Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

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from the smallest rill to the greatest river, it attacks whatever has emerged
above the level of the sea, and labours incessantly to restore it to the deep.” 14
Adopting Hutton’s radical concept of geologic time, Playfair saw how
erosion worked gradually to destroy land that dared rise above sea level. Yet
the land remained covered by soil despite this eternal battle.
The soil, therefore, is augmented from other causes, ...and this augmentation
evidently can proceed from nothing but the constant and
slow disintegration of the rocks. In the permanence, therefore, of a coat
of vegetable mould on the surface of the earth, we have a demonstrative
proof of the continual destruction of the rocks; and cannot but admire
the skill, with which the powers of the many chemical and mechanical
agents employed in this complicated work, are so adjusted, as to make
the supply and the waste of the soil exactly equal to one another. 15
The soil maintained a uniform thickness over time even as erosion continuously
reshaped the land.
About the time Hutton and Playfair were trying to convince Europe’s
learned societies of the dynamic nature of soil over geologic time, parallel
arguments about the controls on the size and stability of human populations
were brewing. Europeans began questioning the proposition that
greater population led to greater prosperity. On an increasingly crowded
continent, limits to human population growth were becoming less abstract.
The Reverend Thomas Malthus infamously proposed that a boom-andbust
cycle characterizes human populations in his 1798 Essay on the Principle
of Population. A professor of political economy at Haileybury College,
Malthus argued that exponentially growing populations increase faster
than their food supply. He held that population growth locks humanity in
an endless cycle in which population outstrips the capacity of the land to
feed people. Famine and disease then restore the balance. British economist
David Ricardo modified Malthus’s ideas to argue that populations rise
until they are in equilibrium with food production, settling at a level governed
by the amount of available land and the technology of the day. Others
like the marquis de Condorcet argued that necessity motivates innovation,
and that agriculture could keep up with population growth through
technological advances.
Malthus’s provocative essay overlooked how innovation can increase
crop yields and how greater food production leads to even more mouths to
feed. These shortcomings led many to discredit Malthus because he treated
let them eat colonies