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Tree Planting

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Tree planting consists of putting seedlings or young trees into the soil. It is mainly done to re-grow a new forest after harvesting, to establish a woodlot or to change the use of a piece of land (e.g., from a pasture to a woodlot or to control erosion on a steep slope). Planting projects can amount to several million plants. Projects may be executed by the forest owners’ private contractors, pulp and paper companies, the government’s forest service, non-governmental organizations or cooperatives. In some countries, tree planting has become a veritable industry. Excluded here is the planting of large individual trees, which is considered more the domain of landscaping than forestry.

The workforce includes the actual tree planters as well as tree nursery staff, workers involved in transporting and maintaining the plants, support and logistics (e.g., managing, cooking, driving and maintaining vehicles and so on) and quality control inspectors. Women comprise 10 to 15% of the tree-planter workforce. As an indication of the importance of the industry and the scale of activities in regions where forestry is of economic importance, the provincial government in Quebec, Canada, set an objective of planting 250 million seedlings in 1988.

Planting Stock

Several technologies are available to produce seedlings or small trees, and the ergonomics of tree planting will vary accordingly. Tree planting on flat land can be done by planting machines. The role of the worker is then limited to feeding the machine manually or merely to controlling quality. In most countries and situations, however, site preparation may be mechanized, but actual planting is still done manually.

In most reforestation, following a forest fire or clear cutting, for example, or in afforestation, seedlings varying from 25 to 50 cm in height are used. The seedlings are either bare-rooted or have been grown in containers. The most common containers in tropical countries are 600 to 1,000 cm3. Containers may be arranged in plastic or styrofoam trays which usually hold from 40 to 70 identical units. For some purposes, larger plants, 80 to 200 cm, may be needed. They are usually bare-rooted.

Tree planting is seasonal because it depends on rainy and/or cool weather. The season lasts 30 to 90 days in most regions. Although it may seem a lesser seasonal occupation, tree planting must be considered a major long-term strategic activity, both for the environment and for revenue where forestry is an important industry.

Information presented here is based mainly on the Canadian experience, but many of the issues can be extrapolated to other countries with a similar geographical and economic context. Specific practices and health and safety considerations for developing countries are also addressed.

Planting Strategy

Careful evaluation of the site is important for setting adequate planting targets. A superficial approach can hide field difficulties that will slow down the planting and overburden the planters. Several strategies exist for planting large areas. One common approach is to have a team of 10 to 15 planters equally spaced in a row, who progress at the same pace; a designated worker then has the task of bringing in enough seedlings for the whole team, usually by means of small off-road vehicles. One other common method is to work with several pairs of planters, each pair being responsible for fetching and carrying their own small stock of plants. Experienced planters will know how to space out their stock to avoid losing time carrying plants back and forth. Planting alone is not recommended.

Seedling Transport

Planting relies on the steady supply of seedlings to the planters. They are brought in several thousands at a time from the nurseries, on trucks or pick-ups as far as the road will go. The seedlings must be unloaded rapidly and watered regularly. Modified logging machinery or small off-road vehicles can be used to carry the seedlings from the main depot to the planting sites. Where seedlings have to be carried by workers, such as in many developing countries, the workload is very heavy. Suitable back-packs should be used to reduce fatigue and risk of injuries. Individual planters will carry from four to six trays to their respective lots. Since most planters are paid at a piece rate, it is important for them to minimize unproductive time spent travelling, or fetching or carrying seedlings.

Equipment and Tools

The typical equipment carried by a tree planter includes a planting shovel or a dibble (a slightly conical metal cylinder at the end of a stick, used to make holes closely fitting the dimensions of containerized seedlings), two or three plant container trays carried by a harness, and safety equipment such as toe-capped boots and protective gloves. When planting bare-rooted seedlings, a pail containing enough water to cover the seedling’s roots is used instead of the harness, and is carried by hand. Various types of tree-planting hoes are also widely used for bare-rooted seedlings in Europe and North America. Some planting tools are manufactured by specialized tool companies, but many are made in local shops or are intended for gardening and agriculture, and present some design deficiencies such as excess weight and improper length. The weight typically carried is presented in table 1.

Table 1. Typical load carried while planting.

