«His Majesty's Government Ministry of Population and Environment Kathmandu, Nepal June 2000 Ministry of Population and Environment 1 State of the ...»
A recent study on forest area concluded that only 39.6 per cent of the total area is covered by forests (29 per cent) and shrub land (10.6 per cent) (MFSC, 1999). The area over 4000 m altitude totals to 22.6 per cent of the total area of the country.
There is increasing pressure on different land uses, particularly the forests and the grazing lands. The land Resource Mapping Project (1986) has identified the possibility of land use changes based on land capability. For
?? In the Terai, the land capability analysis shows that forests are occupying good agricultural land.
?? Throughout the mountains and hills, a large part of the land currently under agriculture is more suitable for forestry purposes.
?? In the country as a whole, there are more degraded grazing and shrub lands and the forests have been converted to shrub lands.
Land use changes have occurred from both natural processes as well as human activities. Decline in agriculture production resulted in cultivation of marginal land. Land degradation process is also intense in different land uses. About one-third of the total area has either little vegetation cover or is totally devoid of it, while two-thirds of the country is geologically fragile. The man-land ration is comparatively high and soil erosion is pronounced in the Middle Mountains. As part of subsistence livi ng, the vegetative cover is replaced by annual crops, and with the same scenario repeating itself the rate of soil loss is also accelerating.
2.4.2 Soil Erosion
Soil loss is more apparent than mass wasting in the mountainous region.
Loss of topsoil by surface erosion is a direct result of heavy rains pounding unprotected soils. Some human activities also cause the soil to become more degraded than it would otherwise be in its natural condition. An increasing proportion of the soil loss is attributable to surface erosion induced by the increased dependence of people on limited land resources.
Forest depletion, overgrazing, poorly maintained marginal land and fire have greatly altered the natural vegetation, leaving the soil open to degradation. Loss of one or two millimetres of topsoil every year from terraces may not make spectacular visual impact, but the cumulative effect leads to the impoverishment of the soil base. Similarly, the high rate of sediment transportation also impairs the water quality. Top soil, lost from the mountain, is raising the riverbeds in the Terai at an estimated annual Ministry of Population and Environment 32 State of the Environment Report, 2000 rate of 15 - 30 cm, increasing the incidence of floods and damaging and reducing the utility of fertile lands, irrigation channels, dams and hydropower projects.
Throughout the hill regions, soil loss from cultivated and grazing land are a major factor in declining soil fertility. Several studies have indicated two broad groups of soil loss namely those with soil loss below 5 t/ha/yr. and those without loss greater than 5 t/ha/yr. Soil loss in undergraded forest areas tends to fall below 1 t/ha/yr. as against in more degraded areas, wherein it is over 4 t/ha/yr.
Soil erosion in cultivated lowland (khet land) is comparatively lower than in rainfed terraces (bari land). The most sensitive period for soil loss in bari land is May, after the land is ploughed and prepared for maize cultivation.
This again occurs in August-September following the maize harvest. In bari land gross soil loss is considered to be close to a maximum tolerable level of about 10 t/ha/yr. in weak to average monsoons.
In sum, soil loss differs greatly in different land uses. Regenerating forest with good levels of ground cover (at least 80 per cent) limits the soil loss, while rainsplash is responsible for much of the soil detachment on exposed and non-crusted surface areas. Ploughed land in the pre-monsoon period is particularly susceptible to high soil loss during high intensity and usually low frequency rainfall events.
At present, in terms of land degradation, about 0.4 per cent, 1.5 per cent and 11.7 per cent of the watersheds are reported in very poor, poor and fair conditions, respectively (Wagley, 1997). It is also estimated that about
1.8 million tons of plant nutrients (N, P2O5, K2O and Ca) are removed by crop harvesting (0.5 million tons) and the soil erosion process (1.3 million tons) (Joshy et al., 1997). Out of this, only 0.3 million tons (16 per cent) are replenished by organic and mineral fertiliser sources. Problems of acidification, alkalisation and salinization have also been reported. These all have cumulative effects on farm production.
