Drylands: Concept

Drylands are among the most productive ecosystems, and their people stand among the most resilient on the planet. Drylands are ecologically diverse and economically important. Drylands- stretched over deserts, grasslands, and woodlands- cover about 47% of earth land surface and are inhabited by more than 2 billion people (about one third of the world’s population) and serve as the world’s breadbasket. Drylands are areas with limited water resources. This first aspect of drylands is therefore based on their climatic character. Rainfall is scarce, unreliable and

concentrated during a short rainy season with the remaining period tending to be relatively or absolutely dry. High temperatures during the rainy season cause much of the rainfall to be lost in evaporation, and the intensity of tropical storms ensures that much of it runs off in floods. Water supply is not only meagre in absolute terms but also of very limited availability for human and natural uses. The two dominant characteristics of dryland climates are aridity and variability. Several classifications

of drylands have been developed. The FAO typology for example, is based on agroclimatic zones defined according to the Length of Growing Period – LGP (production perspective) – arid (<75 days/year); semi-arid (<120 days/year) and dry sub-humid (<180 days/year).

Drylands in general can be characterized like, low precipitation and extremely variable: recurrent droughts that may persist for several consecutive as a rule and not as an exception; particularly in more arid area, diurnal temperature variability is high thus required special adaptation from all species. Technically dryland can be defined as the areas where rainfall is less than the potential moisture losses through evaporation and transpiration. According to the World Atlas of Desertification (UNEP, 1992), dry lands have a ratio of average annual precipitation (P) to potential evapotranspiration (PET)1 of less than 0.65. Dryland” refers to the arid (excluding the polar and sub-polar regions), semi-arid and dry sub-humid areas in which the annual precipitation to potential evapotranspiration falls within the range from 0.05 to 0.65. Many of these dryland areas face severe land degradation, in which marginal areas are turned into wastelands and natural ecosystems are altered through destruction of surface vegetation, poor management of water resources, inappropriate land use practices, overuse of fertilizers and biocides, and disposal of domestic and industrial wastes. This has serious implications for food security and the livelihoods of between 250 million and 1 billion people across the world. As a result, dryland populations on average lag far behind the rest of the world on human well-being and development indicators. In the absence of any remedial measures, the situation is likely to get worse over time due to population increase, land cover change, and global climate change.

3.1. Extent of drylands (Arid-Semi Arid- Dry Sub-humid) in India

In India drylands, inclusive of the arid, semi arid and dry sub humid regions cover about 228.3 m ha (69% of total cover). Table 2. It extended from the cold deserts of the Himalaya to semi arid Telegana, Tamilnadu uplands and western Karanataka;

Orissa and North Andhra Pradesh to the Hot desert of western Rajasthan and Kutch and the northern part of the Kathiawar peninsula, passing the central Malwa Highlands, the ravines of Chambal and Deccan plateau (including Maharashtra and Northern Karnataka).

Nine states viz., Rajasthan, Madhya Pradesh, Maharashtra, Gujrat, Chhatisgarh, Jharkhand, Andhra Pradesh, Karnataka and Tamilnadu accounts for over 80% of the drylands.

Drylands are not wastelands

• They are one of the most biodiverse areas of the world in terms of species per square metre;

• They provide local and national food security; large, sometimes the majority, production of key food items, such as meat; and a significant proportion of GDP; • They provide livelihoods and food security for large numbers of people.

The list of prominent dryland regions with their salient features:

1. Western Himalayas: Cold arid region with rainfall<150mm and shallow skeletal soils

2. Western Rajasthan, Kutch and northern part of Kathiawar peninsula. Hot arid region with rainfall <300mm, desert and saline soils.

3. Rajasthan uplands (Aravallis) and Chambal districts of Madhya Pradesh: semi arid region with alluvium derived soils and extensive land degradation leading to ravines.

4. Central highlands, including Gujarat plains and western Madhya Pradesh: semi arid region with rainfall of 500-1000mm, medium and black deep soils 5. Deccan plateau including Maharashtra and northern Karnataka; semi arid

region with rainfall of 600-1000mm, red and black soils

6. Interior Andhra Pradesh (Telangana): semi arid region with 600-1000 mm rainfall, red and black soils

7. Tamil Nadu uplands and western Karnataka, Semiarid region with red loamy soils

8. Sub humid eastern plateau (Chhatisgarh), with rainfall of 1000 to 1600 mm, red and yellow soils

9. Sub humid eastern Chhotanagpur plateau including Jharkhand, western Orissa and northern Andhra Pradesh with rain fall of 1200 to 1600 mm red and laterite soils

3.2. Forests of dryland

In drylands broadly 3 types of forests occur viz., tropical dry deciduous type, tropical moist deciduous type and tropical thorn forest. Dryland shows diversity of local factors and hence diversity of forest type and its composition.

