~ CHAPTER 5 ~ (Continued)
~ EROSION AND ORGANIC MATTER LOSS BY COUNTRIES ~
Edition 9 of March 2010 (
NOTE: The first half of this Chapter (Sections (5-A) and (5-B)) is in another file. (se5.html)
(5-A) ~ Asia ~ [A1]~Central Asia, [A2]~Far East, [A3]~Asian Sub-Continent, [A4]~Southeast Asia, [A5]~Middle East,
(5-B) ~ Africa ~ [B1]~Africa Overall, [B2]~North Africa, [B3]~Eastern Africa, [B4]~Western Africa, [B5]~Southern Africa, [B6]~Sahel, ~
~ Table of Contents of this second half of Chapter 5:
(5-C) ~North America ~
NOTE: The notation (su1) means that the data is used in the document analyzing the sustainability of the productivity of the world's food, fiber and water supply systems. (See elsewhere in this website.)
SECTION (5-C) ~ Erosion and Organic Matter Loss ~ North America ~ [Ca]~Gully Erosion, [Cb]~Wind Erosion, [Cc]~Land Removed from Agriculture, [Cd]~Total Soil Erosion in the US, [Ce]~Sheet- and Rill Erosion, [Cf]~Canada and Specific States and Regions, ~
North and Central America's main types of degradation are loss of topsoil (75% of the degraded area) and terrain deformation from water erosion (16%, but 40% in Central America). (Costa Rica, El Salvador and Panama are the most affected countries.) (96M3).
Part [Ca] ~ Erosion and Organic Matter Loss ~ Gully Erosion ~
About 405,000 km2 of US farmlands are badly eroded by gully erosion ((74C1), p. 238).
In 1977, 0.41 Gt. of soil were lost through gully erosion in the US. Stream-bank- and roadside erosion took even more (80U2).
Gully erosion took 0.271 Gt. in 1977 from all US land (81B1). Comments: This data is obsolete. The Conservation Reserve Program and the greater use of no-till agriculture have greatly reduced soil erosion in the US.
Carbon (topsoil) erosion during 1880-1920, a period of cotton cultivation in one catchment in the Georgia Piedmont is estimated at 19 cm. (about 0.5 cm/ year or 7200 tonnes/ km2/ year), with 8% of the carbon (topsoil) erosion coming from gully erosion (94H2).
Part [Cb] ~ Erosion and Organic Matter Loss ~ Wind Erosion ~
The Soviet "Virgin Lands" Project between 1954-1960 centered on plowing an area of grassland for wheat that was larger than the wheat land in Canada and Australia combined. Initially this resulted in an impressive expansion in Soviet grain production, but the success was short-lived as a dust bowl developed there as well. Kazakhstan, at the center of this "Virgin Lands" Project, saw its grain land area peak at just over 250,000 km2 around 1980, then shrink to 140,000 km2 today. On the remaining land the average wheat yield is scarcely 100 ton per km2, vs. nearly 800 tons per km2 that farmers get in France, Western Europe's leading wheat producer (07B1). Comments: Some refer to this Soviet project as the "Great Lands."
In early January 2005, the National Aeronautics and Space Administration (NASA) released images of a vast dust storm moving westward out of central Africa. This vast cloud of tan-colored dust stretched over some 5300 kilometers. NASA noted that if the storm were relocated to the US, it would cover the entire US and extend into the oceans on both US coasts (07B1).
Saharan dust storms have increased 10-fold (in frequency) during the last half-century. Among the countries in the region most affected by topsoil loss from wind erosion are Niger, Chad, Mauritania, northern Nigeria, and Burkina Faso. In Mauritania, in Africa's far west, the number of dust storms jumped from two/ year in the early 1960s to 80/ year today (07B1).
The BodXX(SP?) Depression in Chad (Africa) is the source of an estimated 1.3 billion tons of wind-borne soil a year, up 10-fold from 1947 when measurements began. The 2-3 billion tons of fine soil particles that leave Africa each year in dust storms are slowly draining the continent of its fertility and, hence, its biological productivity. In addition, dust storms leaving Africa travel westward across the Atlantic, depositing so much dust in the Caribbean that they cloud the water and damage coral reefs there (07B1).
In China, plowing excesses became common in several provinces as agriculture pushed northward and westward into the pastoral zone (typically semi-humid) between 1987 and 1996. In Inner Mongolia (Nei Monggol), for example, the cultivated area increased by 1.1 million hectares (11,000 km2), (22%), during 1987-1996. Other provinces that expanded their cultivated area by 3% or more during this 9-year span include Heilongjiang, Hunan, Tibet (Xizang), Qinghai, and Xinjiang. Severe wind erosion of soil on this newly plowed land made it clear that its only sustainable use was controlled grazing (07B1).(su1)
A 1994 China policy requires all cropland used for construction be offset by land reclaimed elsewhere. Coastal provinces are losing cropland to urban expansion and industrial construction, and are paying other provinces to plow new land to offset their losses. Many of these provinces, already suffering from over-plowing and overgrazing, have plowed ever more marginal land, and wind erosion has intensified. Erosion of soil and the resulting land abandonment are forcing people to migrate eastward. The increasing numbers of livestock are denuding the land of vegetation. Today China has 127 million cattle vs. 98 million in the US. A new desert is forming on the eastern edge of the Quinghai-Tibet Plateau, once known for grass reaching as high as a horse's belly and home for centuries to ethnic Tibetan herders (01U2).
US satellites images show that thousands of lakes in North China have disappeared (01U2).
In April, 2001, the National Oceanic and Atmospheric Administration (NOAA) reported that a huge dust storm from northern China had reached the US "blanketing areas from Canada to Arizona with a layer of dust," and that along the foothills of the Rockies dust from China obscured the mountains. The dust storms were reported in March 2001, by The People's Daily as one of the earliest on record and among the worst in memory, signaling a widespread deterioration of the rangeland and cropland in China's vast northwest. Routinely these dust storms travel hundreds of miles to cities in northeastern China, including Beijing, obscuring the sun, reducing visibility, slowing traffic, and closing airports (01U2).
Wind erosion has damaged 19,000 km2/ year in the Great Plains of the U.S. since 1955 (89P1) (89P4). The US SCS estimates 1982 US wind-erosion at 1.8 Gt. on all non-federal lands (89P1). 1.6 Gt./ year are lost west of the Mississippi. Some 1.1 Gt./ year was stripped from croplands in the west, while 0.544 Gt./ year came from rangelands in the West (89P1). Wind accounts for about 1 Gt./ year of US soil erosion. So gross (wind+ water) soil erosion in the US is about 5 Gt./ year (76P2). (This figure apparently considers more than just croplands.) For the US as a whole, 25% of total erosion is due to wind (Ref. 24 of (76P2)). Wind erosion damaged 50,600 km2 nationwide in 1980 (81U3). This damage was distributed as follows (in million acres and km2):
Montana~ | 2.5 |(10000 km2)|N. Dakota| 2.10|(8500 km2)
S. Dakota| 1.3 |( 5260 km2)|Wyoming~ | 0.31|(1260 km2)
Colorado | 2.3 |( 9310 km2)|N. Mexico| 0.57|(2310 km2)
A US SCS report noted that wind erosion damaged nearly 3 times as much land in the Great Plains of the US between 11/1979-2/1980 as 11/78-2/79 (3.1 million acres damaged vs. 1.2 million acres). Some 96% of the damage was to croplands (80U1).
A 1977 NRI survey by the US SCS found US wind erosion to be 0.81 Gt./ year ((83C1), p.15).
Wind erosion on US croplands increased from 3.1 tons/ acre/ year in 1982 to 3.3 tons/ acre/ year in 1987 (89G2).
A map of the US showing areas where wind erosion occurs on croplands is given on p.107 of (91H1).
Wind erosion moved 1.33 Gt. in 1977 from all US land (81B1).