Nepal's Himalayas are geologically young and fragile. The Himalayan ecosystems are vulnerable and even a low level of human intervention can lead to soil erosion and landslides. The scale and dimension of land degradation in the mountains has also been aggravated by their ecological sensitiveness, fragility, and other natural disturbances, leading to land further degradation.
Ministry of Population and Environment 33 State of the Environment Report, 2000 Although Nepal has no desertitification problems in the form of dry lands, land degradation is severe and its productivity is also declining. The available statistics reveal that about 10,000 ha in Dolpa and Mustang highlands in West Nepal - features a process of desertitification, particularly in the form of cold deserts or the symptoms of brown cancer.
The cold desert has been spreading along with human intervention on the marginal lands.
In order to address these problems, soil and water conservation programmes and community forestry programmes have been implemented in many parts of the country through integrated and participatory approach (Wagley, 1997).
Nepal has joined the international movement to combat desertitification by ratifying the UN Convention to Combat Desertification in 1996 and this Convention has entered into force in Nepal since January 1997.
2.4.4 Natural Hazards About 75 per cent of all landslides in Nepal are natural (Laban, 1979). This high rate of natural erosion is possibly due to the frequent tectonic uplifting of the major mountain ranges and consequent down cutting of the river systems, which result in unstable slopes. Mass wasting is also caused by rock failures, landslides, riverbank cutting and gullying. The instability is natural and the effect of man's activities on erosion process is incidental.
One of the most spectacular geomorphic events was the glacial lake outburst flood on Seti Khola in the Pokhara Valley. Around 600 years ago, a 10 sq. km lake behind Mount Machhapuchhre broke through its icemoraine dams and surged down the Seti gorge, picking up colluvial debris as it proceeded. In a relatively short period of time, over 5.5 cubic kilometres of glacio-fluvial material was deposited in the Valley (Fort and Freytel, 1982; Yamanaka, 1982). As the Main and Central Boundary Thrusts cross the entire country, Nepal also experiences frequent earthquakes. A large number of landslides also occur during the monsoon seasons due to slope instability. Events of landslides and earthquakes are presented in Annex 1 (Sharma, 1988).
Natural and human-induced disasters have greatly affected the country's infrastructures. Road destruction from heavy rain and floods during the monsoon caused more than 2.5 per cent billion rupees worth of rehabilitation work between 1979 -1993 (Sharma, 1988; Annex 2). In
Man-induced and natural factors have greatly affected the land systems.
Cultivation of marginal lands by seasonal crops may have also aggravated landslide occurrences. In 1996, Nepal experienced a devastating flood.
Losses due to natural calamity are depicted in Table 2.4.2.
Figure 3. Loss of humans and livestock due to Natural Hazards
Changes in land uses and erosion problems have contributed towards expanding cultivation to steeper slopes, increasing settlements on floodplains, and continuing deforestation in upper slopes. These have all contributed to further soil loss and land degradation. The cumulative effects are decline in farm production, high sediment load in valleys and plain areas, and destruction of the infrastructures. Therefore, the need is to regulate land use changes through land zoning, and forest development.
The inherently unstable nature of mountain areas is one of the major causes of land degradation, spreading the process of desertification and land use changes. Man-induced and frequent occurrences of natural hazards such as landslides, debris flow, slope failures a increasing nd sediment loads have also caused the rural people to change the land system from perennial crops to seasonal crops. These events may continue to occur due to geological fragility and tendency of cultivating steep slopes, overgrazing, and inadequate soil conservation measures.
2.5 Forests and Biodiversity 2.5.1 Forests Variation in Nepal's altitude, climate and topography presents diversity in forest types and their composition. About 50 per cent of Nepal's surface area is under some form of vegetation cover, i.e., forest and shrub land 39 per cent, and grasslands 12 per cent. About 4.2 million ha (29 per cent) is occupied by forests and 1.6 million ha (10.6 per cent) by shrub lands Ministry of Population and Environment 36 State of the Environment Report, 2000 (MFSC, 1999). Far Western Development Region is the most forested region with about 35 per cent of the total forest area (Table 2.5.1). Shrub land cover is evenly distributed in all the regions ranging from 8.5 per cent in the CDR to 13.5 per cent in the MWDR.
