Bringing Life Back to the Rainforest – Lessons from a Long-Term Restoration in Borneo

The Goal: bring back the entire ecosystem

Tropical rainforests are Earth’s most diverse ecosystems. Despite covering 14% of the planet’s surface, they harbor half of the terrestrial species. Countless forms thrive here, from butterflies and other insects to frogs, monkeys and elephants – to name just a few.

The vegetation is equally remarkable. In the rainforests of Borneo alone, there are more than 3,000 different tree species, growing in layers with the tallest trees reaching nearly 100 meters.

Rainforests also act as critical carbon ­reservoirs. A single hectare can store 300–400 tons of carbon in forest biomass and soil. In severely degraded forests, however, this storage can drop to less than 100 tons per hectare.

For human wellbeing, undamaged forests are indispensable. They reduce erosion, provide clean water and healthy aquatic ecosystems, and reduce the spread of wildfires that cause smog and other problems. Rainforests are not only important carbon storage mitigating the effect of global warming but can regulate temperatures and rainfall both locally and regionally. With an exceptional biodiversity rainforests are also sources of many not-timber forest products valued by local communites including medicinal plants.

Today’s tropical rainforests face significant threats and pressures. Currently, one-third of these vital ecosystems have already been lost globally due to activities such as deforestation, agriculture, and urban development. Of those that remain, nearly half are considered degraded, meaning their ecosystems have been significantly altered by humans.

When a forest degrades, it can result in reduced biodiversity, such as fewer animal species, trees and other plants, and harmed ecological processes that are essential for the forest’s health and regeneration.

Such damage not only weakens the forests’ ability to function fully but also threatens the countless species that depend on them for survival.

Restoring these tropical forests presents a powerful opportunity for environmental recovery. 

In 1983, Borneo was ablaze. Millions of hectares burned during the El Niño drought, and the worst affected were forests that had undergone intensive logging. In Sabah, Malaysia, one million hectares of forest were damaged.

Such large-scale disturbances drastically change forest ecosystems. Instead of supporting diverse community of slow-growing hardwood trees typical of old forests, the area becomes dominated by fast-growing lightwood pioneer species, climbers, and weeds. The climbers and weeds spread quickly and hinders the growth of both pioneers and ­late-­sucessional species.

Due to the extensive area affected by the fire and the poor seed dispersal of dipterocarp trees, it was thought that it would take over a 100 years for the forest to recover. It was also considered unlikely that the forest would ever regain the same species as before the fire on its own.

In 1996 the founder of the global Swedish home furnishing company IKEA, Ingvar Kamprad, wrote a personal letter to the company management, asking for their support on responsible forestry: “Our forests are humanity’s greatest asset... essential for the survival of a growing population. The world needs sustainable forestry, and we need to restore large areas of what has already been logged.” 

Ingvar Kamprad reached out to the Swedish University of Agricultural Sciences (SLU) and was introduced to researcher Jan Falck, who worked with the ­Sabah Foundation on Borneo on natural forest management. 

Ingvar Kamprad invited Jan Falck to a lunch meeting. During the conversation, Jan explained his project in Borneo, focused on ­developing methods to ­harvest timber in a way that minimizes forest damage. Not long after, the phone call came. It was the middle of winter, and Jan had biked to work. Running late, he rushed down the corridor as he heard the phone ringing in his office. Hastily unlocking the door, he threw off his hat and answered.

“It was Ingvar Kamprad on the line, asking if I’d consider starting a rainforest rehabilitation project. Just a week later, I was on a plane to Sabah with   Kamprad’s closest colleague, heading to meet our partners at the Sabah Foundation.”

Together they created what is today one of the world’s largest rainforest restoration projects with the goal of bringing back the entire ecosystem, the Sow a seed project.

Local trees and people!

