What They Did
The researchers used global databases to examine the effects of forest management systems on animal and plant biodiversity. The data used compared the abundance of individual plant and animal species in managed forests and unmanaged reference forest sites. The biodiversity metrics used were: intactness (how much the abundance of each species at the reference site matches the managed site), similarity (the degree to which the managed and reference sites have the same species), relative species richness (a comparison between the number of species in the managed and reference sites), and relative total abundance (a comparison between the abundance of each species found in managed or reference sites).
They found that reduced-impact logging (harvesting a few trees with the intention of preserving biodiversity while acquiring wood resources) had the least impact on intactness. Both the intactness and the similarity of species between the managed and reference sites were lowest for plantations of perennial trees, such as oil palms, for food production. Selective cutting, clear cutting followed by regrowth, and agroforestry (growing food crops beneath a forest canopy) did not affect total species richness for plants or animals, though the species abundance changed. Timber plantations had a lower total relative abundance of animal species.
By comparing managed sites with different amounts of time since harvest (for logging) or establishment (for plantations and agroforestry), the researchers found that intactness and similarity to reference sites increased over time for selective cutting systems, timber plantations, and agroforestry systems and declined over time after clear cutting.
Further Exploration
One of the major results of the study was that intactness of the forest was significantly affected even with reduced-impact logging. On one hand, it makes sense that any amount of forest disruption, whether by removing trees, planting different species, or disturbing the space with machines, will have an impact. On the other hand, it shows the difficulty of ecological problems. Human activity always affects other species, even when we try to minimize our impact. Of course, this is true to varying degrees for all species: predators affect prey, parasites affect hosts, and “ecosystem engineer” species like beavers change the landscape.
Humans are different partly because of the size of our impact and partly because we can reflect and potentially make choices about it. Besides the questions of our physical dependence on other species, we also get to decide how much we value them for their own sake. Do we want just enough biodiversity to maximize the number of humans living healthy and fulfilled lives or do we want room for species that don’t affect our physical well-being? Can we have fulfilled lives in a world where all species are managed for human benefit?
These questions assume a degree of knowledge and skill at ecosystem management that we’re nowhere near achieving, but the more understanding we gain, the more relevant they become. I wonder what kind of personal and cultural traits will allow people to be happiest in the world we’re transforming, but that’s a rabbit hole for another day!
Image credit: Marco Schmidt
https://commons.wikimedia.org/wiki/File:Faidherbia_albida.JPG
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