Wind Erosion on Croplands of the Great Plains in 1977 (84U2)
(Col.2 and 5 = thousands of acres damaged; Col. 3 and 6 = % of state's croplands)
About 12,000 km2 of cotton-producing area of the southern US High Plains (Texas, southeastern Colorado, etc.) are highly susceptible to wind erosion because so little residue remains after cotton is harvested, soils are sandy, and the fallow season (Jan-April) coincides with the period of highest wind and least precipitation (89B4).
Ref. (82S1) tabulates wind erosion rates on croplands and rangelands in Great Plains states in 1977 based on USDA 1980 RCA data. Totals:
5-10 tons/ acre/ year on 16.7 million acres of cropland
More than10 tons/ acre/ year on 22.4 million acres of cropland
5-10 tons/ acre/ year on 5.68 million acres of rangeland
More than10 tons/ acre/ year on 13.36 million acres of rangeland
Wind erosion in Canada's prairie region accounts for twice as much soil loss as water erosion (Refs. 2, 16 of (86D1)).
Estimated US soil eroded by wind at 1.0 billion tons/ year. Adding 4 billion tons/ year of water erosion gives 5 billion tons/ year of topsoil loss in the US (76P3). Comments: Obsolete data - Conservation Reserve programs and conservation tillage have cut US erosion rates by about 1 billion tons/ year.
The SCS estimates 2 billion tons of US soil lost in 1982 from non-federal land via wind erosion, 90% of it from west of Mississippi River. About 1.2 billion tons came from cropland, and 600 million tons from rangeland (89P6). Comments: US river sediment data suggest greater loss from rangelands.
Part [Cc] ~ Erosion and Organic Matter Loss ~ Land Removed from Agriculture ~
Some 8100 km2/ year of US farmland are lost to erosion, salinization, and waterlogging related to unsustainable agricultural practices (97P1).
About 200 million acres (810,000 km2) (of US farmland?) have been totally ruined for crop production by erosion, or so severely eroded as to make it only marginally suitable for production in the past 2 centuries (76P2).
During 1949-1969, 58 million acres (235,000 km2) of US cropland were withheld from production (76P2). Comments: Conservation Reserve Program?
In the last 200 years of US farming, one million km2 of farmland has been abandoned because of erosion, salinization and waterlogging (Refs. 13, 18, 20 of (95P1)). Comments: This land typically returns to forestland.
US Cropland Idled under US Commodity Programs (1965-88) (USDA data in (88B4)) (Land areas are in 1000 km2)
Part [Cd] ~ Total Soil Erosion ~ US (sheet+ rill+ wind+ gully) ~[Cd1]~US Erosion Rates, [Cd2]~Regional US Erosion Rates, [Cd3]~Erosion on newer Croplands, [Cd4]~Long-term Effects, [Cd5]~Sediment Delivery, [Cd6]~Erosion Spectrum, 1982 NRI, [Cd7]~Soil Conservation, ~
Nearly 2 billion tons of soil erodes into US waterways each year. Despite significant gains in erosion control during the past 15 years, there has been no additional improvement since 1995 (Reuters, 12/7/99).
A report by David Pimental at an early-1995 annual meeting of the AAAS said that the US now loses 4000 km2/ year of agricultural land to urbanization, and 8000 km2/ year to erosion and salinization (Pittsburgh. Post Gazette (2/19/95)) (See Section (6-B) for urbanization data).
Research in the 1920s showed that 200,000 km2 of US croplands had been abandoned ((76E1), p. 50).
Surface-mine-disturbed land in the US ((79D1), p. 23) (million acres):
Comments:US strip-mine reclamation rarely restores land to use as cropland.
Sub-Part [Cd1] ~ Erosion and Organic Matter Loss ~ US Erosion Rates ~
US Cropland Erosion (Gt./ year) (94B2)
Total loss of croplands to sheet- and rill erosion, urbanization and water projects is 6 million acres/ year (= 4% of the US supply of surplus cropland (135 million acres) (79S1)). The breakdown according to cropland Class is as follows (Areas are in thousands of acres):
US Erosion Rate Estimates (1992 NRI) based on USLE and WEQ (Wind Erosion Equation) (tonnes/ km2/ year)(94K2)
* Areas are in 1000 km2
Reference (84B4) has map of dots showing where water/ wind erosion exceeded 5 tons/ acre/ year (1100 tonnes/ km2/ year) in 1977.
Reference (84L3) has map of wind/ water erosion on US cropland when equal to or greater than 10 tons/ acre/ year (2200 tonnes/ km2/ year).
Conservation tillage, plus retirement of erosion-prone land (Conservation Reserve Program), has reduced US soil erosion (wind+ water) by 25% during 1982-1992 (Ref. 26 of (96G1)).
In the 1920s at least 800,000 km2 in the US were suffering from accelerated erosion ((76E1), p. 50).
Estimates of average topsoil loss from US agricultural cropland range from 6 tons/ acre/ year (Ref. 6 of (76P2)) to 12 (Refs. 30 and 45 of (76P2)) and 14 (Ref. 46 of (76P2)).
In 1977 over 2 billion tons of US soil were lost through sheet- and rill erosion (80U2).
The total 1977 US erosion rate was 2.8 billion tons/ year (83C1).
Today the US loses 4 billion tons/ year of topsoil (1980 EPA est.) ((82S1), p. 36). The 413 million acres of US croplands lose 1.53 billion tons of soil/ year, with most coming from less than 10% of the croplands (84B2).
Agricultural topsoil loss in the US has been estimated by Pimentel to be 2700 tonnes/ km2/ year (3 billion tons/ year) ((78B1), p. 49). Comments: The Conservation Reserve Program and expanded use of conservation tillage (low-till, no-till, etc.) have reduced this by around 1 billion tons/ year.
A nation-wide survey by the SCS indicated that 1975 cropland soil losses were nearly 3 billion tons (2200 tons/ km2/ year) ((78B2), p. 24).
US croplands lose soil at 1700 tonnes/ km2/ year from combined water- and wind erosion. US pastures lose 600 tonnes/ km2/ year (Ref. 13 of (95P1)).
Fertile topsoil is not flowing down the Mississippi River into the Gulf of Mexico as fast as thought, according to research published in the 8/20/99 issue of the journal Science. A study by Stanley Trimble from U. of California, Los Angeles uses 140 years of information on sediment buildup and erosion from Coon Creek River in Wisconsin farm country. Soil erosion in this watershed, he concludes, has been steadily decreasing, to 6% of what it was during the 1930s ("US Soil Erosion Not as Severe as Thought", ENN (8/25/99)).
Soil Loss from Highly Erodible/ fragile Cropland, by Region (86W3)
Sub-Part [Cd2] ~ Erosion and Organic Matter Loss ~ Regional US Erosion Rates ~
Sub-Part [Cd3] ~ Erosion and Organic Matter Loss ~ Erosion on Newer Croplands ~
A number of studies have established that much of the land bought into crop production since 1972 is much more vulnerable to erosion than land previously cropped (83C2).
If non-cultivated US croplands (279,000 km2) were farmed under "average" conditions reflected in the USLE factors for land actually cropped in 1977, it would erode at an average rate of 2670 tonnes/ km2/ year (83C2).
Sub-Part [Cd4] ~ Erosion and Organic Matter Loss ~ Long-term Effects ~
Average US topsoil depth = 23 cm. in 1776 (15 cm. today) (Ref. 82 of (95P1)). A USDA study (part of the 1980 RCA (Resource Recovery Act) Assessment) contends that continuing 1977 cropland erosion rates for 50 years would reduce crop yields by 8%. A second study by soil scientists at the U. of Minnesota concluded that continuing 1977 erosion rates for 100 years would reduce yields 5-10%. A third RFF study concluded that, in the US Corn Belt, erosion reduced corn- and soybean yields by 4% during 1950-1980 (83C1). 95% of US croplands lose topsoil above the sustainable rate (Refs. 23 and 24 of (95P1)).