Element

 Weight in kg    

Commercially available harness

 2.1

Three 45-seedling container trays, full   

 12.3

Typical planting tool (dibble)

 2.4

Total

 16.8

 

Planting Cycle

One tree-planting cycle is defined as the series of steps necessary to put one seedling into the ground. Site conditions, such as slope, soil and ground cover, have a strong influence on productivity. In Canada the production of a planter can vary from 600 plants per day for a novice to 3,000 plants per day for an experienced individual. The cycle may be subdivided as follows:

Selection of a micro-site. This step is fundamental for the survival of the young trees and depends on several criteria taken into account by quality control inspectors, including distance from preceding plant and natural offspring, closeness to organic material, absence of surrounding debris and avoidance of dry or flooded spots. All these criteria must be applied by the planter for each and every tree planted, since their non-observance can lead to a financial penalty.

Ground perforation. A hole is made in the ground with the planting tool. Two operating modes are observed, depending on the type of handle and the length of the shaft. One consists of using the mass of the body applied to a step bar located at the lower extremity of the tool to force it into the ground, while the other one involves raising the tool at arm’s length and forcefully plunging it into the ground. To avoid soil particles falling into the hole when the tool is removed, planters have the habit of smoothing its walls either by turning the tool around its long axis with a movement of the hand, or by flaring it with a circular motion of the arm.

Insertion of the plant into the cavity. If the planter is not yet holding a seedling, he or she grabs one from the container, bends down, inserts it into the hole and straightens up. The plant must be straight, firmly inserted into the soil, and the roots must be completely covered. It is interesting to note here that the tool plays an important secondary role by supplying a support for the planter as he or she bends down and straightens up, thus relieving the back muscles. Back movements can be straight or flexed, depending on the length of the shaft and the type of handle.

Soil compaction. Soil is compacted around the newly planted seedling to set it in the hole and to eliminate air that could dry the roots. Even though a trampling action is recommended, a forceful stamping of the feet or heel is more often observed.

Moving to the next micro-site. The planter proceeds to the next micro-site, generally 1.8 m away. This distance is usually evaluated by sight by experienced planters. While proceeding to the site, he or she must identify hazards on the way, plan a path around them, or determine another evasive strategy. In figure 1, the planter in the foreground is about to insert the seedling in the hole. The planter in the background is about to make a hole with a straight-handle planting tool. Both carry the seedlings in containers attached to a harness. Seedlings and equipment can weigh up to 16.8 kg (see table 1). Also note that the planters are fully covered by clothes to protect themselves against insects and the sun.

Figure 1. Tree planters in action in Canada

FOR050F1

Hazards, Outcomes and Preventive Measures

Few studies worldwide have been devoted to the health and safety of tree planters. Although bucolic in appearance, tree planting carried out on an industrial basis can be strenuous and hazardous. In a pioneering study conducted by Smith (1987) in British Columbia, it was found that 90% of the 65 planters interviewed had suffered an illness, injury or accident during life-time tree-planting activities. In a similar study conducted by IRSST, the Quebec Institute of Occupational Health and Safety (Giguère et al. 1991, 1993), 24 out of 48 tree planters reported having suffered from a work-related injury during the course of their planting careers. In Canada, 15 tree planters died between 1987 and 1991 of the following work-related causes: road accidents (7), wild animals (3), lightning (2), lodging incidents (fire, asphyxia—2) and heat stroke (1).

Although scarce and conducted on a small number of workers, the few investigations of physiological indicators of physical strain (heart rate, blood haematology parameters, elevated serum enzymes activity) all concluded that tree planting is a highly strenuous occupation both in terms of cardiovascular and musculoskeletal strain (Trites, Robinson and Banister 1993; Robinson, Trites and Banister 1993; Giguère et al. 1991; Smith 1987). Banister, Robinson and Trites (1990) defined “tree-planter burnout”, a condition originating from haematological deficiency and characterized by the presence of lethargy, weakness and light-headedness similar to the “adrenal exhaustion syndrome” or “sport anaemia” developed by training athletes. (For data on workload in Chile, see Apud and Valdés 1995; for Pakistan, see Saarilahti and Asghar 1994).

