Mini rainforest initiative seeks to become a model for reforestation in Kalimantan

The government, researchers and companies are combining forces to build a miniature tropical rainforest in Kalimantan, hoping it will serve as a blueprint for the reforestation of barren lands in the region of Indonesia’s planned new capital, Nusantara.

Tree species of different heights – tall, low and understory – will create layers of vegetation in a reforestation method that hasn’t been used in Indonesia before; the program is the first of its kind to reintroduce tropical rainforest into a degraded ecosystem in Indonesia. Image: , CC BY-SA 3.0, via Flickr.

Indonesian authorities, academics and companies are working together to build a miniature tropical rainforest they hope will serve as a blueprint for the reforestation program in Indonesia’s new capital in eastern Borneo.

In 2019, President Joko Widodo announced plans to relocate the capital to Kalimantan, Indonesia’s part of the Borneo Island, to ease some of Jakarta’s burdens, including pollution, traffic congestion and rising sea waters.

The president says the move will also allow the government to reforest lands that had been degraded by decades of industrial activities such as mining and pulpwood and oil palm plantations.

Under the reforestation program, the government aims to replant lush tropical rainforest on 82,891 hectares (204,800 acres) of barren lands that dominate the area where Indonesia’s planned new capital, called Nusantara, will sit.

Forestry experts have cautioned that the program may be overly ambitious due to its sheer scale and because it’s the first of its kind that aims to reintroduce tropical rainforests into a degraded ecosystem in Indonesia.

Past rehabilitation programs in the country have mostly entailed efforts to rehabilitate secondary forests, rather than landscapes that are totally barren due to monoculture plantations and mining activities. The programs have primarily relied on techniques known as enrichment planting, involving the introduction of economically valuable tree species, usually just a few of them, to enhance the diversity of degraded but still-standing forests.

By contrast, establishing tropical rainforest in a completely deforested area requires a totally different approach, one that involves the planting of a large number of tree species from a wide variety of species.

Efforts to replant native tree species [in Indonesian rehabilitation programs] are still lacking so far. Therefore, we hope that the miniature tropical rainforest could showcase what real rainforests are like in the new capital.

Syahrinudin, researcher, Mulawarman University

The selected tree species have to represent different heights — tall, low and understory — to create layers of vegetation within the reforested lands.

Tall trees provide shade and nutrition to the soil, while the understory — the layer of trees and shrubs between the forest floor and canopy — provides food and shelter for small animals and birds and large predators that live in the forest.

However, Indonesia is inexperienced in using this multilayered and multispecies method in its past reforestation programs, said Syahrinudin, a lecturer and researcher at the soil sciences and forest nutrition lab of the Mulawarman University’s forest faculty in Samarinda, the capital of East Kalimantan province.

That’s why the Nusantara Capital City Authority (OIKN), a government agency that oversees the progress of the new city’s development, Mulawarman University and three companies — Danone, PT Indo Tambangraya Megah (ITM) and PT Multi Harapan Utama (MHU) — are building a miniature tropical rainforest on a 96-hectare (237-acre) plot of land some 2 kilometres (1.2 miles) away from the central government’s core area of the new capital, he said.

The miniature tropical rainforest is estimated to cost up to 20 billion rupiah (US$1.27 million).

“The Mulawarman University serves as an adviser [in the development of the miniature tropical rainforest], and the ones who do the replanting are vendors, which we will directly observe,” Syahrinudin told Mongabay. “PT ITM and PT MHU will also help [the program], and the Mulawarman University is working together with Danone. So there are three companies involved.”

Mining companies operating in Indonesia such as PT ITM and PT MHU are legally mandated to rehabilitate their concessions once they’re done mining and also to rehabilitate watershed areas.

But the two mining companies’ involvement in the miniature tropical rainforest project are not part of their legal obligations, said Myrna Asnawati Safitri, the deputy for environment and natural resources at OIKN.

“It [their involvement] is for their corporate social responsibility programs,” she told Mongabay. “So it’s outside their obligation to rehabilitate watershed areas.”

PT ITM sustainability director Ignatius Wurwanto said his company’s involvement in the miniature tropical rainforest project shows a commitment to go beyond the legal minimum. “As a company that works in forest areas, there’s an obligation to rehabilitate former mining concessions. But beyond that, there’s a more important obligation, which is to protect the sustainability of Indonesia’s forests,” he said.

