Forests are quietly collapsing under climate stress

Forests breathe life into our planet. They shape landscapes, stabilize ecosystems, and absorb carbon. Yet tree mortality rates are rising across continents.

Scientists warn this trend extends beyond environmental issues, with deep social consequences that remain poorly understood.

“We don’t currently know whether climate change will lead to the death of 10 percent or 50 percent of all trees worldwide,” said Samuli Junttila, associate professor of laser scanning at the University of Helsinki.

Junttila worked with more than 100 researchers worldwide. Together, they reviewed nearly half a million forest monitoring studies spanning 89 countries and five continents.

The results pointed to climate change, driven by human activity, as the main culprit. Rising temperatures, drought, forest fires, storms, insect infestations, and disease are all fueling tree losses.

Carbon loss and forest-climate balance

Finland treats its forests as a cornerstone of climate policy. Trees act as powerful carbon sinks, balancing emissions and supporting Paris Agreement goals to limit warming below 2 °C (35.6 °F).

Protecting forests means ensuring they continue to absorb carbon even as global temperatures rise. Reliable knowledge of tree health is critical for this effort.

Globally, forests absorb about 20 percent of the carbon dioxide released by human activity. Mortality rates now create major uncertainty in predicting whether this sink will remain stable.

Large droughts, such as the one in the Amazon in 2010, have already shown how quickly forests can flip from storing carbon to releasing it.

Monitoring forests from above

To track forest health, Junttila and colleagues launched the Global Ecosystem Health Observatory. They use satellite and aerial images alongside computer-vision tools to detect tree deaths.

“We need monitoring periods of at least five years to determine whether a particular tree is dead or alive. In addition to this basic knowledge, it’s essential to understand the characteristics of local habitats and to have data on the age, size, and species of trees,” said Junttila.

“Only then can we begin to infer how tree mortality is progressing as the climate continues to warm. The good news is that modern technology already makes much of this possible.”

Forest monitoring needs more detail

Scientists stress that monitoring requires repeated surveys of tree status, size, and condition. Mortality drivers such as drought, fire, insects, and storms can only be linked with confidence when observations are frequent.

Information about whether trees died standing, uprooted, broken, or harvested provides vital clues. Combining ground checks with remote sensing makes it possible to estimate losses in biomass and carbon, not just tree counts.

Forest data missing worldwide

The study, published in New Phytologist, highlights gaps in forest mortality monitoring. Coverage is poorest in Africa, Central America, and parts of Russia. In many cases, plots exist but lack regular remeasurement.

Improving this requires long-term investment, shared standards, and collaboration across countries. Without consistent data, scientists struggle to connect local mortality patterns with global climate drivers, weakening forecasts.

Strengthening monitoring networks, while ensuring equitable access to technology and training, would allow both richer nations and those with vast tropical forests to contribute effectively.

Ultimately, bridging these data gaps will determine how accurately humanity can anticipate forest resilience in a warming world.

Satellites see only the surface

Remote sensing, from satellites to LiDAR, helps reveal canopy losses at a global scale. But satellites mainly track top-layer trees, leaving understory mortality hidden.

Integrating satellite signals with field data remains challenging yet essential. Emerging tools, such as UAV surveys and high-resolution imagery, promise finer detail but are costly and unevenly available.

Equity in global carbon monitoring

Researchers also call for fairer global collaboration. Many tropical forests hold immense biodiversity but face monitoring challenges due to cost, remoteness, and even safety risks.

Too often, scientists from wealthier countries lead studies while local researchers provide data without recognition. A fairer model would empower scientists in data-poor regions to lead analyses and shape policies.

Climate solutions need local forests

Tree mortality is both a scientific and social challenge. Forests store carbon, provide resources, and sustain biodiversity. Addressing rising tree deaths requires not only technology but also policies shaped by accurate data.

A global monitoring system, rooted in fair collaboration, could transform scattered studies into robust predictions. The health of forests is bound to the health of societies, making this research urgent and essential.

The study is published in the journal New Phytologist.

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