Loss in biodiversity with desertification in Arid Rajasthan

Desertification is a long-term process leading to biodiversity loss including habitat degradation, reduction in soil health, reduction in ecosystem productivity, depletion of aquifers, and the expansion of invasive species. The link between land degradation and desertification is abundantly clear.

Degradation removes natural predators and biotic regulation that occur in less managed ecosystem as in arid regions and can result in increase of pathogens and pests that affect humans, animals and plants. A loss in natural vegetation leads to a loss in soil organic matter (SOM) and a loss in soil stability.

Original ecosystems are suitably adapted to the harsh environments (e.g. arid and dry semiarid). The major changes in these ecosystems include, grasslands degradation, grass composition and livestock dynamics; neglect of surface water bodies (nadis) and rainwater harvesting systems (khadins); overexploitation of groundwater; disappearing community driven traditional protection approaches (Orans); loss of species (eg., Great Indian bustard) due to either greed or other activities like mining, urbanization and modernization in agricultural activities.

For instance, introduction of massive irrigation through Indira Gandhi Nahar Project (IGNP) and tube wells, mechanization and extensive cultivation, too drastically affected the biodiversity. Introduction of IGNP which covers an area of 1.869 Mha in Rajasthan did result in considerable loss in biodiversity, be it land use (crops, grasslands etc) or be it natural impediments leading to water logging or be it the consequent changes in soil biota.

Declining traditional systems

Introduction of Indira Gandhi Nahar Project in Rajasthan resulted in considerable loss in biodiversity and changes in soil biota.

Orans, the traditional forest resources are repositories of biodiversity. Orans for ages have been the source of food for livestock and birds, medicines for people and livestock, and water for people and livestock.

There are 1100 orans covering 100,000 hectares. Several plant species are grown in these orans – Prosopis cineraria, Zizyphus nummularia, Salvadora, Capparis decidua, Calatropis procera, Acacia catechu, Anogeissus pendula, Acacia catechu, Butea monosperma, Syzygium cumini, Ficus religiosa, etc. The grasses include Lasiurus sindicus and Cenchrus ciliaris.

Similarly, dependent animals include jackals, deers, rabbits, snakes, mongooses, squirrels and birds include peacock and parrot. While the precise composition of plants and animals vary depending on the ecosystem, there is a fine equilibrium among fauna and flora. These Orans are fast vanishing, though some civil societies are doing exemplary work trying to revive them. Over a million people who depend on them are now struggling with the decline.

Traditional water systems include nadis, khadins and talabs which were the most important water sources in the extreme arid ecosystem (Jaisalmer, Bikaner and Barmer). On a community basis (generally same caste, religion, social group), farmers used to farm the area around these water bodies in the post monsoon period with an understanding for equitable share of the harvested produce.

Unfortunately, all these traditional systems are getting dismantled or demolished, particularly in IGNP command area. Talabs (tanks) declined with quantum jump in well and canal irrigation.

Grazing areas are shrinking as well as degrading. Earlier, the climax grass cover was Dicanthium – Chenchrus – Lasiurusspecies. Now it stands degenerated and replaced by ephemeral grasses, Eragrostis (Chiri grass) and Aristida fumiculata (Lamp) which are less palatable.

Degradation of grasslands / pastures is not only leading to poor and less palatable low yielding grasses, but also increasing soil erosion and runoff depending on the grazing regime. Overgrazing has become a rule than an exception. The herbage yield as well as the carrying capacity of these areas is seen to be drastically coming down while on the other hand the livestock population (small ruminants) is on the rise.

Several people dependent on small ruminants are now struggling owing to shrinkage and decline in quality of the community grazing bodies as well as shifting of pasture management from community to the state. Emerging alternative source is bajra as fodder.

Changing biodiversity with modern irrigation systems

In so far as the plant species are concerned, multi purpose tree species are vanishing in the command area while unwanted weeds that are persistent (e.g. Doob and Motka) are showing up. While canals are getting choked with obnoxious hydrophytic weeds, water logging is on the rise along with unwanted weeds. Changes in plant species as a consequence of IGNP is indicated in the Table.

There are changes in the crop species as well. The land races of bajra, the staple crop of the region, are ideally suitable for the region with their apical dominance and thin stems which can withstand moisture stress. They are also useful as fodder for the livestock. Famers too preferred such land races for their suitability to the ecosystem and being of low-cost. But the government departments special drive on hybrid bajra with external inputs is gradually replacing the traditional land races.

There have been changes in composition of rodent communities also in IGNP areas. The shift to mesic forms of rodents is leading to damage of stored food grains. Coming to invertebrates, irrigation resulted in loss of several of them which have been helping in soil building and in enhancement of soil productivity in extreme dry conditions. While one could observe white ants, large and small black ants, beetles, grasshoppers, mites during the pre IGNP period, presently earthworms, nematodes, snails, and mosquitoes are seen.

With mechanization and growing of commercial crops, some of the multi purpose tree species and birds are becoming endangered. The endangered tree species include Commiphora mukul (Cuggal), Salvadra Oleiodes (Jal), S. persica (Pillu), Colligonum polygonoides (Phog), Cardia myxa (Gonda),Capparis decidua (Ker), Carissa corandus (Karanda), Citrullus colocynthus (Thumba), and birds (Great Indian bustard).

Mechanization and use of tractors has led to bush and grass clearance retaining only trees like khejri and Rohida. This clearing of land resulted in exposing barren soil surface in summer resulting in more arid erosion. Further, the exposed soil also led to changes in soil biota. biodiversity. Soil microbes and the tiny animals in earth provide a wide range of ecosystem services including nutrient cycling, nitrogen fixation, decomposition, pest control, pollination, soil moisture retention, drainage, carbon sequestration, waste recycling etc. They even play little known but major role in climate regulation.

Land degradation and desertification spell the gradual death of soil’s complex web of biota. Soils harbour the larvae of pollinating wasps, beetles, flies and bees. The invertebrates in the arid ecosystem prove the point. FAO states that about 70% of the food crops in 146 countries are bee-pollinated. If we lose these ‘keystone’ species whole edifice will collapse. The monetary value of the eco-system goods and services provided by soils and their terrestrial systems was estimated in 1997 to be 13 trillion US$. The soil biota underwrites much of this value. So (FAO says) “enhancing soils anywhere enhances life everywhere’. And Soil Organic Matter is the key for enhancing the soils.

Conclusion

Biodiversity is a good indicator of land degradation and desertification. Degradation has become the net result leading to desertification and loss of biodiversity in relation to the composition of pastures, livestock, tree and crop systems, the soil biota (particularly the fauna) and the hydrological systems.

It is advisable to focus on prevention of land degradation – because attempts to rehabilitate areas are costly and tend to deliver limited results. And the best way to achieve the prevention is to improve the natural vegetation and restore soil organic matter. Let us remember prevention is cheaper than rehabilitation. Hence preservation of biodiversity in drylands is important, particularly as a third of the global population make a living in such an ecosystem.

J. Venkateswarlu
Former Director,
Central Arid Zone Research Institute,
Jodhpur, Rajasthan.
E-mail: jagarlapudi34@yahoo.co.in