Active restoration is a critical approach to repairing damaged ecosystems and fostering biodiversity. There are several strategies under this umbrella, each tailored to different environmental contexts and restoration goals. As with the three main types of restoration strategies, multiple active restoration strategies might be applied across a landscape, where appropriate based on localized conditions. In this section, we'll explore key active restoration strategies, examining how they work, where they are most effective, and the benefits they offer.
Reforestation/Afforestation: Rebuilding Forests
Description: Reforestation and afforestation involve planting trees to restore or create forests. Reforestation focuses on areas that have lost their historic forest cover, while afforestation creates new forests in areas that were not recently forested but are now suitable for such an ecosystem.
Optimal Use Case: These strategies are ideal for lands lacking forest cover due to deforestation, degradation, or suitable lands never forested.
Species Spatial and Temporal Arrangement: Trees are planted in patterns that consider future growth, canopy structure, and species interactions (potentially including higher early planting densities that help exclude invasive species). Early successional species may be planted first, followed by later successional species to mimic natural forest succession.
On-the-Ground Techniques: Techniques include selecting native species adapted to local conditions, sourcing plant materials from appropriate locations to balance genetic diversity and local adaptation, site preparation to enhance survival rates, protective measures against herbivory, and maintenance to ensure successful establishment.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: Very high, given the direct focus on tree planting. Forests are among the most effective ecosystems for carbon sequestration.
Community Benefits in Carbon Project Context: Reforestation and afforestation enhance biodiversity, support water cycles, and provide sustainable wood resources. They offer immediate financial benefits through labor, with long-term benefits from timber, carbon credits, and improved ecosystem services.
For further reading, please refer to:
- Siyag, P. R. (2013). Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics: A Manual of Technology & Management. Springer Science & Business Media.
Mangrove and Riparian Restoration: Protecting Shorelines & Waterways
Description: Mangrove restoration focuses on stabilizing coastlines by restoring native mangrove ecosystems. Riparian restoration focuses on restoring the interfaces between land and a river or stream. Both aim to restore vegetated buffers along bodies of water to improve ecosystem health and water quality.
Optimal Use Case: This strategy is ideal for coastal or riparian zones impacted by erosion, pollution, or vegetation loss.
Species Spatial and Temporal Arrangement: Native coastal or riparian vegetation is planted in strategic layers from the water's edge to the upland zone, considering the species’ tolerance to water level ranges (seasonal inundation and/or diurnal tides) and their root structures for erosion control. Mangrove restoration also requires species selection and arrangement based on salinity tolerance.
On-the-Ground Techniques: Hydrology studies may be required prior to planting design. Restoration may involve stabilizing streambanks or coastlines with bioengineering methods (e.g., coir logs and erosion control blankets, vegetated geogrids, bamboo structures for soil retention, tidal or drainage channels), planting multi-layered vegetation (canopy, understory, shrub, and ground cover layer), controlling invasive species, and possibly altering hydrological flows to more natural states.
Mangroves can either be planted directly as propagules or by using nursery-grown seedlings, but note that most mangrove seeds are recalcitrant (cannot be stored) and require appropriate handling protocols.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: Mangrove biomes are among the most carbon-rich ecosystems in the tropics. The restoration of these ecosystems is therefore of primary importance for climate change mitigation. Although there is a large amount of variance, they contain an average of 937 tC ha-1. Most mangrove carbon is stored belowground, in the soil and dead roots.
Moderate to high for riparian restoration, depending on the biomass potential of planted species and the restoration of soil organic matter. Riparian zones can be significant carbon sinks, especially when restoring wetlands or peatlands.
Community Benefits in Carbon Project Context: Enhances water quality, coastal protection and flood regulation, directly benefiting agricultural productivity and local water security. Restoration activities can create local employment, while improved ecosystem health supports fisheries and ecotourism, providing sustainable income sources. Immediate financial benefits come from restoration labor, with longer-term benefits from improved agricultural productivity and tourism opportunities.
For further reading please refer to:
- Alongi, D. M. (2012). Carbon sequestration in mangrove forests. Carbon Management, 3(3), 313–322. https://doi.org/10.4155/cmt.12.20
- Harris, R. R. (1999). Defining reference conditions for restoration of riparian plant communities: examples from California, USA. Environmental Management, 24, 55-63.
- Hughes, F. M. R., Colston, A., & Mountford, J. O. (2005). Restoring riparian ecosystems: the challenge of accommodating variability and designing restoration trajectories. Ecology and society, 10(1).
- Teutli-Hernández, C., Herrera-Silveira, J., Cisneros-de la Cruz, D. J., & Román-Cuesta, R. (2020). Mangrove ecological restoration guide: Lessons learned. Mainstreaming Wetlands into the Climate Agenda: A Multilevel Approach (SWAMP). CIFOR/CINVESTAV-IPN/UNAM-Sisal/PMC, p. 42.
Description: Staggered (also called phased, sequential, or stepwise) restoration is a strategic approach where restoration activities are implemented in phases to gradually build ecosystem complexity and resilience. It is a strategic approach to ecological restoration where planting and other restoration activities are spread out over multiple phases or time periods, rather than implemented all at once.