Pimentel et al estimate that the US has lost (net) 1/3 of its original topsoil in the past 200 years, and that the loss rate on agricultural lands is increasing ((80H1), p. 273) (Refs. 34, 35 of Ref. (80P2)). Chapter 2 of (83C1) examines whether US soil erosion in the 1970s was more or less than in the 1930s. Their review of limited evidence suggests that it almost surely was less. Soil loss rates in the US are now greater than they were when the Soil Conservation Service (SCS) was founded in 1935 (78E1). On balance, cropland erosion/acre/ year declined from the 1930s to the late 1970s. (Total cropland was about the same in both periods.) ((83C1), p. 16).
US farmers lose 1" (37,000 tonnes/ km2) of topsoil every 8-10 years on average - ten times the natural rate of soil creation under agricultural conditions ((81W1) - quoting D. Pimentel). The USDA contends that US soil erosion is causing a steady drop in land productivity equivalent to the loss of 1.26 million acres/ year (81W1).
The Council for Agricultural Science and Technology estimated in 1975 that, as of the mid-1970s, 1/3 of US croplands was suffering soil losses too great to be sustained without a gradual but ultimately disastrous decline in productivity ((78B1), p. 49) ((78B2), p. 24).
Ref. (76P1) concludes, in a review article, that soil erosion in US agriculture continues at seriously high levels (76P2). Comments: Obsolete data - no-till agriculture and Conservation Reserve Program.
Some 34% of US croplands lose topsoil at a rate that degrades long-term productivity ((81B4), p. 999).
US soil-erosion rates exceed new-soil-formation rates on over 1/3 of US croplands (84B1). Comments: Obsolete data.
Estimates of average loss of topsoil from US agricultural cropland range from 6 tons/ acre/ year to 12 and 14 tons/ acre/ year (76P2).
Over 50% of all US erosion was on croplands, and 1/3 was on rangelands (81B1). Comments: River sediment data suggests otherwise.
Sub-Part [Cd5] ~ Erosion and Organic Matter Loss ~ Sediment Delivery ~
Wadleigh estimates that 4 billion tons/ year of sediment go into waterways in the 48 contiguous US states ((71R1), p. 86) (76P2). 3 billion tons of this comes from agricultural land ((76P2), p. 150).
Nearly 50% of sediments reaching US streams and lakes come from agricultural land; 10% comes from rangelands and forestland; 10% comes from eroding roadsides, construction activities, surface-mined land and other disturbed areas. The remaining 30% is geological erosion (EPA Water Quality Mgmt. Bull. of 1980) ((82S1), p. 36).
Sub-Part [Cd6] ~ Erosion and Organic Matter Loss ~ Erosion Spectrum ~
The 3.5% of US cultivated land undergoing sheet-and-rill erosion of over 25 tons/ acre/ year (5600 tonnes/ km2/ year) accounts for 32% of total US soil loss. 7% of cultivated acreage erodes at over 15 tons/ acre/ year, but that 7% accounts for 44% of total US soil loss. In the US corn belt, 1/2 of total soil loss originated on 10% of the cultivated land. The average erosion rate on this land is 35 tons/ acre/ year (7860 tonnes/ km2/ year) (86O1).
Reference (81U1) tells how many acres were eroding in each of a number of erosion-rate ranges in 1977. Total acreage covered = 1,396,397,000, so it apparently covers more than just croplands (National Resource Inventories (NRI) data, SCS-USDA).
Apportionment of US Soil Losses Among Cropland Classes (USDA data) ((79S1), p. 92)
(Col.2 = 1977 cropland acreage in indicated class (million acres))
(Col.3 = 1977 soil loss attributed to indicated Class (million tons/ year))
(Col.4 = average soil loss for soils in Class (tons/ acre/ year) (=Col. 3/ Col. 2)
1982 NRI: National Resources Inventory occurred in 1982, 1987 and 1992 (94K2).
The 1982 NRI found the average soil erosion rate on cultivated US croplands dropped from 5.1 tons/acre/ year in 1977 to 4.8 tons/acre/ year in 1982 (84U4) (sheet and rill only). Nearly half of new land bought into cropland (421 from 413 million acres) during 1977-1982 is highly susceptible to erosion (84U4). 189,000 km2 in the US in 1982 is urban or built up, vs. 262,000 km2 in the 1977 NRI. The drop is attributed to improved mapping, data collection and quality control (84U4). Erosion on pasturelands and range lands averaged 1.4 tons/acre/ year. Erosion on grazed forestland averaged 2.3 tons/ acre/ year. non-grazed forestlands erosion averaged 0.7 ton/ acre/ year. Wind erosion on cultivated cropland averaged 3.3 tons/ acre/ year. Rangeland wind erosion averaged 1.5 tons/ acre/ year. Wind- and sheet-and-rill erosion on cultivated cropland averaged over 8 tons/ acre/ year (84L1).
US Soil Erosion (million tons/ year) from RFR Environmental Data Inventory (86G1)
Sub-Part [Cd7] ~ Erosion and Organic Matter Loss ~ Soil Conservation ~
In 1987, Year 2 of the US Conservation Reserve Program, the CRP helped reduce US soil losses by 460 million tons, the greatest year-to-year reduction in US history (Ref. 88 of (88B4)).
About 32 million acres (130,000 km2) of US cropland are identified as highly erodible and fragile. Seven major crops use 75% of cropland. Only erosion considered is water erosion. Current level of highly erodible land erosion is 20 tons/ acre/ year (4490 tonnes/ km2/ year). Putting the highly erodible land in these 7 crops into conservation reserve would reduce erosion rate 90%. If all highly erodible land were put in reserve, government would save $5 billion in storage- and deficiency payments (86W3).
Over 60% of topsoil savings on US croplands since 1985 are credited to the CRP (Ref. 78 of (96G2)).
Conservation practices of all kinds contributed to a 25% reduction in US soil erosion during 1982-92 (Ref. 79 of (96G2)).
Go to Top of this Review's Appendices (units, conversions, definitions)
Part (Ce) ~ Erosion and Organic Matter Loss ~ Sheet- and Rill Erosion ~ US ~
Estimates of National Sheet- and Rill Erosion and Water Pollutant Discharge by point- and non-point Sources (tons/ year?) from RFF, Environmental Data Inventory (86P2)
(1) Includes both federal- and non-federal lands
(2) farmsteads, other land in farms, mines, quarries, pits, other rural lands
(3) Includes livestock-, dissolved nutrient-, acid mine drainage-, and urban runoff
Distribution of 1977 Cropland Sheet/Rill Erosion Among Erosion Levels ((84U2), p. 56) (Obsolete data - of historical interest only.)
(Col. 1 = Erosion level (tons/ acre/ year)
(Col. 2 = croplands with the given erosion level, million acres (1000 km2)
(Col. 3 = percentage of all croplands in the given erosion level)
(Col. 4 = Total erosion in that erosion level category (million tons/ year)
(Col. 5 = percentage of total erosion within the given erosion level)
Erosion Status of 7 Major US crops(86W3)
Note: All data (preceding and succeeding) are from 1982 NRI.
Erosion Status for Highly Erodible Land (86W3)
(Soil Loss (Col. 4) is in millions of tons/ year.)
(Erosion (Col. 5) is in tons/ acre/ year.)
Excess sheet/ rill erosion by crop-production region is tabulated in Ref. (82S1). Cropland acreage by state is also given. A map of 1977 cropland erosion across the US is in (81B1). Comments: Obsolete data: the Conservation Reserve Program and increased use of conservation tillage have greatly reduced US soil erosion on croplands.
The most serious sheet/ rill erosion occurs in the US Corn Belt, the Delta states, and western Tennessee (81B1).
Some 87% of US farmland suffers sheet/ rill erosion at 5 tons/ acre/ year or less. 80% of all excess sheet/ rill erosion on agricultural land is concentrated on the 4% of the acreage that is eroding at over 14 tons/ acre/ year (Ref. 1 of (81U1)).
Much information on US soil erosion rates comes from a 1977 National Resources Inventory (NRI), a survey by the SCS ("Soil, Water and Related Resources in the US: Status, Conditions and trends: 1980 RCA Appraisal, Part I" from USGPO). The survey found US sheet/rill erosion to be 1.7 Gt./ year ((83C1), p. 15) (and wind erosion = 0.82 Gt./ year). If all of this erosion is attributed to the 413 million acres (1.672 million km2) of croplands, it suggests an erosion rate of 6.8 tons/ acre/ year.
