The Amazon accounts for about 50% of all existing rainforests on the planet; it is home to over 400 mammal species, 1,700 bird species, and an undetermined number of insect species, numbering in the millions.
It is also vital to sustaining life on Earth, as the Amazonian forests mitigate the effects of climate change by sequestering some 560 million tons of carbon per year and support agriculture by increasing local and continental rainfall.
Indispensable and threatened spaces
The Amazon rainforest and its vast biodiversity are disappearing at an alarming rate due to the growing production and export of livestock in Brazil. The rest of the forests are under constant threat from human destructive activities such as deforestation, fires and climatic disturbances (extreme droughts and floods).
To date, research on climate and biodiversity issues in tropical forests has largely been based on short-term studies that focus on plant and carbon responses. As a result, most of us are aware of the importance of forest trees in climate regulation. Our study in the Amazon found that tree mortality and carbon loss remain high years after drought-driven wildfires.
However, to fully understand the resilience of tropical forests, long-term studies are also needed that take into account the impact of climate disturbances on wildlife and evaluate their role in forest restoration after disturbances.
Stability in conditions
Animals play a key role in understanding the sustainability of tropical forests.
Birds, for example, are seed dispersers, and their extinction could reduce the size of tropical palm seeds, making revegetation unlikely or impossible.
Likewise, large fruit-eating animals, including howler monkeys and arachnids, also ingest and disperse seeds, so if their numbers decline, it could affect forest restoration pathways.
Although it is now well known that small creatures rule the world, our understanding of the role of invertebrates is still in its infancy. In tropical rainforests, termites have been shown to improve drought tolerance, and dung beetles may contribute to the restoration of tropical forests.
Although we know that fauna and their functions are essential to understanding forest restoration mechanisms, it is not easy to count them.
Despite the diversity of trees and the difficulty of identifying them, tracking them is relatively easy: they do not move, they can be measured from year to year, samples can be taken and their structural and chemical characteristics can be assessed, and their physiological responses can be assessed in the field. . Of course, all this requires complex work, but our understanding of the climatic sensitivity of tropical forest vegetation is undoubtedly facilitated by its immobility.
On the other hand, animals are much harder to track. Up to 160 species of birds can live on one hectare of forest, and on 100 hectares – an area eight times smaller than the area of the Bois de Boulogne in Paris – up to 245.
Listen to this bird choir. How many types do you distinguish? In this simple 32-second passage, a specialist could name 12 species… but few in the world have this ability.
If it is already difficult to make an instant assessment of the species present, then let’s not talk about the assessment of changes over time! Species that sing at any time change throughout the year, from day to day, throughout the day, and even according to the cycles of the moon.
What about invertebrates? Most species have not yet been formally classified by taxonomists and their identification depends on a few specialists with access to comprehensive reference collections.
Their numbers fluctuate throughout the year, from year to year, depending on climate change, climate extremes and other factors that are not yet understood.
Trails for wildlife watching
Luckily, there are solutions for tracking forest wildlife. In this context, our Bioclimate project uses both innovative and well-established methods to assess how small and large animals can help rainforests recover from disturbances such as deforestation, drought or fires.
In terms of insects, we can rely on certain groups to act as indicators of forest health. Dung beetles are ideal for this: many of their activities benefit the forests, they are easy and cheap to collect; they may be indicative of the disturbance’s effect on other animals whose excrement they use for food and nesting.
Thus, by analyzing the DNA of the dung beetle feces, we can estimate which mammals live in the Amazonian forests. This knowledge is useful for better understanding how environmental changes affect the relationship between these insects and mammals.
As for birds, continuous monitoring of populations is possible with stand-alone audio recorders, which also help to understand how they occupy space in different places – many forest birds are rare and have large territories, so they are likely to be missed during one-time visits.
Having multiple audio recorders running simultaneously for a long period of time allows you to monitor a large number of locations and animals at the same time. To overcome the challenges of humans listening to multiple bird songs at the same time, we are also developing machine learning algorithms that make it easier to identify vocalizations of certain species.
Toward a better understanding of interactions
To ensure the future of the Amazon, it is important to move towards research aimed at answers that accurately analyze how the many insects, birds and other animals living in these places contribute to the health of the forest.
Thus, the aim of our work is to combine both datasets collected over a long period of time and these new experimental data in order to improve our understanding of the relationship between biodiversity and climate in tropical forests.
With this knowledge, we want to gain a better understanding of how the Amazon is responding to human activity and how we could better conserve it.
The Bioclimate research project is supported by the BNP Paribas Foundation through the Climate and Biodiversity Initiative..