TABLE OF CONTENTS  

(8-A) - Desertification
[1] Global, [2] Africa 

(8-B) - Eroded Lands Generally
[1] Global, [2] Africa, [3] Southeast Asia, [4] Asian Sub-Continent, [5] Latin America, [6] Developing Countries, [7] Europe, [8] Middle East 

(8-C) - Ravine-Degraded and Gullied Lands
[1] Global, [2] Africa, [3] Asian Sub-Continent 

Go to the Table of Contents of this Area-Data Document
Go to the Home Page of this Web Site

------------------------------------------------------------------------------la8

(8-A) - Desertification - [1] Global, [2] Africa

A UNEP survey estimates that 45 million km² (35% of the world's ice-free land area of about 131 million km²) are in various stages of desertification (se88J1), (se89J1). (la) Comments: For perspective, the global inventory of reasonably biologically productive land is about 85 million km². Much of this degraded land is arid rangeland that is of very low productivity, even at its best, so it is hard to assess the significance of this statement.

Desertification along the Sahara Desert border proceeds at an estimated 1000 km²/ year for all of North Africa (p. 238 of (og70L1)). (la) Comments: This border has gone in the opposite direction in more recent years.

About 74% of Africa's rangelands, 61% of Africa's rain-fed croplands and 18% of its irrigated lands are affected by desertification at a moderate or higher degree (25+% fertility-loss) (se97D1).

Estimates based on the GLASOD (Global Assessment of Soil Degradation) approach indicate that, by 1992, nearly 3.2 million km² of dry lands in sub-Saharan Africa had degraded soils, ranging from light and moderate (77%) to strong and extreme (23%). These estimates are almost two-thirds less than the area previously thought to be suffering desertification as a result of human activities (se95M1).

As much as 65% of Africa is prone to some degree of desertification (Refs. 6, 7, 69 of (se88L1)).

Desert + cumulative desertified land in Africa = 7.42 million km² (25% of Africa's land area) (Ref. 38 of (se88L1)).

National Environment Secretariat (NES) says 483,830 km², 85% of Kenya's land area of 569,137 km², is experiencing some form of desertification. NES says 19.3% (109,800 km²) of Kenya is severely affected by desertification, and 9.4% (53,500 km²) of Kenya is moderately affected by desertification (se91D2).

Tunisia's 13,500 km² of alfa-grass steppe (arid land) have shrunk to 6,000 km² due to desertification (p. 238 of (og70L1)).

Return to Table of Contents of Chapter 8?  
Go to Table of Contents of this Document 

(8-B) - Eroded Lands Generally
[1] Global, [2] Africa, [3] Southeast Asia, [4] Asian Sub-Continent, [5] Latin America, [6] Developing Countries, [7] Europe, [8] Middle East

Asia has the largest area of degraded dryland, 3.7 million km² (22%) ((og97M3), p. 19). (la) Comments: Dryland is more prone to degradation than more humid lands. Also it is much less productive even in its non-degraded state.

Degradation status of global land (croplands + permanent pasture + woodlands) based on work of Oldeman et al (Ref. 15 of (og97C1)) and Dregne and Chou (Ref. 17 of (og97C1)) (Land areas (Col. 2) are in millions of km²) (la)

A study by Oldeman et al (Ref. 15 of (se97C1)) calculated that, of the world's 87.35 million km² of croplands, grasslands and forestlands: (la)

• 19.65 million (22%) were degraded to some extent;
• 33% of this 22% were degraded lightly,
• 46% of the 22% were degraded moderately,
• 20% of the 22% were degraded strongly, and
• 1% of the 22% was degraded severely (se97C1).
• The remaining 77% were judged not degraded at all ***.
• Wind and water were believed to account for 85% of the degradation.
• Chemical degradation (loss of soil nutrients and salination) and physical degradation (compaction of soil by heavy farm machinery and cattle) accounted for the remaining 15% (se97C1).

Comments: *** The 77% are probably forestland and non-grazed grasslands. The total global area of reasonably biologically productive land is roughly 90 million km² out of the total area of ice-free land of about 131 million km². So the world's croplands, grasslands and forestlands must total somewhat less than 90 million km² since wetlands, etc. must be part of this 90 million km².

The UNEP GLASOD study concluded that, globally, 2.95 million km² are so degraded that restoration to full productivity is beyond the normal means of a farmer, but could be restored with major investments. 9.1 million km² are moderately degraded to the point that original biotic functions are partly destroyed, and agricultural productivity is greatly reduced (se92N1) (la). Comments: Urbanized lands (about 4.745 million km² (se00W1)) should be added to this list.

Comments: To be more meaningful, the percent of total land area that is forested lands and wetlands should be deducted from the percentages in the above table.

* Urban Development data is from Ref. (se00W1). A partial allocation of urban developments among various regions is in Table FG.5 of (se00W1).
Sources: (se90O1) ((se92N1), Table 4)

• 20 million km² -- 17% of the Earth's 117 million km² of vegetated land (UNEP study).
• 38% of the 20 million is lightly degraded -- full potential for recovery;
• 46% of the 20 million is moderately degraded -- restorable only through considerable financial and technical investment;
• 15% of the 20 million is severely degraded -- no agricultural utility under local management systems and reclaimable only with major international assistance;
• 0.5% is extremely degraded -- incapable of supporting agriculture and irreclaimable (se95D3).

