Force of Nature

The  Trillion Trees  map of Regeneration Hotspots reveals an estimated 55.7 +/- 6.6 million hectares of natural forest have grown back since 2000. What’s driving these areas of recovery? How can we encourage future regeneration? And how can you play your part? Scroll and explore the map to find out more. Read the paper  here .

"We call on the restoration community, forestry experts and policymakers to prioritize the regeneration of natural forests over other types of tree planting — by allowing disturbed lands to recover to their previous high carbon state."

-- Prof. Simon Lewis et al.  Nature 2019 

With millions of hectares of old-growth forest disappearing every year, along with tens of thousands of forest species, scientists are calling for a greater emphasis on forest regeneration, in which natural forests are allowed or encouraged to recover under their own steam, for the benefit of ecosystems, communities and the climate.

Answering this challenge, in 2018 Trillion Trees commissioned a pioneering mapping survey, led by partner WWF, to find out where regeneration is already happening, and why.

“Natural regeneration is a low-cost, low-tech and high-impact strategy for restoring forests, sequestering carbon, and conserving biodiversity.”

--  R. Crouzeilles et al. 2020 

Forest regeneration sounds simple: let nature take the lead. Some areas need nothing more than to be left alone to begin regenerating, while others need active encouragement to grow back, depending on the condition of the soil and the local land-use. Broadly speaking, there are three categories:

1. Active restoration is necessary if land is degraded or obstructed from recovering on its own. This often involves planting areas of native trees and shrubs, including agroforestry approaches.

2. Assisted natural regeneration is the process of encouraging former forest to re-assert itself, for example by removing invasive vegetation or fencing the land to reduce grazing pressure.

3. Spontaneous natural regeneration is often considered the best-case scenario for reforestation: a hands-off approach, in which an area of land is able to reforest itself of its own accord. Natural regeneration can take place without human input, and even without human knowledge.

The Trillion Trees map of Regeneration Hotspots displays all three of the above types of regrowth, and deliberately excludes commercial plantations. As a result, the study represents the first thorough effort to track natural forest expansion.

“Assisted or unassisted...naturally regenerating forests conserve biodiversity, provide a wide array of ecosystem goods and services, and support rural economies and livelihoods.”

• -- R. L. Chazdon et al.,  Environmental Research Letters, 2020 

Back in January 2021, WWF published its latest Deforestation Fronts report, identifying 24 areas worldwide where forests are suffering the severest losses. In these areas alone, an area twice the size of the UK was lost between 2004 and 2017, and annual figures remain alarmingly high. This new study hopes to offer a counterpoint: a map of Regeneration Hotspots, where natural forests are beginning to recover. 

Of course, replacing lost forests is practically impossible. It would take decades or even centuries for a regenerated ‘secondary forest’ to become as rich in carbon and wildlife as an existing, old-growth forest, and some ecosystems can never recover from deforestation.

Nevertheless, restoring and expanding forests are central parts of the global challenge to absorb carbon, stabilize the climate and restore wildlife.

In order to identify areas of forest that have undergone successful regeneration, remote sensing analyses were combined with feedback from experts. We received feedback from 29 countries and across 124 different sites in 13 ecoregions. Multiple land use and land cover datasets, as well as remote sensing products were used to identify areas that were 1) non-forested before 2000, 2) showed an increase in forested area between 2000 and 2015, and 3) remained forested from 2015 to 2018. Commercial plantations were excluded based on additional datasets and expert feedback.  

To date, the map shows an estimated 55.7 +/- 6.6 million hectares of forests which have regenerated since the year 2000. But we need more information. With additional feedback, the map can be improved in its accuracy and we can learn more about the drivers behind regeneration success. See below for how you can help us improve the map and share your stories.

A quick look at the map shows that, while deforestation fronts are concentrated in the tropics, most regeneration has taken place in the northern hemisphere. This is broadly consistent with the forest transition theory: developing economies tend to be more dependent on domestic agriculture and primary industries, and thus have higher rates of deforestation. As countries grow richer, they move towards manufacturing and service industries, freeing up land for regeneration. Developed countries also tend to be more urbanized populations, and rely more on imported food.

But a closer look at the map shows that some of the regeneration hotpots sit alongside the deforestation fronts identified by WWF, in southeast Asia, sub-Saharan Africa and Brazil. This is not as surprising as it sounds. Regeneration can occur in the same locations as deforestation because some of that land cleared for timber or agriculture is abandoned shortly after. Regeneration is likeliest to occur in areas which naturally support trees, and although clear-felling can harm the quality and stability of soil, deforested areas are natural candidates for regeneration.

Thanks to site-specific surveys from experts, we can start to understand the local parameters that may have allowed or encouraged natural regeneration. Among the determining factors for successful regeneration, two key conditions stand out:

Let’s take a closer look at two important landscapes where regeneration has flourished in different ways.

The  Mata Atlântica , or Atlantic Forest, along the coast of South America was once one of the natural wonders of the world. Stretching from Northern Brazil to Argentina, it occupied more than a million square kilometers, harbouring an unparalleled variety of life.

Less than 15% of the original forest now remains, a patchwork of fragments interspersed with farmland and urban sprawl. But it remains a home to thousands of indigenous people, and a remarkable haven for endemic birds, plants, and amphibians, as well as flagship species like the woolly spider monkey and the jaguar.

As the world’s largest UNESCO biosphere reserve, the Atlantic Forest has been the focus of concerted conservation efforts. In 2009 the Atlantic Forest Restoration Pact was established by businesses, conservation organisations, landowners and more, to plant or restore 15 million hectares of lost or degraded forest by 2050 - effectively promising to double the size of the remaining forest.

