As the race to save the world’s biodiversity rages on, we are becoming acutely aware of the need for ecosystem restoration. However, a clear framework for restoring coral reefs is lacking. Could the ‘golden rules’ of reforestation help
these vital marine ecosystems thrive?
Healthy coral reef cover has declined by up to half since 1950, due to human activities such as overfishing, coastal development and fertiliser runoff. As the value of their ecosystem services is estimated to be in the trillion dollar
range, it is clear we need to not only protect the remaining reefs, but restore what we have lost. Yet, the same vulnerability to environmental conditions that are killing them off makes them hard to restore.
The challenge of preventing ecological collapse worldwide is enormous, given the innate complexity of living systems. It requires funding, scientific know-how and international cooperation. Investments in ecosystem restoration are growing,
yet we lack a clear framework for scalable restoration in many habitats, and time is running out.
Learning from mistakes
Back on land, we can look at very different terrestrial ecosystems that need our attention: forests. Forests are easier to access and study than coral reefs, so we can draw inspiration from successful large-scale reforestation attempts, as
well as learn from attempts that have failed.
The complex, layered, and resilient structures of forests contain tremendous amounts of biodiversity. Their importance, public support and perceived ease have made reforestation initiatives extremely popular. After all, if the problem is
cutting down trees, the solution is as simple as planting more, right?
Several ambitious initiatives with this mindset have failed to meet their goals and some have even further damaged the environment. From the destruction of non-forest ecosystems resulting in lost biodiversity, to decreased albedo
(reflective surface) in boreal forests resulting in increased temperatures, and a reduction in pollinator services, even projects with strong scientific backing can fail to take all factors into account.
Simultaneously, scientific advancements and political gains in the fight against deforestation facilitate goals that would have been impossible 30 years ago.
How is any of this relevant to corals?
Despite the obvious differences, forests, especially rainforests, have significant similarities with coral reefs. Both are diverse, layered ecosystems that rely on either trees or corals as both primary producers and main habitat builders.
Both house a disproportionately large quantity of species compared to the areas they occupy. Both are adapted to low-nutrient conditions and suffer from the pressure of human activity.
And both can be saved and restored.
The 10 golden rules of reforestation and applying them to corals
Based on knowledge accumulated by trial and error, and local and indigenous experience, Di Sacco and Hardwood et al. (2021) formulated 10 rules for reforestation. Designed to maximize carbon sequestration, biodiversity recovery and
livelihood benefits, the first five golden rules are:
1. Protect existing forests first
Protecting existing forests is overall easier, less resource intensive and better for biodiversity and ecosystem services than reforestation. A new forest can take more than a hundred years for its ecosystem services to reach the same level
as those provided by an old-growth one. Established practices suggest restoration as the last resort of ecosystem management.
Multiple goals have been formulated as part of international initiatives, such as the United Nations-sponsored New York Declaration on Forestry. This aimed to reduce deforestation by 50% by 2020 and was signed by 37 national governments
along with multinational companies, NGOs and groups representing indigenous peoples. Despite this relatively wide support, none of its goals were met.
Similarly, while due to raising public awareness no politician or company is likely to say they are ‘pro killing corals’, coral cover has been steadily declining. Worryingly, this loss of established, natural ecosystems and their functions
is unlikely to be fully compensated for by new coral growth.
While some coral restoration efforts are showing signs of success such as increases in structural complexity and coral cover, the long-term effects are unclear. Protection of existing reefs using enforceable, binding agreements needs to be
the highest priority.
2. Work together, involving all stakeholders
When it comes to reforestation, there are always multiple stakeholders, sometimes with competing interests. From environmental NGOs to smallholder farmers, there is an a need to balance everyone’s needs to achieve the goals of biodiversity
conservation, carbon sequestration and enhanced rural livelihoods. Thus, it is necessary to involve the affected communities throughout the entire project, from planning to delivery.
