Why some tropical forests regenerate naturally

Previous research has shown that fast-growing “pioneer trees” are often the first to thrive on affected land. They can eventually be overtaken by larger trees capable of storing more carbon. Dent’s research helped explain the mechanisms behind this process and why it succeeds in some places but not others.

In areas dominated by stubborn grasses planted by ranchers, the grasses can cover the ground and prevent other trees from taking root. These grasses may persist for 150 years, blocking sunlight and preventing a second wave of large-trunked trees from becoming established.

To plant or not to plant?

Dent was well positioned to contribute to the surge of interest in tree planting that began in 2015. She had already become a principal investigator at 2ndFor, an international research network focused on how to manage secondary forests.

Using data collected from the Barro Colorado plot, the team published a 2016 paper in Nature. The study found that one hectare of naturally regenerated secondary forest can absorb 11 times more carbon each year than primary forest. Young trees absorb carbon rapidly as they compete to grow toward the sun.

In a 2022 survey published by the Royal Society, Dent and her colleagues showed that places such as Barro Colorado can represent a best-case scenario for forest recovery without planting a single seed. Clearings are often surrounded by lush environments filled with birds, bats and other animals that help restore tree cover and return native levels of forest richness within a few decades.

Using data from Panama and Brazil, Dent published a follow-up study in 2024 showing that areas with as little as 35% tree cover can regenerate as forest.

“Having forest patches that have been mapped over such a long period of time is really valuable,” says Riza Komita, a professor of tropical forest ecology at Yale University. She is collaborating with Dent on a project that translates research findings into action. “This provides a really great research infrastructure on which we can build projects.”

When forest restoration requires intervention

In Panama, Dent is working with nonprofit organizations and carbon credit schemes to accelerate forest recovery. The groups have mapped corridors to reconnect forest fragments and developed a plan to reintroduce animals to a “quiet forest” that had lost much of its wildlife.

They are also replanting tree species that can promote forest growth, an approach Komita describes as rewilding. Although leaving a plot alone may seem like the easiest option, Dent says passive recovery is not possible everywhere. Many sites are too degraded to regenerate without help.

Clearings are often surrounded by lush environments filled with birds, bats and other animals, all of which help the trees return to native forest-level abundance.

Dent and Komita are working with London-based carbon credit startup Pontera to develop a solution for an area in southern Panama where remnant forests line the edges of abandoned ranches. Komita explains that such sites almost always require some form of intervention, including practical measures such as reinforcement planting.

What natural regeneration means for carbon credits

Dent says the questions being asked by projects such as Pontera are increasingly aligned with her research. For example, the team wants to understand whether isolated trees left standing by ranchers to provide shade for cattle can help degraded land regenerate more quickly.

These insights can help Pontera sell higher-quality carbon credits and avoid costly mistakes that could literally send a new plantation up in smoke. Credits can be purchased for as little as $5 per ton, while major companies such as Microsoft, one of Pontera’s customers, pay more than 10 times that amount for high-quality carbon removal.

There are many places where some degree of natural regeneration can work well. According to the Brazilian Restoration and Forestry Observatory, millions of hectares of rainforest have already regenerated naturally in Brazil.

Still, Dent questions why those responsible for large-scale restoration projects continue to assume that imposing human will on the landscape is the best solution.

Why tree planting alone may not be enough

As Latin America faces drought, policymakers and carbon creditors may be forced to confront the shortcomings of conventional plantations.

“When extreme events occur, such as droughts, floods, heatwaves or pathogens, the resilience of the system is significantly reduced,” Dent said.

Next year’s El Niño could provide a moment of reflection, she says. “I think there’s a growing recognition that we can’t just plant trees. We need to rebuild the system.”