A national park in Indonesia that was established to safeguard some of the world’s rarest wildlife has lost more than half of its forest in just two decades. New research tracking changes over time shows that the destruction did not happen overnight or through a single dramatic event. Instead, it spread quietly from the edges inward, steadily hollowing out the park’s core.
The study focuses on Tesso Nilo National Park in Riau province on the island of Sumatra, a protected area created in 2004 to conserve lowland rainforest and provide habitat for critically endangered Sumatran tigers and elephants. Despite its legal status, satellite images and field observations reveal that forest loss has continued almost uninterrupted, raising serious concerns about how protected areas are enforced on the ground.
Forest loss spreads from the edges to the heart of the park
Researchers analysed two decades of satellite data alongside field visits to understand how the landscape changed over time. Using images from NASA’s Landsat satellites, which have monitored Earth’s surface since the 1970s, they classified land into forest, agriculture and bare ground. This long-term record allowed them to see patterns that short studies often miss.
The clearing did not appear randomly. Instead, deforestation began along the park’s boundaries and gradually advanced toward the centre. As forest blocks were broken into smaller pieces, the amount of forest “edge” increased, exposing more land to human activity. This process, known as fragmentation, reduces the size of undisturbed core forest areas, making them warmer, drier and less suitable for wildlife that avoids human presence.
Lowland rainforests are especially vulnerable to this kind of damage. When tall canopy trees are removed, sunlight reaches the forest floor, drying soils and streams that once stayed shaded. Over time, the forest becomes structurally simpler, with fewer layers and fewer safe spaces for animals to hide and move.
Oil palm plantations quietly push into protected land
The research traced much of this forest loss to the expansion of oil palm plantations. Clearing often begins with mixed forest removal, followed by soil drainage that lowers groundwater levels and accelerates drying. Once established, oil palm plantations are managed for decades, making forest recovery increasingly difficult.
The study found that agricultural land and bare ground expanded alongside forest loss, suggesting that plantations continued pushing into newly cleared margins. Even where national policies restricted new permits for clearing primary forests and peatlands, enforcement gaps allowed illegal planting to continue, particularly by smallholders operating beyond effective oversight.
Certification systems such as the Indonesia Sustainable Palm Oil programme exist to promote responsible production, but the research indicates that these measures often fail to reach remote areas or informal growers. When paperwork does not match conditions on the ground, park boundaries lose their meaning, and protected forests become vulnerable to gradual encroachment.
As roads and transport networks expand, access improves for settlers, traders and equipment, further accelerating land conversion. Mapping of human infrastructure shows that almost the entire park has been altered in some way, leaving only small forest fragments that are increasingly difficult to defend.
For species like Sumatran tigers, which require large, connected territories, this fragmentation is especially dangerous. As forests shrink and break apart, animals are forced closer to people, increasing the risk of conflict, poaching and habitat loss.
The researchers argue that saving what remains of Tesso Nilo National Park will require more than drawing boundaries on a map. Protecting the largest remaining forest blocks, restoring habitat corridors that reconnect fragments, and supporting sustainable livelihoods in surrounding communities are all essential steps.
Without consistent enforcement and local trust, even the most carefully designated protected areas can fail. The study warns that the window to restore connectivity and protect wildlife is narrowing, and that long-term monitoring combined with fair economic alternatives offers the best chance of reversing the damage.