In the case of coral reefs, stakeholders can include traditional owners and indigenous peoples, NGOs, local government, developers, and tourist associations. Focusing on creating links and networks minimises conflict and facilitates access
to unique local knowledge and experience.
This also builds social infrastructure, instils education and stewardship as values, and can assist in data collection and policy enforcement. It creates trust in science, ensures cost-effectiveness, and can economically benefit the local
community. Global research and investment must be driven by the needs, knowledge and experiences of the people closest to the reefs to ensure successful long-term restoration.
3. Aim to maximise biodiversity recovery to meet multiple goals
Restoration helps ensure humanity’s access to several vital ecosystem services. Results are often influenced by which particular benefit is the overall goal of such efforts. By focusing on achieving high levels of biodiversity, biomass, and
ecosystem services, this can be accomplished.
While certain factors might make it impossible to completely mimic the species composition of the original forest, we can still aim to introduce other native species to avoid further damage to local species.
With corals, biodiversity ensures the most ecosystem resilience, which in turn sustainably protects a whole host of other ecological and socioeconomic benefits. Biodiversity must be maintained on all levels and scales.
For example, phenotypic diversity—the variation in traits due to both genetic and environmental factors—within the reef ensures a range of functional groups and growth forms. Diversity in the reef community maximises structural complexity
and provides habitats and refuge for fish, while genetic diversity within a single species can sustain sexual reproduction and prevent extinction.
4. Select appropriate areas for restoration
On land, this tip refers to ensuring the areas chosen not only provide the best ecological benefits but are also socially, economically and practically feasible to restore. This includes choosing land which connects or expands existing
forest and avoiding previously non-forested land.
It is also important to consider whether reforestation is likely to displace agricultural and forestry industry activities and thus cause deforestation elsewhere, also known as leakage.
Establishing forests in areas where there previously were none, such as grasslands or peatlands, can result in a net loss of carbon sequestration capacity and biodiversity. If the area is already facing water stress, trees can reduce river
flow and groundwater, resulting in negative consequences for both the newborn ecosystem and local people.
Similarly, not all reefs are fit for restoration. To ensure resiliency, restoration sites should be picked using quantitative data surrounding their biodiversity and capacity to recover. Reefs beneficial to human communities (such as those
tied to indigenous fisheries or tourist resorts) make for more financially viable restoration projects.
5. Use natural regeneration wherever possible
Under suitable conditions, natural regeneration can be cheaper and more effective than direct human intervention (such as tree planting). Natural regeneration has different levels of human interaction, including the hands-off passive
restoration approach, protection from further damage such as grazing or fires, enrichment of naturally regenerated forests by planting missing species or clearing weeds around naturally regenerating areas.
Similarly, natural regeneration can be a vital pathway to reef restoration. Low or intermediate intervention approaches can be used to reduce external acute and chronic stressors and in turn, facilitate healing. By focusing on nature-based
restoration, natural capital is used to its full capacity and issues associated with artificial selection are avoided. These issues include biases favouring growth speed over resilience, and low genetic diversity.
Moreover, by focusing on natural regeneration as a goal, it becomes easier to track progress and, through monitoring, identify what impedes it, and by extension what threatens reef health. This allows targeting of the most immediate issues,
thus increasing efficiency.
Featured Image: Renata Romeo | Ocean Image Bank
HBetts R.A. (2000) Offset of the potential carbon sink from boreal forestation by decreases in surface albedo. NatureVolume 408, Issue 6809, Pages 187-190.
Bloomfield G., Meli P., Brancalion P.H.S., et al (2019) Strategic insights for capacity development on forest landscape restoration: Implications for addressing global commitments. Tropical Conservation Science.Volume 12, Pages 1-11.
Boissière M., Herold M., Atmadja S., et al. (2017) The feasibility of local participation in Measuring, Reporting and Verification (PMRV) for REDD+. PLoS One. Volume 12, Issue 5, Pages 1-9.
