This article was written by UNEP as part of the UNEP Restoration Factory Program.

On the edge of Viet Nam’s Cát Tiên National Park, there is a hill that should not be a forest. A decade ago, it was little more than exposed stone, so barren that locals called it Đồi Đá, the stone mountain. Today, the same hillside hums with insects, glows with fireflies, and produces award-winning cacao beneath a canopy of native trees. Children come to learn how forests work. Farmers gather for workshops on regenerative practices. Weaver ants march between cacao branches the team has tied together, tiny ecological bridges that help keep pests away. This is Stone Hill Farm, where restoration agriculture transformed a stone mountain into a thriving ecosystem.

Pioneering Restoration Agriculture

The story begins with Dr. Phạm Hồng Đức Phước, a cacao specialist and experienced agroforestry scientist. When he first walked the barren hill in 2010, he saw what others could not: a chance to put his deep sustainable agriculture into practice.

With a small team of students and volunteers, he planted hardy pioneers, ficus, acacias, jackfruit, and native species, to anchor eroding slopes and rebuild organic matter. They carved terraces, dug ponds to trap monsoon rains, and sheltered young cacao seedlings beneath fast-growing canopy trees.

The early years were unforgiving. Trees struggled and soil baked. But season by season, the canopy grew higher and denser. Leaf litter accumulated. Earthworms reappeared. The ponds helped recharge groundwater and irrigate during the dry season, critical because the farm committed early on to relying entirely on rainwater for irrigation.

By 2021, eight hectares of biodiverse forest covered the hill. That same year, Dương Ngọc Duy Thư arrived for a sustainable agriculture course. What she found changed her life. Within months, she left Ho Chi Minh City to join the farm full time.

Watch this video for a glimpse of the transformation of Stone Hill Farm from a barren rock to a biodiverse forest and learning center.

Ecological Innovation and Natural Cacao

Conventional agriculture, including cacao, is usually associated with two major problems: heavy dependence on chemical pesticides, which damage soil and endanger farmers, and deforestation driven by high-yield monocultures that exhaust the land.

Stone Hill chose another path, becoming the only fully pesticide-free cacao farm in Viet Nam. Instead of chemicals, the team has spent years building an ecosystem that protects cacao naturally.

Weaver ants and black ants patrol the trees, keeping Helopeltis, the main cacao pest, at bay. Farmers raise mealybugs as a food source for ants and use recycled materials to connect tree branches together to create ant highways across the canopy. At night, bats, given handmade homes to host them, hunt flying insects, while owls help control rodents. Fruit trees attract birds that remove caterpillars, and dense undergrowth shelters spiders, beetles, and other natural enemies of cacao pests. Over a decade, these relationships have formed a resilient food web that protects the cacao forest.

Beyond pest control, Stone Hill follows a traditional Vietnamese Garden–Pond–Barn–Forest model. Vegetables and fruit trees provide food; rain-fed ponds raise fish and cool the microclimate; livestock and insects turn waste into fertilizer; and eight hectares of restored forest stabilize slopes and create a hospitable habitat for a range of species. Within this landscape, cacao grows symbiotically with local biodiversity, rather than displacing it.

Nothing is wasted. Cacao pod husks return to the soil. Farmed insects turn scraps into protein-rich feed. Goats munch on farm waste while enriching the soil. Even cacao processing has been redesigned: leftover cacao pulp, once discarded, now becomes Viet Nam’s first cacao cider, a golden, tangy drink created through months of experimentation.

By centering cacao in ecosystems and circular systems, the forest stays intact, soils grow richer, and cacao becomes a driver of restoration rather than deforestation.

Growing Flavor, Spreading Knowledge

Stone Hill is also a center of cacao innovation. Dr. Phước maintains Viet Nam’s largest cacao collection, with more than 70 varieties. This rare diversity gives Stone Hill chocolate its distinctive flavours. Their true tree-to-bar approach keeps every step, from seedling to finished bar, on-site. Today, the farm produces around four tons of chocolate per year.

But perhaps the farm’s greatest impact lies beyond its boundaries.

Thư now co-manages the farm, and her vision extends far beyond restoring one hillside. She is shifting the focus toward education and sharing regenerative practices across Viet Nam, a mission strengthened through the UNEP Forest Ecopreneur Incubation Programme, implemented with Bridge for Billions and the Institute for Innovation and Development, and supported by the Korea Forest Service under the ‘Sustaining and Abundance of Forest Ecosystems’ project. 

“The programme helped us look deeply and in more detail at our existing and new venture, including our education programme. The expert sessions also helped me understand more about the market, our products, and build connections with others working in the same field"

Stone Hill has already trained more than 300 farmers and technicians through field schools, workshops, and hands-on sessions. Many return home to replicate what they learned. Most programmes have focused on adults, but Thư believes lasting change begins earlier. “If we want long-term change, we must start with the young.”

Stone Hill is now expanding its forest school and youth education programmes, offering nature classes, hands-on workshops on soil, trees, and insects, and weekend activities where local children can plant, observe, and explore.

Where Stone Hill once held rock and heat, it now holds a biodiverse ecosystem. Children learn beneath its canopy, and farmers carry its lessons back to their communities. More than cacao, Stone Hill is cultivating a generation committed to restoring ecosystems across Viet Nam.

Discover more innovative restoration ventures like Stone Hill Farm through the UNEP Restoration Factory Programme, and learn more on how it is working to accelerate private investment in nature-based solutions by growing the pipeline of investment-ready sustainable land-use businesses.