Summary
Forestry Management means practices to preserve forest ecosystems for particular objectives. In the context of CDR, this means maximizing forest ecosystems capacity to capture and sequester carbon dioxide, rather than for production of timber.
Forest management activities generally include fire control measures, protecting against invasive species, restoring disturbed ecosystems, and sometimes extracting products such as timber or removing undergrowth, and providing various recreational opportunities.
Forest ecosystems are of three main types: boreal, temperate and tropical (1) In 2010, boreal forests covered 11 million km2 (7% of total land area) and stored an average of 24000 tonnes of carbon per square kilometer. Temperate forests covered 8 million km2 (5% of total land) and stored about 15500 tonnes/km2. Tropical forests covered 14 million km2 (9% of total land) and, like boreal forests, stored about 24000 tonnes/km2 - but with a greater proportion (almost 60%) in biomass whereas boreal forests store only about 20% of carbon in biomass. For comparison, worldwide land area in cultivation for food is about 11 million km2 , and grazing land and other animal feed growing occupies about 37 million km2 (2). About 29% of the Earth’s land surface is not readily inhabitable (glaciers and ice, deserts, exposed rock, etc.)
Globally there are about three trillion trees, with about 1.3 trillion in tropical forests, 0.7 trillion in boreal forests, and 0.7 in temperate forests (4). Combining these data, we can estimate tree density in the different forest types to be 67k, 82k and 93k trees per square kilometer for boreal, temperate, and tropical forests respectively. For per-hectare values, divide by 100 - there are 100 hectares per square kilometer.
{is it more efficient in some respect to grow forest biomass and sequester the carbon therein by means such as BECCS or biochar production, or to increase forest area and promote old-growth forests as the primary means of sequestering carbon?}
History
" 1000 years [ago] it is estimated that only 4 million square kilometers – less than 4% of the world’s ice-free and non-barren land area was used for farming." (3). Forests have declined in area by about 46% since the beginning of human civilization (4)
“of the 28,000 species evaluated to be threatened with extinction on the IUCN Red List, agriculture is listed as a threat for 24,000 of them.”
Forms and Variations
The tools of forestry management are various types of tree removals (or “harvesting”) (5).
Thinning of some young trees can help the remaining trees be more healthy and can increase understory vegetation which creates greater habitat diversity.
Clearcutting lets a forest manager choose the type of trees that will regrow, and favors tree species that thrive in full sun as saplings. It also opens area for forest-border habitat that is favored by many forest animal and plant species. It is a cost-efficient way to remove old timber.
Shelterwood harvest is the removal of selected mature trees, to allow saplings languishing in their shade to grow to maturity. Because only the mature trees are removed, the forest biome remains intact.
Seed Tree harvest is like clearcutting, but about 15 trees per hectare are left to reseed the forest (note that in mature tropical forests, the density of many tree species may be less than one per hectare, so this method is not inherently sustainable in the tropics)
Group Selection harvest is small-scale clearcutting. Different harvest area sizes can favor differrent tree species. In temperate forests, all of the trees in the forest under this form of management will be harvested every 40 or 50 years, but the overall maturity of the forest is high.
Single Tree Selection is removal of specific trees whether for commercial use, or because the tree is competing with a desired species or harboring disease. The surrounding forest can be maintained as late-succession or high maturity.
Prescribed Burning is used in forests that have evolved with recurring wildfire. A controlled burn reduces the “fuel load” of forest debris so more intense forest fires are less likely. Prescribed burns also lead to increased understory growth which is favorable wildlife habitat. Some conifer species depend on wildfire for seed dispersal.
Reforestation (regrowing forest) and afforestation (growing new forest), can be “natural” - growing from existing seed stock in an area or from the stumps of harvested trees - or “artificial” - growing from planted seeds and saplings. Although the artificial method is more expensive, it allows for greater control of species selection and initial tree spacing. It is often the only option for afforestation.
Forest management involves an understanding of “succession” - the ecosystem of a forest evolves as the forest ages. The mature forest trees create an environment in their shade that is notably different and supports different species than unforested terrain. As the forest matures, different tree species may dominate, so a young forest may be necessary to provide the habitat for old forest trees to begin growing.
{other CDR approaches related to forestry: BiCRS, BECCS, biochar, Soil Carbon Sequestration, Macroalgae}
Notable Projects
{detailed description of exemplar project(s)}
{policy issues and initiatives related to forestry and CDR}
https://www.science.org/doi/10.1126/science.aax0848 - The Potential for Global Forest Cover. This table describes that potential by biome:
Biome | Canopy Cover (Mha) | Median, 75th
percentile, and 95th percentile tree cover (%) | Carbon density (tC ha–1)
Boreal forests/taiga 178 90,100,100 239.2
Desert and xeric shrublands 77.6 20,65,100(corrected) 202.4
Flooded grasslands and savannas 9 55,100,100 202.4
Mangroves 2.6 100,100,100 282.5
Mediterranean forests, woodlands, and scrub 18.8 55,90,100(corrected) 202.4
Montane grasslands and shrublands 19.3 90,100,100 202.4
Temperate broadleaf and mixed forests 109 100(corrected), 100, 100 154.7
Temperate conifer forests 35.9 100 100 100 154.7
Temperate grasslands, savannas, and shrublands 72.5 80 100 100 154.7
Tropical and subtropical coniferous forests 7.1 100 100 100 282.5
Tropical and subtropical dry broadleaf forests 32.8 100 100 100 282.5
Tropical and subtropical grasslands, savannas, and shrublands 189.5 45 90 100 282.5
Tropical and subtropical moist broadleaf forests 97.1 100 100 100 282.5
Tundra 50.6 80 100 100 239.2
Further Learning
This Is CDR E28 - Future Forests biomass and sequestration approaches
https://www.frontiersin.org/articles/10.3389/ffgc.2021.629198/full - Challenges to the Reforestation Pipeline in the United States
{universities and companies engaged in forestry CDR projects}
{literature and conferences related to forestry CDR}
Forest failure rate issues
{foundations, trusts, and agencies funding forestry-related CDR projects}