Of the 193 biogeographic provinces recognised worldwide in Udvardy's
classification, only three provinces are known to exist in Nepal. They are:
?? Himalayan highlands within the Palaearctic realm, ?? Indo-Ganges monsoon forests within the Indo-Malayan realm; and ?? Bengalian rainforest representing the later realm.
A total of 118 forest ecosystems, with 75 vegetation types and 35 forest types have been identified in different physiographic zones in these realms.
Out of these, 38 types of ecosystems are represented in the protected areas (national parks, wildlife reserves and conservation areas).
Stainton (1972) broadly divided Nepal's forests into the following categories: tropical and subtropical, temperate and alpine broad-leaved, temperate and alpine conifers, and minor temperate and alpine associations. Tropical forests are predominated by sal (Shorea robusta), while khair (Acacia catachu) and sissoo (Dalbergia sissoo) dominate riverine forests. Mixed forests prevail in different parts of the country with deciduous and evergreen associate species. In other forest types, species compositions differ in eastern and western parts of the country. Species regeneration is comparatively good in the lowlands, and it is limited in the high mountain regions due to climatic and altitudinal factors.
Forests are the main sources of firewood (energy) to about 70 per cent of the total population. Per capita fuelwood consumption in the mountains is estimated at 640 kg, while for the Terai it is 479 kg/person/yr. The household and industrial biomass fuel consumption was estimated at 14 million tons/yr. in 1995/96 as against 11.3 million tons/yr. in 1985/86. This is projected at 15.4 million tons/yr. for the year 2000/01. Based on this assumption, with the exception the Far Western Development Region and the High Himalayas, there will be a fuel deficit in the country. The annual fuel deficit at the national level is estimated to be 3 million tons in 2000/01.
With regard to timber, the per capita consumption was estimated at 0.07 m3/yr. in 1985/86. It is projected that this will increase to 0.11 m 3/yr. by the year 2001, and the total projected timber consumption for Nepal will be 2.5 million m3 for 2000 respectively. Based on this assumption, the projected timber deficit will be 1.1 million m 3 in 2000/01 with the Central Development Region suffering the most. About 42 per cent of the total digestible nutrients (TDN) as fodder is met from forests. Based on projected fodder supply and livestock TDN requirements, fodder surplus will continue till 2000/01. However, about 0.2 million tons of fodder will be deficit by the year 2010 at the national level. But the fodder surplus is projected to continue for Eastern and Western Development Regions in 2010/11 (HMG/ADB/FINNIDA, 1988).
Loss of forest area started along with the malaria eradication and planned resettlement programmes in the late 1950s, particularly in the Terai and Inner Terai areas. Forest depletion has become most pronounced in the course of meeting the increasing demand for fuelwood, timber and other forest products. Depletion of forest area is further aggravated by overgrazing, fire, conversion to cropland, and use for settlements and infrastructure development such as roads, canals and transmission lines.
The Terai and the Middle Mountain region have been most severely affected by the change in forest cover.
Use of forests and their products for different purposes has significantly changed forest cover during the last four decades. Of the total 6.4 million ha of forests estimated in 1964, only 5.5 million ha of forest area was in
Considering the forest estimates made during the LRMP (1978-''79), Master Plan (1985-'86) and the 1994 inventory, the annual reduction rate of forest cover for the whole country is 1.7 per cent in between 1978/79 to 1994 and decrease in forest and shrub together is 0.5 per cent annually (MFSC, 1999). However, the situation is different in the Hilly area where the forest and shrub cover has declined from 43.1 per cent in 1952 to 37.7 per cent in 1994. It has been estimated that the annual change in forest cover is 2.3 per cent from 1978/79 to 1994 in the Hills (MFSC, 1999). The per capita forest has also declined from 0.63 ha in 1965 to 0.442 in 1979 and further declined to 0.198 ha in 1998.
A study conducted by ICIMOD in 1996 concluded that forest conditions are comparatively better in terms of forest area. This information has been derived from a macro-scale land-cover assessment using remote sensing and geographic information system.