Old growth rain forests are comprised of massive trees — centuries-old behemoths that tower above the biological exuberance thriving beneath. Scientists have long known that these forests are irreplaceable, supporting countless species that can live nowhere else on Earth.
However, around the world, vast tracts of forest now exist where these large hardwoods have been selectively removed by conventional logging practices. What is the biological value of these forests, and what are the economic and ecological tradeoffs of conserving them?
In Southeast Asia, pioneering research is answering this question for the first time. In a historically rare case of ecologists and economists working together, researchers from Conservation International, Princeton University and collaborating institutions have quantified the tradeoff between biodiversity conservation and financial returns from logging.
Our team spent months working in the field in Danum Valley, Malaysian Borneo to measure the diversity and abundance of birds and dung beetles in unlogged forests, once-logged forests, and twice-logged forests.
Walking through a primary, unlogged forest in Danum Valley is fun and relatively effortless; the understory is open and cool, well-shaded by the spreading crowns of large dipterocarp trees above. Walking through a heavily logged forest at Danum, however, is a sweaty struggle. Increased sunlight reaching the forest floor results in dense, tangled growth of thorny vines and weeds, making passage impossible without a sharp machete.
Why measure birds and dung beetles? Separate studies have shown these to be the two most cost-effective indicator groups for understanding broader trends in biodiversity, making them an ideal model system. For example, dung beetles are tightly linked with large mammal communities which they depend upon for food, yet can be sampled much more easily and efficiently than mammals.
By analyzing the relationship between timber extraction, timber value and biodiversity in each forest type, we found that selectively logged forests represent a surprisingly cost-effective opportunity for biodiversity conservation.
The value of standing timber dropped 80 percent after two rounds of logging (yielding over $8,000 per hectare), yet twice-logged forests lost only 25 percent of their species.
Beyond species, these logged forests also provide several valuable ecosystem services for people, which include carbon storage, regulation of river flows and sedimentation, and aesthetic and cultural benefits. In stark contrast, the conversion of forests to oil palm plantations provides large financial returns, but is ecologically devastating, leading to declines of more than 75 percent in biodiversity and loss of ecosystem services.
These conclusions will be important for guiding conservation strategies in Southeast Asia, where oil palm and logging dominate much of the landscape. While unlogged forests remain an irreplaceable priority for species conservation, our findings indicate that conserving forests that have already been damaged by selective logging — which occur over about 50 percent of Indonesia and Malaysia — is a highly cost-effective complement to primary forest conservation. For example, logged forests should be used to enlarge and connect existing protected areas by acting as wildlife corridors, allowing threatened species populations — along with the altered forests they inhabit — to recover.
Trond Larsen is a research scientist in CI’s Science and Knowledge division. To learn more about this analysis on biodiversity and logging tradeoffs in Southeast Asia, check out this paper recently published in the science journal Conservation Letters.