Pakistan is fortunate in having a number of trees and shrubs that can provide emergency fodder during droughts

By Dr. S.M. ALAM, NIA, Tando Jam
July 29 - Aug 04, 2002 



To plant trees is to ensure for the community unending social, economic and environmental advantages. It is to bequeath what Our Holy Prophet Muhammad (Peace Be Upon Him) described as Sadqa-e-Jariya. Unfortunately, ours in wood-deficit country. Although, our efforts over the past four decades have enabled us to increase the forest area 2 to 5 per cent, our wood resources still lag far behind our actual requirements. More distressing perhaps are the handicaps in ecological balance, pollution fighting, soil conservation and productivity and climate moderation. National interest demands that are make Pakistan even greener. What is needed is the willing participation of the common people, horticulturists and particularly the farmers. By utilizing the available resources and planting trees on farm boundaries, along water channels and on marginal lands without much adverse impact on the yield of crops, they can change the face of our land. Farmers have realized the economic benefits of growing trees on farmlands, and have planted million of sapling under farm energy development programme.

Trees are like jewels strung around the earth. They add to the beauty and glitter of our planet on one hand and fulfil our enormous needs on the other. They add fragrance and colour to enliven the environment, which motivates man towards creativity. And it is such creativity that contributes to overall progress of mankind. Like all other living beings, too bow to Allah Almighty in prayer and praise. It will, therefore, be sinful to pluck even one leaf unnecessarily. That would affect the environmental balance of our planet. It is not enough to merely plant trees in field and gardens and on farms and orchards and along roads and canals. They have to be watered, nursed and protected till they are full-grown trees.

Farmers in Pakistan have always planted trees. Trees are part of their subsistence and farmers consider the timber, firewood, fodder, fruit, shade and many other non-wood products from the trees as immediate primary benefits. In the past, farmers had enough wood on their farms to provide for their own needs and they considered it a free commodity. Population increases industrialization and farmer profit motives have changed that wood is becoming scarce and valuable commodity. When the Pakistan Forestry Planning and Development Project (FPDP) was launched in 1987, the immediate purpose was to encourage farmers to raise trees on their farms to meet shortages of fuel wood. As more wood came from farms, the project then turned its attention to the market links between producers and users that are needed to make and to keep tree planting profitable.

Some of the most popular trees for agro-forestry systems in Pakistan are the hybrid poplars, attractive to farmers because they grow rapidly and are accepted in the marketplace. Farmers have cultivated the poplar on a large scale, resulting in the 'poplar boom' of the past decade. Poplar logs harvested in the valleys are hauled long distances to feed the lucrative match industry and other urban wood markets in cities such as Peshawar, Lahore and Karachi. On farmlands in Sindh Province, one of the most sustainable agro-forestry systems involves Acacia nilotica locally known as babul in compact tree plantations under the traditional irrigated wood lots. In Sindh Province, extensive cultivation of crops that demand large amounts of water, such as rice, sugarcane and banana, have badly affected soils. Thousands of hectares of prime agricultural land have been degraded by waterlogging and salinity. Farmers view cultivation of babul and other tree crops as a cost-effective way to recapture the productivity of these lands. Some farmers now bring in more income from their wood plantations than they do from agricultural crops.

The tree plantations have reclaimed unproductive and barren land, and reduced waterlogging caused by seepage from different reservoirs of the country. Farmers believe that eucalyptus plantations act as 'mini tube wells', lowering the water table to permit cultivation of agricultural crops. Of course, farmers reaction to the idea of planting trees on their farms was not always so wholehearted. In the beginning feelings were mixed; the Forestry Planning and Development Project (FPDP) provided free seedlings as an incentive. Poplar nurseries in the Northwest Frontier Province and the Punjab are now all in private hands, although the project initially assisted some nurseries in Sialkot, Punjab. Other benefits of planting trees on farms are as:

SHELTER FROM WIND: Trees planted as windbreaks have significant benefits for livestock, crops and pastures by reducing stress from heat and cold. The area protected by a windbreak is related to the height of the trees. An effective windbreak can reduce wind speed for a distance of up to 30 times the tree height on the downwind side, and five times the tree height on the upwind side. The greatest reduction of wind speed is in the part of the paddock from five to 15 times the tree height away from the windbreak.

CROPS AND PASTURES: The most visible effect of a windbreak on crops and pastures is the area of reduced growth close to the trees caused by competition for soil moisture by the trees roots. What is not so easily seen is the increased yield in the protected area. Increases in both dry weight and wet weight of crops and pastures are greatest in the area from two to six times the tree height way from the trees. This increased yield is a result of reducing the moisture stress caused by strong winds. Soil moisture loss, through evaporation and plant use, is roughly proportional to wind speed. Where wind speed is reduced behind a windbreak, more moisture is available for plant growth.

