Loss of tropical forests accelerated greatly during the mid-20th century and continues today. More than half of the world’s tropical forests have been cleared, fragmented or heavily transformed, leading to species loss and reduction in multiple ecosystem services. Between 1981 and 2003, 28% of the land in the tropics experienced some form of degradation compared with 16% for the rest of the world. Despite declines in extreme poverty worldwide, more than two-thirds of the poorest people in the world live in the tropics. The concentration of poverty and land degradation in the tropics calls for a sustained, multi-sectoral focus on large-scale restoration of tropical forests and landscapes for conserving biodiversity, mitigating climate change and providing sustainable livelihoods. Forest restoration is therefore a key approach for alleviating impoverishment of people and nature.
Here, I provide an overview of advances and challenges in large-scale forest restoration in the tropics. Most of these advances have taken place during the past ten years. The overview focuses on advances and challenges in three arenas of activity; each arena involves different actors, different types of institutions, and different modes of action (Figure 1). I also discuss the critical need for actions and institutions that link these three arenas more effectively.

Figure 1. The three arenas of forest restoration and their intersections.

In the “theory” arena are social and natural scientists; they conduct research on restoration opportunities, approaches, and biophysical and social outcomes. Researchers predominantly work within academic institutions, but also within government agencies and non-governmental organizations.
In the “policy” arena are decision-makers at different levels of government who determine restoration targets and objectives, seek and allocate funding and other sources of support for forest restoration, and make policies and regulations regarding how to incentivise and promote forest restoration in different regions. Decision-makers can also be leaders of local communities that influence land-use decisions and regulate activities.

In the “practice” arena are practitioners who work on the ground to engage stakeholders, plan restoration interventions, and implement and monitor them. Practitioners can work within government agencies or non-governmental organizations and may work closely with the private sector to raise funds and develop supply chains (seeds, seedlings, or technical expertise) and value chains (products for local or commercial use) to promote and sustain forest restoration. Practitioners can also include community-based groups that implement forest restoration and monitoring.
In the middle of this triangle is the process of forest restoration, which involves civil society and the environment – locally, regionally, and globally.

Advances and challenges in theory, concepts, and scientific understanding

The scientific understanding of forest restoration in tropical regions has advanced in several dimensions. A narrow focus on restoring forest structure and diversity to the condition of a “reference forest” is shifting to more holistic perspectives that incorporate concepts of complex systems, resilience, and landscape principles. Forest restoration is now envisioned as part a “continuum” of activities that take place within landscapes, ranging from remediation and recuperation to rehabilitation and ecological restoration interventions.


Forest degradation and restoration processes are linked though several common components. Recovery debt is effectively the cost of lost ecosystem functions, services, biodiversity, or other attributes due to degradation processes over time. Restoration actions strive to recover those lost properties, but the greater the extent or duration of degradation, the higher is the recovery debt to be “repaid” through restoration processes. Further, new research is providing a more nuanced understanding of how climate, rates of tree growth and mortality, and tree succession influence tropical forest recovery and variation in temporal patterns.
Yet we still face major challenges in theory, concepts, and scientific understanding. Scientists grapple with how to define and measure degradation and how to identify restoration opportunities at different scales. Unavoidable trade-offs between different restoration objectives (carbon storage, water flows, biodiversity conservation, livelihoods, and implementation cost) are challenging to quantify. Yet, there is a need to understand how multiple objectives can be achieved with minimal cost within different landscapes or regions. It is rarely possible to maximize all of the benefits of forest restoration in particular locations, so compromise solutions need to be proposed. But we lack detailed knowledge of how different types of restoration interventions influence the supply and quality of ecosystem goods and services over time and how they actually benefit local communities. The evidence for the outcomes of forest restoration within landscapes and regions remains largely anecdotal.

Advances and challenges in policy

Several important advances in policy have propelled forest restoration to a high global priority, including incorporation into three multilateral treaties: Convention on Biological Diversity (CBD), United Nations Framework Convention on Climate Change (UNFCCC), and the United Nations Convention to Combat Desertification (UNCCD). Ambitious global targets established by the Bonn Challenge and the New York Declaration on Forests call for restoration of 150 million hectares by 2020 and 350 million hectares by 2030, respectively.
Since 2011, 45 countries have committed to restore a total of 160 million hectares, and new country-level commitments are rapidly growing. These global restoration targets are based on forest landscape restoration principles and support the Aichi Targets of the CBD and the United Nations Sustainable Development Goals. Regional initiatives are promoting national-level Bonn Challenge commitments in Latin America (Initiative 20×20), Africa (AFR100), and Asia-Pacific (FAO Asia-Pacific Forestry Commission). National policies to incentivise forest restoration on private land are being implemented in Brazil, USA, Costa Rica, and Vietnam and on communal or state land in China and Philippines.
Despite this international momentum, many countries have yet to acknowledge the need to restore their deforested and degraded forests and landscapes. Even in countries that have made restoration commitments, lack of land tenure or forest-use rights impede progress with forest restoration, as farmers cannot obtain economic benefits from restoring trees or forests if they lack these rights. Large-scale monoculture forestry plantations restrict land access for local communities and can worsen environmental degradation. A major challenge is to integrate forestry, agriculture, and conservation sectors in forest restoration activities. Finally, while restoration activities in one area, region, or country may increase forest cover and ecosystem services, these gains may be causally linked to deforestation and forest degradation in other areas. Avoiding this type of leakage is a major challenge, as it requires a holistic assessment of the impacts of forest restoration on land use and deforestation outside of target areas.

