Approximately a quarter of Earth's land endures degradation, a detrimental state that can be reversed, leading to the sequestration of substantial atmospheric carbon in the soil. This endeavor simultaneously addresses the needs of millions, enhances wildlife habitat, and augments water availability. Leveraging existing commitments such as the Bonn Challenge and New York Declaration on Forests, it is postulated that 161.36 -- 230.77 million hectares of degraded tropical land could be rejuvenated into thriving forests. Natural regrowth has the potential to sequester 1.4 metric tons of carbon dioxide equivalent greenhouse gases per acre annually, culminating in an impressive 54.45 -- 85.14 gigatons by 2050. The United Nations underscores that the restoration of 350 million hectares of degraded ecosystems by 2030 could eliminate 13 to 26 gigatons of greenhouse gases from the atmosphere.

Tropical forests have endured decades of relentless clearing, fragmentation, degradation, and biodiversity loss. These forests are critical reservoirs of carbon, with trees, vegetation, soil, and leaf litter absorbing and retaining significant quantities of this vital element. Restoration is widely recognized as a potent avenue for climate change mitigation, provided it is executed on a grand scale.

The Tropical Forest Restoration solution pertains to the restoration and safeguarding of tropical forests. It involves the rehabilitation of degraded forests within tropical regions, replacing the previously deteriorated ecosystem with one that thrives.

The mechanics of restoration are multifaceted, ranging from simple natural regrowth following the cessation of non-forest land use activities, to more intensive strategies. Protective measures may be instituted to shield the newly regenerating forests from potential threats like fire, erosion, or overgrazing. In more intensive cases, native seedlings are cultivated and planted, invasive species are removed to expedite ecological recovery and ensure legal protection to prevent future degradation.

Tropical forest regrowth is renowned for its rapidity, leading to remarkable rates of carbon sequestration. Importantly, it offers a plethora of co-benefits, such as biodiversity conservation, protection of watersheds, soil preservation, resilience against pests and diseases, as well as the provision of food, medicine, fiber, and housing. Moreover, it serves as a hub for adventure and spiritual nourishment.

To avoid duplication, Drawdown's integration model assigns land area among the various solutions within the sector. This model categorizes global land areas into agro-ecological zones based on land cover, soil quality, and slope, designating them into thermal moisture regimes. Zones are further categorized as "degraded" or "non-degraded." Solutions are then allocated to these zones in order of suitability, with the most appropriate solution receiving priority. The total land area is assumed to remain constant, representing both the area of implementation and its functional unit.

For the purpose of this model, 287 million hectares of degraded tropical forests have been allocated for tropical forest restoration.

Future tropical forest restoration was calculated based on targets from the New York Declaration of Forests, which commits to reforesting 350 million hectares by 2030. Additional estimates from the World Resources Institute suggest that 304 million hectares of land are available for widespread restoration.

Ten custom adoption scenarios were formulated, incorporating current and potential restoration commitments, the proportion of committed land restored to intact forest, and the year commitments are realized (2030, 2045, or 2060). The impacts of increased adoption were calculated for the period from 2020 to 2050, with a reference scenario where the market share remained at current levels.

The scenario assumes the restoration of 161.36 million hectares (56% of available land), sequestering 54.45 gigatons of carbon dioxide equivalent emissions by 2050. Financial impacts were not modeled.

Austin et al. (2020), however, did monitor the financial impact. Using the Global Timber Model, they project mitigation potential and costs for four abatement activities across 16 regions for carbon price scenarios of $5–$100/tCO2. They project 0.6–6.0 GtCO2 yr−1 in global mitigation by 2055 at costs of 2–393 billion USD yr−1, with avoided tropical deforestation comprising 30–54% of total mitigation. Higher prices incentivize larger mitigation proportions via rotation and forest management activities in temperate and boreal biomes. Forest area increases 415–875 Mha relative to the baseline by 2055 at prices $35–$100/tCO2, with intensive plantations comprising <7% of this increase. Mitigation costs borne by private land managers comprise less than one-quarter of total costs. For forests to contribute ~10% of mitigation needed to limit global warming to 1.5 °C, carbon prices will need to reach $281/tCO2 in 2055.

As further data becomes available on soil carbon sequestration in tropical forest restoration, the sequestration rate, and thus mitigation impact, is anticipated to increase. The inclusion of economic aspects, such as costs borne by governments and non-governmental organizations, will be valuable in future updates. Additionally, new benchmarks should be incorporated as they become available.

In light of its enormous sequestration potential and numerous co-benefits, tropical forest restoration is deemed an immensely high priority in the global effort to combat climate change.

Individuals can actively contribute to tropical forest restoration by supporting organizations and initiatives that undertake these critical projects. Donations, volunteering, and advocacy for large-scale restoration efforts are powerful ways to become involved in this essential endeavor.

References.
Griscolm, B., et al. (2017). Natural Climate Solutions. Proceedings of the National Academy of Sciences, 114(44) 11645-11650. DOI: 10.1073/pnas.1710465114.

Defining the Real Cost of Restoring Forests: Practical steps towards improving cost estimates. https://trilliontrees.org/wp-content/uploads/2022/08/Trillion-Trees_Defining-the-real-cost-of-restoring-forests.pdf

Austin, K.G., Baker, J.S., Sohngen, B.L. et al. The economic costs of planting, preserving, and managing the world’s forests to mitigate climate change. Nat Commun 11, 5946 (2020). https://doi.org/10.1038/s41467-020-19578-z