Organizational factors. Long workdays, commuting and strict quality control, coupled with the piece-work incentive (which is a widespread practice among tree-planting contractors), may strain the physiological and psychological equilibrium of the worker and lead to chronic fatigue and stress (Trites, Robinson and Banister 1993). A good working technique and regular short pauses improve daily output and help to avoid burnout.

Accidents and injuries. Data presented in table 2 provide an indication of the nature and causes of accidents and injuries as they were reported by the tree-planter population participating in the Quebec study. The relative importance of accidents by body part affected shows that injuries to the lower extremities are more frequently reported than those to the upper extremities, if the percentages for knees, feet, legs and ankles are added together. The environmental setting is favourable to tripping and falling accidents. Injuries associated with forceful movements and lesions caused by tools, cutting scraps or soil debris are also of relevance.

Table 2. Frequency grouping of tree-planting accidents by body parts affected (in percentage of 122 reports by 48 subjects in Quebec).

 Rank  

 Body part  

 % total  

 Related causes

 1

 Knees

14

 Falls, contact with tool, soil compaction

 2

 Skin

12

 Equipment contact, biting and stinging insects, sunburn, chapping

 3

 Eyes

11

 Insects, insect repellent, twigs

 4

 Back

10

 Frequent bending, load carrying

 5

 Feet

10

 Soil compaction, blisters

 6

 Hands

8

 Chapping, scratches from contact with soil

 7

 Legs

7

 Falls, contact with tool

 8

 Wrists

6

 Hidden rocks

 9

 Ankles

4

 Trips and falls, hidden obstacles, contact with tool

 10

 Other

18

 -

Source: Giguere et al. 1991, 1993.

A well-prepared planting site, free of bushes and obstacles, will speed up planting and reduce accidents. Scrap should be disposed of in piles instead of furrows to allow easy circulation of the planters on the site. Tools should have straight handles to avoid injuries, and be of a contrasting colour. Shoes or boots should be sturdy enough to protect the feet during the repeated contact with the planting tool and while trampling the soil; sizes should be available for male and female planters, and the sole, sized properly for both men and women, should have a good grip on wet rocks or stumps. Gloves are useful to reduce the occurrence of blistering and of cuts and bruises from inserting the seedling into the soil. They also make the handling of conifer or thorny seedlings more comfortable.

Camp life and outdoor work. In Canada and a number of other countries, planters often have to live in camps. Working in the open requires protection against the sun (sun glasses, hats, sun block) and against biting and stinging insects. Heat stress can also be significant, and prevention calls for the possibility of adjusting the work-rest regimen and the availability of potable liquids to avoid dehydration.

It is important to have first aid equipment and some of the personnel trained as paramedics. Training should include emergency treatment of heat stroke and allergy caused by the venom of wasps or snakes. Planters should be checked for tetanus vaccination and for allergy before being sent to remote sites. Emergency communication systems, evacuation procedures and assembly signal (in case of a forest fire, sudden wind or sudden thunderstorm, or the presence of dangerous wild animals and so on) are essential.

Chemical hazards. The use of pesticides and fungicides to protect the seedlings (during cultivation or storage) is a potential risk when handling freshly sprayed plants (Robinson, Trites and Banister 1993). Eye irritation may occur due to the constant need to apply insect-repelling lotions or sprays.

Musculoskeletal and physiological load. Although there is no specific epidemiological literature linking musculoskeletal problems and tree planting, the forceful movements associated with load carrying, as well as the range of postures and muscular work involved in the planting cycle, undoubtedly constitute risk factors, which are exacerbated by the repetitive nature of the work.

Extreme flexions and extensions of the wrists, in grabbing seedlings in the trays, for example, and shock transmission to the hands and arms occurring when the planting tool hits a hidden rock, are among the possible biomechanical hazards to the upper limbs. The overall weight carried, the frequency of lifting, the repetitive and physical nature of the work, especially the intensive muscular effort required when plunging the dibble into the ground, contribute to the muscular strain exerted on upper limbs.

Low-back problems could be related to the frequency of bending. Handling of seedling trays (3.0 to 4.1 kg each when full) when unloading delivery trucks is also a potential risk. Carrying loads with harnesses, especially if the weight is not properly distributed on the shoulders and around the waist, is also likely to engender back pain.