Optimal Use Case: This approach is well-suited for large-scale or complex restoration projects where conditions vary widely across the site or resources are limited. It allows for focused efforts on priority areas first, with subsequent phases expanding restoration efforts based on initial successes and adjustments.
Species Spatial and Temporal Arrangement: Species and interventions are planned in stages, with early-phase species (e.g., pioneer) providing shelter or improving conditions (soil or microclimate for more sensitive species) for later-phase species, culminating in the establishment of a diverse, multi-layered forest structure that mirrors natural forests. Species or techniques are applied depending on the evolving conditions of the site, success of earlier efforts, planting seasons, and growth rates of previously planted species.
On-the-Ground Techniques: Initial activities may include site preparation, planting of pioneer species, and establishment of infrastructure for fire prevention and pest management. Subsequent phases might introduce more shade-tolerant species, structural diversity enhancement, and additional measures for ecosystem function restoration. Monitoring and adaptive management are continuous across all phases to guide adjustments.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: Moderate to high. Phased restoration can optimize carbon sequestration as the ecosystem develops.
Community Benefits in Carbon Project Context: Early phases offer immediate benefits through job creation and improved ecosystem services, such as soil stabilization and water regulation. As the forest matures, additional benefits include enhanced biodiversity, climate regulation through carbon sequestration, and potential revenue from carbon credits. Engaging local communities in the restoration process ensures that benefits align with local needs and support the long-term sustainability of restoration efforts.
For further reading please refer to:
- Dudley, N., & Maginnis, S. (2018). A stepwise approach to increasing ecological complexity in forest landscape restoration. Ecological Restoration, 36(3), 174-176.
- Dyste, J. M., & Valett, H. M. (2019). Assessing stream channel restoration: The phased recovery framework. Restoration Ecology, 27(4), 850-861.
Description: The Framework Species Approach introduces or enhances populations of key species to drive ecosystem processes and recovery. It involves planting carefully selected tree species that can recreate forest conditions conducive to natural regeneration. This method aims to re-establish forest structure and ecosystem processes like nutrient cycling, thereby accelerating biodiversity recovery.
Optimal Use Case: This strategy is particularly effective in degraded ecosystems lacking keystone, foundational, or ecosystem engineer species. It is best applied in areas where substantial forest tracts and remnants still exist, and the goal is to restore biodiversity while requiring fewer inputs than planting all species from the original climax forest (i.e., having some overlap with Assisted Natural Regeneration for non-focal species). It is particularly suitable for restoring damaged tropical rainforests and seasonally dry tropical forests on deforested sites.
Species Spatial and Temporal Arrangement: Key species are introduced in a manner that reflects their natural roles and spatial requirements within the ecosystem. Timing and sequence of introduction consider ecological succession stages and interspecies dependencies. The method involves the strategic selection and planting of 20-30 native, non-domesticated tree species that promote natural forest regeneration mechanisms (chosen for their rapid growth, dense canopies, and early production of resources to attract wildlife). These species are planted in a way that shades out weeds, re-establishes a multi-layered canopy, and improves conditions for seed germination and seedling survival of non-planted species.
On-the-Ground Techniques: Activities include planting the selected framework species (20-30), ideally within a single planting event during the rainy season to facilitate establishment and growth, performing weeding and fertilizer application for the initial years to support the planted trees, and ensuring protection from fire and hunting to preserve the regenerating ecosystem and its seed-dispersing wildlife.
The selected native tree species are planted all at once, rather than in stages, during one coordinated effort. This approach is designed to rapidly initiate the process of ecological restoration, creating a foundation that mimics the diversity and structure of a natural forest. Planting simultaneously helps to establish a variety of tree species that can interact with each other and the environment from the outset, setting the stage for a more dynamic and resilient ecosystem.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: The capacity varies depending on the species introduced and their role in carbon dynamics, but it generally supports significant carbon storage as forests mature.
Community Benefits in Carbon Project Context: Engages local communities in biodiversity conservation, offering educational opportunities and fostering a sense of stewardship. It can also support ecotourism initiatives centered around key species, providing a sustainable source of income.
For further reading, please refer to:
- Elliott, S., Tucker, N. I., Shannon, D. P., & Tiansawat, P. (2023). The framework species method: Harnessing natural regeneration to restore tropical forest ecosystems. Philosophical Transactions of the Royal Society B, 378(1867), 20210073.
- Forest Restoration Research Unit, 2005. How to plant a forest: The principles and practice of restoring tropical forests. Part 5 – The framework species method of forest restoration – page 63. Compiled by S. Elliott, D. Blakesley, J. F. Maxwell, S. Doust, & S. Suwannaratana. Biology Department, Science Faculty, Chiang Mai University, Thailand, 200 pp.
Description: Direct seeding involves sowing seeds directly into the restoration site to regenerate vegetation, bypassing nursery cultivation, but accepting a high rate of seed loss in the field.
