WHEN first ventured into the canopy of a cloud forest, almost nothing was known about this unique ecosystem. To explore it, she and a small group of pioneers had to develop special tree-climbing techniques, which, over the intervening four decades, have allowed her and others to unlock the mysteries of forest canopy biology. Monteverde in Costa Rica, where Nadkarni does much of her fieldwork, is home to some remarkable species, including the . But it turns out that the entire ecosystem depends on a more modest and unlikely group of organisms called epiphytes. These tree-dwelling plants – which include a dreamy array of wonders from ephemeral mosses that drip off branches and luscious ferns that nestle in crevices to a dazzling variety of orchids – act like nutrient sponges, extracting chemicals from mist and rain and conveying them to the forest floor.
Seven years ago, Nadkarni, who is at the University of Utah, fell from the canopy and broke her back in five places. Nevertheless, she was back in her tree-climbing harness a couple of years later. Such grit is a hallmark of her career, which, as well as reaching the forest heights, has taken her to some other unusual places. As a self-professed secular “missionary” for ecology, she has , and has . Now, aged 68, Nadkarni acknowledges that her tree-climbing days are nearing an end. But she also knows that climate change poses unprecedented challenges to cloud forests and is determined to document how it is affecting the epiphytes on which they depend.
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Matthew Ponsford: When did you realise that you wanted to explore the forest canopy?
Nalini Nadkarni: When I first came to Costa Rica in the summer of 1979, it was clear to me that there was so much action going on up there, with the howler monkeys and bird flocks, and plants growing too. But when I asked my professors “What’s going on in the canopy?”, they said: “Well, we don’t really know much about it. We don’t have a way to get up there safely or non-destructively.” So, I thought, if a scientist is supposed to be exploring the unknown, it seems like the canopy would be a really important place to look.
At 68, Nadkarni is still using the tree climbing techniques she helped pioneer four decades ago[/caption]
How did you set about it?
Many tropical trees have noxious insects or big thorns on their trunks, or their first branches are 100 feet above the forest floor. So you can’t rely on the old childhood method of just throwing your leg over a lower branch and making your way up. In Costa Rica, I encountered a graduate student named Don Perry, who was one of the true pioneers of canopy research in the lowland rainforests at La Selva Biological Station. To rig trees with climbing ropes, he would first shoot up a 20-pound fishing line with a powerful crossbow. The arrow goes up and over the branch and then comes back down to the forest floor. But this was 1979, when the Nicaraguan Sandinista rebellion was going on, so customs officials were not very happy about my bringing a crossbow from the US to Costa Rica.
I ended up inventing an alternative I called the Master-Caster, which is a short, aluminium rod with a slingshot mounted on one side and a fishing reel below it. I follow the same protocol: shoot a fishing line over a branch, use that to pull over a parachute cord, then a climbing rope. After that, it’s standard mountain climbing gear: harnesses and ascenders that clamp onto the rope.
What is it like up there?
You’re sitting on a branch high above the forest floor and you get the sense of being in the middle of this three-dimensional volume of a thousand-thousand leaves all moving. You see bromeliads and orchids and ferns and hemi-epiphytes like strangler figs, just covering these branches and trunks – all are canopy-dwelling plants that you never encounter on the forest floor. You almost feel you’re in an open field because you are above the foliage where photosynthesis is going on, where pollination is going on, where fruit dispersal is going on.
What did you learn on those early explorations?
It was like doing 19th-century biology, being Alfred Russel Wallace or Alexander Humboldt. The first 20 years of canopy research were almost entirely descriptive and observational. We found that there’s canopy soil that accumulates underneath these living mats of canopy-dwelling plants, and asked how it compares to soil on the forest floor. We asked who’s pollinating this bromeliad and who’s dispersing the fruits of this ericaceous shrub. As we started documenting patterns, we began generating ideas about the processes that determine these distributions. Is there more mist and fog at the edge of the canopy, and is that going to foster a different set of plants? We began to understand the importance of epiphytes as a keystone to this whole system. We began looking at processes of regeneration by removing epiphytes from some branches and learned that it takes over four decades for them to grow back. In the 1990s, we finally started being able to make predictions.
One crucial prediction is how climate change will affect epiphytes. What are you finding?