The muscular load on lower limbs is obviously extensive. Walking several kilometres a day while carrying a load on rough terrain, sometimes going uphill, can rapidly become strenuous. Additionally, the work involves frequent knee flexions, and the feet are used continuously. Most tree planters use their feet to clear local debris with a lateral movement before making a hole. They also use their feet in putting weight on the tool’s footrest to aid penetration into the soil and to compact the soil around the seedling after it has been inserted.

Prevention of musculoskeletal strain relies on the minimization of carried loads, in terms of weight, frequency and distance, in conjunction with the optimization of working postures, which implies proper working tools and practices.

If seedlings must be carried in a pail, for instance, water can be replaced by wet peat moss to reduce carried weight. In Chile, replacing heavy wooden boxes for carrying seedlings by lighter cardboard ones increased output by 50% (Apud and Valdés 1995). Tools also have to be well adapted to the job. Replacing a pickaxe and shovel with a specially designed pick-hoe reduced workload by 50% and improved output by up to 100% in reforestation in Pakistan (Saarilahti and Asghar 1994). The weight of the planting tool is also crucial. For example, in a field survey of planting tools conducted in Quebec, variations ranged from 1.7 to 3.1 kg, meaning that choosing the lightest model may save 1,400 kg of lifted weight daily based on 1,000 lifts per day.

Planting tools with long, straight handles are preferred since if the tool hits a hidden rock, the hand will slip on the handle instead of absorbing the shock. A smooth, tapered handle allows an optimum grip for a greater percentage of the population. The Forest Engineering Research Institute of Canada recommends adjustable tools with shock-absorbing properties, but reports that none were available at the time of their 1988 survey (Stjernberg 1988).

Planters should also be educated about optimal working postures. Using the body weight to insert the dibble instead of using muscular effort, avoiding back twisting or exertion of the arms while they are fully extended, avoiding planting downhill and using the planting tool as a support when bending, for example, can all help minimize musculoskeletal strain. Novice planters should not be paid piece rate until they are fully trained.

 

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Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Agriculture and Natural Resources Based Industries
Beverage Industry
Fishing
Food Industry
Forestry
Hunting
Livestock Rearing
Lumber
Paper and Pulp Industry
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides

Forestry References

Apud, E, L Bostrand, I Mobbs, and B Strehlke. 1989. Guidelines on Ergonomic Study in Forestry. Geneva: ILO.

Apud, E and S Valdés. 1995. Ergonomics in Forestry—The Chilean Case. Geneva: ILO.

Banister, E, D Robinson, and D Trites. 1990. Ergonomics of Tree Planting. Canada–British Columbia Forest Resources Development Agreement, FRDA Report 127. Victoria, BC: FRDA.

Brown, GW. 1985. Forestry and Water Quality. Corvallis, OR: Oregon State University (OSU) Book Stores Inc.

Chen, KT. 1990. Logging Accidents—An Emerging Problem. Sarawak, Malaysia: Occupational Health Unit, Medical Department.

Dummel, K and H Branz. 1986. “Holzernteverfahren,” Schriften Reihefdes Bundesministers für Ernätrung, Handwirtschaft und Forsten. Reihe A: Landwirtschafts verlag Münster-Hiltrup.

Durnin, JVGA and R Passmore. 1967. Energy, Work, Leisure. London: Heinemann.

Food and Agriculture Organization (FAO) of the United Nations. 1992. Introduction to Ergonomics in Forestry in Developing Countries. Forestry Paper 100. Rome:FAO.

—. 1995. Forestry—Statistics Today for Tomorrow. Rome: FAO.

—. 1996. FAO Model Code of Forest Harvesting Practice. Rome: FAO.

FAO/ECE/ILO. 1989. Impact of Mechanization of Forest Operations on the Soil. Proceedings of a seminar, Louvain-la-neuve, Belgium, 11–15 September. Geneva: FAO/ECE/ILO Joint Committee on Forest Technology, Management and Training.

—. 1991. The Use of Pesticides in Forestry. Proceedings of a seminar, Sparsholt, UK, 10–14 September 1990.

—. 1994. Soil, Tree, Machine Interactions, FORSITRISK. Proceedings of an interactive workshop and seminar, Feldafiraf, Germany, 4–8 July. Geneva: FAO/ECE/ILO Joint Committee on Forest Technology, Management and Training.