Optimal Use Case: This method is suitable for large, inaccessible, or budget-constrained projects needing rapid vegetation cover (such as post-wildfire revegetation), with access to an abundant supply of appropriately sourced seeds. It is often more suitable for grassland restoration than reforestation.
Species Spatial and Temporal Arrangement: Seeds are mixed and sown to create diverse plant communities that mimic natural succession patterns. The timing of seeding is crucial and often aligned with seasonal rainfall patterns for germination success.
On-the-Ground Techniques: Techniques include seed pre-treatments and/or coating for dormancy, water retention, nutrient uptake, etc. This method may also require site preparation to enhance seed-to-soil contact, selecting a diverse seed mix tailored to site conditions, protecting seeded areas from predation, and supplemental watering if necessary.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: High, especially in large-scale reforestation or grassland restoration projects. However, it may depend on mortality rates.
Community Benefits in Carbon Project Context: Direct seeding offers immediate employment opportunities in seed collection, preparation, and sowing activities. The rapid improvement in ground cover helps prevent soil erosion and enhances water retention, supporting local agriculture and livestock grazing.
For further reading, please refer to:
- Camargo, J. L. C., Ferraz, I. D. K., & Imakawa, A. M. (2002). Rehabilitation of degraded areas of central Amazonia using direct sowing of forest tree seeds. Restoration Ecology, 10(4), 636-644.
- Cole, R. J., Holl, K. D., Keene, C. L., & Zahawi, R. A. (2011). Direct seeding of late-successional trees to restore tropical montane forest. Forest Ecology and Management, 261(10), 1590-1597.
- Freitas, M. G., Rodrigues, S. B., Campos-Filho, E. M., do Carmo, G. H. P., da Veiga, J. M., Junqueira, R. G. P., & Vieira, D. L. M. (2019). Evaluating the success of direct seeding for tropical forest restoration over ten years. Forest ecology and management, 438, 224-232.
- Pedrini, S., Balestrazzi, A., Madsen, M. D., Bhalsing, K., Hardegree, S. P., Dixon, K. W., & Kildisheva, O. A. (2020). Seed enhancement: Getting seeds restoration‐ready. Restoration Ecology, 28, S266-S275.
- United Nations Decade on Ecosystem Restoration. (n.d.). Seeds of change: Embracing the muvuca method for biodiversity and social restoration. Retrieved August 14, 2024.
Description: Applied nucleation uses clusters or "islands" of plantings to kickstart ecosystem restoration, attracting seed dispersers and facilitating natural regeneration.
Optimal Use Case: This strategy is effective for degraded lands with natural regeneration potential but lacking seed sources.
Species Spatial and Temporal Arrangement: Clusters or "islands" are planted in strategic locations to maximize ecosystem connectivity and seed dispersal effectiveness. Species selection is based on ecological roles and attractiveness to dispersers. The spatial arrangement aims to optimize interactions with seed dispersers and provide shelter for emerging seedlings. Temporally, planting can be staggered over multiple seasons to mimic natural successional processes and ensure diversity.
On-the-Ground Techniques: Techniques include performing site assessment for optimal cluster placement, choosing native species that fulfill various ecological functions, creation of microhabitats (e.g., brush piles, water sources) to support seed dispersers and pollinators, mulching around planted clusters to retain soil moisture and reduce weed competition, monitoring and adaptive management to address challenges (e.g., invasive species, pest outbreaks around clusters), and periodic evaluation of cluster growth and spread.
Carbon Sequestration Capacity within the Lifetime of a Carbon Project: The capacity is uncertain due to limited research, but it may depend on the species planted and subsequent natural regeneration.
Community Benefits in Carbon Project Context: Applied nucleation offers employment in planting and monitoring, with potential for ecotourism and enhanced ecosystem services that benefit agriculture. While immediate financial benefits may be limited, they can grow over time through ecotourism and potential carbon credits.
For further reading, please refer to:
- Corbin, J. D., & Holl, K. D. (2012). Applied nucleation as a forest restoration strategy. Forest Ecology and Management, 265, 37-46.
- Corbin, J. D., Robinson, G. R., Hafkemeyer, L. M., & Handel, S. N. (2016). A long‐term evaluation of applied nucleation as a strategy to facilitate forest restoration. Ecological Applications, 26(1), 104-114.
- Holl, K. D., Reid, J. L., Cole, R. J., Oviedo‐Brenes, F., Rosales, J. A., & Zahawi, R. A. (2020). Applied nucleation facilitates tropical forest recovery: Lessons learned from a 15‐year study. Journal of Applied Ecology, 57(12), 2316-2328.
- Reis, A., Bechara, F. C., & Tres, D. R. (2010). Nucleation in tropical ecological restoration. Scientia Agricola, 67, 244-250.
- Wilson, S. J., Alexandre, N. S., Holl, K. D., Reid, J. L., Zahawi, R., Celentano, D., Sprenkle-Hyppolite, S., & Werden, L. (2021). Applied nucleation restoration guide for tropical forests. Conservation International.