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close this bookObstacles to Tree Planting in Arid and Semi-Arid lands: Comparative Case Studies from India and Kenya (UNU, 1982, 63 p.)
close this folder1. Introduction and purpose of the study
View the documentThe United Nations University programme
View the documentObjective of the study
View the documentChoice of study areas
View the documentDefinitions and distribution of arid and semi-arid lands
View the documentBenefits of trees-the "4-E Package"
View the documentRecent trends in forestry

Benefits of trees-the "4-E Package"

Tree planting, even if constraints can be overcome, must take its place in an overall programme of arid zone develop meet. There are four major components (the four E's) of any such development, namely ecology, employment, energy, and economics. All components include a strong human dimension, and it is important to emphasize the potential contribution that local people can make. Development projects are intended to be for people, but they should also be designed to operate with people. Specific instances of local participation are outlined below. Too often schemes that are laudable with respect to one or two of these components fail to consider the others adequately.


If, in ecology, we include the amelioration and protection of the environment for man and his domestic animals, trees can play a significant role in the ASAL.

FIG. 1. Isohyets in India (based on Government of India 1975, ICRISAT 1978, Subrahmanyam et al. 1965)

FIG. 2. Isohyet for 500 mm in Kenya (based on Kamweti 1979)

Climatic Effects

There is still controversy about the effect of forests on rainfall at a continental or regional level but there is little doubt that trees and forests can modify local environment, e.g., individual trees that provide shade, and shelterbelts, which affect windspeed, temperature, and evaporation.

Soil and Water Effects

Trees, through their widespread roots, can stabilize soil in sand dunes and on hillsides thus preventing soil erosion, river pollution, and dam siltation. Deep-rooted trees may reach underground water supplies not accessible to other plants. Trees tap nutrient reserves and recycle them through leaf fall, making them available to other crops; this is particularly important in tropical areas where high temperatures and intense rainfall cause leaching. It is true that clear-felled industrial plantations may themselves cause nutrient loss and require artificial inputs for second and later rotations, but this type of tree planting is not widespread in the ASAL, where agro-forestry systems and coppice cutting are preferable.

Amenity and Recreation Benefits

In more developed countries the inhabitants have the leisure time and sufficient money to enjoy recreational pursuits and appreciate amenity values of trees and forests, but residents of the dry areas have different perceptions. However, trees are widely appreciated for one quality- shade. In the hot season (i.e., for much of the Year) it is a common sight to see a herdsman and his stock resting in the welcome shade of a tree.


For employment in the ASAL, tree planting and harvesting require more individual and group labour per unit area than pastoral or annual crops. Trees can provide employment and income, particularly during slack agricultural periods, through the development of industries processing minor and major products. Employment and income from trees can benefit diverse sectors in the ASAL, particularly the land poor and the landless, but also middle- and upper income households. Guaranteed land tenure and access to trees are essential to encourage tree planting.


Trees have traditionally been regarded as a low-input/ high-output, free energy source, and over half of the wood currently consumed throughout the world is used for fuel, largely for domestic purposes; within the ASAL the proportion is far higher. Some 1.5 x 109 people use wood daily for cooking their food and for maintaining essential levels of warmth in their homes (FAO 1978). (See also Arnold and Jongma 1978; Arnold 1978; IDRC 1979.) Even in developed countries far from the ASAL, with the recognition that reserves of non-renewable energy sources, particularly oil, are finite and diminishing rapidly, wood has recently attained new prominence as a potential source of energy, including its use for fuelwood, charcoal, and chemical feedstock (alcohols).


In economic terms, trees yield products that facilitate monetarization and diversification of the economy and, by encouraging settlement, improve marketing and transport system and encourage enterprise. In the ASAL, in addition to fuelwood, fencing material, poles, and some sawn wood are the major forest products, either from single trees on farms and along edges of canals, railways, and streets or from relatively large plantations in smallholder, community, or government forests. Minor products include directly used material such as animal fodder, roofing and smoking materials, or drugs and indirect products such as honey or wildlife. Overall in the ASAL, timber takes second place to products and services from trees, and conventional timber management systems often conflict with local needs for these other services and goods.

In appraising projects for financial support, national and international institutions have traditionally considered mainly the financial benefits of the projects. Only recently have social benefits been included so that the interactions of the "4-E package" can be examined. Techniques of social cost-benefit analysis and environmental impact analysis now permit approval of some projects that are not financially feasible and the rejection of others that, while financially attractive, have undesirable effects on the ecological or social situations in the project area. Techniques of analysis have advanced in recent years, with the emphasis of USAID, World Bank, and other agencies on social soundness analysis. Such analysis should preferably be made before the project gets under way and should continue during the life of the project. However, even if the analysis is done in good time (which in fact seldom happens), there are many associated problems. These include isolating the effects of one specific action-e.g., afforestation-from other actions, especially as successful development usually requires an integrated plan with many social and economic aspects. Then there is the problem of time-should costs and benefits be estimated for a short period or, more realistically, for the long term? Multiplier effects and indirect effects of projects are often significant, but are also difficult to measure with any precision. Even now there remain considerable problems of quantification and evaluation in the use of social cost-benefit analysis at the subsistence forestry level.