Eyes in the sky: drones climb into the Atlantic Forest canopy to find out how plants will cope with climate change
A scientific study is following orchids, bromeliads and other epiphytes at REGUA and in neighbouring reserves in Rio de Janeiro for three years.
Orchids, bromeliads and other plants that grow on the trees of the Atlantic Forest are being photographed by drones, metre by metre, in three protected areas: the Guapiaçu Ecological Reserve (REGUA), Três Picos State Park and the Alto da Figueira RPPN (private nature reserve), in the neighbouring municipalities of Nova Friburgo and Cachoeiras de Macacu. The aim is to predict how Atlantic Forest biodiversity will respond to a warming climate.
Plants that live in trees: a thermometer for the forest
Epiphytes are plants that grow on other plants, using the tree only for support and doing it no harm. Orchids and bromeliads are the best-known examples. They occupy the whole tree, from the trunk near the ground to the canopy, where there is more sun and less humidity, and they are highly sensitive to changes in temperature and humidity.
The study, titled Biodiversity dynamics along environmental gradients under impending environmental change, led by researcher Zachary Chu of the University of Birmingham, aims to understand how these communities vary with altitude and with height in the tree. The three study areas span altitudes from 400 to 1,600 metres, which makes it possible to compare different climates within a single region of the Atlantic Forest.
How the study is carried out
Choosing the trees: large trees with plenty of epiphytes are marked at a range of altitudes.
Drone photography: the drone climbs alongside each tree and photographs the plants every metre. Species are identified later from the images, with their height recorded.
Returning every year: the same trees are photographed again. By comparing the images, researchers can see which plants survived, grew, reproduced or died, and which are new to the tree.
Measuring the environment: sensors for temperature, humidity and light are installed at various heights using climbing equipment, and a laser scanner (LiDAR) maps the structure of the trees in 3D.
Minimal collection: plants are collected only when the species is in doubt, preferably those that have already fallen, and they become herbarium specimens or are grown on at partner institutions.
Why the Atlantic Forest needs this attention
The Atlantic Forest is one of the most species-rich biomes on the planet and, at the same time, one of the most threatened, and is considered a global biodiversity hotspot. Much of this richness lives in the treetops, precisely where the climate changes fastest and where science has the most difficulty reaching. Understanding epiphytes means understanding the health of the whole forest: they store water, shelter insects, amphibians and birds, and depend on a humid, stable climate to survive.
The project plans one field season each year, always from early August to late September. In each season, the team starts at REGUA for one or two weeks and spends the rest of the time between Três Picos State Park and the Alto da Figueira RPPN, based at the Projeto Araçá field station. They then return to Europe to process the data.
The Atlantic Forest originally covered more than 1.3 million square kilometres (around 15% of Brazilian territory), stretching across 17 states along the coast and into the interior. Today, only about 12.4% to 24% of the original vegetation remains, depending on the measurement criteria (general forest fragments, or secondary vegetation and smaller areas). Most of what is left lies in small, isolated fragments, mainly in the Serra do Mar region.
At REGUA, around 57 species of epiphyte have already been catalogued in the floristic list of the reserve’s management plan. “This contribution certainly goes far beyond a study with local impact. This research and its results will resonate for a long time and with great force in the scientific and academic community,” said researcher and REGUA research coordinator Jorge Bizarro.
First results: what the drones have already revealed
The method has already shown that it works. A study by researcher Zach, titled Eye in the sky: using drones to assess canopy diversity for vascular epiphytes in the Brazilian Atlantic Forest, compares altitude and height in the tree as drivers of plant diversity.
According to the study, lowland forests have the potential to harbour many epiphyte species, because they combine a large surface area for plants to attach to with high local humidity. The authors also highlight the value of drones for understanding the diversity of tropical forests, from the base of the trees to the canopy.
The value of the research lies in looking at the future from the present. Because the climate already varies with altitude and with height in the tree, scientists can observe today how plants live under each set of conditions and estimate what will happen to them if the climate in one place comes to resemble that of another.
For REGUA, hosting the research reinforces the role of private reserves and protected areas as open-air laboratories for Brazilian science. The research is ongoing, and its results will be published over time by Zachary Chu and his collaborators.
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