US Sheet/ Rill Erosion by Land Class (tons/ acre/ year) (80U2)
Some 95% of cropland erosion occurs where cultivated and close-grown crops are produced. The average loss here is 8 tons/ acre/ year (1800 tonnes/ km2/ year). Sheet-and-rill erosion accounts for 5.4, and wind accounts for 2.6, of these 8 tons ((81B1), p. 82). Erosion due to water run-off (sheet-and-rill erosion only) in 1977 was 3.68 Gt. from all US land (81B1).
Sheet-and-rill erosion removes 1.8 Gt./ year of topsoil from US croplands ((81B3), p.18).
Erosion exceeds 10 tons/ acre/ year on 17% of US croplands (Ref. 7 of (82O2)).
Corn- and soybean production accounts for most of the sheet-and-rill erosion in the US (Ref. 2 of (82O2)). Maps of the US plotting erosion rates (1977) on corn-, cotton-, soybean- and wheat croplands are shown in (82O2).
In 1982, sheet-and-rill- and wind erosion on US non-federal rural land claimed 4.9 Gt. of soil. 80% of this occurred on croplands (89P3).
In Idaho, more than 45 million tons of soil were lost from 26,000 km2 of cropland via sheet, rill, and wind erosion in 1982 (89P3).
On US croplands, sheet-and-rill erosion caused by water decreased from 4.3 tons/ acre/ year in 1982 to 3.8 tons/ acre/ year (850 tonnes/ km2/ year) in 1987 (89G2). Nation-wide, sheet-and-rill erosion totaled 2.62 Gt./ year in this period. 1.36 Gt./ year of this occurred on croplands, and 0.45 Gt./ year occurred on rangelands (89G2).
Some 75% of water erosion sediments in the US comes from agricultural (crop?) lands (Refs. 29-31 of (76P2)).
Go to Top of this Review's Appendices (units, conversions, definitions)
Part (Cf) ~ Data on Canada and Specific US States and Regions ~ [Cf1]~General, [Cf2]~Southeastern US, [Cf3]~Far West, [Cf4]~Canada, [Cf5]~Rocky Mountains, [Cf6]~Great Plains, [Cf7]~Iceland, [Cf8]~Midwest, [Cf9]~Northeastern US, ~
Sub-Part [Cf1] ~ Erosion and Organic Matter Loss ~ Canada and US ~ General
In North America, about 0.95 million km2 of land are degraded. (UNEP data)
Major US Erosion Areas from the 1982 NRI (84L1)
Col.2 = Erosion Rate (tons/ acre/ year)
Col.3 = Land Area (millions of acres)
Col.4 = Total Erosion (millions of tons/ year)
Sub-Part [Cf2] ~ Erosion and Organic Matter Loss ~ Southeastern US ~
In a study of the old plantation belt in the southern US Piedmont, 44% of the area (10,900 km2) had reached the stage of gully erosion (85H1).
[Cf2a] ~ Erosion and Organic Matter Loss ~ Southeast US ~ Alabama ~
Soil erosion on Alabama croplands exceeds 2000 tonnes/ km2/ year (89Y1).
[Cf2b] ~ Erosion and Organic Matter Loss ~ Southeast US ~ Florida ~
Of the 700,000 acres of organic muck soils in the Florida Everglades Agricultural Area, 99% initially had depths exceeding 36" (Ref.14 of (85H1)). 13% of the area will retain a depth of more than 36" by 2000, and 45% will have a depth of 12" or less. (The loss is due largely to oxidation.) (85H1).
[Cf2c] ~ Erosion and Organic Matter Loss ~ Southeast US ~ Georgia ~
"Highly erodible" cropland in Georgia erodes at an average of 13.9 tons/ acre/ year (3120 tonnes/ km2/ year) (89M2).
Soil erosion in the southern Piedmont was recognized as a serious problem by 1860, and peaked around 1920, and has declined steadily since then (82M2).
[Cf2d] ~ Erosion and Organic Matter Loss ~ Southeastern US ~ Mississippi ~
(Cropland?) soil erosion in Mississippi is 2450 tonnes/ km2/ year ((81B3), p.18). Sheet and rill erosion was 7.3 tons/ acre/ year (vs. 8.1 in 1982) (1987 NRI study) (89G2).
[Cf2e] ~ Erosion and Organic Matter Loss ~ Southeastern US ~ Kentucky ~
(Cropland) sheet-and-rill erosion in Kentucky as reported in the 1987 NRI study was 8.5 tons/ acre/ year (vs. 8.9 in 1982) (89G2).
[Cf2f] ~ Erosion and Organic Matter Loss ~ Southeast US ~ Tennessee ~
Conversion from cattle grazing to soybeans caused erosion rates of 4500 tonnes/ km2/ year (85R1).
A description of the very severe erosion near Dutchtown Tennessee due to air pollution is described in (56E3).
Tennessee is losing topsoil (from croplands?) at 3170 tonnes/ km2/ year ((81B3), p. 18).
(Cropland) sheet/ rill erosion in Tennessee as reported in the 1987 NRI study was 8.8 tons/ acre/ year (vs. 10.0 in 1982) (89G2).
Sub-Part [Cf3] ~ Erosion and Organic Matter Loss ~ Far West ~
[Cf3a] ~ Erosion and Organic Matter Loss ~ Far West ~ California ~
Air pollution has changed the agricultural economy of the Los Angeles area. Many ornamental plants and trees no longer grow there. Leafy vegetables cannot be grown profitably in the area (71H1).
[Cf3b] ~ Erosion and Organic Matter Loss ~ Far West ~ Columbia River Drainage ~
Soil erosion in the Columbia River drainage of the US is 100 million tonnes/ year, of which 27 million are deposited in streams, rivers, lakes and harbors (82O1). Comments: Much is deposited on the down-slopes, since only a small fraction gets to the ocean ~ see Section (4-G) in this document.
[Cf3c] ~ Erosion and Organic Matter Loss ~ Far West ~ Palouse ~
(parts of Washington, Oregon and Idaho) In 1977 sheet-and-rill erosion was 11,200 to 22,400 tonnes/ km2/ year on slopes of 15-25%. In southeast Idaho, sheet and rill erosion is 3600 tonnes/ km2/ year (80U2). Comments: The Palouse is known to have wind-deposited soils (loess) of low organic matter content. Hence it is erosion-prone and has low fertility.
"Sod-busting" occurred in the Palouse from 1870 to 1910. Power farming predominated from mid-1930s to mid-1940s when tractors became common. Soil slides downhill when plowed across-slope. By end of the era, 10% of the land had lost all topsoil, and 60% had lost 25-75% of topsoil (90J1).
Palouse River Basin of eastern Washington and northern Idaho is 58% croplands (Ref.19 of 88O1). Cropland soil loss rate = 3144 tonnes/ km2/ year. Cumulative loss = 80,800 tonnes/ km2 since 1939 (Ref. 19 of (88O1)). The Palouse is one of the ten most critically eroding regions in the US (Refs. 17, 18 of (88O1)). The Palouse Region of Washington and Idaho has 8000 km2 according to Journal of Soil and Water Conservation 44 (1989) p. 303.
Average soil erosion loss from 4212 km2 of cultivated land in the Palouse since 1930 is 2100 tonnes/ km2/ year. (Intensive cultivation began about 1890.) (82K1). Comments: Palouse has loess (wind-deposited) soil (highly erosion-prone).
Based on USLE, average soil erosion loss in the Palouse River Basin is 3100 tonnes/ km2/ year. In the most erosion-prone central part, erosion averages 4500 tonnes/ km2/ year (83F1). Over 90% of loss is cropland erosion (sheet/ rill).
Average annual erosion rates in Palouse range from 1000 tonnes/ km2/ year to over 3000 tonnes/ km2/ year using conventional farming practices (91M1). About 1/3 of the eroded soil enters streams and other water bodies. Soil erosion in Columbia River drainage system in 1975 estimated at 110 million tons/ year. About 1/3 is deposited in water bodies (91M1).
