Fast-growing trees with high biomass production efficiency open up new possibilities for forestry
Updated by Hiroto Toda on June 20, 2025, 10:50 AM JST
Hiroto TODA
Graduate School of Tokyo University of Agriculture and Technology
Professor, Graduate School of Agriculture, Tokyo University of Agriculture and Technology Publications: Practical Guide to Forestry and Forestry, Second Edition, Revised Edition (co-authored, Asakura Shoten, 2024), Forest Balance (co-authored, Tokai University Press, 2012), etc.
The Support Program for the Formation of a Place for Co-Creation led by TUAT is promoting the "Carbon Cultivation Center to Challenge the Limits of Carbon Negativity". This project aims to fix carbon dioxide (CO2) released into the atmosphere from fossil resources through photosynthesis in agriculture, forestry, and other fields, and to effectively use and store that carbon. Here, as one of the research subjects, we introduce the possibility of new forestry using fast-growing trees with high biomass production efficiency.
More than 60% of Japan's planted forests are over 50 years old, and reforestation after logging has become a major issue as the main harvesting season approaches. Cedar, cypress, and larch, Japan's main forestry tree species, take more than 30 years to grow, even during the short harvesting season. We are exploring the possibility of converting some of these species to fast-growing trees to achieve more efficient forestry and carbon fixation.
According to the Global Forest Resources Assessment 2020 (FRA2020), the world's forested area is about 4.06 billion ha (31% of land area), 45% of which is distributed in the tropics. The global deforestation area has increased from 15.8 million ha/year (1990-2000) to 10.97 million ha/year (2010-2020), and the net deceleration of forest area, after subtracting the increase in forest area due to afforestation, is slowing from 7.84 million ha/year (1990-2000) to 4.74 million ha/year (2010-2020). The decrease in forest area is more than 90% of the total. More than 90% of the decline in forest area is occurring in the tropics, while the increase is greater in China, Australia, India, and other countries.
FRA2020 classifies planted forests into "plantations" and "other planted forests," with "plantations" being intensively managed plantations consisting of a single species or two species, of the same age, uniformly spaced, and planted primarily for production. Plantations" are defined as intensively managed plantations consisting of a single tree species or two tree species, of the same age, with uniform spacing, and planted primarily for production activities. On the other hand, "other planted forests" are those that are not intensively managed and are intended for functions such as ecosystem restoration and water and soil conservation. Plantations cover an area of 131 million hectares, accounting for 3% of all forests and 45% of all planted forests.
CO2 emissions from deforestation and other land use changes account for 10-20% of annual greenhouse gas emissions. Since most of these emissions occur in tropical forests, the international framework "Reducing Emissions from Deforestation and Forest Degradation in Developing Countries and Enhancing Forest Conservation, Sustainable Forest Management, and Forest Carbon stocks" (REDD+ from the English acronym) is an important initiative to curb these emissions.
In plantations, promoting efficient forestry management to support the local economy will help conserve valuable primary and natural tropical forests from logging and development, and reduce greenhouse gas emissions. Early harvesting of fast-growing trees is significant in implementing efficient forestry management in an area that is very small in relation to the total forest area.
Fast-growing trees are fast-growing trees, typically tropical species. When fast-growing forestry is defined as plantations with an average annual volume growth rate of 15 cubic meters/ha or more, harvested within 20 years of planting, it is estimated that in 2000 there were approximately 10 million hectares of fast-growing forested areas worldwide, with an annual growth rate of 1 million hectares. This includes approximately 6.4 million ha of eucalyptus, 1.4 million ha of acacia, and 1.2 million ha of pohla, pine, and other tree species combined (Iwasaki et al., 2012).
While the world's planted forest area of fast-growing trees is approximately 10 million hectares, the world's plantation area is 13 times that amount, and Japan's planted forest area is 10 million hectares. Therefore, it is necessary to conduct forestry management with a clear understanding of the gains and losses involved.
The annual average lumber volume growth of Japanese cedar, a typical Japanese plantation species, is about 10 cubic meters/ha, and 18 cubic meters/ha for elite trees, which are selected for their very good growth. In Japan, the potential for afforestation with eucalypts, kouyouzan, kendan, and willow trees is also attracting attention.
The average annual volume growth of the world's most commonly planted eucalypts ranges from 40 to 60 cubic meters per hectare in good sites, with koyozan (Eupatorium japonicum) and willow (Salix spp.) growing at 20 to 30 cubic meters per hectare and 25 cubic meters per hectare, respectively. Cendus species grow at a rate of 10 cubic meters per hectare, and although each tree grows quickly, the canopy spread and density is kept low, resulting in a smaller volume growth per hectare.
Advantages of short-season forestry using fast-growing trees include the following
Reduced undercutting, low-density planting, etc.
The cost of reforestation for the next generation can be reduced if the trees have good sprouting ability.
High economic cycle can be expected due to early recovery of funds invested in afforestation.
New income opportunities will be created in the region, leading to the revitalization of forest utilization and the forestry industry as a whole.
New sources of hardwood raw materials, laminated wood, plywood, pulpwood, energy materials, etc., which are in short supply.
The use of forest resources as a renewable material and energy alternative to petrochemicals will be promoted in order to become carbon neutral.
Since energy use (fuel) alone is not economically viable or effective for carbon neutrality, it is important that the Japanese fast-growing forestry industry be able to use the wood in a variety of ways, i.e., the species and characteristics of the wood can be used as lumber and plywood.
In addition, it is necessary to find a simple and cost-effective system to improve planting density, efficiency of operations, and the production of straight, nearly cylindrical trunks that are suitable for felling, collection, and commercialization. Of course, it is essential to select a site (zoning) that is suitable for fast-growing forestry and does not impair the public benefit function of the forest, which will be discussed later. ＝(Hiroto Toda, Professor, Graduate School of Agriculture, Tokyo University of Agriculture and Technology)
■References
FAO (2020) Global Forest Resources Assessment 2020: Main report. Rome. 165pp.
Iwasaki, M., Saka, S., Fujima, G., Hayashi, T., Matsumura, J., Murata, K. (eds.) (2012) Fast-growing trees. Industrial Afforestation and its Utilization, KAISEISHA. 259pp.
