Future Forests Will Be Dominated by Fast-Growing Trees

The world’s forests are projected to undergo a profound transformation in the coming decades, with fast-growing tree species increasingly dominating ecosystems once shaped by slow-growing native trees now facing extinction. The findings come from a global study titled “Global functional shifts in trees driven by alien naturalization and native extinction,” published Jan. 28, 2026, in the scientific journal Nature Plants.

The international research was led by Wen-Yong Guo of East China Normal University, alongside scientists from multiple countries. The team analyzed data from 31,001 tree species worldwide to assess how the spread of alien naturalized species and the accelerating extinction risk of native trees are reshaping forest composition and function.

Their conclusion: future forests are likely to be increasingly dominated by species with so-called “acquisitive” traits — trees that grow quickly, rapidly absorb light and nutrients, and tolerate a wide range of environmental conditions.

What Are Fast-Growing Trees?

Fast-growing trees typically share several key characteristics: thin leaves with high photosynthetic rates, low wood density, rapid trunk and branch growth, and relatively short lifespans. Species such as acacia, sengon (Falcataria moluccana), certain eucalyptus species, and poplars fall into this category. These trees often thrive in disturbed landscapes, including logged areas, abandoned agricultural land, or regions experiencing climate stress.

Because of their rapid growth, such species are frequently used in commercial plantations and reforestation projects. Ecologically, however, their dominance can simplify forest structure and alter long-term ecosystem processes.

In contrast, slow-growing trees tend to have dense wood, thicker leaves, steady but gradual growth, and long lifespans. Examples include many dipterocarps in Southeast Asia, old-growth teak, mahogany, and key canopy species in the Amazon and Central African rainforests. These trees typically evolve in stable forest environments and play a crucial role in long-term carbon storage and structural complexity.

Functional Shifts in Ecosystems

According to Jens-Christian Svenning of Aarhus University, a senior co-author of the study, alien species that successfully naturalize outside their native range often possess broader ecological tolerance than many threatened native species.

“Species that adapt quickly often have high ecological flexibility. They can survive in colder, drier, or more disturbed conditions,” Svenning said in a statement accompanying the study.

By contrast, many species currently at risk of extinction are slow-growing and highly specialized. They depend on stable climates, nutrient-rich soils, and intact forest systems. When habitats are fragmented or degraded by deforestation and climate change, these trees struggle to recover.

The shift is not merely about which species are present. It represents a fundamental change in how forests function.

Fast-growing trees can absorb carbon rapidly during early growth stages. However, because their wood is generally less dense and their lifespans shorter, stored carbon may return to the atmosphere more quickly when the trees die or decompose. Slow-growing trees with dense wood, by contrast, can lock away carbon for decades or even centuries.

As a result, forests dominated by fast-growing species may still appear green and productive, but their long-term carbon storage capacity could decline.

The study also warns that reduced functional diversity may weaken ecosystem resilience. Forests rich in slow-growing, structurally diverse species typically feature complex canopy layers that provide habitat for birds, mammals, insects, and countless microorganisms. If that structural diversity diminishes, forests may become more vulnerable to pests, diseases, drought, and wildfire.

The Risk of Global Homogenization

Researchers highlight the growing threat of “biotic homogenization,” in which forests in different parts of the world become increasingly similar due to the spread of species with comparable functional traits.

Over time, such homogenization could make global forest systems more susceptible to large-scale shocks, including extreme climate events or emerging pathogens.

Guo and his colleagues stress that conservation strategies must look beyond forest area alone. Protecting the functional diversity of forests — especially slow-growing, threatened species — is critical to maintaining long-term ecosystem stability.

Restoration efforts that prioritize rapid canopy recovery without considering species composition may inadvertently accelerate functional simplification.

Implications for Tropical Forests

The projected functional shift carries particular weight for tropical forests, which harbor the highest tree diversity on Earth. Tropical ecosystems in the Amazon Basin, Central Africa, and Southeast Asia contain large proportions of slow-growing, dense-wood species that anchor long-term carbon storage and ecological stability.

In Southeast Asia, for example, dipterocarps form the dominant canopy of lowland rainforests. These trees grow slowly but define forest architecture and sustain biodiversity. If they continue to decline and are replaced by faster-growing species, the long-term resilience of tropical ecosystems could weaken.

Tropical forests also support millions of people by providing clean water, food sources, building materials, and protection from flooding and erosion. The loss of slow-growing native species is therefore not only a biodiversity issue but also a socio-economic concern.

The study published in Nature Plants underscores that the future of forests will not be determined solely by how much forest remains standing, but by which types of trees survive within them. Forests may remain green in the decades ahead — but functionally, they could become profoundly different from those that have shaped Earth’s ecological balance for centuries. (Sulung Prasetyo)

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