‘Costa Rica’s rainforest canopies tower 150-feet tall these are the last biotic frontier’

Nalini Nadkarni is Professor Emeritus of biological sciences at the University of Utah. Speaking to Srijana Mitra Das at Times Evoke, she explains the science and enigma of Costa Rica’s rainforest canopies:
What is the core of your research?

I’m a forest ecologist. I study the plants and animals that live up in forest canopies or the top of trees in tropical rainforests. Until about 30 years ago, this was an unknown world but it was very interesting for me. My early work was more descriptive about the species that lived their entire lives in the canopy. As I grew more aware of the human effects on tropical rainforests, I started researching disturbances like deforestation and climate change impacting these canopy communities.




What are some important features of such rainforest canopies?
The environment of a canopy is very different from the forest floor — the latter is very dark and lacks sunlight. But the canopy is full of sunshine. It’s much windier too, with greater extremes of temperature and humidity — due to this, a tremendous diversity of plants and animals evolved to live in this micro-environment. Thousands of such species which you’d never see on a rainforest floor flourish in the canopy. These beings also perform several important functions — they capture nutrients and provide resources for birds, mammals and insects in the canopy, further fostering diversity in the forest. Anything which affects them impacts the rainforest as a whole.



Why are such canopies termed ‘the last biotic frontier’?

One reason is that it has been very difficult to get up into these there was no way to safely climb 150 foot plus rainforest trees until scientists like me decided to treat them like mountains. I started using mountain climbing techniques to access the rainforest canopy we’ve also used hot air balloons, cranes and walkways and recently, drone technology and satellite imagery to better observe and understand this world.

AS THE LAND SWAYS: Costa Rica is part of the elegant Central American isthmus. Images: iStock


Can you tell us about your discovery of epiphytes in these environments?
Epiphytes are plants which grow on the trunks and branches of trees — lacking roots which can descend thus, they don’t get nutrients from trees or the ground. Instead, they derive nutrients from rainfall, mist and cloud, incorporating these into their stems, flowers and roots — when they perish and fall to the forest floor, they pass these nutrients to other members of the ecosystem. So, these epiphytes function as giant sponges high up in the canopy which move nutrient resources down into the forest ecosystem. A student and I also conducted a study where we sat up in the canopies for six hours each day and observed which birds came to the host trees to use their flowers and fruit for nutrients and nesting materials versus which came to the epiphytes — we found about one-third of all the bird visits were to the epiphytes, not the host tree. Our conclusion emphasised the importance of these epiphytes for the lives of the birds and animals occupying such rainforests.

RISING TO THE OCCASION: Nadkarni’s rainforest climbs have inspired movies. Photos Courtesy: N. Nadkarni

Do these rainforest canopies also have a bearing for human life?

Absolutely this is where oxygen is produced through photosynthesis conducted by these trees and epiphytic plants. This is crucial for human life. Additionally, canopies produce materials for medicines and researchers are studying more varieties for their compounds and chemicals to see if these could combat several ailments. Finally, these are also incredibly beautiful think of domesticated epiphytes like orchids, bromeliads or ferns. These give us beauty that too is very important for the human spirit.

Picture and graph courtesy: Sybil Gotsch via N. Nadkarni & Our World in Data

What is the conservation status of such forest canopies?

Costa Rica has actually been at the forefront of forest conservation — it’s a very small country. Yet, it has tremendous diversity in its natural habitat. Not having an army, which was disbanded in 1948, the country could invest considerable resources into education and conservation. They have a system now of national parks and educational activities which has made their population aware of the importance of preserving rainforests. They’ve also established economic incentives to not cut down forests. Many countries, including the US, look to Costa Rica for ways to enable education, protection for land and incentives to maintain forests which provide oxygen, watersheds and biodiversity.

What has been your most memorable experience so far of climbing a Costa Rican rainforest canopy?

Every time I get into my mountainclimbing harness, start pulling my way up and see, smell, hear and feel the transition as I move from the dark forest floor up into this bright, windy canopy full of life, I’m filled with excitement. One of my most memorable experiences was when I actually spent the whole night up in the canopy. I used a cot which mountain climbers carry into the heights — at night, around two AM, I heard something moving on a branch next to me. When I looked, a poodle-sized anteater was walking along, eating leaf-cutter ants foraging at night. It looked back at me — I think we were both just amazed to see each other there. I really felt a part of the rainforest at that moment — I also belonged there, as a scientist and a being.

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