The Louder, The Better? Monitoring the success of the REDD+ Gola Rainforest project using Soundscape Saturation
Updated: 7 days ago
How effective are protection measures truly? The same scenario plays out all over the world in environmental protection: a new initiative, policy, or protection zone is established, and funds, energy, and time are spent to enforce it, but when it comes to monitoring the actual success throughout the years, many challenges present themselves. The very characteristics that make a region worthy of protection can also make it difficult to study. Protected areas are often designated because they still contain relatively intact ecosystems, support high levels of biodiversity, and have experienced limited human disturbance. As a result, these areas are frequently remote, difficult to access, and characterised by minimal infrastructure and signs of human activity, making regular, long-term monitoring both logistically challenging and expensive.
The Gola Rainforest in West Africa is a prime example of this. Here, conservation efforts supported by the REDD+ initiative have been underway for more than a decade but finding a holistic measure to assess whether these labours have born any fruit has proven difficult. The project has therefore provided a valuable opportunity for a young researcher in need of a PhD topic to look beyond whether this forest is being protected on paper and investigate a more fundamental question: is the success of these conservation efforts reflected in the biodiversity that the forest supports?
Protecting forests worldwide, and locally
In the dense Gola rainforest of Sierra Leone, a global initiative has set up to protect biodiversity and support communities that call this region their home. REDD+ (Reducing Emissions from Deforestation and forest Degradation in developing countries, with the “+” denoting the additional forest conservations included in the UNFCCC scope) is a large voluntary climate change mitigation framework developed by the United Nations Framework Convention on Climate Change (UNFCCC); its main aim is to encourage developing countries to reduce their carbon emissions by stopping deforestation and forest degradation. By combining forest protection with financial incentives and sustainable livelihood opportunities for local communities, REDD+ aims to promote conservation, sustainable forest management, and community support. Worldwide, over 600 locally acting REDD+ initiatives all work towards the global goal of lessening the effects of the climate catastrophe.
The Gola Rainforest REDD+ initiative has been a part of this network since 2013. At the time of its founding, it was the first of its kind in West Africa and is projected to run until 2030. The project draws its funding from the sale of carbon credits in the region, and uses it to support the management and conservation of the National Parks, promote sustainable resource use by improving local communities’ livelihoods, and fund a monitoring programme designed to track the initiative’s progress and inform future management decisions. But its ambitions extend beyond 2030: the Gola Rainforest REDD+ initiative aims to establish a national Conservation Trust Fund, creating a source of long-term funding to keep conservation efforts going even after the project itself comes to an end.
While the work of such initiatives is no doubt valuable and highly important to preserve biodiversity and support communities, its actual effectiveness for biodiversity conservation and enhancement is rarely monitored. As with all biodiversity monitoring, the problems that present themselves are manifold: how to create an index that shows biodiversity without a doubt? How to prove that it is the initiative, and not other factors that are responsible for the monitored change? And, how to collect the data in the first place, in a region that is mostly untouched, unfarmed, and therefore difficult to access by researchers?
Monitoring the progress
In 2022, H. S. Sathya Chandra Sagar, now a postdoctoral researcher at the Future Forest Research Excellence of the University of Freiburg, set out to make the Gola Rainforest REDD+ subject of his PhD thesis. His main goal was to understand the effectiveness of the REDD+ strategy, and the project in Sierra Leone was deemed a perfect fit for this cause. Sagara’s personal connection to the initiative, as well as its established long-time presence in the region made it a great set up to test his hypotheses, along with the fact that as the first such project in all of West Africa, it set a gold standard for how REDD+ should operate on this continent.
Sagara’s focus lay on the effects the strategy had on the biodiversity of the Gola Rainforest, specifically the fauna. His chosen methodology was a combination of arthropod eDNA, and bioacoustic monitoring. These two methodologies combined offered a viable way to extract conclusive data from a landscape as vast and diverse as the Gola Rainforest, with the bioacoustic method offering the unique advantage of having “spare time” while the recorders were out on deployment, making it the perfect opportunity to collect data through alternative methods while waiting for the recordings to be completed.
Sagara used fifteen BAR-LTs to survey an area of near inaccessible rainforest, which stretched across two countries at once. With traditional research methods, this task would have demanded many months of fieldwork, as well as a large number of researchers and volunteers to produce a comparable amount of data. Using bioacoustic recorders, it merely took three people to survey 133 sites over the course of three months.
Sagara chose the early beginning of the dry season between December and February for his fieldwork, as this time of the year ensured not only a higher call activity for many of the animal species inhabiting the rainforest, but also lower chances of audio material being rendered useless by loud rain and weather noise. Three categories of forest were identified, and study sites in all three of them were subsequently chosen: REDD+ protected forest, forest under more general protective policies, and community forest free of protective measures. To understand how the remoteness of a location played a part in the level of biodiversity found at the site, the study sites were also chosen in categories of proximity to the nearest human settlement, and each round of recording would have sites of each category present as to eliminate potential biases introduced by stacked recording over a certain timeframe.
