Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

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the constitution, proposed a ban on plowing steep slopes. By the time of the Peloponnesian War (431–404 bc), Egypt and Sicily grew between a third and three-quarters of the food for Greek cities. Plato (427–347 bc) attributed the rocky slopes of his native Attica to pre- Hellenistic soil erosion following deforestation. He also commented on soil’s key role in shaping Athenian society, maintaining that the soils of earlier times were far more fertile. Plato held that the soil around Athens was but a shadow of its former self, citing evidence that bare slopes were once forested. “The rich, soft soil has all run away leaving the land nothing but skin and bone. But in those days the damage had not taken place, the hills had high crests, the rocky plain of Phelleus was covered with rich soil, and the mountains were covered by thick woods, of which there are some traces today.” 2 Seeing how harvesting the natural fertility of the surrounding land allowed Athens to blossom into a regional power, Plato held that the root of his city’s wealth lay in its soil. Aristotle (384–322 bc) shared Plato’s conviction that Bronze Age land use degraded soil productivity. His student Theophrastus (371–286 bc) recognized six distinct types of soil composed of different layers, including a humus-rich layer above subsoil that supplied nutrients to plants. Theophrastus made a point of distinguishing fertile topsoil from the underlying earth. Both Plato and Aristotle recognized signs that Bronze Age land use had degraded their region’s soil. Several thousand years and several civilizations later, archaeologists, geologists, and paleoecologists vindicated Aristotle’s estimate of the timing: farmers arrived about 5000 bc and dozens of agricultural settlements were scattered throughout the region by 3000 bc; cultivation intensified about the time Aristotle posited the first serious effects of soil erosion there. Such knowledge, however, did not prevent classical Greece from repeating the pattern. Over the past several decades, studies of soils throughout Greece—from the Argive Plain and the southern Argolid in the Peloponnese to Thessaly and eastern Macedonia—showed that even the dramatic climate change at the end of the last glaciation did not increase erosion. Instead, thick forest soils developed in the warming climate as oak forest replaced grassland across the Greek countryside. Over thousands of years the soil grew half a foot to several feet thick depending on local conditions. Soil erosion began to exceed soil production only after introduction of the plow. The first Greek settlements were located in valleys with good soils near reliable water supplies. As the landscape filled with people, farmers began graveyard of empires 51
52 N E P I R U S IONIAN SEA 0 150 km 0 100 mi advancing onto steeper, less productive slopes. Extensive tilling and grazing stripped soil from hillsides and piled thick deposits of reworked dirt in valleys. Ancient agricultural artifacts can still be found on the rocky slopes of areas that lack enough soil to grow much vegetation. Sediments trapped in valley bottoms, and remnant pockets of soil on the slopes themselves, record cycles of erosion and soil formation throughout Greece. The deepest layers of valley-filling sediments date from glacial to interglacial climate changes during the past quarter million years. Higher layers in the stack of dirt tell of more recent episodes of hillslope erosion as well as intervening periods when soils developed. The first postglacial graveyard of empires M A C E D O N I A Mt. Olympus Figure 6. Map of ancient Greece. THESSALY Mt. Parnassos Delphi BOETIA Corinth Mycenae Sparta Athens PELOPONNESUS A TICA Mt. Parnes AEGEAN SEA
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Dirt
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Dirt the erosion of civilizations D
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For Xena T. Dog, enthusiastic field
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acknowledgments This book could nev
Page 13 and 14: 2 Yet what is dirt? We try to keep
Page 15 and 16: 4 discovered ways to enhance soil f
Page 17 and 18: 6 quent centuries, nutrient depleti
Page 20 and 21: two Skin of the Earth We know more
Page 22 and 23: villa in Gloucestershire lay undete
Page 24 and 25: When we behold a wide, turf-covered
Page 26 and 27: Soil not only helps shape the land,
Page 28 and 29: ter and mineral soil. Billions of m
Page 30 and 31: Topography also affects the soil. T
Page 32 and 33: Wind can pick up and erode dry soil
Page 34 and 35: Combinations of soil horizons, thei
Page 36: much. This leaves the issue in a po
Page 39 and 40: 28 Ice Age was not a single event.
