Planting trees to save the planet has captured the public imagination, and with good reason. It’s a tangible way individuals feel able to do something about the climate and biodiversity crises. Forest restoration is recognized globally as a critical component of any pathway to limit dangerous warming to 1.5 degrees Celsius. Countries around the world have made ambitious restoration commitments – coordinated under the Bonn Challenge – in recognition of the benefits of restoring forests for biodiversity, climate, and local communities.
However, up to now most of the global restoration conversation has focused on re-establishing forests where they have been cleared, known as “reforestation.” While reforestation is crucial to deliver on international climate and biodiversity commitments, this focus overlooks more than half of the world’s existing forests that haven’t been cleared, but have been modified by logging or other human activities.
A degraded landscape in the Maya Biosphere Reserve. Once forest is cleared, the resulting vegetation can become susceptible to fire, which prevents the natural regeneration of tree cover. Photo credit: ©WCS Guatemala
Because these degraded areas still retain many essential characteristics of healthy forests, they should be considered the first priority for restoration, since they can recover quickly and provide benefits much sooner than cleared areas that need time to regrow.
In a new study in the journal Conservation Biology, we estimate that there is at least as much area of degraded forest that could be restored as deforested land that could be returned to forest cover—1.5 billion hectares, in fact, an area almost the size of Russia. These forests still hold between 50-80 percent of their maximum potential carbon, remain relatively intact, and could naturally recover if human pressures were better managed.
An additional 1.3 billion hectares of forest are more severely degraded, but still currently hold 25-50 percent of their maximum potential carbon. These areas would likely require a mix of active tree planting and management of human pressures to facilitate recovery. By better understanding the extent of forest degradation, governments and land managers can identify which actions to take and where to prioritize restoration efforts.
The aftermath of deforestation for cattle pasture in the Maya Biosphere Reserve. Photo credit: ©WCS Guatemala
Degraded forests represent untapped potential for climate change mitigation. Their restoration is a fast and reliable way to achieve positive climate and biodiversity outcomes. Degraded forests appear in many ways very similar to undisturbed forests, and support significantly more species compared to deforested areas. Studies have also shown that forest restoration is more successful in areas with a greater share of existing natural forest cover. As such, degraded forests that occur near forests that are in better shape can rapidly rebound to previous levels of biodiversity, carbon and ecosystem services.
Forest restoration efforts on degraded forests that occur near high integrity forests have the potential to rapidly generate large biodiversity benefits. Increasing connections between adjacent degraded forest areas can improve the abundance, richness and diversity of native species. Large areas of restored forests can also help species adapt to climate change.
The Maya Biosphere Reserve is an important stronghold for the scarlet macaw, which nests in mature trees. Photo credit: ©WCS Guatemala
Restoring degraded forests also costs less than planting, growing, and maintaining trees on deforested lands. Restoring degraded forests may also lead to fewer conflicts over land, as such areas are not actively farmed, so restoring them will not impact crop production.
Our study provides a tool for prioritizing restoration areas. Take, for example, the 5 Great Forests of Mesoamerica — the largest remaining expanse of intact forest in Central America, where an alliance of national governments, nongovernmental organizations, and Indigenous groups have together committed to the restoration of 500,000 hectares of forest by 2030.
These forests are critical for wildlife, carbon sequestration, and clean water, and they provide food security for five million people. Our prioritization approach has identified areas in this region that should be restored first to provide the highest return on investment.
Tree cover being re-established through assisted natural regeneration in recovered cattle pasture in the Maya Biosphere Reserve. Photo credit: ©WCS Guatemala
Restoration priority maps are one part of a complex decision-making process. As a next step, we will refine our assessment of restoration priorities in the 5 Great Forests in collaboration with key decision makers, to support local stakeholders shaping decisions about priorities, investment, and operational planning for restoration success.
Restoring forests where they have been totally lost is vitally important in the fight against climate change and biodiversity loss, but it is also crucial to recognize the opportunities and benefits that come from improving the condition of degraded forests. We hope that decision makers globally will recognize this approach and seek opportunities for efficient, cost-effective options to bring it to fruition.