Degraded lands occupy 20% of Asia's vegetated lands, 22% of Africa's and 23% of Europe's. Direct causes: overgrazing (35%), deforestation (30%), other agricultural activities (28%), over-exploitation for fuel wood (7%), and bio-industrial activities (1%) (se95D3). (la)

170,000 km² of Philippine forestland; 90,000 of 130,000 km² (total) of cropland are eroded. 13 Philippine provinces have over 50% of total area eroded: Batangas (83%), Cebu (76%), Ilocos Sur (73%), La Union (70%), Batanes (68%), Bohol (66%), Masbate (66%), Abra (65%), Iloilo (63%), Cavite (60%), Rizal (56%), Capiz (55%), and Marinduque (51%) (se85C5). 58% of Philippine cropland has slope over 11% and is therefore at risk (se85C5) (copied to slopes data table). (la)

90,000 of 130,000 km² of Philippine croplands are eroded (Ref. 7 of (se92D1)).

In 13 of the Philippines' 73 provinces, over 50% of the total cropland area is eroded (Ref. 38 of (se92D1)).

As much as one meter of soil has eroded away since WWII, exposing a boulder/ stone substratum (in the Province of Zamboanga del Sur) (se92D1). (1 m/ 46 years = 2 cm/ year) (la)

[4] Asian Sub-Continent

In Uttar Pradesh (in India), nearly 55,000 km² are "affected" by soil erosion: 9000 by wind erosion; 1500 by "glacial" erosion; 29,400 by sheet/ rill erosion; 15,300 by gully-erosion (se85P1). Comments: "affected" is a poorly defined term with no clear meaning.

The GLASOD study estimates that, in developing countries, agricultural productivity has declined significantly on 16% of agricultural lands (croplands plus planted pastures) ((se99S1), p. 18). (la).

China loses 1200 km²/ year of farm- and pastureland to drifting sand dunes (se86W4).

About 11% of cropland in Asia is seriously degraded (se00L1).

The GLASOD study estimates that 38% of Asia's agricultural land (defined by GLASOD as cropland and planted pastures) is degraded ((se99S1), p. 18). (la). Comments: "planted pastures" probably refers to what others refer to as permanent pasture or pastures other than rangeland that is typically semi-arid or arid land.

A follow-up study for South Asia addressed some of the weaknesses of GLASOD (se91O1). It introduced more information from national studies and greater detail on the different forms of degradation (se94F1). The broad picture for South Asia remains similar in the two studies: 30-40% of agricultural land in South Asia is degraded to some degree, and water erosion is the most widespread problem (Table 12.5) (se03N1).

Europe has 1.0 million km² of degraded dryland ((og97M3), p. 19). (la) Comments: Europe's total land area is 4.73 million km² . (See Chapter 1 [D] )

26% (130,000 km²) of Spain has "serious" soil erosion. 28% of Spain has "moderate" soil loss (se90L3). (la) Comments: Presumably these numbers are relative to cropland area. Spain's total land area is 499,000 km² . (See Chapter 1 [D] )

Terraced lands in Lebanon cover 950 km². Nearly all exhibits clear signs of terrace degradation and decay (se94Z1). (la) Comments: Lebanon's total land area is 10,000 km² . See Chapter 1 [D].

Some characteristics of land degradation in the Arab States region -- results of a worldwide assessment of soil degradation problems, the GLASOD project, (ISRIC, 1991). (la)
C.2 Total degraded land (% of total land)
C.3 lightly degraded land (% of total land) (C.3+ C.4+ C.5 = C.2)
C.4 moderately degraded land (% of total land)
C.5 strongly degraded land (% of total land)
C.6 % of degradation by water erosion (C.6+ C.7+ C.8+ C.9= 100%)
C.7 % of degradation by wind erosion
C.8 % of degradation by chemical degradation
C.9 % of degradation by physical degradation
C.10 % of degradation caused by deforestation (C.10+ C.11+ C.12= 100%)
C.11 % of degradation caused by overgrazing
C.12 % of degradation caused by agricultural activities

(8-C) - Ravine-Degraded and Gullied Lands - [1] Global, [2] Africa, [3] Asian Sub-Continent

Globally, 1.6 million km² of hillside land were identified as "severely eroded" in 1989 (se96G2).

Of 78,612 km² in southeastern Nigeria, 70% (55,000 km² ) are affected by sheet and gully erosion. 1,300 km² are affected by gully erosion ((se88G1) (Cites Oformata, 1981)). (la)

In Tanzania's Kondoa Province, nearly 1500 km² are so badly damaged by gully erosion that they cannot be rehabilitated (Ref. 13 of (se87E2)). (la)

Ethiopia's highlands lose 3 billion tons of soil/ year (Stmt. By Ethiopia's Ministry of Agriculture in Ref. (se87M3)). Half of the farmland (140,000 km²) in Ethiopia's highlands is severely degraded. On 20,000 km², soil lost forever (meaning "land" lost forever) (Statement by Ethiopia's Ministry of Agriculture in Ref. (se87M3)). (la)

India's wastelands -- areas affected seriously by salinity, alkalinity, wind- and water erosion -- cover one million km², of which 420,000 km² are still being cultivated (se87U1). Comments: India's total land area is 2,973,000 km² and it croplands total about 1,693,000 km² . (See Chapter 1 [D] .)

Ravines cover 40,000 km² in India (se87U1). Comments: This land could be primarily grazing lands.

1980 data give a total degraded, non-forest land area of 940,000 km² of India's national land area of 3,290,000 km² (se88B1). Water erosion accounts for 74,000, wind erosion accounts for 13,000, and salinity and alkalinity account for 7000 of the 94,000 km² of degraded land (se88B1). Comments: Something is wrong with this data -940,000 should probably be 94,000 km² .