*# STEEP is Solutions to Economic and Environmental Problems.
USDA estimates that, in 100 years of cultivation, 10% of soils will have lost all topsoil, and 25-75% of original topsoil will have been lost on another 60% of cropland. Previous work indicates (for 1975) 1.1 tonnes/ km2/ year loss in wheat-yield/cm. of topsoil lost when topsoil thickness is 55 cm, and 9.4 tonnes/ km2/ year for soils with a topsoil thickness of 7 cm. (85B5). Average erosion for soils of the Walla Walla association is 3600 tonnes/ km2/ year. For soils of the Palouse-Thatuna-Naff (PTN) association, erosion loss is 6300 tonnes/ km2/ year. Soil loss from upper slopes in PTN association is 3037 tonnes/ km2/ year. For lower slopes, loss is 7100-7500 tonnes/ km2/ year. OM in topsoil of PTN association declined from 4.5 to 2% (85B5).
Using USLE calculations, all topsoil will be lost on Naff, Garfield, and Risbeck soils if current tillage continues for 50 years at present estimated rates of erosion. About 1/3-2/3 of topsoil will be lost from Walla Walla, Palouse and Thatuna soils in 50 years (85B5).
Sub-Part [Cf4] ~ Erosion and Organic Matter Loss ~ Canada
Potato lands of New Brunswick and Prince Edward Island have some of the worst water erosion problems in Canada (Refs. 7, 8 of (86D1)). In Prince Edward Island, loss rates of 2000 tonnes/ km2/ year are common. Land in row crops (potatoes, corn, tobacco and horticultural crops) can erode at rates as high as 10,000 tonnes/ km2/ year (86D1).
New Brunswick soil losses of up to 4000 tonnes/ km2/ year have been recorded (84S2). In New Brunswick and Prince Edward Island, potatoes are grown with rows running up-and-down-hill, with no winter protection crop, no crop rotation, with heavy fall- and winter rains and late-winter-early-spring freeze-thaw cycles, and rain and melt-water flowing over partially frozen soil (erosion = 2000 tonnes/ km2/ year) (84S2).
Soil loss on Canada's Prairie Provinces croplands is 160 million tonnes/ year by wind, and 117 million tonnes/ year by water on 300,000 km2 (84S2). Comments: This implies 533 tonnes/ km2/ year (wind), and 390 tonnes/ km2/ year (water) - too low to be realistic.
Canada's Prairie Province soils are naturally high in organic matter. They have lost 45% of their original organic matter content since cultivation began at the turn of the Century (84S2).
Sub-Part [Cf5] ~ Erosion and Organic Matter Loss ~ Rocky Mountains ~
[Cf5a] ~ Erosion and Organic Matter Loss ~ Rocky Mountains ~ Colorado
(Cropland?) soil erosion is 2000 tonnes/ km2/ year (mainly due to wind) ((81B3), p.18). Dry cropland in Crowley County Colorado suffers tremendous soil erosion. Its rangeland shows signs of severe over-grazing. A few pastures are almost completely devoid of grass, and many others have extremely sparse grass-cover. Fences are half-buried under drifts of soil, and active gully erosion is under way on steeper slopes. In flatter areas, "blowouts" (spots stripped of all vegetation and winnowed by the wind into shallow sand pits) are readily apparent (81S1, p.87). 150,000 acres of Class IV cropland (land that should be grassland, not farmed) in western Kiowa County was under cultivation and was eroding at 20 tons/ acre/ year (45 tonnes/ km2/ year) or more when the Feb. 1977 windstorm hit ((81S1), p. 78). Dust storms that hit Kiowa and Crowley Counties Colorado in Feb. 1977 (and darkened skies to the Atlantic Ocean) removed 150 tons of soil/acre (33,700 tonnes/ km2). Average rainfall in this area is about 15" (5" below the minimum recommended for dryland farming). Much of the area's native grasses had been plowed under for dryland crop farming (wheat) or over-grazed by cattle ((81S1), p.77). Dust storms between 11/1/76 and 2/28/77 damaged 3646 km2 in 37 eastern Colorado counties, including 980 km2 of crops lost. Another 8900 km2 are in a condition to blow in eastern Colorado (US SCS data) (77C1).
Some 2310 km2 of fragile Colorado grassland were plowed for planting to croplands in the past 6 years. This arid land is ill-suited to crops and will suffer frequently from dust storms. Colorado loses 2470 tonnes/ km2/ year to erosion and regenerates at a rate of less than half of that. Colorado as a whole loses 0.206 Gt. of topsoil/ year (84D1).
[Cf5b] ~ Erosion and Organic Matter Loss ~ Rocky Mountains ~ Idaho ~
Erosion on wheat-fallow land in the Idaho-Utah Intermountain area has removed the brown topsoil and exposed whitish, lime-enriched subsoil on 15-20% of the area (85M1).
[Cf6] ~ Erosion and Organic Matter Loss ~ Great Plains ~
Many of the shelter-belts planted in the US Great Plains in the 1930s and 1940s were removed during the 1973-74 period when wheat hit $5/ bushel and the Secretary of Agriculture, Earl Butz, urged farmers to plant fields fence-to-fence ((81S1), p. 79). Droughts on the Great Plains seem to follow the sun's 20-22-year sun-spot cycle (mid-30s, mid-50s, 1976-7) (Don Kirkman, Scripps Howard Science writer, 2/22/76). A map of the Great Plains Shelter Belt planting of the 1930s is shown on p. 11 of (58R1). During 1935-1942, more than 200 million trees and shrubs were planted on 30,000 farms in windbreak strips totaling 18,600 miles (58R1). A history of the Dust Bowl of the 1930s and an analysis of its causes is in Ref. (79W1). Comments: This cropland conversion probably owes its existence to generous federal crop subsidies.
Ref. (76P1) shows a map showing the extent of the 1936 Dust Bowl, the 1976 dust storms, and the shelterbelts planted in the F. D. Roosevelt Administration (76P1). Shelterbelt removal is discussed in (75C1). The Soil Conservation Service (SCS) reported that in June, 1977, 32,400 km2 in the Great Plains were damaged by wind erosion in the past 7 months. That's the most area damaged since the mid-50s. 80% of the damage was to croplands. 28,000 km2 more were in a condition to blow in 6/77 (77U1).
[Cf6a] ~ Erosion and Organic Matter Loss ~ Great Plains ~ New Mexico ~
A 1986 GAO study found 19 of 28 farms in New Mexico's Portales area (Roosevelt County) losing soil at 2700-4000 tonnes/ km2/ year. (Wind erosion on the Great Plains averages 1190 tonnes/ km2/ year.) In 1987 the Portales area was one of two causes of a major dust storm that covered the South-Central US to the Atlantic Ocean. Wind scoured plowed fields to depths of 3 ft. and smothered others under blankets of sand ((81S1), p. 74).
A 1977 GAO study of 28 farms in Roosevelt Co. New Mexico found 9 eroding at 10-20 tons/ acre/ year, and 10 eroding at 20-40 tons/ acre/ year (81S2).
During 1885-1962 (77 years), 1.-1.4 Gt. of soil washed from the 511,916-acre Rio Puerco (NM, just west of Albuquerque) River basin into the Rio Grande River (Ref. 18 of (probably) the 1983 Yearbook of Agriculture (p. 350). Comments: This averages out to 6266-8545 tonnes/ km2/ year.
[Cf6b] ~ Erosion and Organic Matter Loss ~ Great Plains ~ Texas ~
In Gaines County of west Texas, 31 of 39 farms were losing 9000 tonnes/ km2/ year, mostly via wind erosion, according to a GAO study ((81S1), p. 89). Gaines Co. has a serious ground-water depletion problem. 1400 km2 are irrigated with ground water. 25% of the rangeland appears over-grazed. Average rainfall: 16"/ year (4" less than the minimum recommended for dryland farming). Crops are cotton monoculture. Wind erosion is so bad that strip-cropped wheat (between cotton) looks like sand dunes ((81S1), p. 89). Texas is losing topsoil (from croplands?) at 3350 tonnes/ km2/ year (mainly to wind erosion) ((81B3), p.18).