So far, only a fraction of this target has been reached, and deforestation rates have risen in recent years. Nevertheless, the mapping study points to the Atlantic Forest as one of the key global success stories for regeneration. According to the result, an estimated 4.2 million hectares have regenerated in Brazil since 2000, much of it focused around the Atlantic Forest biome, and these findings are backed up by other research.

Much of this growth was planned - the fruit of decades-long projects to restore the Atlantic Forest. Among these projects is WWF’s 16-year portfolio of restoration across three countries, and community-backed habitat protection from BirdLife and SAVE Brasil.

In the past 20 years, many more nature reserves have been established in the region, along with landscape-scale biodiversity initiatives like ecological corridors and habitat ‘mosaics’. The pulp and paper industry has begun to adopt more responsible practices, and despite fluctuating national policy approaches in recent years, studies have shown that targeted law-enforcement against deforestation can result in localized regrowth.

Other areas in the biome have grown back without human agency, again for several possible reasons:

• Declining  coffee prices  in the 90s, leading growers to release land or change its use.

• Improvement or intensification of  dairy and beef  farming, requiring less land for grazing.

• A trend of migration towards Rio de Janeiro or São Paulo, the two megacities contained within the Atlantic Forest biome.

• Grow-back after short-term deforestation, such as temporary grazing or illegal logging.

Mapping these areas of ‘hidden healing’ is valuable in itself, as it allows them to be protected, to consolidate the progress they have already shown. But these areas of passive regeneration also offer a golden opportunity for future activity. If nature can recover without expensive intervention, then by identifying and attending to similar areas with the potential to self-regenerate, conservationists could achieve much more with their resources.

Over the coming decade, as projects within and beyond Brazil seek to upscale reforestation in the Atlantic Forest and the Amazon, these findings could prove a useful guide. By identifying areas which are ripe for release from agriculture - very low-density grazing, for example, or steeply sloping arable land - conservation efforts can pin-point potential natural regeneration, and tailor their efforts to suit local conditions.

But the authors of the study warn that this tremendous regeneration cannot be taken for granted. Forests across Brazil face significant threats today, even the Atlantic Forests – a recognized success story in restoration. And such is the extent of historic deforestation that the remaining area of this unique forest still needs to more than double to reach what scientists believe is a minimal threshold for its lasting conservation.  Guedes Pinto and Voivodic 2021, Nature Climate Change 

While Mongolia is known as a land of desert and steppe, along its northern border with Siberia are vast swathes of pinewoods, remnants of the great Transbaikal conifer forests.

Climate change is increasingly wreaking havoc on these boreal forests. Melting tundra has allowed some areas to spread north, but up to 60 devastating fires scorch through huge tracts of woodland every year, impacting 14% of the entire tree cover annually.

Nevertheless, our map suggests 1.24 million hectares of forest have regenerated in Mongolia this century, making it a key hotspot. 

Among the factors contributing to this revival is an increased emphasis from the Mongolian government on protected areas, in regions like the Onon River Basin and the Tujiin Nars pinewoods.

Partly thanks to the efforts of Trillion Trees partner WWF, Mongolia has continually increased its nature reserves over the past 20 years.

• Mongolia now has 32.7 million hectares under official protection.

• 21% of the entire national landmass is protected.

• Mongolia boasts the  oldest nature reserve  in the world: the Bogd Khan Uul Strictly Protected Area.

Our results, along with local field studies, suggest a correlation between these increased protections and natural regeneration. As well as helping to prevent fires, these areas either prohibit or control the other threats to Mongolian forests: mining, logging and grazing.

This forest in Khargiastai, in Onon Balj National park, has undergone significant natural regeneration after the area burned in 2011. Field studies, like the one photographed above, have confirmed the efficacy of increased protection.

Mongolian conservationists can take encouragement from these findings, and further research could help to inspire better protections for boreal forests elsewhere in the Northern Hemisphere.

The mapping study shows that, all over the world, forest regeneration is already taking place, with and without human intervention. By understanding how forests are flourishing, we stand a much better chance of protecting and expanding them further.

By helping us build on this research, you can play a role in placing natural regeneration at the heart of global conservation.

The  Trillion Trees  partnership would like to invite further contribution from anyone with local knowledge, data or insight into one of the identified regeneration areas. A digital contribution platform has been made available by the research team, allowing local experts and informed citizen-scientists to contribute their findings, complete a detailed survey, and shape the future of the map.

To contribute to the map, please email forestregeneration@trilliontrees.org and someone will get in touch with further details. 

With your help, we can build an evidence base to support a new movement in better restoration, inspiring landowners, land managers and governments to acknowledge hidden areas of wilderness, and grant them the attention and protection they deserve.

This is a preliminary report of the Trillion Trees regeneration-mapping project. In-depth details on how the map was created will be available in a future scientific paper, awaiting review and publication.

In the battle against climate change, reducing emissions is by far the most urgent requirement, and no amount of regeneration can replace existing old-growth forest. Ending the loss of existing forests is always the top priority.

Globally, we are still losing forests at a terrifying rate, much faster than we are able to plant or restore them. Studies have shown that between 2001 and 2019 - a similar time-period to the Trillion Trees study - 386 million hectares of tree cover were lost worldwide. That’s over seven times the area of naturally regenerated forest identified in our research. It is a global imperative to shift from a deforestation economy to a regeneration economy, supporting biodiversity, a stable climate and thriving communities.