Page 41 and 42: 30 For much of the last century, th
Page 43 and 44: 32 Abu Hureyra sat on a low promont
Page 45 and 46: 34 wheat dating from 10,000 years a
Page 47 and 48: 36 Domesticated livestock not only
Page 49 and 50: 38 inated the southern Mesopotamian
Page 51 and 52: 40 of a high load of dissolved salt
Page 53 and 54: 42 direct water to particular place
Page 55 and 56: 44 by the color of dirt eroded from
Page 57 and 58: 46 out the region, he concluded tha
Page 60 and 61: four Graveyard of Empires To Protec
Page 64 and 65: Figure 7. Parthenon. Albumen print
Page 66 and 67: est soils from hillsides disturbed
Page 68 and 69: Figure 8. Map of Roman Italy. follo
Page 70 and 71: the Roman heartland became increasi
Page 72 and 73: ically let a piece of ground lie fa
Page 74 and 75: foot thick, it probably took at lea
Page 76 and 77: into densely planted olive farms—
Page 78 and 79: families a few centuries earlier. T
Page 80 and 81: classic, supporting three editions
Page 82 and 83: on the edge of the Arabian Desert a
Page 84 and 85: When Moses and company arrived, Can
Page 86 and 87: urned before the onset of the rains
Page 88 and 89: sion in the Mayan of the Petén not
Page 90 and 91: Archaeological records from this pe
Page 92: The contrast between how the Pueblo
Page 95 and 96: 84 forest soils as it went, agricul
Page 97 and 98: 86 to a thousand years. Soil profil
Page 99 and 100: 88 land and birch forest. Following
Page 101 and 102: 90 Figure 10. Miniature from an ear
Page 103 and 104: 92 the early 1300s to about two mil
Page 105 and 106: 94 the Danes improved their sandy d
Page 107 and 108: 96 layers, ’till we arrive to the
Page 109 and 110: 98 recipe for degrading soil fertil
Page 111 and 112: 100 vived on vegetables, gruel, and
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102 French Alps lost a third to mor
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104 Despite such profiteering, by 1
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106 from the smallest rill to the g
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108 A potato blight that arrived fr
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110 uries such as sugar, coffee, an
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112 Subsequent foreign investment o
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six Westward Hoe Since the achievem
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A few miles in from the forest edge
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wherein one man by his owne labour
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Particularly in the South, the read
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worn out, and washed and gullied, s
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explained that American farmers had
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marle County Agricultural Society i
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purchased a farm in the 1820s. A de
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Figure 14. Charles Lyell’s illust
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Traveling through much of the South
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Tensions came to a head after the S
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But this still doesn’t explain th
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Figure 16. North Carolina gully sys
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more than three thousand years and
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settlements for several thousand ye
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seven Dust Blow One man cannot stop
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land-hungry settlers. From 1878 to
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without the least reference to the
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Figure 18. Breaking new land with d
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Figure 19. Dust storm approaching S
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taxes, and other unavoidable expens
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Figure 21. Plowing a steep hillside
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tion of heavy machinery and agroche
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Soil erosion rapidly became a major
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egion. There are few reliable measu
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ing with the Germans, Kalmyks were
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grazing animals doubled; the human
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years. Present rates of erosion, ho
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land was being exhausted. Although
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In 1958 the Department of Agricultu
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eplacing water-holding capacity los
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ing on access to fresh land or find
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180 our way in that the backyard wo
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182 Figure 23. Chinese farmers plow
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184 less, he experimented with agri
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186 Figure 24. Lithograph of mounta
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188 fiscated the remaining lands th
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190 Hilgard rightly dismissed the p
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192 important was the mix of silt,
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194 ping would exhaust the natural
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196 atmospheric nitrogen. On July 2
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198 increases in crop production.
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200 Estimates for when petroleum pr
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202 ground—turning our dirt into
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204 greater tonnage of machinery pe
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206 may prove our best hope for mai
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208 tilizers, hosts the longest ong
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210 soil fertility and exporting po
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212 No-till farming is very effecti
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214 It is no secret that if agricul
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216 some consumed their future and
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218 Pollen preserved in lake sedime
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220 washed off the slopes now bury
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222 ply. So topsoil loss retarded f
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224 different fates. Tikopia develo
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226 where vegetation stabilizes the
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228 0 50 100 km inhabitants. Two ce
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230 pushes peasants from hillside s
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232 gardens grew up throughout the
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234 Credible scientists also disagr
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236 notice the problem. Like a dise
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238 asters. Larger societies, with
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240 before plants have all they can
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242 faster than it is replaced dest
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244 figuring the downstream end of
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246 Meeting this challenge would al
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248 10. Marsh 1864, 9, 42. 11. Lowd
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250 6. USDA 1901, 31. 7. Whitney 19
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252 Schwartzman, D. W., and T. Volk
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254 Beach, T., S. Luzzadder-Beach,
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256 and human response. In Environm
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258 Lang, A. 2003. Phases of soil e
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260 Cronon, W. 1983. Changes in the
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262 Bennett, H. H., and W. R. Chapl
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264 Saiko, T. A. 1995. Implications
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266 Jackson, W. 2002. Farming in na
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268 ———. 1925. Soil and Civil
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270 and economic costs of soil eros
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272 agricultural practices (continu
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274 Columella, Lucius Junius Modera
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276 farm subsidy programs: conventi
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278 Joppa Town, Maryland, 140 Judso
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280 nitrogen fertilization (continu
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282 Sea of Galilee (Lake Kinneret),
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284 technological innovation (conti
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