Since 1998, the Sabah Foundation and IKEA have jointly funded the restoration efforts of the rainforest under the project Sow a Seed, locally known as INIKEA. The restoration has been carried out in various ways, depending on the level of damage, ranging from assisted natural regeneration to the planting of a diverse range of native tree species to mimic the original forest’s structure and biodiversity.

Moreover, the way it was carried out is unique in many ways.

A helicopter flight over the damaged rainforest marked the beginning of the project. The collaborators scanned the landscape for a site suitable for the restoration project. The search led them to the village of Luasong where they identified a remote commercial state forest that had been damaged by logging and earlier fires. It was located between the two conservation areas, Maliau Basin and Danum Valley, with pristine rainforest and rich biodiversity. The restoration could be a first and important step in connecting these separated conservation areas. Additionally, it was conveniently close to the project where Jan Falck was conducting research on sustainable tropical forestry. Luasong also presented a practical benefit: it already had a nursery set up previously used for rattan production, which could now be repurposed for growing native tree species.

In 1998, an 18,500-hectare area was designated for restoration through a collaboration between the Sabah Foundation, IKEA, and the Swedish University of Agricultural Sciences (SLU).

The primary goal was to restore biodiversity and support the natural succession of the forest, with the ultimate goal of recreating conditions that existed before the disturbance. To achieve this, the focus was to favor late-successional tree species, particularly dipterocarps and other slow-growing hardwoods with limited natural dispersal, as well as fruit-bearing trees essential for wildlife.

Only local workers

All workers, including nursery, planting, and maintenance staff, have been recruited locally from nearby villages, with no external contractors involved.

Temporary positions have also been offered to family members during peak work periods, such as seed collection and filling planting bags with soil to prepare for seedlings.

Employees and their families have been provided with free housing, electricity, and water. The village also has a school and a health clinic, providing access to education and healthcare.

A diversity of native tree species

In this restoration project, 92 ­native tree species have been planted, a significantly higher ­number compared to the average of three species in replanting projects in the region. Many of the species used are red-listed of conservation concern. The trees planted are mostly dipterocarps and fruit trees, all native species.

Sourcing enough planting material is a major challenge in large-scale forest restoration. In Southeast Asia, this issue is further complicated by the irregular flowering cycles of many tree species. Some species flower only once every 5 to 15 years, with a single year of synchronized flowering, a phenomenon known as mast fruiting. This limits both the quantity and diversity of seeds available each year.

To address the irregular availability of seeds from year to year, the project developed protocols for using wildlings during non-fruiting years. These wildlings, which originate from mast fruiting events, can remain small under the forest’s canopy for several years before being harvested and propagated in the nursery.

The germinated seedlings and wildlings are kept in the nursery for 1.5 to 2 years. No chemical fungicides, insecticides, or herbicides are used in the nursery or during out-planting.

The project prioritized natural regeneration, supplementing it with enrichment planting when natural growth was insufficient or lacked diversity.

For moderately disturbed forest areas, the team implemented a gap-cluster planting method. This technique mimics the natural distribution of trees by taking advantage of openings in the forest canopy created by disturbances which provide space and light for new trees to grow. In heavily degraded sites with open canopies, traditional line planting was implemented to systematically restore diverse tree cover.

Areas with enrichment planting were managed for 10 years with activities like weeding, climber cutting, girdling, and thinning. This improved the growth of both planted seedlings and the trees remaining after the fire. Importantly, no pesticides were used in either the nursery or the forest.

From the start the project implemented a comprehensive monitoring of planted trees so it was possible to follow the survival of trees over the 25 years. This is unique since most other projects in the region are short lived and evaluate planting efforts after 3–5 years, if evaluated at all.

Enhancing restoration through scientific evaluation

The project has been carried out in five-year phases. Starting in 2015, the fourth phase adjusted the operational restoration to include a broader scientific evaluation. 

This study design allows for the comparison of different restoration methods under similar conditions, offering valuable insights into the effectiveness of each method. The data collected will help guide future restoration efforts, improving outcomes for similar projects moving forward. 