Plant growth is reduced by high winds. At speeds of 40-60 km/hr, growth stops completely. Damage to the tips and edges of leaves buffeted by strong winds can reduce plant growth rate and may change the developmental pattern of crops. Reducing this physical damage by providing windbreaks can increase plant productivity. The resultant increase in pasture production due to shelter will be reflected by increases in livestock productivity. Shelter from wind is particularly important for horticultural crops. Strong winds cause physical damage to fruit trees and vegetable crops, reducing the quality and quantity of produce. In some parts of New South Wales, horticultural production is only possible when windbreaks are established before planting fruit or nut trees.

LIVESTOCK: The main benefit of windbreaks to livestock is in reducing cold stress provided that stock uses the shelter. Cold stress occurs when increasing wind speed raises the rate of heat loss from an animal's body. So, to maintain body temperature, the animal has to eat more feed or use its body reserves of fat. For example, in cold conditions, a 15 km/hr wind can double the amount of feed an animal needs to maintain its body temperature. The animal's productivity is reduced in cold, windy conditions because more of its feed intake is being used to maintain body temperature, instead of producing wool, meat or milk. Providing shelter in the form of windbreaks can improve the animal's productivity under these conditions.

Acute cold stress can result in death of animals, particularly new-born lambs, freshly shorn sheep or animals in poor body condition. Exposure during the first three days is the major cause of lambing losses in Australia. However, studies in south-eastern Australia have shown that lamb deaths can be halved by providing adequate shelter from wind in wet and cold weather during the first critical hours of life. A tragic example of stock loss occurred in Victoria in March 1983 when at least 30,000 sheep died of exposure after being shorn for the live sheep export trade. On one Victorian property, 11 % of the sheep in unsheltered paddocks died, but all of the sheep protected by windbreaks survived.

SHADE: Trees provide shade for animals in hot weather. Heat stress has a variety of effects on animals, including reduced fertility, decreased live-weight gain and reduced milk production. Heat stress affects breeding ewes at two periods in the breeding cycle. At joining it can cause suppression of estrous, failure to conceive and early embryonic mortality during the first 7 days after ovulation. Ewes stressed by heat in the last 6 weeks of pregnancy are likely to give birth to higher lambs. Since survival is related to birth weight, light lambs born to heat-stressed ewes are more likely to die soon after birth than their heavier counterparts. In bot climates, lack of shade increases lamb mortality in the first 6 days, before the lamb can properly regulate its body temperature. In studies in northern Queens-land, shade trees reduced the heat load on ewes at joining and lambing. This resulted in 10 to 16 % more lambs at marking, as well as a faster growth rate and more wool from the lambs over their first 16 months of life.

Newly shorn sheep are also affected by heat. Providing shade to protect against radiation and high temperatures is important. Effects of heat stress on breeding cows are similar to those on ewes. Cattle in hot climates seek shade as part of their survival behaviour pattern. Observations of cattle health showed that cattle which preferred to rest in shade during the heat of the day were generally heavier, in better condition, had sleeker coats and were more alert than cattle not using shade.

SOIL EROSION: Soil erosion occurs through the action of wind and water on unprotected soil. Wind erosion is mainly associated with loss of the finer particles of soil, together with drifting and accumulation of the sand fractions. Water movement over and through the soil can result in sheet, rill, gully and tunnel erosion, as well as land-slip. Trees, together with under-storey and groundcover layers, play a crucial role in intercepting rainfall and reducing impact of raindrops on the soil surface. Trees help the water soak into the soil and reduce surface runoff. The root system and leaf litters provide structural stability within the soil. Widespread removal of trees and poor land management can significantly alter the water cycle, leading to increased rainfall runoff, rising water tables and increased surface seepage. The results of these changes can include increased flooding, soil erosion, sedimentation and salinity.

Tree clearing should not occur where lands are inherently unstable or prone to uncontrollable land degradation. Specific sites where trees can play a positive role in soil and water management will vary on each farm. Generally, however, excessively steep slopes, degraded or eroded areas, and lands with soil problems such as severe acidity, fertility imbalance, poor structure, shallowness, stoniness, tunneling susceptibility and salting will benefit from tree retention, regeneration or planting. Tree can be used to stabilize steam-banks and gullies, but great care is needed in choosing species and in locating plantings. Unwise planting can lead to channel choking, destructive redirection of water flows and the creation of rabbit harbours that are difficult to manage.

SALTING: Soil salinity, occurring as either irrigation or dry land salinity, affects about 6.31 million hectares of arable land in Pakistan. Irrigation salinity occurs when the water table is raised by adding more water to the land than can be used by the crop or pasture. The rising water table brings to the surface dissolved salts from within the soil profile. Plantations of trees can lower the water table, but only directly underneath them, so tree planting does not offer a practical solution to irrigation salinity. Dry land salinity occurs as a result of clearing deep-rooted vegetation, such as trees, from areas where large volumes of water can enter the groundwater, and where there is an excess of salt in the underlying strata. As the rate of water use from the soil decreases, the water table rises, carrying dissolved salt with it. Salting becomes apparent in depressions or at changes of slope where the water table comes to the surface. Evaporation of water increases the salt concentration, killing vegetation and leaving the land bare and susceptible to erosion. Restricting the amount of groundwater flowing through the soil reduces dry land salting. Reestablishing trees in groundwater recharge areas reduces the volume of water flowing through the root zone and replenishing the groundwater. Trees can also be used on discharge areas to control the height of the water table by drawing on groundwater for transpiration. Salt-affected areas can be gradually rehabilitated by planting salt-tolerant trees around the fringes. As the water table falls, more trees can be planted towards the centre of the area.

