Are Tropical Forests Approaching a Tipping Point?
YSE experts weigh in on tropical forest degradation, biodiversity loss, and pathways to restoration.
Tropical forests are powerful carbon sinks, accounting for approximately 55% of global forest above ground-carbon stock and 40% of the total global terrestrial carbon sink. Yet recent research suggests many of these forests may be losing their capacity to sequester carbon, edging closer to tipping points that could transform them from carbon sinks into net carbon sources. This shift threatens biodiversity, local livelihoods, and the stability of the global carbon cycle.
YSE News spoke with Mark Ashton, senior associate dean of The Forest School and the Morris K. Jesup Professor of Silviculture and Forest Ecology; Liza Comita, the Davis-Denkmann Professor of Tropical Forest Ecology; and Paulo Brando, associate professor of ecosystem carbon capture, about tropical forest degradation, its impact on biodiversity, and pathways to effective conservation and restoration.
Q. Recent research suggests that tropical forests are losing their capacity to act as carbon sinks. From your work on forest dynamics and species diversity, how does biodiversity loss affect a forest’s ability to sequester carbon and remain resilient under climate stress?
Comita: Biodiversity serves as a kind of insurance in the face of disturbance. Tropical species vary in their ecological strategies and ability to withstand and recover from different stressors. Having a diversity of species, therefore, increases the likelihood that at least some species will be able to persist and function in the face of climate stress. In contrast, biodiversity loss increases the risks faced by tropical forest ecosystems. Biodiversity loss in tropical forests also is typically associated with human impacts that select for disturbance-adapted species. Such species tend to have lighter wood and, therefore, store less carbon compared to dense-wooded, mature forest species.
Q. With growing evidence that parts of the Amazon basin may already be shifting from carbon sink to carbon source, how close are we to the tipping point — and what does this mean for the stability of the global carbon cycle?
Brando: The idea of a “tipping point” in the Amazon refers to a moment when the forest changes so much that it can no longer sustain itself and begins to collapse — triggering widespread biodiversity loss, disrupting regional and global climate systems, and threatening the well-being of millions of people. Once such a threshold is crossed, the damage becomes extremely difficult, if not impossible, to reverse.
However, research from our group and others shows that the story is more complex. The Amazon is remarkably resilient. These forests have endured significant pressures over time and continue to show a capacity to recover — if given the chance.
Many people imagine the tipping point as a single moment when deforestation creates a chain reaction of climate-forest feedbacks, less tree cover leads to less rainfall, hotter temperatures, and more fires, all of which make it harder for forests to recover and can turn them from carbon sinks into carbon source. They unfold at different spatial and temporal scales. Some forest areas already show signs of stress, while others remain relatively intact. This means that even as climate change and natural disturbances reshape the Amazon, the most immediate threats are still direct human actions: deforestation, illegal logging, land grabbing, and fire.
The good news is that many of these pressures are within our control. Reducing these destructive activities gives the forest a real chance to recover and to keep playing its vital role in stabilizing the global climate.
However, if we continue to push — clearing land, lighting fires, and stripping the forest of its natural defenses — we risk losing much more than trees. We risk tipping the scales of the global carbon cycle with consequences that will reach far beyond the Amazon.
Q. Given the increasing pressures on tropical forests, what role can forest restoration and silviculture play in reversing carbon losses? What strategies do you see as most promising for restoring forest function at scale while also supporting local livelihoods?
Ashton: Restoring carbon stocks in deforested tropical landscapes is complex. It ranges from intensively managed tree plantings and commercial timber production to promoting natural forest regrowth. These approaches must balance carbon goals with local livelihood needs and other forest uses. For example, growing trees for wood products can store carbon both on-site and in harvested materials and potentially replace energy-intensive products like steel and concrete. However, economic incentives for planting trees primarily for carbon are currently limited. Most landowners prioritize income and livelihood, with carbon benefits as a secondary value.
Unsurprisingly, successful large-scale restoration depends on strategies adapted to the place. One example of this is Brazil’s Mata Atlântica, where my colleagues and I work, and where degraded agricultural lands are being transformed through a mix of commercial timber plantations and protected natural regrowth. This dual approach sequesters significant carbon and allows biodiversity and water quality to recover while providing economic returns to landowners. Similarly, once cleared by small-scale farmers, denuded marginal lands in mountainous and hilly areas of Central and South America are undergoing natural forest regrowth as people stop farming and obtain jobs in the cities. While the carbon sequestration potential here is enormous, sustaining these forests requires recognizing their ecological services and incentivizing landowners to prevent conversion to other uses.
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This is where silviculture — the science and art of managing forest growth and composition — comes in. It involves applying ecological techniques to protect, restore, or sustainably manage forests to meet diverse societal needs, including carbon sequestration, biodiversity, timber, and water resources. The effectiveness of restoration depends heavily on applying the proper silvicultural methods tailored to each site’s specific social, economic, and ecological conditions.
In all cases, integrating carbon sequestration with local economic realities and forest-dependent livelihoods is critical. Restoration initiatives that align with landowner motivations — whether for income, wood products, or ecosystem services — are more likely to succeed. Organizations like the Environmental Leadership and Training Initiative at YSE exemplify efforts to effectively empower local communities with the knowledge and tools to restore tropical forests.
Ultimately, forest restoration initiatives and silviculture can play a vital role in reversing carbon losses, but they must be carefully tailored, socially inclusive, and economically viable to achieve lasting climate and livelihood benefits.
Published
June 17, 2025