—. 1996a. Manual on Acute Forest Damage. UN/ECE/ FAO discussion papers ECE/TIM/DP/7, New York and Geneva: Joint FAO/ECE/ILO Committee on Forest Technology, Management and Training.

—. 1996b. Skills and Training in Forestry—Results of a Survey of ECE Member Countries. Geneva: FAO/ECE/ILO Joint Committee on Forest Technology, Management and Training.

FAO/ILO. 1980. Chainsaws in Tropical Forests. Forest Training Series No. 2. Rome: FAO.

Gellerstedt, S. 1993. Work and Health in Forest Work. Göteborg: Chalmers University of Technology.

Giguère, D, R Bélanger, J-M Gauthier, and C Larue. 1991. Étude préliminaire du travail de reboisement. Rapport IRSST B-026. Montreal: IRSST.

—. 1993. Ergonomics aspects of tree planting using multi-pot technology. Ergonomics 36(8):963-972.

Golsse, JM. 1994. Revised FERIC Ergonomic Checklist for Canadian Forest Machinery. Pointe Claire: Forest Engineering Research institute of Canada.

Haile, F. 1991. Women Fuelwood Carriers in Addis Ababa and the Peri-urban Forest. Research on women in fuelwood transport in Addis Ababa, Ethiopia ETH/88/MO1/IRDC and ETH/89/MO5/NOR. Project report. Geneva: ILO.

Harstela, P. 1990. Work postures and strain of workers in Nordic forest work: A selective review. Int J Ind Erg 5:219–226.

International Labour Organization (ILO). 1969. Safety and Health in Forestry Work. An ILO Code of Practice. Geneva: ILO.

—. 1988. Maximum Weights in Load Lifting and Carrying. Occupational Safety and Health Service, No. 59. Geneva: ILO.

—. 1991. Occupational Safety and Health in Forestry. Report II, Forestry and Wood Industries Committee, Second Session. Geneva: ILO.

—. 1997. Code of Practice on Safety and Health in Forest Work. MEFW/1997/3. Geneva: ILO.

—. 1998. Code of Practice on Safety and Health in Forest Work. Geneva: ILO.

International Standards Organization (ISO). 1986. Equipment for Working the Soil: ROPS—Laboratory Testing and Performance Specifications. ISO 3471-1. Geneva: ISO.

Jokulioma, H and H Tapola. 1993. Forest worker safety and health in Finland. Unasylva 4(175):57–63.

Juntunen, ML. 1993. Training of harvester operations in Finland. Presented in seminar on the use of multifunctional machinery and equipment in logging operations. Olenino Logging Enterprise, Tvor Region, Russian Federation 22–28 August.

—. 1995. Professional harvester operator: Basic knowledge and skills from training—Operating skills from working life? Presented in IUFRO XX World Congress, Tampre, Finland, 6–12 August.

Kanninen, K. 1986. The occurrence of occupational accidents in logging operations and the aims of preventive measures. In the proceedings of a seminar on occupational health and rehabilitation of forest workers, Kuopio, Finland, 3–7 June 1985. FAO/ECE/ILO Joint Committee on Forest Working Techniques and Training of Forest Workers.

Kastenholz, E. 1996. Sicheres Handeln bei der Holzernteuntersuchung von Einflüssen auf das Unfallgeschehen bei der Waldarbeit unter besonderer Berücksichtigung der Lohnform. Doctoral dissertation. Freiburg, Germany: University of Freiburg.

Kantola, M and P Harstela. 1988. Handbook on Appropriate Technology for Forestry Operations in Developing Counties, Part 2. Forestry Training Programme Publication 19. Helsinki: National Board of Vocational Education.

Kimmins, H. 1992. Balancing Act—Environmental Issues in Forestry. Vancouver, BC: University of British Columbia Press.

Lejhancova, M. 1968. Skin damage caused by mineral oils. Procovni Lekarstvi 20(4):164–168.

Lidén, E. 1995. Forest Machine Contractors in Swedish Industrial Forestry: Significance and Conditions during 1986–1993. Department of Operational Efficiency Report No. 195. Swedish University of Agricultural Science.

Ministry of Skills Development. 1989. Cutter-skidder Operator: Competency-based Training Standards. Ontario: Ministry of Skills Development.

