The study was carried out in the tropical natural forest of the Amazon near Manaus, Amazonas, Brazil. Precious Woods Company Ltd. initiated the project to demonstrate the economic viability of sustainable forest management integrated with a wood-processing industry. This, as an alternative to the timber exploitation usually carried out in the Amazon region of Brazil.
The study documents each phase of the environmentally sound forest harvesting system as applied by Precious Woods and compares its efficiency and environmental impacts with those of the traditional logging systems generally used in the Amazon region.
Comparable data on harvesting operations were collected under almost identical conditions. Work and time studies on harvesting activities in both systems and postharvest assessments of environmental impacts were carried out in adjacent cutting units of the project area.
Felling in the traditional way was done by unskilled workers hired only for the single job as is usually done by the companies. Whereas for the extraction phase, the skidder operator already engaged in the skidding phase of the environmentally sound forest harvesting system was assigned to the skidding operation using the traditional process.
The time required for felling a single tree was greater in the environmentally sound forest harvesting system (21.42 min) than in the traditional logging system (17.59 min). But the cubic metre productivity for the environmentally sound forest harvesting system was higher because only the most mature trees of commercial interest are selected to be felled, which results in a higher average utilisable volume per tree felled. For felling in the environmentally sound forest harvesting system, a productivity of 19.76 m³/h workplace time was found, whereas the felling-productivity in the traditional logging system was 17.92 m³/h workplace time.
The productivity of timber extraction is more difficult to compared since there are two extraction activities in the environmentally sound forest harvesting system: first, the pre-skidding phase with a productivity of 31.04 m³/h workplace time and then the skidding phase with a productivity of 65.53 m³/h workplace time. By contrast, the skidding operation is the only timber extraction activity in the traditional logging system. This skidding productivity was 24.90 m³/h workplace time.
The system difference in the average volume per piece is less noteworthy in the extraction phase than in the felling phase. The heaviest stems had to be cut into pieces for pre-skidding by the crawler tractor.
If the cost per cubic metre of saw logs delivered at the landing site for the traditional logging system is 100%, then the comparable cost for the environmentally sound forest harvesting system would amount to 101.5% when recommended system changes are used.
The marked superiority of the environmentally sound forest harvesting system over the traditional logging system is underscored by the results of the assessment of environmental impacts for both systems.
Severe harvesting damage to potential crop trees was found to be more than twice as high with the traditional logging system (51.5%) as compared to the environmentally sound forest harvesting system with 22.2%.
With the environmentally sound forest harvesting system an average area of about 4.5% per cutting unit is affected by forest infrastructure, whereas in the traditional logging system the corresponding value amounts to about 20%.
The disturbance of canopy by tree felling was 10.8% of the area for the environmentally sound forest harvesting system. By contrast, the traditional logging system resulted in created canopy openings of 24.7%.
Investigation of timber losses revealed a potential for improvement in the environmentally sound forest harvesting system, where the total in timber losses came to 3.9% of the utilisable stem volume. The total timber losses for the traditional logging system were more than twice as high at 8.5%.
In summary, the results of the study show that environmentally sound timber harvesting is not necessarily more expensive than timber harvesting done in the traditional way. The advantage easily goes to the environmentally sound forest harvesting system when it comes to meeting other economic, social, and environmental objectives.
The implementation of environmentally sound forest harvesting systems is deemed necessary to produce tropical forest products guided by the principles of sustainable forest management for the benefit of the company, the population as a whole, the consumer, and the environment. The environmentally sound forest harvesting system as applied by Precious Woods is considered a solution that serves the needs of the economy, the natural environment, and social integration policy.
The FAO Model Code of Forest Harvesting Practice is a response to the need for the improvement of standards of utilisation and the substantial reduction of the environmental impacts of timber harvesting. The Model Code has been shown to be useful under the conditions of this case study. It is recommended for general use. However, the specific details of carrying out individual activities of harvesting operations may vary or be adjusted to particular conditions. This indicates that further case studies should be undertaken to develop national, regional, or local codes of practice that will best serve the particular needs of governmental agencies, the private sector, non-governmental organisations, and other constituents.