PT MHU mining support general manager Wijayono Sarosa said the company had already planned to establish 1,000 hectares (2,470 acres) of protected forest in Nusantara. Then, Wijayona says, OIKN asked the company to also participate in the construction of the miniature tropical rainforest.

“So we will build 30 hectares (74 acres) of forests in the miniature [tropical rainforest] site,” Wijayono said.

A blueprint for reforestation

The miniature tropical rainforest will serve as a blueprint for the kind of reforestation envisioned by the president, Syahrinudin said.

Efforts to reforest the new capital had started in late 2022 by the Ministry of Environment and Forestry, and so far the ministry has reforested 2,141 hectares (5,291 acres) of the Nusantara site.

Experts have identified a number of obstacles in the reforestation efforts, which include a preference for nonnative tree species, poor planting practices and monitoring, and a general misapplication of reforestation principles.

OIKN wasn’t involved in that reforestation work.

“Efforts to replant native tree species [in Indonesian rehabilitation programs] are still lacking so far. Therefore, we hope that the miniature tropical rainforest could showcase what real rainforests are like in the new capital,” Syahrinudin said.

The miniature tropical rainforest will host at least 150 of endemic tree species, he said.

This is far fewer than the 1,433 endemic tree species identified in Kalimantan, but more than the number of tree species that is usually planted in Indonesian reforestation programs.

According to data from the biological technology school at the Bandung Institute of Technology, there are only 60 tree species known to be planted in various reforestation programs, whether they’re carried out by the government or by companies.

“So there’s a huge gap between the number of endemic tree species known in Kalimantan and the number of tree species often used in reforestation programs,” Endah Sulistyawati, the dean of the school, said during a webinar last year. “I suspect this happens because replanting activities so far have only been focused on specific tree species. Maybe there’s a preference towards specific species needed by people, ones with commercial values. That’s understandable.”

The 150 tree species in the miniature tropical rainforest are intended to resemble lowland dipterocarp forest, the original ecosystem of East Kalimantan, in which as many as 240 different tree species can grow within 1 hectare (2.47 acres).

So far, Mulawarman University has collected 50 endemic tree species to be planted at the initial phase of the establishment of the miniature rainforest, Syahrinudin said.

The university obtained the seeds mostly from Indonesia’s association of forestry businesses, APHI, and vendors around Samarinda, he said.

Emphasis will be place on planting trees that can grow well in shaded areas and are widely available in the nearby ecosystem, Syahrinudin said.

The miniature rainforest will also house a smaller number of dominant tree species, which have the largest, fullest crowns in the stand, extending above the general level of the canopy to receive full light from above, he said.

The 96-hectare mini-rainforest will be divided into clusters measuring 20 by 20 meters (66 by 66 feet). A cluster will host two dominant trees, four codominant trees whose crowns make up the general level of the canopy and six tolerant trees — all of which will be planted in random spacing.

To make sure the seedlings grow well, conservation workers will intensively maintain the seedlings for the first four years and monitor their growth, Syahrimudin said.

“The rehabilitation methodology [used in the miniature rainforest] has to differ from the conventional way. If we use conventional methodology with business-as-usual funding and input, it’ll be very difficult [to make the program succeed],” he said. “So we have to be innovative and pay attention to the tree species that we will plant, what kind of treatment we have to give and what environment we need to prepare [for the trees to grow well].”

The conservation workers will also make sure that the seedlings are at least 1 m (3.3 ft] in height and healthy, so that they can compete with other crops and survive, he said.

The miniature will have its own nursery, where seedings are prepared for the replanting program, Syahrimudin said.

“We will try to increase the quality of the seeds in the nursery so that their heights can reach 1 m before moving them to the field,” he said.

The development of the miniature tropical rainforest started in November 2023, and the goal is to fully plant all seedlings by the end of 2024, he said.

President Joko Widodo, together with other public officials, visited the miniature rainforest and did some replanting work there on Dec. 20, 2023.

The president planted a dipterocarp tree species called Shorea laevis, locally known as Bangkirai. The tree species is considered vulnerable due to deforestation for agriculture and logging for its timber.

“This is an effort to reforest and rebuild tropical rainforest, from monoculture [plantations dotting the landscape of the new capital] to tropical rainforest,” Widodo said after planting the tree. “From just eucalyptus [plantations] to a variety of tree species.”

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