Moos, H and B Kvitzau. 1988. Retraining of adult forest workers entering forestry from other occupation. In Proceedings of Seminar on the Employment of Contractors in Forestry, Loubières, France 26-30 September 1988. Loubiéres: FAO/ECE/ILO Joint Committee on Forest Work Techniques and Training of Forest Workers.

National Proficiency Test Council (NPTC) and Scottish Skill Testing Service (SSTS). 1992. Schedule of Chainsaw Standards. Warwickshire, UK: NPTC and SSTS.

—. 1993. Certificates of Competence in Chainsaw Operation. Warwickshire, United Kingdom: National Proficiency Tests Council and Scottish Skills Testing Service.

Patosaari, P. 1987. Chemicals in Forestry: Health Hazards and Protection. Report to the FAO/ECE/ILO Joint Committee on Forest Working Technique and Training of Forest Workers, Helsinki (mimeo).

Pellet. 1995. Rapport d’étude: L’ánalyse de l’áccident par la méthode de l’arbre des causes. Luzern: Schweizerische Unfallversicherungsanstalt (SUVA) (mimeo).

Powers, RF, DH Alban, RE Miller, AE Tiarks, CG Wells, PE Avers, RG Cline, RO Fitzgerald, and JNS Loftus. 1990.
Sustaining site productivity in North American forests: Problems and prospects. In Sustained Productivity of Forest Soils, edited by SP Gessed, DS Lacate, GF Weetman and RF Powers. Vancouver, BC: Faculty of Forestry Publication.

Robinson, DG, DG Trites, and EW Banister. 1993. Physiological effects of work stress and pesticides exposure in tree planting by British Columbian silviculture workers. Ergonomics 36(8):951–961.

Rodero, F. 1987. Nota sobre siniestralidad en incendios forestales. Madrid, Spain: Instituto Nacional para la Conservación de la Naturaleza.

Saarilahti, M and A Asghar. 1994. Study on winter planting of chir pine. Research paper 12, ILO project, Pakistan.
Skoupy, A and R Ulrich. 1994. Dispersal of chain lubrication oil in one-man chain-saws. Forsttechnische Information 11:121–123.

Skyberg, K, A Ronneberg, CC Christensen, CR Naess-Andersen, HE Refsum, and A Borgelsen. 1992. Lung function and radiographic signs of pulmonary fibrosis in oil exposed workers in a cable manufacturing company: A follow up study. Brit J Ind Med 49(5):309–315.

Slappendel, C, I Laird, I Kawachi, S Marshal, and C Cryer. 1993. Factors affecting work-related injury among forestry workers: A review. J Saf Res 24:19–32.

Smith, TJ. 1987. Occupational characteristics of tree-planting work. Sylviculture Magazine II(1):12–17.

Sozialversicherung der Bauern. 1990. Extracts from official Austrian statistics submitted to the ILO (unpublished).

Staudt, F. 1990. Ergonomics 1990. Proceedings P3.03 Ergonomics XIX World Congress IUFRO, Montreal, Canada, August 1990. The Netherlands: Department of Forestry, Section Forest Technique and Woodscience, Wageningen Agricultural University.

Stjernberg, EI. 1988. A Study of Manual Tree Planting Operations in Central and Eastern Canada. FERIC technical report TR-79. Montreal: Forest Engineering Research Institute of Canada.

Stolk, T. 1989. Gebruiker mee laten kiezen uit persoonlijke beschermingsmiddelen. Tuin & Landschap 18.

Strehlke, B. 1989. The study of forest accidents. In Guidelines on Ergonomic Study in Forestry, edited by E Apud. Geneva: ILO.

Trites, DG, DG Robinson, and EW Banister. 1993. Cardiovascular and muscular strain during a tree planting season among British Columbian silviculture workers. Ergonomics 36(8):935–949.

Udo, ES. 1987. Working Conditions and Accidents in Nigerian Logging and Sawmilling Industries. Report for the ILO (unpublished).

Wettman, O. 1992. Securité au travail dans l’exploitation forestière en Suisse. In FAO/ECE/ILO Proceedings of Seminar on the Future of the Forestry Workforce, edited by FAO/ECE/ILO. Corvallis, OR: Oregon State University Press.