ecology and their march southward and northward with the pulses of glacial and interglacial epochs. His natural history accounts are generally technically correct while being accessible to the lay reader. His maps and illustrations are clear and informative. And the book’s organization, taking each of the dominant species in turn and explicating its role in the boreal band around the globe, I find especially informative.
Chapters describe principle species in each portion of the taiga, the pan-global boreal forest, corresponding to his investigations around the northern portion of the planet. He begins each chapter with fine drawings of one boreal species, illustrating its male and female flowers and the seed-bearing body (cone, catkin, etc.) He also reports on discussions with local experts and his adventures into lands historically frozen.
Rawlence reports: “I learned that the Arctic tundra is getting shrubbier, turning green; but this is not a simple story of trees gorging themselves on carbon dioxide and racing north. It is a picture of a planet in flux; of ecosystems adjusting to massive changes and trying to find their balance. Of forests the size of nations being destroyed by fire, parasites, and humans every year while elsewhere the precious tundra is being colonized by trees now rendered as invasive species.”
As dwellers in the northern region of our continent, Vermonters are especially susceptible to results from climate contortions still further north. Forests and oceans greatly affect global climates. The degradation of boreal forests, the melting of the permafrost, and the change in the balance of absorption versus reflection of sunlight strongly influence climate patterns in high latitudes, far north of our secure habitation in Vermont. These changes bring atypical weather here. And, of course, our own forests do not exist independently from global weather trends. Vermont’s forests moderate our weather and govern the flow of life-giving water through our landscape. Those seemingly distant boreal forests helped regulate our weather, along with much of the rest of North America. Their burning contributes to chaotic weather here.
Rawlence’s “The Treeline” provides us with insights that pertain to our well being, and to the well being of humanity at large, and of the beautiful creation in which we are privileged to live.
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