Replanting tropical rainforests after logging may appear to be a straightforward solution to environmental damage, but new scientific research suggests recovery is far more complex and uncertain than previously believed. A long-term study conducted in the rainforests of Malaysian Borneo shows that even decades after logging, replanted forests struggle to support the survival of young trees when compared to untouched natural forests.
The research was carried out by scientists from the University of Exeter, ETH Zürich, the Smithsonian Tropical Research Institute, and the United Kingdom Centre for Ecology and Hydrology. Over an 18-month period, the team tracked the survival of 5,119 seedlings across different forest conditions in northern Borneo, including pristine forests, naturally regenerating logged forests, and areas where active restoration and tree planting had taken place.
Thousands of Seedlings Monitored Across Logged and Natural Forests
The study was conducted in the Danum Valley Conservation Area and the surrounding Ulu Segama region, where selective logging occurred between 30 and 35 years ago. Some of these logged areas were later subjected to restoration efforts, including tree planting, between 15 and 27 years after logging ended.
During the monitoring period, researchers observed a rare mast fruiting event, a natural phenomenon in which trees across large areas simultaneously produce massive amounts of fruit. This event led to a surge in new seedlings across all forest types, initially giving the impression that restoration efforts were proving successful.
At the early stages of observation, both natural forests and restored areas showed high seedling numbers. This seemed to support the idea that planting trees could help logged forests recover and regain ecological balance.
Long-Term Seedling Survival Raises Concerns About Restoration Methods
As the study progressed, however, a different pattern emerged. By the end of the 18-month period, seedlings in restored and naturally regenerating logged forests showed significantly lower survival rates than those growing in undisturbed natural forests. The sharp decline raised serious questions about the long-term effectiveness of current rainforest restoration strategies.
Dr. Robin Hayward, who conducted the research during their doctoral studies, said the findings were unexpected. Despite strong seedling growth after the fruiting event, very few seedlings survived in restored areas. The results suggest that even decades after logging, environmental stress continues to limit forest recovery and species diversity.
Scientists found that logged forests create harsher conditions for young plants due to changes in canopy cover, soil quality, temperature, and moisture levels. These altered conditions place ongoing stress on seedlings, which restoration efforts have not been able to fully address.
Specialized tree species were found to be particularly vulnerable, resulting in lower plant diversity compared to intact forests. Researchers also noted that animals such as bearded pigs may be drawn to restored areas with abundant seeds, increasing seedling loss through consumption and disturbance.
The findings, published in the journal *Global Change Biology*, highlight major challenges for tropical forest conservation worldwide. While restoration can help degraded forests store carbon and improve greenery, it may not be enough to rebuild the complex ecosystems found in untouched rainforests.
Experts involved in the study stress that protecting remaining natural rainforests must be a global priority. Restoration alone cannot replace what is lost through logging. The research team is now examining different stages of forest regeneration, including seed production, germination, and early plant survival, to identify better strategies for supporting long-term recovery.
The study serves as a reminder that preserving existing rainforests is far more effective than attempting to rebuild them after damage has already occurred.