A 1977 GAO study of 39 farms in Gaines Co. Texas found 31 of them losing soil at 40+ tons/ acre/ year, and 5 more losing 20-40 tons/ acre/ year. Of the 10 counties (283 farms), the GAO studied, Gaines Co. had the worst soil erosion, Gaines Co. has 400,000 acres of dryland farms, and 350,000 acres of irrigated (by ground-water) farms. Cotton is raised on 90% of the area. 150,000-175,000 acres of grassland remain, but it is being plowed at 10,000-15,000 acres/ year to raise more cotton (Ref.39 of (81S2)). Average rainfall: 16"/ year. Comments: Recommended minimum rainfall for dryland farming = 20"/ year. (See Section (2-D-g)
Sub-Part [Cf7] ~ Erosion and Organic Matter Loss ~ Iceland
Severe wind erosion has been a problem since Iceland's settlement in 875-930 AD. Bad drifting-sand problem during 1860-1990 is attributed to over-grazing by sheep (90M2).
Sub-Part [Cf8] ~ Erosion and Organic Matter Loss ~ Midwest ~
[Cf8a] ~ Erosion and Organic Matter Loss ~ Midwestern US ~ lllinois ~
Average (cropland?) erosion is 1500 tonnes/ km2/ year. The Illinois EPA estimate that 40% of Illinois croplands erode at a rate of over 2500 tonnes/ km2/ year (84S1).
[Cf8b] ~ Erosion and Organic Matter Loss ~ Midwestern US ~ Iowa ~
(Cropland?) soil erosion is 2220 tonnes/ m2/ year ((81B3), p.18). An average of perhaps 1/3 of the original A-horizon of the surface of Iowa land has been lost since settlement, while the depletion of mineral nutrients now makes necessary the use of chemical additives ((56S2), p. 477).
Iowa had an average of 8" of topsoil when it was settled. Today (100 years later) it has 4" (81W1) (4"/100 years = 1350 tonnes/ km2/ year). Iowa initially had 16" of topsoil. 100 years of farming carried off 8" of this (8"/100 years = 2700 tonnes/ km2/ year. In 1974, 18,200 km2 of Iowa's 83,800 km2 of corn and soybeans land suffered severe erosion of over 10 tons/ acre/ year (excess) (15 tons/ acre/ year gross) (75G1). 9000-11,000 tonnes/ km2/ year weren't uncommon, and some farms lost 45,000 tonnes/ km2/ year (75G1).
A study by J. F. Timmons (Iowa State University) showed Iowa's annual soil loss to be (83B1): 4770 tonnes/ km2/ year (1949); 3166 (1957), and 3860 (1974) (partly due to rapid rise in price of wheat, corn and soybeans) (83B1) (76P2, p.152). Iowa sheet-and-rill erosion as reported in the 1987 NRI study was 6.5 tons/ acre/ year (vs. 8.2 in 1982) (89G2).
Iowa had lost 50% of its topsoil by 1981 and continues to lose topsoil at 3000 tonnes/ km2/ year (97P3).
[Cf8c] ~ Erosion and Organic Matter Loss ~ Midwestern US ~ Minnesota ~
According to estimates based on the 1982 NRI, erosion in Olmstead County Minnesota averaged 10.2 tons/ acre/ year (2300 tonnes/ km2/ year) on croplands 1058 km2 with total soil movement of 2.2 million tonnes. More than 50% of this erosion occurred on Class III or higher croplands, and 1/6 on Class IV or higher croplands. In 1989 less than 3% of the county's cropland area eroded at a rate of 6060 tonnes/ km2/ year or more, but this accounted for more than 25% of the total soil movement in the county (90W2).
[Cf8d] ~ Erosion and Organic Matter Loss ~ Midwestern US ~ Missouri ~
(Cropland?) soil erosion in Missouri is 2560 tonnes/ km2/ year ((81B3), p. 18). Sheet-and-rill erosion was 7.0 tons/ acre/ year (vs. 9.0 in 1982) (1987 NRI study) (89G2).
Sub-Part [Cf9] ~ Erosion and Organic Matter Loss ~ Northeastern US ~
In the potato croplands of Aroostook County Maine, the upper 24" of soil have been lost since cultivation began. Some sloping croplands (25% maximum slope) lose 1"/ year (33,700 tonnes/ km2/ year) (80U2).
Go to Top of this Review's Appendices (units, conversions, definitions)
SECTION (5-D) ~ South- and Central America ~ [D1]~Southeastern South America, [D2]~Brazil, [D3]~Northwestern South America, [D4]~Central America, [D5]~Andean Mountain Region, ~
South America's main types of degradation are loss of topsoil from water erosion (39% of degraded area), loss of soil nutrients (28%) and terrain deformation from water erosion (12%) (96M3).
Part [D1] ~ Erosion and Organic Matter Loss ~ Southeastern South America ~
Patagonia Desert (Argentina) winds are very strong, causing soil erosion to be a big problem ((70C1), p. 374).
Part [D2] ~ Erosion and Organic Matter Loss ~ Brazil ~
A massive cropland expansion is now taking place in the Brazilian Amazon Basin in the Cerrado, a huge savannah-like region bordering the Amazon basin on its south side. Land in the Cerrado is like that in the U.S. semi-arid plains where the "Dust Bowl" took place, and in the semi-arid region of Kazakhstan where the massive Soviet expansion (and subsequent abandonment)of wheat acreage occurred. The Cerrado region is vulnerable to soil erosion via wind erosion like virtually all semi-arid plains. This cropland expansion is pushing cattle ranchers into the Brazilian Amazon forests, where ecologists are convinced that continuing to clear the area of trees will end in disaster. Reporter Geoffrey Lean, summarizing the findings of a 2006 Brazilian scientific symposium in London's Independent, notes that the alternative to a rainforest in the Amazon Cerrado would be "dry savannah at best, desert at worst." (Lester R. Brown, "Civilization's Foundation Eroding" Earth Policy Release, Book Byte (9/28/10). www.earth-policy.org/index.php?/book_bytes/2010/pb4ch02_ss2) (To og99.doc and se99.doc and df99.doc and su1.doc and Food-Pop-Link.doc)
Brazil's harvested area has more than doubled since 1950, but crop yields per unit area have not increased despite heavy use of fertilizer and modern techniques. This is attributed to new croplands being more marginal and less productive ((78B2), p. 32).
An agricultural area of 35,000 km2 in eastern Amazonia that was abandoned early in the 20th century has little vegetation aside from scrub and brush 50 years later (Ref. 48 of (95D3)).
In Brazil's Parana, conversion from coffee plantation to soybeans-wheat rotation increased erosion. With tillage on the contour, losses up to 40,000 tonnes/ km2/ year were recorded. Even with terraces, maximum losses in order of 10,000 tonnes/ km2/ year (85H2). Comments: Typical topsoil inventory: 400,000 tonnes/ km2.
In Brazil's central and western Sao Paulo State, the rate of cropland erosion is over 2000 tonnes/ km2/ year (77L1).
In Northeast Brazil (1.6 million km2, 18% of Brazil; 30 million people):
Part [D3] ~ Erosion and Organic Matter Loss ~ Northwestern South America ~
In the Cauca region of the southern mountains of Colombia, important landslides occur every few months. Sediment deposits regularly block the Cali and Canaveralejo Rivers, causing major flooding problems for the City of Cali. The lower Anchicaya Reservoir filled with silt in 7 years -destroying 2/3 of its hydroelectric capacity (75E1). The UN estimates topsoil erosion at 0.387 Gt./ year ((78B2), p. 25).
In Colombia's llanos, erosion problems are due to over-grazing. 20% of the Llanos land has lost most of its native productivity (77L1).
In parts of Venezuela the fallow period for shifting cultivation has become so short that soil fertility is in a state of decline ((78B2), p. 30).