FODDER: Pakistan is fortunate in having a number of trees and shrubs that can provide emergency fodder during droughts. Feed accumulates during good seasons and because of its low palatability is not eaten until there is a shortage of other vegetation. In this way, the quantity and quality of leaf is preserved for use in poor seasons. Even during droughts, the leaves of trees and shrubs retain their crude protein content. However, fodder trees are only equivalent to fair quality hay and palatability is low, so stock lose the desire to eat it after several months. A leaf diet will maintain stock for up to 9 months, depending on the tree species used. If fodder tree foliage is being fed to young growing stock or pregnant or lactating females, a supplement will be necessary. Impaction, particularly from twigs, can become a problem if foliage is fed for too long. This can be overcome by feeding generous amounts of lopping. Take care to avoid serious long-term damage to trees and shrubs by overgrazing or over-cutting during droughts. Most of the research on fodder trees has been in the arid and semi-arid parts of Australia where browse shrubs are an important part of the diet of livestock. However, introduced trees such as tagasaste, willow, carob and honey locust can also provide useful fodder during droughts or periods of pasture shortage.

WILDLIFE HABITAT: Trees and shrubs provide the necessary habitat for maintaining the diversity of wildlife in the landscape. Viable populations of insect-eating birds, lizards spiders and predatory insects can play a significant role in combating mass outbreaks of crop and pasture pests. An example is the sculled wasp that helps to control scarab beetles. The adult wasps feed on nectar from native shrubs and will only fly about 200 metres from the nectar source to seek out and parasite scarab beetle larvae. In addition, adult gliders can each eat about 3.2 kg of insects in a year and a colony of bent winged bats can eat about 200 kg of insects in a day. Grasshopper cleared from 100 acres (40 hectares) at Trundle and 24 acres (9.7 ha) at Gunning bland in Australia by feeding on one- day-old nymphs. Other useful wildlife such as birds of prey, kingfishers, honeyeaters are attracted by the shelter and food provided by trees. Clearing stands of natural timber reduces breeding space for populations of birds and animals that aid in the control of pests. Farm tree plantings and retained areas of natural timber along roadsides and watercourses are important in the ecology of these animals, especially where the plantings act as corridors linking up larger areas of natural timber. Isolated trees provide roosting or nesting sites for some birds, but are generally of limited value as wildlife habitat.

WOOD LOTS: Trees can be established as wood lots for wood supplies and wildlife habitat. Wood lots also provide shade and some protection from wind. As the trees grow they can be thinned out, producing fencing materials, firewood, poles and even saw timber. Thinning usually encourages natural regeneration of native species. If exotic conifers are used they may produce profitable wood crops and still provide useful shelter. Cooperation with neighbours can lead to strategically placed wood lots throughout a catchment, which may improve water quality, protect the soil and provide wildlife corridors.

FIRE PROTECTION: Windbreaks can reduce the speed of fire advance. The speed of a fire is proportional to the square of wind speed, so an effective windbreak can slow the speed of a fire to one-tenth that in open grassland. Some tree and shrub species can be used as living firebreaks to protect vulnerable areas. Trees with a high moisture content and low flammable resin and oil content are best because they are difficult to ignite. Silky oak, kurrajong, pepper tree and tagasaste are good examples. Most deciduous trees also fall into the category, because of the high moisture content of their leaves. Most native species have survival mechanisms such as thick bark, lignotubers or woody seed capsules that enable them to survive or re-grow after a fire.

BEAUTY: Trees can be used to beautify the landscape and make living environments more pleasant. Trees planted around living areas provide protection from heat in summer and cold in winter. Dense plantings help to block noise and dust and screen out unsightly views. A large range of autumn colouring trees and shrubs can be grown in most homestead gardens to beautify and give diversity to the surroundings.

ECONOMIC BENEFITS: It is difficult to put a value on the benefits of farm trees, but it is clear that there are many advantages in establishing and maintaining trees in strategic locations. Direct economic benefits of tree result from increased yields of crops and pastures, and increased survival and productivity of livestock due to shelter. More difficult to quantify are the indirect benefits such as improved living and working environment due to trees around homesteads and buildings, and the increased capital value of farms. Other economic benefits of trees come from marketable products such as fence posts and droppers, firewood, pulpwood, sawlogs and rough building materials. Many land degradation problems such as erosion and soil salinity can be attributed to the clearing of trees. Retention of trees on sensitive sites may help to avoid costly reclamation work later on. Careful planning of all stages of a tree establishment programme is needed in order to achieve these benefits. This involves assessing why trees are needed and the planning the location and type of trees accordingly.