SOIL is the foundation of the entire biosphere. The sun is the basis for most life on earth. It provides radiant energy for heating the biosphere and photosynthetic conversion of carbon dioxide (CO2) and water by green plants into sources of food and oxygen for consumption by animals and other organisms.
Most living organisms utilise oxygen to metabolise these food sources, capture their energy, and recycle heat, CO2 and water to the environment to begin this cycle of ‘life’ again.
Decomposition processes, as mediated by organisms in soil, play a predominant role in completing this cycle of life, in recycling of building block nutrients to plant and C as CO2 to the atmosphere. Thus, the thin layer of soil covering the surface of the earth is a major interface between agriculture and environment and represents the difference between survival and extinction for most land based life.
The quality and health of soil determine agricultural sustainability and environmental quality which jointly determine plant, animal and human health.
The various functions of soil, as for land are : (i) production function; (ii) living space function, (provides a physical, chemical and biological setup for living organisms); (iii) climate-regulative function, (regulate and partition water flow, storage and recycling of nutrients and other elements); (iv) hydrologic function, biotic environmental function, (support biological activity and diversity for plant growth and animal productivity); (v) storage function, waste and pollution control function, (filter, buffer, degrade, immobilise and detoxify organic and inorganic substances), (vi) archive or heritage function and connective space function.
In this context, land refers not just to soil, but to the combined resources of soil, water, vegetation and terrain that provide the basis for land use.
Land degradation is a broader term used to indicate the continuous decline in the soil quality in different aspects (physical, chemical and biological).
Therefore, the land degradation can be defined as “the continuous deterioration of soil/land either physically, chemically or biologically by natural or man induced factors”. Soil degradation is one of the greatest environmental problems in the world. Land degradation leads to a significant reduction of the productive capacity of land.
Land degradation is a worldwide problem that has revived the issue of production sustainability. It has been estimated that 23 per cent of all usable land (excluding mountains and deserts, for example) has been affected by degradation to a degree sufficient to reduce its productivity.
Types of land degradation include: water erosion (56per cent), wind erosion (28per cent), chemical degradation (12per cent) and physical degradation (4 per cent).
In our country, land degradation mainly encompasses deforestation and desertification, salinity and soda city, soil erosion, water logging, depletion of soil fertility and negative nutrient balances.
The country has a total forest area of about 12 million hectares. Out of which, the total forest, scrub, and planted trees spread on 4.2 million hectares, natural and modified coniferous scrub, riverian and mangrove forests spaced 3.5 million hectares, tall tree forests encompass 2.4 million hectares, scrub forest exist on 1.1 million hectares, and plantations occupy 0.7 million hectares.
The increasing extent of area affected by salinity and sodicity is of great concern.
In majority of the soils of plains in Pakistan, the rainfall is usually low and the evapo-transpiration is higher than the annual precipitation resulting in build up of salts in the soil profile and their accumulation on the soil surface.
At country level, 6.28 million ha of area is affected with salinity and sodicity. The majority of salt-affected soils are saline-sodic in nature. These salt-affected soils are causing potential reduction in yield.
Soil erosion implies loss or removal of surface soil material through the action of moving water, wind or ice. About 13.05 million hectares of the area is affected by water erosion and about 6.17 million hectares is affected by water erosion. Soil erosion is taking place at an alarming rate and is mainly due to deforestation in the north.
Water erosion is prominent on steep slopes such as the Potohar track and surrounding areas, an area extensively used for cultivation. The highest recorded rate of erosion is estimated to be 150-165 tonnes/hectare/year.
The Indus River carried the fifth largest load of sediment (4.49t/h) in the world in 1990. According to some estimates the Indus is adding 500,000 tonnes of sediment to the Tarbela reservoir every day, reducing the life of the dam by 22 per cent and the capacity of reservoir by 16 pr cent.
Wind erosion has a relatively lower impact than water erosion. However, the combination of the two is more devastating.
The fertility status of soils here is rapidly depleting. The data generated by the public and private organisations in the country reflect the general agreement about the deficiency of nitrogen and phosphorus 100 and 90 per cent in soils.
Same is the situation with organic matter content, which is on around average 0.5 per cent only. Potassium deficiency in the soils here is also increasing due to imbalance fertilisation of NPK fertilisers.
Among micronutrients, field scale deficiencies of economic significance prevail in case of zinc, boron, and iron.
All of the above environmental issues are summarily heading the country towards more economic instability.
According to an estimate, the impacts of degradation and biodiversity loss on productivity and public health are 4.5 per cent of GDP per year. It would be higher if toxic waste disposal, biodiversity, river and coastal resource depletion were taken into account.
It is, therefore, very necessary for the sustainable economic future of Pakistan and a friendly environment to cope with land degradation problem on war-footing bases.