Rules for reforestation

Optimising carbon sequestration, biodiversity and social benefits isn't as simple as just planting trees. But there are rules to maximise these benefits.

Photo by Sebastian Unrau on Unsplash

As I’ve previously opined, the rapid climate change we are experiencing and expecting means we need urgent and immediate solutions. One such solution is the widespread planting of trees globally. Ambitious programmes have been launched in recent years, including the one trillion trees programme in support of the United Nations Decade on Ecosystem Restoration.

Trees and forests provide countless benefits to people, like food, medicine, recreational opportunities, water storage, and building materials, not to mention their key role in sequestering carbon.

Well-designed reforestation programmes can help to sequester large amounts of carbon, increase biodiversity, and provide diverse social benefits. There are certainly win-wins to be had here in terms of benefits to biodiversity and climate change mitigation. However, there are also many risks associated with large-scale tree planting programmes. In fact, poorly planned reforestation efforts can actually increase the amount of carbon entering the atmosphere, not to mention the widespread impacts they can have on biodiversity and human wellbeing.

And many current programmes are failing to meet their goals. Much of this failure has been due to the reliance on monocultures of exotic species, like Pinus radiata.

It is fundamentally important to focus on strategies to get the most from restoration efforts, particularly when there is so much at stake in terms of climate change and biodiversity loss.

However, optimising carbon sequestration, biodiversity and social benefits when restoring forests isn't as simple as just planting trees. Instead, careful consideration of a wide number of factors is needed. Thankfully, I recently came across an extremely useful guide to help with this. So this post is me summarising that paper for your benefit. I certainly can’t claim credit for these ideas — I’m simply summarising this excellent paper.

The paper focuses on a ‘native forest approach’ to forest and landscape restoration. This differs from typical monoculture-based forest practices—instead focusing on regaining the functionality of ecosystems, while simultaneously promoting human wellbeing. In this approach, the goal is to increase carbon sequestration and other ecosystem services, promote the recovery of biodiversity, and improve livelihoods.

So, here are “Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits” with my summaries of each rule.

1. Protect existing forests first

Prioritising the conservation of existing forests is crucial as they are already effective carbon sinks and biodiversity reservoirs. There is much more to be gained by protecting current old-growth forests than to start from scratch. In fact, losses of old-growth forests cannot be compensated for easily by reforestation. These are a massive long-term carbon sink because of their complexity, diversity, soil structure and ability to buffer fire and drought. So they are of the highest priority to maintain for their carbon storage capacity among many other benefits. And they could take centuries to return to their previous state. Nonetheless, other existing forest types also need protection.

These protection efforts need to be at multiple levels, from local to national to international. But the first step is to identify the drivers of deforestation.

2. Work together

Collaboration among all stakeholders, including local communities, governments, and organisations, is essential for successful reforestation. Local people need to be part of the project. Project failures can arise when local communities are left out of the equation and when they have conflicting goals to the project managers. To avoid conflicts, local communities need to be involved from the very beginning. When they are and they are informed about the wider benefits of the project, they are more likely to support it and help to deliver the project successfully. Involvement can also provide jobs, diversifying local income streams. But participation needs to be active otherwise conflicts can arise.

3. Aim to maximise biodiversity recovery to meet multiple goals

Reforestation efforts should focus on restoring diverse ecosystems to achieve multiple environmental and social goals. Focusing on restoring biodiversity can provide widespread ecological and socio-economic co-benefits. Reforestation is not the end goal, it is the means to achieving widespread benefits, including climate change mitigation, curbing biodiversity loss, returning critical ecosystem services such as the provision of medicine, and increasing the wellbeing of local communities. Defining such objectives from the outset will benefit the project by helping to plan and monitor progress.

Biodiversity includes not only taxonomic diversity but also the diversity of the functions that species provide. Increasing the diversity of functional traits (e.g. body size, feeding strategy such as processing organic matter or frugivory, reproductive mode, the ability to fix nitrogen) can result in a wider diversity of functions that the ecosystem performs. More diversity also acts as a form of resilience to various shocks because the more species or functions you have, the less likely they’ll all respond to the same stressors (e.g. fire or heatwaves).

However, note, it won’t always be possible, at least in the short term, to restore diversity of forests to their previous levels. Pragmatism is key here, but also understanding that sometimes conditions are irreversible on human timescales.

As I’ve often mentioned in the past, decision making requires understanding tradeoffs. The particular goals of a reforestation project will determine which particular tradeoffs are required. Focusing on landscape-scale restoration will benefit from a variety of approaches and thus local tradeoffs can be accounted for at the landscape scale.

Prioritising native biodiversity in reforestation programmes over fast growing monocultures is important for maximizing carbon capture over long timescales. Fast-growing monocultures produce timber rapidly but much of the captured carbon is released back into the atmosphere upon harvesting.

There are a number of approaches to maximising biodiversity recovery in reforestation, including tree-level (prioritising particular species of tree), ecosystem-level (prioritising the recovery process of the whole ecosystem), and landscape level (prioritising the connectivity of ecosystems across landscapes). The approach will be dependent on the context, such as how much land is available to be reforested.

