Only 40% of Global Forests Remain Ecologically Intact: Why Quality Matters More Than Quantity

Redacción HC
24/11/2023

Forests are often viewed as the lungs of the Earth, but recent research shows that most of them are no longer breathing freely. Despite growing awareness of deforestation, a new global study reveals a deeper problem: even many forests that appear green and standing are functionally degraded. According to a landmark study published in Nature Communications, only 40% of the world's remaining forests maintain high ecological integrity—meaning they remain largely undisturbed and functional ecosystems.

This insight reframes our understanding of forest conservation. It's not just about how much forest is left, but how healthy and connected these landscapes are.

What Is Forest Integrity, and Why Does It Matter?

Forests with high ecological integrity provide essential ecosystem services: climate regulation, carbon storage, biodiversity refuge, and water cycling. However, human activities—like roads, agriculture, logging, and infrastructure—can severely impair these functions even without cutting down entire forests.

The concept of “forest integrity” evaluates not only the presence of trees but their ability to function as complete, undisturbed systems. The study’s central question was clear: How much of the world's forest still works as it should?

Measuring the Invisible: The Forest Landscape Integrity Index

To answer this, the research team led by H.S. Grantham and colleagues developed the Forest Landscape Integrity Index (FLII). This global metric integrates three critical factors:

1. Observed human pressures — such as roads, agricultural lands, and recent deforestation.
2. Inferred pressures — disturbances inferred from proximity to human activity, even when not directly visible.
3. Forest connectivity — the extent to which forest patches are connected or fragmented.

Each hectare of forest worldwide was scored on a continuum, categorizing it into high, medium, or low integrity. The analysis relied on a range of geospatial datasets, including satellite imagery and infrastructure maps.

Key Findings: The Global State of Forest Health

Only 40% of Forests Are Ecologically Intact

Out of 57.4 million square kilometers of remaining forests, only about 17.4 million km² (40.5%) retain high ecological integrity. This means that nearly 60% of global forests are moderately or severely degraded, despite still being forested in appearance.

Where the Last Intact Forests Are Found

The highest-integrity forests are clustered in:

• Canada and Russia (boreal forests)
• The Amazon Basin (especially in Brazil, Peru, and Colombia)
• Central Africa (e.g., Congo Basin)
• Papua New Guinea and parts of Southeast Asia

Surprisingly, only 27% of these high-integrity forests fall within formally protected areas such as national parks or reserves.

Human Pressure Is Nearly Universal

• 31% of forests show direct human pressure, like infrastructure and farmland.
• A staggering 91% are affected by indirect pressures, including fragmentation and proximity to disturbed areas.

These pressures can reduce biodiversity, disrupt ecological processes, and limit the forest's ability to support species and store carbon.

Beyond Tree Cover: A New Lens on Forest Conservation

This study challenges the conventional metric of conservation success: forest cover alone is insufficient. Two forests with the same canopy area may have vastly different ecological value.

Quoting the authors: *“Protecting what remains intact is far more cost-effective than restoring degraded forests.”* Restoration, while important, is often slow and expensive—and in some cases, irreversible degradation means full recovery is impossible.

Implications for Conservation and Policy

Prioritizing the Most Intact Forests

Conservation strategies must shift from solely preventing deforestation to actively protecting high-integrity landscapes, many of which lie outside current protected areas. Once degraded, these forests lose not only biodiversity but also their climate-regulating potential.

Tools for Smarter Land-Use Planning

The FLII offers policymakers a powerful cartographic tool to identify high-integrity zones, guiding infrastructure development away from ecologically sensitive regions.

Recognizing Indigenous and Community Stewardship

Many high-integrity forests lie in territories managed by Indigenous Peoples and local communities. Strengthening their land rights and governance can enhance forest protection without depending solely on formal protected area status.

Urgent Recommendations

• National mapping of high-integrity forests and targeted legal protections.
• Incorporating the FLII into environmental impact assessments and zoning.
• Focusing restoration where it improves forest connectivity and ecological functionality.

Conclusion: Rethinking Forest Conservation for the 21st Century

Forests are more than just green spaces on a map—they are complex, living systems. The study by Grantham et al. reveals a sobering truth: most of the world’s forests are no longer functioning naturally. Protecting the remaining 40% of high-integrity forests must become a central pillar of global climate and biodiversity strategies.

As we face accelerating environmental crises, the message is clear: quality, not just quantity, must guide the future of forest conservation.

Topics of interest

Biodiversity Climate