Want to plant more trees this season? Then work harder.

The physical nature of reforestation work is painfully obvious to anyone who has spent at least one day working as a tree planter. Tree planters like to consider that the work is the most difficult job in Canada, and that the job is as physically demanding as running a marathon every day. But, perhaps due to the isolated workplace, there has been a relative paucity of data on the physiological, metabolic, or psychological demands of the work.  Some previously published research describes the physical exertion, energy demands, and physiological stresses of the work^3,6,7,8 but recent work we published in the Journal of Occupational Medicine and Toxicology⁴ last year attempted to investigate the elusive question of what makes some tree planters faster than others?

We measured heart rates on tree planters throughout a working day and video recorded workers on the cut block. The video was subsequently analyzed to determine the production speed (trees/hour) and the proportions of time spent planting each tree versus walking between microsites. The heart rate data was analyzed to establish a baseline exertion level through an entire working day including breaks, and the exertion level during an average bag-up. The data were then analyzed to answer the following questions: 1) Does production speed increase with experience? 2) Are faster tree planters exerting themselves more? 3) Are more experienced planters more efficient as measured by a lower heart rate for a given production speed?

We found that tree planters maintain an average heart rate of 115 bpm throughout the working day (figure 1) and a working heart rate during bag-ups of 128 bpm (figure 2). To put this in perspective, the average resting heart rate in a healthy, fit, young individual (such as our group of workers of average age 24 years) is between 50 – 70 bpm, and the average maximum heart rate of a 25 year-old is 195 bpm, meaning that tree planters work at an average of about 65% of maximal heart rate. In comparison, elite marathon runners typically maintain a heart rate of about 175 bpm (91% of maximal heart rate) during their race of just over two hours², putting their exertion at about 80 – 85% of maximum aerobic  effort¹. Tree planters may not be working at a marathon pace, but their “race” lasts an average of 9 hours a day compared to just over 2 hours for a world-class marathoner. Running a marathon, it should also be noted, requires about 2,300 – 2,400 kCal⁵ while the amount of energy a tree planter goes through in a day is slightly more than double that³. Tree planters might not work as intensely as marathoners, but they do work harder and longer day after day.

Not surprisingly, we found that more experienced planters had a higher production speed than less experienced planters (though we only had 3 rookies in our data, we had an experience level that ranged from 1 – 9 seasons). Production speed also increased with working heart rate (or exertion). This latter finding is not necessarily intuitive. Although hard work typically pays off, anyone who has watched a smooth veteran outpace a struggling rookie might think that exertion actually decreases with experience, but we found the opposite. Finally, we also found that the exertion level for a given production speed was lower for more experienced planters. This means that with experience comes efficiency. More experienced planters don’t struggle as hard for each tree as less experienced planters do, even though overall they seem to exert themselves more. This is not surprising, but it does combine with the finding of increased exertion in more experienced planters to tell an interesting story.

More experienced planters clearly plant more trees than their less experienced comrades. They are also more efficient at putting trees in the ground. But, their increased production doesn’t only stem from increased efficiency. More experienced planters simply work harder. This is not necessarily a snub of the motivation and effort of less experienced planters. Rather, we hypothesize that with experience comes the ability to work harder because less time is spent wandering around looking for that next spot. Unfortunately, the video analysis of time spent planting trees versus looking for microsites does not support this theory, but it does not contradict it either. According to our findings, the average tree planter spends 53% of the time planting trees versus 47% walking between trees and, surprisingly, this ratio does not change significantly with experience level. A finding that more experienced planters spend less time walking between trees would have nicely supported the theory that veteran planters are more efficient at finding microsites and are therefore able to maintain both a higher exertion level and production speed. But, we suggest that the reason this ratio is not variable with experience is that more experienced planters are equally faster at both skills: walking between microsites and the mechanics of putting a tree in the ground. The fact that both exertion level and production speed are higher in more experienced planters seems to support this.

Production is the bottom line in tree planting. Anyone who has spent any time at all on a tree planting crew knows that everything else, including occupational health and safety, environmental regulations, and stock care and handling, can end up taking a back seat to production. Being able to slam in an extra couple of hundred trees each day is worth hard cash to the worker and the contractor, and ultimately benefits the client also. But as long as the only solution to making more money is to work harder, as suggested by our findings, tree planters will find ways to work harder and harder to make ends meet, even when it leads to compromises on other values, including their own health and safety. It will take significant industry leadership to recognize and reward those contractors who place a priority on worker health and safety (which could impact production) and penalize those who don’t. Thus far, unfortunately, the industry seems to have followed the opposite philosophy.

So, how can tree planters increase productivity? As so often happens with research, the answer appears obvious (work harder) while the explanation remains elusive. But, for now at least, acquiring the skills to increase pay appears to require a lengthy and often painful apprenticeship in the bush repeatedly turning soil with the business end of a shovel.

References:

1. Bassett DR and Howley ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Medicine and Science in Sports and Exercise, 32:70-84, 2000.

2. Fox EL and Costill DL. Estimated cardiorespiratory response during marathon running. Archives of Environmental Health, 24:316-324, 1972.

3. Hodges ANH, Ellis JD, and McKenzie DC. The Effects of 10 Weeks of Reforestation Work on Body Composition. Wilderness and Environmental Medicine, 16:3-8, 2005.

4. Hodges ANH and Kennedy MD. Physical exertion and working efficiency of reforestation workers. Journal of Occupational Medicine and Toxicology, 6:20, 2011.

5. McArdle WD, Katch FI, and Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance (7^th ed.). Lippincott Williams & Wilkins, Philadelphia, PA. 2010.

6. Roberts D. In-season physiological and biochemical status of reforestation workers. Journal of Occupational and Environmental Medicine, 44:559-567, 2002.

7. Robinson DG, Trites DG, and Banister EW. Physiological effects of work stress and pesticide exposure in tree planting by British Columbia silviculture workers. Ergonomics, 36:951-961, 1993.

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

The original publication of our work can be found in the Journal of Occupational Medicine and Toxicology, 2011, 6:20 pages 1-7, and is available as a free PDF download on the internet at: http://www.occup-med.com/content/pdf/1745-6673-6-20.pdf

Dr. Alastair Hodges is an exercise physiologist in the Department of Kinesiology and Physical Education at the University of the Fraser Valley. He worked as a tree planter, crew foreman, and supervisor from 1990 – 2006 in the reforestation industry in Northern British Columbia and Alberta.