4. Select appropriate areas for restoration

Identifying the right locations for reforestation ensures that the efforts are ecologically and socially beneficial. It also avoids the widespread negative consequences I’ve already discussed. In particular, it is important to understand historical forest status before beginning any new programme. As I pointed out in a previous post, forests don’t belong in naturally treeless ecosystems. The authors of this paper highlighted a number of useful questions to ask in selecting areas for reforestation: “1. Was the area previously forested and is it now degraded? 2. Has the area been occupied historically by a non-forested biome such as grassland, savanna, non-forested wetland or peatland? 3. What are the wider effects of reforestation in the target area, including impacts on groundwater, biodiversity, climate, ecosystem services and livelihoods? 4. How close is the land to areas of natural forest? 5. Who is currently using the land, how will they be compensated for any income losses and where will they move their activities?” Asking these questions will help to define “no-go zones” for reforestation efforts but also maximise the return on investment.

5. Use natural regeneration wherever possible

Leveraging natural processes can be more effective and sustainable than planting new trees and can lead to much greater carbon capture and biodiversity gains. And, in fact, it can be substantially cheaper. The level of human intervention required will be context dependent, ranging from passive restoration where no intervention is needed through to high intervention where efforts are much more proactive and hands-on. Many factors could determine the level of intervention required. For instance, the condition of soil will determine whether certain species are needed during initial phases to improve soil quality or to outcompete pre-existing weeds.

6. Select species to maximise biodiversity

Choosing a variety of native species helps in creating resilient ecosystems and focusing on key mutualistic partners (e.g. seed dispersers, helpful fungal partners, pollinators) will benefit the establishment of target species. Choosing species with the right functional traits will help to establish target species over weeds. These include species with high survival and growth rates, those able to shade out the understory, and those that attract seed-dispersing animals. Targeting rare, endemic species will need careful planning. There will be times when non-native species can be considered as strategic additions, but the inclusion of invasive non-natives should never occur given the risk they pose to other ecosystems. Finally, the susceptibility of species to localised climate change should always be included in decision making.

7. Use resilient plant material

Ensuring genetic variability and provenance in the plant material increases the resilience of reforested areas. This includes selecting seeds from a number of source individuals, with a general rule being at least 30 individuals from outcrossing species and at least 50 individuals in selfing species. Ideally, seed collection should occur randomly from the full extent of the parent population. This insures rare alleles are captured. Overlooking this can lead to population genetic bottlenecks, lowering resilience, reducing evolutionary potential and leading to inbreeding depression.

8. Plan ahead for infrastructure, capacity and seed supply

Proper planning and resource management are vital for the long-term success of reforestation projects. Standards must be followed for seed quality. Decisions will depend on whether seeds are sourced and raised in house vs. purchasing from reliable suppliers. As part of this process, care must be taken to ensure source populations are not damaged by over-collecting.

9. Learn by doing

Adopting an adaptive management approach allows for continuous learning and improvement in reforestation practices. Restoration should begin by leveraging the best science, including indigenous knowledge. And, most importantly, progress needs to be monitored. All too regularly, restoration efforts are performed and subsequently forgotten about. These are major learning opportunities and ongoing monitoring helps to learn on the job and revise efforts in a continuous, iterative process.

10. Make it pay

Ensuring the economic viability of reforestation projects is crucial for their sustainability and for providing benefits to local communities. The sustainability of reforestation programmes depends on support from local communities, which depends on income streams from the land. There are many ways to monetise and prioritise efforts. However, one that is more difficult to monetise is the service mature forests provide for water supplies. Healthy functioning forests filter water for drinking supplies and mitigate flood risks for downstream communities. These services are a public good that requires governments to fund.

Summary

Remember: Poorly planned reforestation efforts can increase CO₂ emissions, and negatively impact biodiversity and human livelihoods. These guidelines help to avoid these negative impacts and increase the likelihood of forests becoming long-term carbon sinks, while also providing positive co-benefits to biodiversity and human wellbeing.

Many of these efforts are not possible without partnership. From local communities through to national scale governments, multiple stakeholders are involved. Solutions require healthy dialogue and strong governance.

I hope you found this useful. Go check out the paper for expanded details on each rule. It’s a very readable and comprehensive piece of work. I will touch on many of the individual rules in future posts.

Stay tuned for some posts on a couple of conferences I’m attending in the next couple of weeks, including on ecological forecasting and nature-based solutions.

Remember to click the ❤️ button on this post if you enjoyed it to help more people discover it, and share it with your friends. I’d love to hear what you think in the comments!

References

Di Sacco, A., K. A. Hardwick, D. Blakesley, P. H. S. Brancalion, E. Breman, L. Cecilio Rebola, S. Chomba, K. Dixon, S. Elliott, G. Ruyonga, K. Shaw, P. Smith, R. J. Smith, and A. Antonelli. 2021. Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits. Global Change Biology 27:1328–1348. https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15498