- A newly published study has found that seedlings in previously logged forests in Borneo struggle to survive compared to those in intact forests, even with restoration efforts.
- Researchers monitored more than 5,000 seedlings for 18 months in three types of landscapes — unlogged forest, naturally regenerating logged forest, and actively restored logged forest — and found the benefits of restoration efforts diminished over time.
- The study suggests that changes in canopy structure, microclimate, soil, low genetic diversity of planted trees, excessive herbivory, and failure to restore soil conditions may contribute to the stress experienced by seedlings in logged forests.
- The low survival rates of seedlings, even 30 years after selective logging, raise concerns about the long-term recovery of biodiversity and the ability of future tree generations to thrive in human-modified tropical forests worldwide.
Young trees face significant challenges surviving in previously logged forests compared to intact forests, even in areas with active restoration efforts, according to a recent study.
The findings, published in the journal Global Change Biology, raise concerns about the long-term recovery of biodiversity in logged forests. This concern is growing as human-modified forests now exceed primary forests by area in the tropics.
The research team, led by Robin Hayward at the University of Stirling in Scotland, monitored more than 5,000 seedlings for 18 months in the Danum Valley Conservation Area and the surrounding Ulu Segama landscape in Malaysian Borneo.
They compared seedling survival and diversity in unlogged forests, naturally regenerating logged forests, and actively restored logged forests that had been selectively logged 30-35 years ago.
Following a mast fruiting event, where many trees produced a lot of fruit all at once, the researchers saw many seedlings in the unlogged and logged forests. However, as time passed, the benefits of the restoration efforts started to fade. By the end of the study, the survival rate of seedlings in the restored forests was significantly lower than in the unlogged forests and was similar to the logged areas recovering naturally.
“Our findings suggest that seedlings are experiencing stress in logged forests,” said study co-author David Bartholomew, from the University of Exeter in the U.K. “This could be due to changes to the canopy structure, microclimate, and soil, with current restoration treatments insufficient to eliminate this stress.”
The study also found that trees in logged forests grew and functioned differently than trees in unlogged forests. This might mean that some types of trees have a hard time adapting to the changes in their environment after logging or that they have to change the way they grow to deal with the new conditions. These findings suggest the potential for long-lasting changes in biodiversity and ecosystem function in recovering forests.
“After such a productive fruiting event in the restored forest, it’s disappointing that so few were able to survive — and to think what this might mean for the long-term recovery of different tree species,” Hayward said.
Even though people have tried to help logged forests recover by planting trees and managing the forest, these efforts didn’t seem to help the seedlings survive better in this case. The researchers say this might be because the planted trees have low genetic diversity, too many animals are eating the seedlings, or because the soil hasn’t been restored properly.
The study’s authors say it’s important to keep researching and monitoring these forests to ensure restoration efforts are helping them recover over long periods. They also point out that the field of restoration ecology is still fairly new, with restoration only being included in the official targets of the Convention on Biological Diversity in 2010.
“While logging in the tropics is unlikely to stop anytime soon, it is important to know that the problems it causes can persist for decades and that post-logging restoration activities can also cause problems,” Francis E. Putz, a researcher with the Forest Research Institute at the University of the Sunshine Coast in Australia, who was not involved in the study, told Mongabay in an email. “My concern is that so much more attention is paid to describing problems than to seeking solutions.”
Selective logging, where only certain trees are cut down, is common in tropical forests worldwide. The low survival rates of seedlings in this study, even 30 years after logging, raise concerns about whether future generations of trees will be able to thrive.
While this study gives us an idea of the challenges logged forests face in Borneo, more long-term research is needed to fully understand the effects of logging and figure out the best ways to help seedlings survive.
Banner image of an endangered long-tailed macaque (Macaca fascicularis) in Borneo. Image by John Cannon/Mongabay.
Liz Kimbrough is a staff writer for Mongabay and holds a Ph.D. in ecology and evolutionary biology from Tulane University, where she studied the microbiomes of trees. View more of her reporting here.
Forest restoration to boost biomass doesn’t have to sacrifice tree diversity
Citation:
Bartholomew, D. C., Hayward, R., Burslem, D. F., Bittencourt, P. R., Chapman, D., Bin Suis, M. A. F., … Dent, D. (2024). Bornean tropical forests recovering from logging at risk of regeneration failure. Global Change Biology, 30(3), e17209. doi:10.1111/gcb.17209
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