We may be underestimating the negative impacts of logging on the biodiversity of tropical forests

In this post Filipe França & Hannah Griffiths discuss their recent paper Do space-for-time assessments underestimate the impacts of logging on tropical biodiversity? An Amazonian case study using dung beetles

The difficulty in developing strong researcher-practitioner relationships is a central ‘stumbling block’ in conservation science. Unfortunately this means that more often than not the policy implications of ecological research don’t reach the people responsible for on-the-ground conservation initiatives. As a result, management decisions are not always made based on robust ecological data, despite it being available. While the importance of effective communication between scientists and practitioners is recognised by both parties, this breakdown in knowledge transfer is caused by distinct hurdles on both sides. Yet going beyond the desired application of academic research for the creation of evidence-based conservation policies, building strong researcher–practitioner partnerships could also improve the way we design our ecological research. With this in mind, a key question is how can practitioners influence the way we assess the biodiversity impacts of human activities?

What the eyes do not see, the forest feels. Selectively logged forest in the Brazilian Amazon, state of Pará, July 2013. Photo credit: Filipe França.

How could effective communication between researchers and practitioners improve the assessment of biodiversity loss?

Before answering this question, we must remember that predicting exactly where and when human-induced disturbances (such as land-use change, wildfires and logging) will take place is almost impossible. As result, most ecological impact assessments occur after the main disturbance event has taken place. Researchers are therefore forced to compare what was found at disturbed sites to results from undisturbed sites in nearby regions. This approach, known as a space-for-time (SFT) substitution, dominates the literature on land-use change and forest disturbance. However, in an ideal world where scientist–practitioner partnerships are strong and well planned, researchers would be able to sample both before and after the disturbance, using the before-after control-impact approach (BACI).

Although most researchers recognize the potential benefits of a BACI design, it is not clear to what extent this approach improves accuracy in assessing the impact of anthropogenic disturbances on biodiversity in terrestrial environments.

To address this our new study recently published in Journal of Applied Ecology, compares whether space-for-time (SFT) and before-after control-impact (BACI) approaches yield different conclusions regarding the relationship between selective logging intensity and changes in dung beetle diversity.

Why dung beetles?

Dung beetles use mammalian dung for feeding and nesting purposes and in doing so they perform a number of key ecosystem processes such as dung burial and secondary seed dispersal. Furthermore, they are sensitive to human-induced habitat disturbances and are a cost-effective group to work with in for field-based investigations. They are, therefore, an ideal model system with which to evaluate the biological impacts of forestry practices.

Coprophanaeus lancifer
Coprophanaeus lancifer, the largest crepuscular tunnelling dung beetle species found in the study region. Photographed in the Brazilian Amazon, 2012. Photo credit: Hannah M. Griffiths.

Why selective logging?

We focus on selective logging because it is one of the most important economic activities in tropical forests and has been suggested as less environmentally damaging compared to other anthropogenic disturbances such as fire, agriculture and fragmentation.

Our study was conducted within a timber concession, located at the State of Pará in the north-eastern Brazilian Amazon. Reduced-impact logging operations are planned following the FAO (Food and Agriculture Organization of the United Nations) guidelines, to log approximately 544 000 ha of native forest over a 30-year cutting cycle. By using the company’s pre-harvest inventory and operational logging plan, we sampled dung beetles before and after logging activities within 34 sample units situated along a gradient of planned logging intensity, from 0 (no logging) to 8 trees removed per hectare.

Tree being logged by a worker within the timber concession in the Brazilian Amazon, 2012. Photo credit: Filipe França.

Our study shows that compared to the BACI approach, results from SFT sampling methods greatly underestimated the consequences of logging intensification for dung beetle local diversity and species composition. More than double the number of species lost were lost from the most disturbed plots when assessed using the BACI approach compared to SFT. Such significantly weaker effects revealed by the SFT approach are of great concern because the SFT designs are the most commonly used method for assessing biodiversity and ecosystem functioning losses caused by anthropogenic forest disturbances.

We understand that BACI approaches are accompanied by many logistical constraints and this makes the continued use of SFT studies inevitable in many cases. We encourage the use of BACI approach where possible, but highlight that incentivizing BACI studies will require long-term funding to gather the data and stronger links between researchers and landowners.

Summary of the comparisons between Space-for-Time substitution (SFT) and the Before-After Control-Impact (BACI) approach. Infographic credit: Filipe França.

This research was only possible due to effective communication links with the logging company we worked with, Jari Florestal. Our main finding was that the SFT substitution approach underestimated the impacts of logging on dung beetle diversity. However, our take home message is not just an ecological one – we also stress that researcher–practitioner partnerships need to start long before research is undertaken. In doing so, both the biodiversity loss assessments and the integration or solution of concerns from researchers and stakeholders will be improved.

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