Right now, I’m working with three colleagues: , a plant ecophysiologist from the University of Kentucky; , who is a plant physiologist at the University of California, Berkeley; and , an ecological modeller at Wake Forest University, North Carolina. All four of us are trying to document the effects of climate change on tropical montane forest canopy communities. They’re called cloud forests because, over evolutionary time, they have been inundated by wind-driven mist and cloud for much of the year. But as land and sea temperatures warm, the cloud bank is lifting. Epiphytes – these canopy-growing plants – don’t have roots that go into the ground or into the trees, so they get their . As the cloud lifts, it is pinching the hose not only of moisture, but also of nutrients into cloud forests.
We’re predicting that will have a . We can see that already. Of course, there’s a lot of variability – some years, there is more rainfall than others – but the general trend is definitely indicative of what has been predicted by global climate change models over the past 20 years. And we anticipate that if we don’t stop pumping carbon dioxide into the air, the trends are going to continue and, if anything, worsen.
How has Monteverde changed since you began your research there?
If you pop up into the canopy and look around, it looks pretty similar. But look at the landscape below and you see more human use of the forest, more trees being cut to make pastures, more isolated trees. We’re trying to figure out whether we can make . One thing we’re doing is carrying out extensive canopy-stripping experiments: physically removing entire communities of epiphytes from experimental trees and leaving control trees intact, and then monitoring the microclimate of the canopy, as well as the water use of the host trees. One of the reasons we’re doing this radical experiment is because we want to get a jump on what might be happening in the future.
Are researchers still using the same climbing techniques you helped develop?
They are probably the most common way to get up into the canopy for individual scientists. But there are also aerial walkways people have put in to study bird behaviour. And there’s a canopy raft, where you go up in a hot air balloon and then collect samples of leaves and insects through the mesh of the raft floor. But that is only feasible in windless areas that are very flat, so montane cloud forests are not suitable. People also use construction cranes: 17 of them have been installed in forests for canopy research around the world. And now researchers are using drones and satellite imagery, like lidar, which is a kind of radar that allows you to look at the structure of forest from the top as well as down to the forest floor.
You are also a passionate advocate of public engagement. How did that come about?
About 15 years ago, I started hearing chainsaws just outside the boundaries of the reserve where I was working and realised that I need to do more than just writing my scientific papers. I started working with museums, with the National Geographic Society [in Washington DC], but soon realised that this was connecting with people who are already part of the choir. That’s when I began thinking about taking these messages further afield.
I began , because 80 per cent of the world’s population self-identifies as being religious or believing in God. Instead of trying to just push science down the throats of religious people, I decided to read the Bible and the Koran and the Talmud and other religious texts, and pull out all the verses that have to do with trees and forests. Then, I put together a sermon – which I’ve given at over 40 churches and synagogues and temples – about what I learned from their holy scriptures. For example, there are 328 references to trees and forests in the Old Testament of the Bible, and all of these are about how positive trees are, how important they are for analogies to God, or practical use, or adornments to temples. Who can argue with that!
You have been working in prisons too. Can you tell me about that?
I started by doing a little project that involved the cultivation of mosses, because people in the Pacific Northwest harvest mosses from old-growth temperate rainforest trees and sell them to florists for the horticulture trade. I thought, if we could learn how to cultivate those mosses, that would take the pressure off collecting them from wild places. So I enlisted prisoners as partners to help me.
That was very successful and led to collaborations with conservation groups who had existing ecological restoration projects. We taught inmates how to raise Oregon spotted frogs, from egg to tadpole to adult frog. Then, the conservationist would release them in protected wetland areas. Other inmates did the same thing with Taylor’s checkerspot butterflies, with rare species of prairie plants, with a Western pond turtle. So area where inmates were actively contributing to ecological restoration and conservation efforts and getting connected to nature. And that’s a very powerful thing to provide for someone whose power has been taken away by being incarcerated.
You seem like a very positive person. Does your optimism extend to the future of cloud forests?
Like so many people, I walk a knife ridge between despair and hope when I think about the social and environmental problems we all face. We have to walk really carefully along that line, especially scientists who want to improve how we’re protecting forests or using energy. It behoves us to continue with some degree of hope, but always keeping that darkness or despair in our minds, because that is a continuing motivator – at least for me. And I’m not willing to give up yet.
Matthew Ponsford is a London-based journalist who writes The Manuals, a newsletter and how-to guide to ecological engineering