In 2018, a network of permanent study plots was established in various areas to better understand the environmental benefits of forest restoration compared to other types of land use. These plots also enable continuous evaluation of how closely restored forests can match the biodiversity of primary rainforests.

By studying restored forests, non-restored forests and nearby oil palm and eucalyptus plantations researchers can asses how different land-use types impact the environment, including carbon storage in soil and trees, and their ability to support biodiversity.

In 2008 an experiment to evaluate the survival and growth of 32 tree species commonly used in restoration efforts in Sabah were set up. These native tree species are planted together in controlled conditions, known as common garden trials, allowing researchers to compare their performance in providing key environmental services, such as supporting biodiversity, storing carbon, and enhancing soil health.

The trials also look at how these tree species affect insects and the bacteria and fungi in the soil. By studying the environmental needs and mortality causes of different species it would be possible to allow site matching for improved survival and growth, and to design tree species mixtures that support various restoration objectives.

Teaming up with students & researchers

The project has attracted a wide range of students and researchers from both Malaysia and internationally. Over the years, various students, including bachelor’s, master’s, and PhD candidates, have contributed to the research efforts. This diverse group of researchers, hailing from institutions in Malaysia, Sweden, and beyond, has been instrumental in advancing the restoration techniques and improving our understanding of the ecological processes at play.

Stakeholder engagement

To ensure input and strategic guidance for the project, the Sabah Foundation, IKEA and the Swedish University of Agricultural Sciences conducted annual steering committee meetings. These meetings brought together key representatives from Sabah Forestry Department, Sabah Wildlife Department, WWF-Malaysia, Forest Research Institute Malaysia, Universiti Malaysia Sabah to provide expert advice and help adapt the project’s approach.

Cost of restoration

Around 14,000 hectares have been restored within the designated 18,500-hectare area. The total project investment of 14.9 million USD translates to an average restoration cost of around 1,000 USD per hectare over 25 years – a rate comparable to planting initiatives in Sweden following logging activities.

Construction and road maintenance accounted for about 30 percent of the project cost. Areas that were less disturbed, such as on upper mountain ridges, were strategically left to recover naturally, while some other areas were designated for scientific research and experimental monitoring.

In addition, investments have gone into ­sup­porting infrastructure and educational ­activities in the Maliau Basin conservation area as well as research projects on rainforest restoration and management.

Restoration that makes a difference for planet and people

Results from 25 years of efforts to rehabilitate a fire-damaged and heavily logged rainforest are now available. Our findings fill a critical knowledge gap regarding the long-term effects of restoration and may serve as an important guide for future efforts to restore damaged ­ ecosystems. Here are some of our key outcomes and impacts.

Diverse­ forests

By planting more than 90 different species, the restoration helps the forests regain the features of a natural, undisturbed forest. Over 20 of the species planted are threatened, and these trees have increased the diversity of dipterocarp species in the more degraded areas by 35 percent. In contrast, in some of the least disturbed areas, natural regeneration alone would have been enough for carbon recovery, as the species composition was already diverse.

Early in the project, limited knowledge about many species affected their survival and growth. Drawing on lessons learned, more effective species combinations can now be chosen to enhance both growth and biodiversity. However, even with improved species selection, maintenance during the first 5–10 years remains crucial to ensure enough trees survive to maturity, particularly in degraded areas where environmental stressors like drought and grazing animals pose significant threats.

Planting species that typically grow in the later stages of forest development helps the restored forest become more structurally complex. These late-successional species usually live longer and grow tall and large, which allows the forest to develop multiple layers of canopy, much like an undisturbed rainforest.

These large trees are essential for certain iconic animals, such as hornbills and giant honeybees. The benefits of planting these late-successional species will grow over time as the trees mature and the forest ecosystem continues to develop.

Improved carbon sink

The carbon stored in the soils and tree biomass in the area is already approximately 250 tons per hectare, which is 3-4 times higher than in oil palm plantations.