Advances and challenges in practice

In the Atlantic Forest region of Brazil, forest restoration has become a growth industry, with investments in supply chains and nurseries that raise hundreds of species of native tree seedlings. Multi-stakeholder partnerships (researchers, different branches of government, businesses, and landowners) such as the Atlantic Forest Restoration Pact in Brazil are forging new public-private partnerships, and enhancing capacity building and broad societal and political support for forest restoration. Species and genetic diversity of seedlings and nursery practices are also increasing in many areas. A broad range of restoration interventions are being widely adopted in dryland areas in Sub-Saharan Africa that are improving land management, water availability, and generating higher incomes for farmers. Overall, forest restoration interventions are being planned and implemented with greater levels of stakeholder engagement, including participatory monitoring.
However, forest restoration practice still has major challenges. Many projects are short-lived and ineffective. It is critical to understand how to sustain the longevity and financial support of forest restoration projects. Sometimes, less costly approaches based on natural regeneration can meet restoration objectives better, and it is important to identify when this is the case. Climate change poses enormous challenges for all land management and conservation activities, including forest restoration. Planning restoration that is resilient to climate change remains a huge challenge both within as well as outside of the tropics.

The importance of integrating theory, practice, and policy for large-scale forest restoration

Despite some progress in each of these sectors, the corners of Figure 1 remain largely disconnected. Far more outreach and interaction across scientists, policy makers, and practitioners is needed to achieve effective, long-lasting, and large-scale forest restoration in tropical regions. Unfortunately, few institutions and organisations support these interactions with sufficient dedication and budgets.

The research-practice or “knowing-doing” gap in forest restoration is well recognised. Many scientists fail to communicate the results of their work to practitioners in effective ways, and many practitioners fail to see the relevance of scientific results in the context of their efforts on the ground. Scientists and practitioners work on different teams and often in different research sites, and their paths rarely cross. However, there is an increasing recognition of the need for a participatory research model. Ideally, local stakeholders should be involved from the very beginning in all aspects of the intervention including study design, data collection, preliminary interpretation of results, and recommendations for future research. Much more progress could be made if practitioners and researchers worked together on the same teams.
Unfortunately, enormous chasms separate science and policy in forest restoration. Scientists and policy-makers seem to differ in every aspect – perspectives, objectives, approaches and vocabulary. Scientists generally shun the need for practicality that is essential in policy-making, and focus on fine distinctions that matter little to policy makers. A common tendency among policy-makers is to equate reforestation with forest restoration, without considering effects on native biodiversity, water resources or forest-based livelihoods. Policy-makers often overlook the potential contribution that natural regeneration of forests can make in large-scale restoration, favouring establishment of tree plantations for economic benefits. Establishing coalitions between policy-makers, scientists, and business sectors can be a starting point for bridging these gaps and creating new approaches to restoration policy that incorporates scientific viewpoints.


Finally, linking policy and practice remains another major frontier area for large-scale forest restoration in the tropics. Although high-level government support is needed for fulfilling many objectives of restoration, the most important level of activity happens within landscapes where practitioners are working with broad and inclusive engagement of local stakeholders. Forest restoration commitments and land-use policy are often generated at the highest government levels and in many cases these policies are disconnected from realities on the ground. Many opportunities for aligning national-scale targets with practice on the ground are not being explored to the full extent possible due to inadequate governance structures and lack of attention on land and use rights. Quality standards and guidelines for good practices are lacking for the broad social and environmental goals of forest and landscape restoration, and are just now being formulated for ecological restoration. In many cases, plantation forestry is disguised as restoration or restoration offsets fail to achieve even their minimal expectations and legal requirements. No system is yet in place to ensure long-lasting, equitable and multiple benefits of restoration for all stakeholders.

Conclusion

Forest restoration is an approach, not a goal in itself. Restoration thinking crosses political, social and economic boundaries, creating a nexus for action and outcomes. But we are not yet there in terms of bringing together the theory, practice, and policy arenas. There is an urgent need to create the time and space for these interactions, and to form local and national institutions that will work effectively toward restoring ecological functions and integrity to forest landscapes. Accountability is needed at multiple levels to ensure that forest restoration achieves broad social and environmental objectives. The role of local governance of restoration at landscape scales deserves more emphasis if forest restoration is to reach the scales needed to ameliorate the devastating effects of deforestation and degradation on people and their environment.

Further reading
Chazdon, R. L., P. H. Brancalion, D. Lamb, L. Laestadius, M. Calmon, and C. Kumar. 2017. A policy-driven knowledge agenda for global forest and landscape restoration. Conservation Letters 10:125-132.
Chazdon, R. L., and M. R. Guariguata. 2016. Natural regeneration as a tool for large-scale forest restoration in the tropics: prospects and challenges Biotropica 48:716-730.
Holl, K. D. 2017b. Restoring tropical forests from the bottom up. Science 355:455-456.
Locatelli, B., C. P. Catterall, P. Imbach, C. Kumar, R. Lasco, E. Marín-Spiotta, B. Mercer, J. S. Powers, N. Schwartz, and M. Uriarte. 2015. Tropical reforestation and climate change: beyond carbon. Restoration Ecology 23:337-343.
Moreno-Mateos, D., E. B. Barbier, P. C. Jones, H. P. Jones, J. Aronson, J. A. López-López, M. L. McCrackin, P. Meli, D. Montoya, and J. M. Rey Benayas. 2017. Anthropogenic ecosystem disturbance and the recovery debt. Nature communications 8:14163.

Robin Chazdon is a retired professor at the University of Connecticut, research professor with the Tropical Forests and People Research Centre at the University of the Sunshine Coast, Australia, and adjunct professor at the University of Colorado.
Sheena Deviah works as an Art Director at a children’s book publisher and enjoys working with her hands while surrounded by her three rowdy cats. She is constantly inspired by nature, both inside and outside.

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