In Venezuela's highlands, most cultivated land is severely or moderately eroded. As much as 75% of Venezuela's highlands cultivated land is on slopes over 25% (77L1). (la)
Part [D4] ~ Erosion and Organic Matter Loss ~ Central America ~
Land degradation affects about 3 million km2 of land in Latin America (UNEP data).
Sub-Part [D4a] ~ Erosion and Organic Matter Loss ~ Central America ~ Dominican Republic ~
Erosion high in the central mountains of Dominican Republic; 10,000-50,000 tonnes/ km2/ year (87H3). Comments: These rates imply a topsoil lifetime of a few decades.
Sub-Part [D4b] ~ Erosion and Organic Matter Loss ~ Central America ~ El Salvador ~
A recent OAS study concluded that 77% of El Salvador's land area is suffering from accelerated erosion. Many hills in the northern mountains have been reduced to rocky, barren "moonscapes" ((76E1), p. 167).
Most erosion in El Salvador is on small farms located on 7-25% slopes (81W2).
Sub-Part [D4c] ~ Erosion and Organic Matter Loss ~ Central America ~ Guatemala ~
USLE erosion estimated to be up to 300,000 tonnes/ km2/ year on 60% slopes in Guatemala (80A1).
Sub-Part [D4d] ~ Erosion and Organic Matter Loss ~ Central America ~ Haiti ~
In Haiti, only 3% of the once lushly forested terrain still has tree cover. Up to one third (9000 km2) has lost so much soil that it is no longer arable, or barely so. Haiti's landscape is crisscrossed by gully-scarred, deforested hills and "rocks" where there used to be dirt (
The UN Development Program has labeled "rapid and increasing erosion" as Haiti's principal problem. Land tenure forces peasants onto steep slopes where cultivation is a futile, temporary proposition ((76E1), p. 169). (su1)
A third of Haiti's land is now virtually useless, and 40% of the population is mal-nourished ((88J1), p. 15) (89J1). (su1)
Much Haitian agriculture occurs on steep slopes, where farmers abandon 60 km2/ year to erosion (Ref. 4 of (90P2)). In the 18th century in Haiti, clean cultivation between plants reduced the life of typical indigo plantations to about 3 years (due to erosion). Coffee plantations were difficult to establish after 3 years (Ref. 1 of (90P2)).
Severe erosion eliminated Haitian cropland at 60 km2/ year during the mid-1980s. (32% of Haitian land is suitable for farming, but 61% is farmed.) (96G2).
Per-capital cereal production declined 30% during 1965-83. Croplands are abandoned at 60 km2/ year to erosion. 50% of Haiti produces crops, mostly on sloping land (90P4).
In a southwest Haiti project area, at least 60% of soils have lost their A horizon, 20% have lost their A- and B horizons. About 10% of that southwest Haiti project area (800 km2) has irreversibly degraded to bedrock (90P4).
Sub-Part [D4e] ~ Erosion and Organic Matter Loss ~ Central America ~ Mexico ~
More than 50% of all Mexican farmers farm on highly erosion-prone slopes (97R3). (su1)
About 70% of Mexico's cropland is seriously affected by soil erosion (97R3). Agriculturally marginal areas now account for 20% of Mexico's cropland (97R3).
At least 29% of Mexico's territory is desertified (97R3).
Mexico abandons 1036 km2 of farmland to desertification per year (M. L. Schwartz, Jessica Notini, "Desertification and Migration: Mexico and the United States", US Commission on Immigration Reform Research Paper, fall 1994).
More than 1000 km2 (of agricultural land??) are abandoned each year in Mexico (03K1).
Soil erosion affects 70% of Mexico's agricultural lands (03K1).
A UN report indicates that 1500-2000 km2 have been rendered unusable by erosion ((48B1), p. 50). 15% of Mexico's land resources have been so severely eroded that they are no longer used for crop production (Ref. 13 of (87N2)). In the valley of Mexico (0.5% of Mexico's land mass) 7.1 km2/ year are removed from crop production (87N2). An official report indicates that 40% of Mexico's topsoil has been lost - a 30% reduction in agricultural productivity (Ref. 17 of (92B2)).
Grain area in Mexico declined 10% during the 1980s -attributed to abandonment of degraded farmland, and to cropland conversion to non-farm uses (Ref. 15 of (88B4)). (su1)
Part [D5] ~ Erosion and Organic Matter Loss ~ Andean Mountain Region ~
Soil erosion rates at Santa Catalina, just south of Quito in Ecuador, have been measured at 7410 tonnes/ km2/ year on typical volcanic soil with a 14% slope (Ref. 1 of (91N1)), a gradient much less than most cultivated slopes in the highlands. This is attributed to low hydraulic conductivity, population pressures that result in farming steeper and more erosion-prone slopes, and poor management (plowing up-and-down slope, flood irrigation, monoculture) (91N1).
Erosion losses on 50% of test plots near Quito in Ecuador measured 20,000-50,000 tonnes/ km2/ year. Pre-Colombian terraces (using rock walls) on 70-100% of the slopes are being abandoned, causing increased gully erosion and land abandonment (87D1). Comments: Erosion rates over about 15,000 tonnes/ km2/ year tend to be associated with gully erosion - a precursor to abandonment.
Air pollution from Peru's mines and refineries kills vegetation on tens of km2/ year of mountainside, producing "truly spectacular" soil erosion ((75E1), Ref. 21).
Intensity of Water Erosion (km2) in Peru (Source: ONERN) (88M3) (la)
SECTION (5-E) ~ Europe and Australia ~ [E1]~Eastern Europe, [E2]~Southern Europe, [E3]~Northern Europe, [E4]~Europe in General, [E5]~European USSR, [E6]~Australia, ~
Part [E1] ~ Erosion and Organic Matter Loss ~ Eastern Europe ~ [E1a]~Bulgaria, [E1b]~Czechoslovakia, [E1c]~Hungary, [E1d]~Romania, ~
In Turkey, 160,000 km2 of farmland is "affected" by soil erosion (Stephen Leahy, "Environment: Millions Flee Floods, Desertification", I.P.S., Brooklin, Canada (10/12/05)).
Sub-Part [E1a] ~ Erosion and Organic Matter Loss ~ Eastern Europe ~ Bulgaria ~
About 80% of cultivable land in Bulgaria is affected by erosion (90F1).
Sub-Part [E1b] ~ Erosion and Organic Matter Loss ~ Eastern Europe ~ Czechoslovakia (former) ~
(47,700 km2 of arable land): 42.8% of Czechoslovakia's cropland is threatened by soil erosion. 16% has medium-to-severe erosion problem - yields may be reduced 40-75%. Yield reductions of 15-20% recorded even on lightly eroded lands (90J2).
Some 54% of agricultural land in Czechoslovakia is endangered by water- and wind-induced erosion. Some 4.5 million tonnes/ year of soil are lost (90F1), (91F1).
Sub-Part [E1c] ~ Erosion and Organic Matter Loss ~ Eastern Europe ~ Hungary ~
Water/ wind erosion affects 35% of Hungary's agricultural land. Accelerated soil erosion became a major hazard since 1970 (90K2).
About 70% of Hungary's total area (67,000 km2) is agricultural land. One third of agricultural land is affected by erosion. As much as 5500 km2 is badly eroded, 8900 is moderately eroded, another 8600 km2 is undergoing gradual erosion. Estimate of arable topsoil loss: as much as 50 million tonnes/ year (92S2).
In Hungary and Romania, water- and wind erosion endangers over 30% of arable land (90F1), (91F1).
Sub-Part [E1d] ~ Erosion and Organic Matter Loss ~ Eastern Europe ~ Romania ~
In Romania's Moldavian Hills in Moldavian Table-lands, 71% of tablelands suffer from erosion. 58% of tableland is cropped. Gullies average 2-4/ km2 (Maximum: 16-18 gullies/ km2). This is attributed to deforestation (90I1).
