Methodology: About the Atlas of Forest Landscape Restoration Opportunity
The Atlas of Forest Landscape Restoration Opportunity was produced by WRI in collaboration with the University of Maryland and IUCN as a contribution to the Global Partnership on Forest Landscape Restoration. The maps in the atlas are presented at a resolution of 1 km.
In creating the maps contained in this atlas, the team sought to answer the following questions: How much of the world’s forest has been lost? Is it realistic to restore forests at a globally meaningful scale? How big are the restoration opportunities and where are they located?
We approached the analysis into two steps. First, we would map how much forest has been lost. Then, we would map the opportunities for forests and trees to return.
How much of the world’s forest has been lost?
To answer the question of how much forest has been lost, we first had to answer the question how much forest would there be if humans hadn’t changed the landscape? An initial thought was to create a map of historical forest extent, but that wouldn't work, since the climate has changed a lot in the ten thousand years since the last ice age and the beginning of the agricultural revolution. We would have to start by mapping where forests would be in today’s climate if it weren't for human influence.
To make this map of potential forest coverage, we combined data on climate, soils, and elevation and maps of current and historical forest extent (FAO, 1999; Bryant et al., 1997; Zomer et al., 2008). Then we derived the composition and density of these potential forests from a map of the world’s terrestrial ecoregions (Olson et al., 2001).
Having established this baseline, we proceeded to map current forest coverage. We used data from MODIS, a satellite-based sensor, to map forest location and tree canopy density (Hansen et al., 2003), which we classified into three types:
Closed forest (canopy density greater than 45 percent);
Open forest (canopy density between 25 and 45 percent); and
Woodlands (sparse, savanna type forest; canopy density between 10 and 25 percent).
By contrasting the maps of potential and current forest coverage, we can identify areas that have been deforested and replaced by other land uses. It is interesting to click back and forth between these two maps in the atlas. The deforested areas of the world are very large and comprise many areas that are seldom thought of as being deforested, given that forests have not existed there for hundreds if not thousands of years. These areas include major portions of China, India, Russia, Europe, United States, and Brazil.
But the human impact on the world’s forests is not limited to deforestation. Some forests have diminished without disappearing completely. These degraded forests are difficult to define and even more difficult to map, as the contrast between what they could be and what they are is not quite as clear. When considering how to map these degraded forests, we decided to define them as forests that exist in a state below their potential density. The reasons for degradation can be because of sustained human influence, such as crop or timber production, grazing, or settlements, but also because of fire or pests.
Many forest areas have also been fragmented by roads or affected by logging without causing a sustained loss in density. These fragmented/managed forests are essentially “working forests” and comprise the remainder of the world’s forests, other than deforested, degraded, and intact forest areas.
The resulting forest condition map shows the current situation in all parts of the world where forests could grow naturally. The map shows four types of forest condition:
Intact: Large blocks of virgin forest (> 50,000 hectares);
Fragmented/managed: Natural forests and woodlands that are fragmented by roads and/or managed for timber production;
Degraded: Forests with reduced density;
Deforested: Formerly forested areas.
Degraded and deforested lands, in a biophysical sense, present areas of opportunity for returning forests and trees to the landscape. Biophysical potential, however, is not the same as actual restoration potential. This led us to the second step in the analysis: where can forest and trees realistically be returned to the landscape?
Where can forests and trees be restored?
The actual potential to bring back forests and trees is obviously much smaller than the total area of degraded and deforested land shown on the forest condition map. A large portion of these lands is used for food production, while cities, settlements and a host of other human uses also require land. A realistic map of restoration opportunities would have to exclude such areas.
To do this, we created a map of human pressure by combining urban areas, areas with dense rural population (> 100 person/km2), cultivated areas, and other intensively used areas (Pittman, et al., 2010; LandScan, 2005; GLC2000, Sanderson, et al., 2002). We then eliminated these areas from further consideration, assuming, for the purpose of this analysis, that they are incompatible with returning forests to the landscape.
After applying these constraints, the remaining area is the world map of restoration opportunity areas.
But opportunities to bring back what, exactly? We decided to distinguish two types of restoration opportunity landscapes with regard to the most likely type of restoration:
Wide-scale restoration aims to restore closed forests to the landscape. This type of restoration is more likely in deforested or degraded landscapes with low population density (< 10 people/km2) that are also areas where closed forests formerly dominated the landscape.
Mosaic restoration integrates trees into mixed-use landscapes, such as agricultural lands and settlements, where trees can support people through improved water quality, increased soil fertility, and other ecosystem services. This type of restoration is more likely in deforested or degraded forest landscapes with moderate population density (10 - 100 people/km2).
Remote restoration is reserved for deforested or degraded forest lands that are completely unpopulated and located far away from human settlements, such as northern Canada and Siberia. The reduced density of forests in these areas is likely due to fire and pests, and their remoteness makes them a more costly and lower-priority restoration opportunity.
The restoration opportunity map shows the result of this analysis and suggests several interesting conclusions regarding restoration opportunity globally:
Restoration opportunity landscapes are widespread. More than two billion hectares worldwide offer opportunities for either wide-scale or mosaic-type restoration—an area larger than South America.
Restoration opportunities exist on all continents.
Restoration opportunities are not tied to ongoing deforestation. Most of the opportunity landscapes were deforested or degraded a long time ago and far away from current deforestation hotspots.
Mosaic restoration is the greatest opportunity. A full three quarters of the total opportunity area (1.5 billion hectares) is in this category.
The Way Forward
Knowing the global extent and location of restoration opportunity landscapes is just the starting point, however. At a resolution of 1 km2 (where one pixel is the combined area of 140 soccer fields), these maps provide the big picture of opportunity and show the locations worthy of a closer look. National and local-level analyses to identify the specific types of restoration needed in specific locations are necessary next steps. WRI, in partnership with IUCN, is already working on these detailed assessments. Work in Brazil, Rwanda, Guatemala, Mexico, and Ghana is underway and with locations on the horizon. WRI and IUCN’s Restoration Opportunity Assessment Methodology provides an overview of how we are approaching these assessments.
In 2011, the government of Germany and the Global Partnership on Forest Landscape Restoration established the Bonn Challenge: a call to action for governments and civil society organizations to restore 150 million hectares of deforested and degraded lands worldwide by 2020. The Bonn Challenge map identifies the countries and organizations that have made pledges toward achieving this goal to date, with more pledges being made each year. Keep checking the map to see which new countries have joined the Bonn Challenge and are making forest landscape restoration a priority.
- WRI and IUCN's Restoration Opportunities Assessment Methodology (ROAM) Handbook
- L. Laestadius, S. Maginnis, S. Minnemeyer, P. Potapov, C. Saint-Laurent and N. Sizer, Mapping opportunities for forest landscape restoration, Unasylva 238, 62, 47 (2011/2).
- WRI's "New Perspectives on Restoration" blog series