Practical Guidelines Aid in Setting Global Restoration Targets in the Lowland Most Tropics
Brancalion, P. H., A. Niamir, E. Broadbent, R. Crouzeilles, F. S. Barros, A. M. Almeyda Zambrano, A. Baccini, J. Aronson, S. Goetz, J. L. Reid, B. B. N. Strassburg, S. Wilson, and R. L. Chazdon. 2019. Global restoration opportunities in tropical rainforest landscapes. Science Advances 5:eaav3223.
Less than half of the world’s tropical forests remain standing today. The previous forests performed many functions simultaneously: they stored large amounts of carbon in forest biomass and soils, they provided habitats and migration routes for species, they provided food, fiber, and fuel for local people; purified and regulated water supplies, and improved air quality. In planning where and how these forests can be restored, multiple factors must be considered. Globally, the need to bring back forests in deforested areas far exceeds the human and financial resources available and conflicts with global needs for crop and forestry production. Where should restoration interventions focus on restoring forests, and where should previously deforested land be used for producing food in a more sustainable way?
This study shines a spotlight on places where reforestation could provide high levels of social and environmental benefits and where these efforts are expected to be most feasible. We examine the distribution of restoration opportunities globally across the tropical lowland moist broadleaf forest biome by computing a restoration opportunity score (ROS) at 1-km resolution with equal weighting of benefits and feasibility. Four variables were selected to assess restoration benefits: biodiversity conservation, climate change mitigation, climate change adaptation, and human water security. For restoration feasibility, we include three variables: land opportunity costs, ecological uncertainty of restoration success, and restoration persistence chance.
Overlaying these global coverages showed that restoration hotspots (areas with ROS≥ 0.6) encompassed 11.8% of the total restoration opportunity (101 Million ha; larger than Spain and Sweden combined), confirming that restoration can have long-lasting successful outcomes across large areas of the moist tropics. The top six countries with the highest mean ROS were found in Africa: Rwanda, Uganda, Burundi, Togo, South Sudan, and Madagascar. The study highlights the high potential for successful forest restoration outcomes in these African countries. Brazil, Indonesia, India, Madagascar, and Colombia are the five countries with the largest hotspot areas.
Most restoration hotspots were within Biodiversity Conservation Hotspots (88.6%) and within countries with Bonn Challenge commitments (73.0%). Only a small proportion of the restorable area within Key Biodiversity Areas were restoration hotspots (19.1%). This finding makes sense given the way conservation hotspots and Key Biodiversity Areas are defined and the focus of the Bonn Challenge to restore 350 million ha by 2030. This finding is also very encouraging, as these areas and countries already have political motivation to restore and conserve forests.
The study also demonstrates significant tradeoffs and synergies between restoration benefits and feasibility factors. For example, landscapes where restoration has a high potential to support biodiversity conservation, climate change mitigation and adaptation, and reduce water security risks generally correspond with areas of lower overall feasibility.
A map of standardized restoration opportunity scores for the Philippines. Non-restorable areas (existing forests with >90% cover) are shown in dark gray.
Our analysis goes beyond the simplistic definition of a total area to be restored by exploring what benefits can be obtained and which limitations are likely to be faced by restoring landscapes in different locations, providing guidance for targeting priority areas for forest restoration in lowland moist forest biomes. Concentrating investments of time, money, and effort in areas with higher potential return of benefits and feasibility of restoration would maximize the potential of restoration to repair anthropogenic impacts and offer a better future for all.
The PARTNERS Connection
The idea for this project originated with Pedro Brancalion. The project began within an initial planning session at the second PARTNERS workshop in October 2015, followed by a full workshop in Piracicaba, Brazil in 2016. Additional co-authors were included to accomplish all of the required data analysis and mapping tasks. In all respects, this paper was made possible by PARTNERS financial and human resources.
(From left: Leandro Tambosi, J. Leighton Reid, Pedro Brancalion, and Robin Chazdon discuss global coverages to use for analysis at the 2nd PARTNERS workshop)