Bond W.J., Stevens N., Midgley G.F., et al. (2019) The trouble with trees: Afforestation plans for Africa. Trends in Ecology & Evolution. Volume 34, Issue 11, Pages 963-965.
Brancalion P.H.S., Lamb D., Ceccon E., et al. (2017) Using markets to leverage investment in forest and landscape restoration in the tropics. Forest Policy and Economics. Volume 85, Issue 1, Pages 103-113.
Chazdon R.L. and Brancalion P.H.S. (2019) Restoring forests as a means to many ends: An urgent need to replenish tree canopy cover calls for holistic approaches. Science. Volume 365, Issue 6448, Pages 24-25.
Chen J. (2016) The Unity of Science and Economics. Springer Science+Business Media New York.Page 125.
Cinner J., Huchery C., MacNeil M., et al. (2016) Bright spots among the world’s coral reefs. NatureVolume 535, Issue 7612, Pages 416-419.
Condie S.A., Anthony K.R.N., Babcock R.C., et al. (2021) Large-scale interventions may delay decline of the Great Barrier Reef. Royal Society Open ScienceVolume 8, Issue 4, Article number 201296.
Costanza R., de Groot R., Sutton P., et al. (2014) Changes in the global value of ecosystem services. Global Environmental Change.Volume 26, Issue 1, Pages 152-158.
Crouzeilles R., Barros F.S.M., Molin P.G., et al. (2019) A new approach to map landscape variation in forest restoration success in tropical and temperate forest biomes. Journal of Applied Ecology.Volume 56, Issue 12, Pages 2675-2686.
Di Sacco A., Hardwick K.A., Blakesley D., et al. (2021) Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood. Global Change Biology.Volume 27, Issue 7, Pages 1328-1348.
Donavan M.K., Burkepile D.E., Kratochwill C., et al. (2021) Local conditions magnify coral loss after marine heatwaves. ScienceVolume 372, Issue 6545, Pages 977-980.
Eddy T.D., Lam V.W.Y, Reygondeau G., et al. (2021) Global decline in capacity of coral reefs to provide ecosystem services. One Earth. Volume 4, Issue 9, Pages 1278-1285.
Elliott S., Blakesley D. and Hardwick K. (2013) Restoring tropical forests: A practical guide. Royal Botanic Gardens, Kew. Pages 1-344.
Gann G.D., McDonald T., Walder B., et al. (2019) International principles and standards for the practice of ecological restoration. Second edition. Restoration Ecology. olume 27, Issue S1, pages S1-S46.
Global Coral Reef Monitoring Network (2021) ‘The Sixth Status of Corals of the World: 2020’. Global Coral Reef Monitoring Network.
Available at: https://gcrmn.net/2020-report/[Accessed October 5th, 2021]
Hughes T., Barnes M., Bellwood D., et al. (2017) Coral reefs in the Anthropocene. NatureVolume 546, Issue 7656, Pages 82-90.
Kittinger J.N., Bambico T.M., Minton D., et al. (2016) Restoring ecosystems, restoring community: Socioeconomic and cultural dimensions of a community-based coral reef restoration project. Regional Environmental Change.Volume 16, Pages 301-313.
León-Lobos P., Way M., Aranda P.D., et al. (2012) The role of ex situ seed banks in the conservation of plant diversity and in ecological restoration in Latin America. Plant Ecology & Diversity.Volume 5, Issue 2, Pages 245-258.
Lewis S.L., Wheeler C.E., Mitchard E.T.A., et al. (2019) Regenerate natural forests to store carbon. Nature.Volume 568, Pages 25-28.
Madin J.S., McWilliam M., Quigley K., et al. (2021) Selecting species for restoration in foundational assemblages. bioRxiv.
Meyfroidt P., Rudel T.K. and Lambin E.F. (2010) Forest transitions, trade, and the global displacement of land use. Proceedings of the National Academy of Science.Volume 108, Issue 49, Pages 20917-20922.