3.3. Arid Zones

everywhere. Here ephemerals are true short lived and completed their life cycle in questionable short time. Indigofera argentea, Euphorbia granulata, Tribulus

pentendrous, Linum indicum etc found on sand dunes and open sandy grounds

show a peculiar prostrate habit to nullify the effect of wind erosion. Other ephemerals are Cenchrus biflorus, C.prieurii, Eragrostis tremuls, E. cilianensis, Latipes

senegalensis, Tragus roxburghii, Farsetia hamiltonii, Tribulus terrestris, Aristida funiculate, A. adscension. They generally acquire well-developed root system of

extra ordinary length in comparison to their aerial parts. Cyperus arenarius, Aerva

persica, Leptadenia pyrotechnica, Citrullus colocynthesis, Caliigonum polygonoides, Capparis deciduas, Crotalaria burhia, Lasiurus sindicus, Ziziphus nummularia, Serocostema pauciflorum, Mollugo ceriana, Talinum portulaifolium are typical

elements found as desert scrub through out the arid zones of Rajasthan.

In south India states parts of Bijapur, Bellery, Tumkur districts of Karnataka and Rayalseema and Anantpur of Andhra Pradesh form hot arid zones. This region is characterized by scrub and thicket formation. This area inhabited chiefly by species of Acacia, Albizia, and Hardwickia binnata, and Cabthium parviflorum, Cassia

auriculata, Dodonea viscose, Erythroxylum monogynum, pterolobium hexapatalum, Rhus mysoorensis, Caralluma umbellate, Coleus canius, Euphorbia antiquorum, Sarcostemma acidum, These plants are well adapted to the increasing dryness of

this area. The gravely soil is sparsely covered with herbs well developed rootstocks among which are Andrographis serpyllifolia, Stylosanthes fruiticosa, Tephrosia

calophyllum, Portulaca wightiana and Sesamum laciniatum. 3.4 Semi Arid Zones

This region extend from Foothills of Siwalik, Punjab to southern parts of Tamil Nadu in length and from Aravalis to Chota Nagpur plateau in width. It is land locked area and surrounded by dry arid zones on western side and humid zones on eastern side. This zone shows diversity of biophysical factors.

• More than 70 per cent of India’s arable land is dryland, and for millions of

farmers and agriculture workers and laborers, who provide 42 percent of the national food basket, it is an important source of livelihood.

• Dryland farming areas grow nearly 90 per cent of the country’s coarse gains

and pulses, 75 percent of all oil seeds and 70 per cent of cotton.

3.5 Degradation of Drylands

Drylands are prone to degradation on account of climatic constraints, fragility of natural resources, and high pressures of humans and animals, as well as industrialization. Soil degradation in the drylands is estimated at 1035 Million hectares, while soil degradation in the humid areas occurs on around 930 Million hectares- LADA FAO 2002. The estimated extent of vegetation degradation in the drylands is much larger than the extent of soil degradation in the drylands- LADA FAO 2002. Arid areas (49.5 mha) are the worst affected, especially in the western part of Rajasthan state that includes the Thar Desert (20.87 m ha), as well as in arid Gujarat (6.22 m ha). Recurrent drought, high wind, poor sandy soils and very high human and livestock demand for food, fodder and fuel wood are causing over-

crop cultivation and livestock rearing, which proved as best practices for sustainability and resource conservation, are now disappearing.

About 174 m ha area in rainfed semi-arid and dry sub-humid regions are mostly affected by water erosion that is getting accelerated due to declining tree cover, land use changes with expansion of cropland and intensive mono-cropping, while the irrigated areas of these regions are being affected by water logging and salinity. Besides, the Indo-Gangetic plains of Punjab and Haryana states, with dominance of rice-wheat cultivation, are showing signs of depletion of groundwater, organic carbon, and deficiencies in essential plant nutrients.

Process of degradation: Whatever the causes, the process of degradation is as

follows:

(i) Loss of vegetative cover due to deforestation, overgrazing and agriculture which leads to

(ii) Degradation of land that terminate into (iii) Desertification

3.6 Deforestation is a much-used, ill-defined, and imprecise term that tends to imply

quantitative loss of woody vegetation. There can also be qualitative changes in forests, from, say, species-diverse tropical forests to single-species eucalyptus or pine plantations, or to less species-rich secondary (regrowth) forests. Each year, around 4 million hectares (ha) of virgin tropical forests are converted into secondary forests (Barrow, 1991). However there is little distinction in most of the literature between vegetation loss that will “heal” and that which will not. Domestic animals in tropical woodlands and forests reduce regeneration through grazing, browsing, and trampling. India alone has about 15 per cent of the world’s cattle, 46 per cent of its buffaloes, and 17 per cent of its goats. The spread of irrigated and cultivated land in India has forced livestock owners into forest areas, where 90 million of the estimated 400 million cattle now reside, whereas the carrying capacity is estimated at only 31 million (Government of India, 1987)

3.7 Causes of deforestation

• Human population growth, agricultural expansion, and resettlement • Grazing and ranching

• Fuelwood and charcoal • Timber exploitation • Plantations