By preventing further degradation and land use changes, the restoration has kept roughly 2.3 million tons of carbon (or 8.44 million tons of CO2) from being released into the atmosphere. Over the 25 years of the project, about 110 tons of carbon have been stored per hectare.

There is significant potential for more storage as the restored forests continue to develop towards a pristine state, potentially storing about 100 tons more per hectare.

Social impact

The project provides more than ecological benefits; it also has significant social value. The initiative offers free accommodation, electricity, and water to its workers. In Luasong, there is also a health clinic and a free government school. Children from the school are regularly taken on visits to field camps to learn about nature and the importance of restoration. Notably, some current workers are second-generation employees of the Sow a Seed project.

”I like this project because it’s contributed a lot to the people of Sabah. We have recruited about 700 people, and if you count with families about 2000 people have benefited with the project until now” says David Alloysius, project manager until late 2022.

The animals are returning

Today we see a rich biodiversity of animals in the area. A rich template of bird sounds is now enriching the orchestra of the rainforest including charismatic hornbills such as the Black hornbill, White-crowned hornbill, Helmeted hornbill and the iconic rhinoceros hornbill. All of the five wild-cats native to Sabah are utilizing the area, while Orangutans and the endemic Borneo pygmy elephants use the area as a refuge.

Conservation

Thanks to the project, the restored area has been elevated to a Class 1 protected forest status—the highest level of environmental protection in ­ Malaysia. This contrasts with the surrounding areas, which have been converted to oil palm plantations, altering the natural character of the landscape.

Let´s restore the future

One-third of the world’s tropical rainforests have been lost, and half of the remaining forests are degraded. As the world now calls for knowledge-based restoration and sustainable stewardship of native rainforests to help mitigate climate change and restore bio-diversity, the insights from this project offer a powerful message: restoring these critical ecosystems is possible.

This project addresses a critical knowledge gap by focusing on native rainforest trees. It not only advances local restoration techniques but also serves as a global model, demonstrating how individuals and businesses can invest in biodiversity conservation and climate mitigation in an environmentally responsible manner.

In collaboration with researchers and practitioners, we aim to establish this area as a model for research-based rainforest restoration. Here, we will advance and share knowledge on the restorative management of native tropical forests. Our goal is to contribute to the advancement of knowledge-based restoration efforts.

Our contribution includes:

• Over 25 years of practical rainforest restoration experience
• Several unique experiments designed to track the recovery of the restored forest by studying biodiversity and ecosystem functions, with comparisons to other land uses
• A unique genetic progeny collection, functioning as a living gene bank for other restoration projects in the region.

Together, these insights can provide valuable help for new restoration initiatives and help answer crucial global questions about forest restoration’s role in climate mitigation, biodiversity preservation, and ecosystem values.

”To prevent further degradation and successfully restore forests, we need to learn from the few early efforts, such as this project”, says Ulrik Ilstedt, project leader and researcher at the Swedish University of Agricultural Sciences (SLU).

One billion hectares to be restored

Today, there are over one billion hectares of ”previous or degraded” tropical forestland that can be restored, according to the World Resources Institute (WRI). Global initiatives like the UN Decade of Ecosystem Restoration and the Bonn Challenge aim to address this challenge, placing forest restoration high on the international agenda.

However, many projects to restore tropical areas are driven by economic interests rather than­ ecological or social needs, often planting exotic species such as eucalyptus or acacia. While these trees grow quickly and have established markets, if managed without environmental considerations, they may lead to soil erosion, reduced water availability, and diminished biodiversity. Native species, although less studied, may provide a more sustainable alternative, fostering biodiversity and resilience. 

Restoring degraded forests not only serves to protect vital ecosystems but can also enhance biodiversity and improve ecosystem functions in forests that are sustainably managed for harvest. A crucial aspect of rainforest restoration is the economic potential for local communities and countries to generate income from their natural resources in different ways.

The core question remains, and is becoming increasingly ­ urgent to answer in the face of a rapidly changing world: