The land that BOS Foundation purchased was, by any reasonable assessment, hopeless. The soil was predominantly clay riddled with hard plinthite clods. Beneath the surface lay coal seams that combusted spontaneously when exposed to dry air. Land prices were rising, and there was not enough funding to buy intact rainforest land -- even if it had been available. So Smits went to work with what he had. His tree nursery started with seeds recovered from orangutan feces, a source that turns out to be surprisingly productive since orangutans eat dozens of fruit species and scatter viable seeds across wide ranges. Drawing on his research into mycorrhizal fungi -- the underground networks that connect tree roots to nutrient sources in the soil -- Smits inoculated his seedlings before planting. By mid-2006, more than 740 different tree species had taken root. By 2009, that number had climbed to 1,200 species, and 137 species of birds had returned to a landscape that five years earlier had supported almost nothing.

Reforestation was never the only goal. Samboja Lestari is, at its core, an orangutan rescue and rehabilitation center, and the growing forest serves a purpose beyond carbon sequestration and biodiversity. Orphaned and confiscated Bornean orangutans -- seized from the illegal pet trade, rescued from deforested areas -- arrive at the facility needing to learn skills that captivity never taught them. The foundation established what it calls forest schools: semi-wild areas where young orangutans roam under the supervision of human surrogate mothers, learning to climb, forage, and build nests before returning to sleeping cages at night. Graduates move on to orangutan islands, larger enclosures where they hone survival skills with minimal human oversight. In April 2012, the first three orangutans rehabilitated at Samboja Lestari were released into the Kehje Sewen forest. By July 2021, 121 orangutans from the program had been returned to the wild. Not every individual can make that journey -- some arrive with chronic illness, physical disability, or behavioral patterns that preclude release -- and for them, the BOS Foundation maintains sanctuary islands and a special care unit offering lifelong veterinary support.

The recovering forest has attracted more than orangutans. At the Indonesian government's request, Samboja Lestari became home to over 70 sun bears confiscated from the illegal pet trade or rescued from cleared land. Hornbills returned. Thirty species of reptiles were recorded, along with porcupines, pangolins, and mouse deer. A secondary forest was growing -- not yet the full biodiversity of Borneo's ancient rainforests, but a functioning ecosystem where species could find food and shelter. Perhaps the most striking claim about Samboja Lestari concerns the weather. In his 2009 TED talk, Smits reported a substantial increase in cloud cover over the reforested area and 30% more rainfall, data he attributed to the absence of the trade-wind disruption that bare ground creates. If accurate, it suggests that reforestation can alter local climate patterns within less than a decade -- a finding with profound implications for degraded landscapes across the tropics.

Samboja Lestari is controversial, and its critics raise legitimate questions. Replanting a forest is dramatically more expensive per hectare than protecting one that still stands. Erik Meijaard, a conservation scientist at the Nature Conservancy who once worked for Smits, has pointed out that the organization and the Indonesian government, in partnership with timber companies, have protected more forest and more orangutans at a fraction of the cost over the same period. Whether Samboja Lestari ultimately justifies its expense, Meijaard has argued, depends on whether it can improve community livelihoods and achieve long-term financial sustainability -- a question that, as he put it, remains unanswered and will remain so for years, because that is the kind of time such projects need to be evaluated. The Samboja Lodge, an eco-lodge built with recycled materials in the style of local architecture, is one attempt at financial sustainability. Visitors and volunteers pay for guided tours of the orangutan sanctuary islands and sun bear enclosures, and the proceeds fund conservation operations. It is a model that blends ecotourism with rehabilitation -- fragile in its dependence on visitor revenue, but imaginative in its refusal to separate conservation from economic reality.