Woods as managers of temperate climate

«George Perkins Marsh (1801-1882) certainly had a varied career. Here’s how Clark University in Massachusetts, which has named an institute in his memory, describes him:

Throughout his 80 years Marsh had many careers as a lawyer (though, by his own words, “an indifferent practitioner”), newspaper editor, sheep farmer, mill owner, lecturer, politician and diplomat. He also tried his hand at various businesses, but failed miserably in all – marble quarrying, railroad investment and woolen manufacturing. He studied linguistics, knew 20 languages, wrote a definitive book on the origin of the English language, and was known as the foremost Scandinavian scholar in North America. He invented tools and designed buildings including the Washington Monument. As a congressman in Washington (1843-49) Marsh helped to found and guide the Smithsonian Institution. He served as US Minister to Turkey for five years where he aided revolutionary refugees and advocated for religious freedom. He spent the last 21 years of his life (1861-82) as US Minister to the newly United Kingdom of Italy.

In other words, he kept himself busy. But I would argue his defining moment came on 30 September, 1847, when, as a congressman for the Whig party (a forerunner of the Republican party), he gave a lecture to the Agricultural Society of Rutland County, Vermont. (The speech was published a year later.) It proved to be the intellectual spark that led him to go on and publish in 1864 his best-known work, Man and Nature: Physical Geography as Modified by Human Action.

More than 160 years on, it really does pay to re-read his speech as it seems remarkably prescient today. It also shows that he was decades ahead of most other thinkers on this subject. After all, he delivered his lecture a decade or more before John Tyndall began to explore the thesis that slight changes in the atmosphere’s composition could cause climatic variations. And it was a full half a century before Svante Arrhenius proposed that carbon dioxide emitted by the “enormous combustion of coal by our industrial establishments” might warm the world (something he thought would be beneficial). (…)

Man cannot at his pleasure command the rain and the sunshine, the wind and frost and snow, yet it is certain that climate itself has in many instances been gradually changed and ameliorated or deteriorated by human action. The draining of swamps and the clearing of forests perceptibly effect the evaporation from the earth, and of course the mean quantity of moisture suspended in the air. The same causes modify the electrical condition of the atmosphere and the power of the surface to reflect, absorb and radiate the rays of the sun, and consequently influence the distribution of light and heat, and the force and direction of the winds. Within narrow limits too, domestic fires and artificial structures create and diffuse increased warmth, to an extent that may effect vegetation. The mean temperature of London is a degree or two higher than that of the surrounding country, and Pallas believed, that the climate of even so thinly a peopled country as Russia was sensibly modified by similar causes. (…)

You can see him grappling with concepts that we now know as the urban heat island effect and greenhouse effect. (…)

As the Clark University biography notes, he wasn’t an environmental sentimentalist. Rather, he believed that all consumption must be reasoned and considered, with the impact on future generations always kept in mind: he was making the case for what we now call “sustainable development”. In particular, he argued that his audience should re-evaluate the worth of trees: (…)

The functions of the forest, besides supplying timber and fuel, are very various. The conducting powers of trees render them highly useful in restoring the disturbed equilibrium of the electric fluid; they are of great value in sheltering and protecting more tender vegetables against the destructive effects of bleak or parching winds, and the annual deposit of the foliage of deciduous trees, and the decomposition of their decaying trunks, form an accumulation of vegetable mould, which gives the greatest fertility to the often originally barren soils on which they grow, and enriches lower grounds by the wash from rains and the melting snows.
The inconveniences resulting from a want of foresight in the economy of the forest are already severely felt in many parts of New England, and even in some of the older towns in Vermont. Steep hill-sides and rocky ledges are well suited to the permanent growth of wood, but when in the rage for improvement they are improvidently stripped of this protection, the action of sun and wind and rain soon deprives them of their thin coating of vegetable mould, and this, when exhausted, cannot be restored by ordinary husbandry. They remain therefore barren and unsightly blots, producing neither grain nor grass, and yielding no crop but a harvest of noxious weeds, to infest with their scattered seeds the richer arable grounds below.
But this is by no means the only evil resulting from the injudicious destruction of the woods. Forests serve as reservoirs and equalizers of humidity. In wet seasons, the decayed leaves and spongy soil of woodlands retain a large proportion of the falling rains, and give back the moisture in time of drought, by evaporation or through the medium of springs. They thus both check the sudden flow of water from the surface into the streams and low grounds, and prevent the droughts of summer from parching our pastures and drying up the rivulets which water them.
On the other hand, where too large a proportion of the surface is bared of wood, the action of the summer sun and wind scorches the hills which are no longer shaded or sheltered by trees, the springs and rivulets that found their supply in the bibulous soil of the forest disappear, and the farmer is obliged to surrender his meadows to his cattle, which can no longer find food in his pastures, and sometime even to drive them miles for water.
Again, the vernal and autumnal rains, and the melting snows of winter, no longer intercepted and absorbed by the leaves or the open soil of the woods, but falling everywhere upon a comparatively hard and even surface, flow swiftly over the smooth ground, washing away the vegetable mould as they seek their natural outlets, fill every ravine with a torrent, and convert every river into an ocean. The suddenness and violence of our freshets increases in proportion as the soil is cleared; bridges are washed away, meadows swept of their crops and fences, and covered with barren sand, or themselves abraded by the fury of the current, and there is reason to fear that the valleys of many of our streams will soon be converted from smiling meadows into broad wastes of shingle and gravel and pebbles, deserts in summer, and seas in autumn and spring. (…)
If the present value of timber and land will not justify the artificial re-planting of grounds injudiciously cleared, at least nature ought to be allowed to reclothe them with a spontaneous growth of wood, and in our future husbandry a more careful selection should be made of land for permanent improvement. It has long been a practice in many parts of Europe, as well as in our older settlements, to cut the forests reserved for timber and fuel at stated intervals. It is quite time that this practice should be introduced among us.
After the first felling of the original forest it is indeed a long time before its place is supplied, because the roots of old and full grown trees seldom throw up shoots, but when the second growth is once established, it may be cut with great advantage, at periods of about twenty-five years, and yields a material, in every respect but size, far superior to the wood of the primitive tree. In many European countries, the economy of the forest is regulated by law; but here, where public opinion determines, or rather in practice constitutes law, we can only appeal to an enlightened self-interest to introduce the reforms, check the abuses, and preserve us from an increase of the evils I have mentioned.

Just three years later, Lincoln approved the legislation which would lead to the creation of Yosemite National Park in California. This acted as a precedent across the world for federal and state governments to purchase or secure wilderness areas so they could be protected in perpetuity from development or exploitation.»

– “The 1847 lecture that predicted human-induced climate change, “The Guardian, Monday 20 June 2011.

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