If I took you to one of Proyecto Tití’s newest restoration sites, you might think we’d made a mistake. Instead of neat rows of trees stretching across the landscape, you would see small clusters of seedlings planted in unusual hexagonal patterns. At first glance, it might not look like the beginning of a forest. But that’s exactly what it is. And there’s a very good reason we don’t simply plant trees wherever there’s an empty space. Over the past several years, Proyecto Tití has planted more than 140,000 native trees across northern Colombia. While that number is something we’re incredibly proud of, I’ve learned that successful forest restoration isn’t measured by how many trees go into the ground. It’s measured by whether an entire ecosystem begins functioning again.

A healthy forest is much more than a collection of trees. It is a living community where everything is connected. Trees create shade that cools the forest floor. Fallen leaves become organic matter that enriches the soil. Moisture is retained beneath the canopy. Birds, bats, insects, and monkeys carry seeds from one place to another. Flowers are pollinated. Young plants establish themselves beneath older trees. Countless interactions between plants, animals, fungi, and microorganisms keep the entire system healthy. When forests are cleared those relationships disappear along with the trees. One of the questions I hear most often is: “If forests know how to grow themselves, why don’t you simply leave the land alone?” It’s a great question. Sometimes, that’s exactly what we do. This approach is called passive restoration. If an area still has healthy soil, nearby forests that can provide seeds, and wildlife that can disperse those seeds, nature often has an amazing ability to heal itself. Given enough time, new trees grow, and the forest slowly rebuilds itself.

But not every landscape has that opportunity.

Many of the areas where Proyecto Tití works have spent decades as cattle pastures. Years of grazing have compacted the soil, making it difficult for young seedlings to take root. Fast-growing pasture grasses dominate the landscape, competing with native plants for sunlight and water. In some places, repeated burning or selective logging has removed many of the native trees that once supplied seeds. Without nearby forests—or the birds, bats, and other wildlife that carry seeds—forest recovery can become incredibly slow or may never happen at all. In these situations, simply waiting isn’t enough. That’s when we turn to active restoration—giving nature a helping hand. But even active restoration isn’t as simple as planting trees. Every restoration site tells a different story. Before we ever plant a single seedling, our team spends time reading the landscape. Has cattle grazing compacted the soil? Are invasive grasses taking over? Are there nearby forest fragments that can naturally provide seeds? Has fire or logging changed the land? Which native tree species are most likely to thrive here?

The answers determine everything that comes next.

This is one of the techniques that we use to plant trees in a restoration site. Each hexagon is like a tiny neighborhood designed by nature. Around the outside of each hexagon are six Peroba-rosa (Aspidosperma polyneuron) seedlings. In the center sits a single Colombian ebony (Libidibia punctata) seedling, one of Colombia’s threatened native tree species. Why plant them this way? Rather than asking one tiny tree to survive the harsh conditions of an abandoned pasture by itself, we’re creating the beginnings of a small forest around it. The Peroba-rosa seedlings form a protective ring around the Colombian ebony. As they grow, they provide partial shade, reduce the intense heat of the tropical sun, and help the soil retain moisture.

This creates the kind of environment where the slower-growing Colombian ebony has a much better chance of thriving. Next the hexagonal planting modules are repeated across the restoration site. Instead of creating one large plantation, we establish many small “forest neighborhoods” that gradually expand and merge together over time. The second photograph provides a closer look at one of these modules, showing how every seedling has been placed with a purpose. These designs aren’t accidental. Every species plays a different role in rebuilding the forest. Some trees grow quickly and provide shade. Others improve soil conditions. Some eventually produce flowers that attract pollinators, while others provide food and shelter for wildlife.

Together, they recreate the conditions that allow a forest to begin functioning again. As these young forests grow, they begin transforming the landscape. Shade suppresses invasive pasture grasses. Fallen leaves gradually rebuild the soil with organic matter. Root systems improve the soil’s ability to absorb and retain water. Birds, bats, insects, and monkeys begin returning, bringing seeds from nearby forests and helping new plants establish naturally.

Little by little, something remarkable happens. The forest begins doing what forests have done for millions of years—it starts growing itself. This is the moment every conservationist hopes for. The trees we planted are no longer doing all the work. Natural regeneration begins taking over. New seedlings appear where no one planted them. Wildlife returns. Ecological relationships are rebuilt. The forest becomes cooler, more humid, and increasingly capable of supporting the incredible diversity of life that once existed there—including the critically endangered cotton-top tamarin.

Watching cotton-top tamarins leap through the canopy of a forest that was once a barren cattle pasture reminds me why we do this work. Every tree we plant is part of something much bigger than restoring a landscape. It’s about giving an entire ecosystem a second chance—and ensuring that future generations will always have a place where cotton-top tamarins can call home.