Part [E2] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ [E2a]~Cyprus, [E2b]~Greece, [E2c]~Italy, [E2d]~Spain, [E2e]~Spain (Southeast), ~
In southern Europe, nearly 75% of soil has organic-matter contents low enough be a cause for concern. In Spain and Italy in particular, erosion by soil and wind is a serious problem. An increasing tendency for croplands to be taken out of cultivation makes the problem worse because it leaves the soil vegetation-free for some time. In the EU's new member states to the east, more than a third of land is affected by soil degradation (data from Soil Atlas (2005) by the EU's Joint Research Center) (08F1).
Sub-Part [E2a] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ Cyprus ~
Considerable sheet erosion occurs on wheat lands in Cyprus (92D1).
Sub-Part [E2b] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ Greece ~
About 35,000 km2 of Greece have high soil-erosion risk (87M4).
Sub-Part [E2c] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ Italy ~
About 20,000 km2 were abandoned in Italy in the past decade. Farming methods caused the soil destruction that led to abandonment ((78B2), p. 18) (Ref. 12 of (85B2)) (OEDC report).
Sub-Part [E2d] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ Spain ~
Some 26% of Spain's land is gravely affected by erosion, 28% is moderately affected by erosion (89L4).
Some 26% (130,000 km2) of Spain has serious soil erosion. 28% of Spain has moderate soil loss (90L3). (la)
Soil loss rates range from 0 to over 20,000 tonnes/ km2/ year in Spain. Average erosion rate over 13000 km2: 4290 tonnes/ km2/ year. Erosion rate over 10000 tonnes/ km2/ year appears to occur on land devoted to permanent agriculture (dry farming, almond trees, and grapes) on slopes over 12% lacking conservation practices (88T1).
In Spain's Cuenca of Segura there is grave erosion on 75% of wooded, shrubby, and grassland, and on 45% of cropland (89L4).
Sub-Part [E2e] ~ Erosion and Organic Matter Loss ~ Southern Europe ~ Spain (southeast) ~
In Segura basin (Southeastern Spain) (18,878 km2) Soil loss one of highest and most severe in Iberian Peninsula. In some parts soil loss reaches a rate of 30,000 tonnes/ km2/ year (90L3).
Murcia (in arid and semiarid southeast Spain) erosion is the worst in Spain, with nearly 50% gravely eroded, and 22% more with important erosion (89L4).
Part [E3] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ [E3a]~England, [E3b]~France, [E3c]~Ireland, [E3d]~Netherlands, [E3e]~Scotland, ~
Sub-Part [E3a] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ England ~
There is evidence that erosion has increased in England in the past few decades. This appears to be due to increased winter cereals (erosion worse in autumn and winter), increased field size, finer tilth, increased compaction, move onto steeper slopes, and declining organic matter content (90B4).
Field study (1973-80) in England found that only on bare sandy soil does erosion (wind) exceed 1100 tonnes/ km2/ year. Mean annual rates of soil loss over 8 years were 50-1200 tonnes/ km2/ year on arable land (somewhat lower than 1000-3000 tonnes/ km2/ year found in other studies) (87M5).
About 20,000 km2 of England have a high risk of erosion by water/ wind (87M4). (Total cropland area = ??)
Sub-Part [E3b] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ France ~
Crop rotation, with plenty of grass and legumes, is an almost universal practice among French farmers. Strip crops and contour tillage are common on sloping fields ((74C1), p. 187).
Central Europe exhibits no extensive areas of soil erosion, nor have sizable areas passed completely out of production ((56P1), p. 241). Peasant folkways call for recovery of soil when rain washes it downhill, and peasants in the steep terraced vineyards carry soil up the slopes in baskets, even today ((56P1), p. 252).
In Provence France erosion and frequent floods caused a rural exodus at end of 1800s. From 1878 to 1988, 3500 km2 of cropland have been abandoned in Provence. This led (the French) government to reforest mountain masses such as l'Aigoual and le Ventoux France and to reforest abandoned land in Provence (89B7).
About 40-50,000 km2 of France are subject to soil erosion (87M4). Comments: Hard to interpret.
Sub-Part [E3c] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ Ireland ~
The infield-outfield method of agriculture was the method for breaking in rough hill pasture that enabled the rapidly expanding population of western Ireland to be supported on the potato in the century preceding the great famine of 1845. Monoculture bought a terrible revenge ((56E1), p. 29). ((56E1), p. 226), gives arguments as to why the dramatic environmental changes in Ireland are more likely to be man-caused than caused by climatic changes. Similar arguments are found on p. 233 pertinent to northwestern Europe.
Sub-Part [E3d] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ Netherlands ~
The Dutch were among the first to use modern crop rotation and other soil-improving practices ((74C1), p.184).
Sub-Part [E3e] ~ Erosion and Organic Matter Loss ~ Northern Europe ~ Scotland ~
More than a third of Shetland Island's (off Scotland) heather moorlands and 75% of its peat bogs show signs of erosion - large areas of bare rock and peat with no heather cover (97M1).
Part [E4] ~ Erosion and Organic Matter Loss ~ Europe in General ~
In Europe, 1.57 million km2 are affected by water and wind erosion alone (UNEP data).
Of Europe's total land area (from the Atlantic to the Urals), 12% is affected by water erosion and 4% by wind erosion, generally as a result of unsustainable agricultural practices (UNEP/ **ISRIC, 1991 data) (05S1).
Europe's main types of degradation are loss of topsoil from water erosion (61% of the degraded area) and soil-compaction (15%) (96M3).
Main soil erosion problem is progressive structural degradation of soils. In western and central Europe, 250,000 km2 are threatened, particularly in loess belt, Alpine forelands, and Mediterranean. Widespread surface sealing, crusting, and soil loss are caused by reduced use of manure, more heavy machinery. No-till on these soils can reduce erosion even while large amounts water run off compact soil, causing more erosion down-slope (91D1).
Soil erosion is not considered a serious problem in Western Europe. The situation may be different in southern Europe. Erosion rates cited are 700 tonnes/ km2/ year and 1000-2500 tonnes/ km2/ year. According to a German study (Jung, 1956), crop yields on eroded slopes are 10-50% lower than on non-eroded land (83R2).
Part [E5] ~ Erosion and Organic Matter Loss ~ European USSR, steppe and wooded steppe ~
Calculations of ratio of gullied- to cultivated land indicate that gullies are man-induced (agricultural). Intensive agricultural use of land in the area lasted 150-300 years or more (77Z1).
Part [E6] ~ Erosion and Organic Matter Loss ~ Australia ~
More than 45,000 km2 of drylands in Australia are degraded (10% of all croplands), and more than 8% of Australia's irrigated area is affected by salinization. The salted area doubled between 1975 and 1989 (96G2). Comments: Australian soils are old, low quality, and quite prone to erosion and salinization.
In July 1989, Australia's Prime Minister said "None of Australia's environmental problems is more serious than soil degradation on over nearly 2/3 of our continent's arable land (90B2)".
Land degradation is perceived to be among Australia's greatest environmental problems (91L2). Comments: Australia has old, generally poor soils with lots of salinity problems in many areas.
Australia's good agricultural land (580,000 km2) are suitable for cultivation - 7.5% of the Australian continent has been carved away in 20-ft.-deep gullies; soil salinization is increasing and serious (attributed to deforestation in Murray River Valley). Reservoirs and rivers are filling with silt. Salinity from irrigation is also of growing concern - both in terms of soil and the waters of the Murray River (81L1).
Australia's government claimed Australia was losing topsoil at a rate of 0.082 Gt./ year (90S2).
Some form of land degradation affects 35% of Australia (90D2). Some 324,000 km2 of Australia are affected by natural and human-induced dryland salinization (90D2). (su1)
Eastern Darling Downs in southern Queensland in the area including Dalby and Milleran on west and on west outskirts of Toowoomba and southeast of Warwick. Erosion rates on bare fallowed land range from 0 to 12,400 tonnes/ km2/ year, with most eroding at a rate of about 2060 tonnes/ km2/ year (86F1).
In Western Australia nearly 2% of cleared land has had its productivity reduced drastically by salt encroachment (83C3).
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