Converting levels of sound into levels of biodiversity
But how to evaluate the level of biodiversity in the first place? Sagara used a metric to link heightened levels of sound to heightened biodiversity: Soundscape Saturation (SS). This metric expresses the percentage of available frequency space which is occupied by acoustic energy above a defined threshold. By analysing how often the SS rises above the defined frequency threshold within a recording, this percentage can be determined. For this metric to be interpretable in an ecological context, it is assumed that a more diverse animal community vocalizes more frequently, and occupies more acoustic niches, leading to a heightened SS.
After analysing the collected acoustic data using this metric, Sagara’s findings were clear: forest which was under REDD+ protection showed a significant increase in SS, compared to forest outside of that protection zone, and community forest without any protection. This difference was especially significant between REDD+-financed protected areas and community forest, with a 12.8 percent lower average in SS at sites located in the latter category, and pronounced spikes around dawn and during the night in the former category. Comparing REDD+ protected forest and forest protected by other policies, the SS average was quite similar, although the times of day when increases in SS happened differed.
This does suggest that protective measures in the Gola rainforest have positive impacts on the residential fauna, given that sound activity was higher than in the community forest.
Monitoring the effectiveness of conservation initiatives with bioacoustics
The work Sagara undertook for his PhD thesis demonstrates beautifully that bioacoustic monitoring is a viable method to measure and correctly assess the impact a conservation initiative has on the very thing it sets out to conserve. Durable, portable, and weatherproof acoustic recorders are an excellent option when it comes to field work in difficult to access terrain, over long periods of time. Not only do they reduce the number of participants needed to run a field study, but they also eliminate the observation bias and can collect far more data over a far larger time span than a human observer ever could. Not only that: the data, once recorded and saved, can be reused for more than one project and purpose. Sagara himself has been using the data he collected during the field work in 2022 for four years now, examining it to research several different hypotheses, and his work with the material is far from finished.
In Sagaras’ experience, bioacoustic methods are very effective tools to understand the effects of forest degradation, as well as deforestation effects, that could be due to presence or absence of the REDD+ initiative. Using regression discontinuity in combination with econometric strategies, he was able to draw a direct comparison between protected areas and community forest which lay outside the reach of REDD+, and could thus demonstrate that without this protection, the former would likely be showing the same level of biodiversity degradation as the latter. When it comes to finding out whether protection actually made a difference in two protected areas of similar habitats, where the only intervention of the REDD+ initiative was the alleviation of hunting pressure in one of the two, SS became the best metric, as it could capture even slight differences in vocal species, and could therefore tell the researchers things other methodologies were unable to capture.
However, through all of this it is prudent to keep in mind that SS is not a direct link to biodiversity. While the theory behind it holds value, a high SS could theoretically result from many other factors which are not linked to heightened biodiversity, such as a larger number of individuals, louder individuals, a higher number of simultaneous vocalizations, changes in the presence of different species, or even anthropogenic or abiotic noise. Therefore, just like other acoustic indices, SS cannot directly and solely be interpreted as a singular measure of species richness and levels of biodiversity. When combined with other methodologies though, it is a very solid way to understand the impact that protective policies can have on a landscape.
Looking into the future
While using carbon credits to support biodiversity protection projects in developing countries might have its downsides, Sagara is convinced of their effectiveness and importance regarding the Gola rainforest. A large contributing factor is that there are few alternatives that would be viable for regions where a community’s economic growth is founded on forest logging, mining, and hunting. By financing itself through carbon credits, REDD+ offers local communities a fast-acting alternative to their previous way of life which was mainly founded on the exploitation of the regions’ resources, including many practices which pose immediate threats to biodiversity. While the REDD+ initiative has many short-acting incentives, it is meant as a long-term strategy. 30 years of runtime should lay the groundwork to ensure a long-term sustainable way of life, and work practices in the region, while also expanding outward into regions which are not yet part of the project.
By moving into a region which thus far has founded its entire economy almost exclusively on forest logging for foreign companies and offering communities other more sustainable ways of earning their livelihood, as well as offering education and financing school courses for future generations, REDD+ has already managed to have a detectable positive impact on the biodiversity of the Gola rainforest.
Noone can accurately predict the future; all we can do is work towards an outcome that allows both human and non-human communities to persist and survive, and protective initiatives are a valuable tool to take significant steps into the right direction.
For more information, read Chandra Sagars' paper "Carbon finance initiatives can provide biodiversity benefits" here
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