Meg Lowman’s head is in the trees. She’s a botanist and the Chief of Science and Sustainability at the California Academy of Sciences in San Francisco. Lowman was one of the first scientists to climb a tree in the name of science and ended up pioneering one of the most important fields of botany. Called “Canopy Meg” in scientist circles, she chatted with us about why the tippy tops of trees are the most important part of a forest and what it’s like to spend hours and days above the canopy.
Why do we care about studying the tops of trees?
In the 1950s scuba gear was discovered and that opened up exploration of coral reefs. In the 1960s, NASA developed spaceships and went to the moon. But it wasn’t until the 1980s that single rope techniques were adapted from mountaineering in order to climb trees.
Started by me in Australia and another researcher in Costa Rica (independently), we started asking questions that required us to reach the top of trees. In Australian rain forests, I welded a slingshot and sewed a climbing harness from seat belt fabric, tools that allowed me to climb a coachwood tree and discover enormous numbers of critters living up there. It turned out to be what scientists call a “biodiversity hotspot” of the planet.
Scientists acknowledge that we know more about the moon then the top of a tree.
We now know that forest canopies are a center for global biodiversity. Almost 50 percent of the biology on the land portion of Earth lives on the treetops. That is a lot of species! And we didn’t know that 30 years ago! Scientists acknowledge that we know more about the moon then the top of a tree. It’s been an amazing journey for me as a scientist to be part of this discovery, virtually in our own backyards.
The canopy is home to so many species on the planet. Tree tops undertake energy production in a humongous way. It is a region of abundant fruits and flowers and lots of sex! Incredible materials that we harvest come from canopies like medicines, building supplies, and food products. And canopies give us clues about forest health in general -- healthy forests provide water conservation, prevent soil erosion, store carbon, provide shade, serve as a genetic library, and influence climate control in a big way. It is amazing to appreciate that millions of trees, while we sleep, are doing all these things for us!
Why is this happening at the canopy and not other parts of the tree?
The sun is the answer! All the fruits and all the flowers live in the tops of trees not on the floor. Because of light all this activity is going on in the upper regions. Only about one percent of light gets to the forest floor of a tropical rain forest, so it is almost dark! Foliage is concentrated at the top and that’s why everything lives up there. If you are a beetle you don’t want to travel 100 feet to get to your salad bar -- it’s easier to just live amidst your lunch. And canopy photosynthesis leads to the production of wood and different leaves.
Trees can’t run away from their enemies like animals can. So it’s a miracle that trees don’t get completely eaten up by their enemies. Leaves defend themselves by producing chemicals, and sometimes by creating thorns or stinging hairs. There is a constant battle of leaves producing defensive chemicals and insects adapting to digest different chemicals. Humans come along, pick the leaves, and utilize leaf chemicals for different medicinal purposes. And this “apothecary in the sky” is essentially due to the incredible and constant tug-of-war of leaves trying to defend themselves from insects. The action of insects eating leaves is called herbivory and that is technically what I study in forest canopies.
Those are just a couple of the things. The canopy is the origin of most of what is going on with the forest.
Do we learn anything at all from the bottom of trees?
For 200 years foresters just saw the first six feet of the tree. It’s like a doctor looking at your big toe and saying: “You’re a really healthy person.” We had a small view and based all of our observations on the bottom or we cut the whole thing down and looked at the top after it was dead. We had no idea there were millions of species living on earth, we didn’t know anything about orchid species or how they got pollinated. Most of what we know now about medicines comes from tree tops. Fruits that can be harvested, photosynthesis, and energy transfer -- all from canopy research.
Now the very uppermost areas of foliage is a key indicator of climate change. The upper canopy is very impacted. We can now make predictions of global health based on our observation of the canopy.
Why didn’t we think to go to the top of the tree?
In the 1930s we probably didn’t think about going to a coral reef. A lot of things occur over time. Our understanding is thanks to the development of equipment.
What tools do you need to study the tree canopy?
Half of my career has been devoted to inventing tools. Most scientists have their microscope or a genomic analyzer already manufactured. In 1979 I was in Australia and I thought, I have to get to the top of the tree because I want to study how long the leaves lived in the tropical forest. So I got a recreational caving club to teach me how to climb. They laughed at me.
I made my own slingshot to put my rope over the branch and then I used the same mountaineering hardware as the cavers. It wasn’t so easily available at that time, especially in Australia. I managed to get a hold of all this stuff and up I went. There was so much going on! I measured damage to leaves, fungal infections, how many bugs were up there eating.
I quickly realized that a rope is not always that good. It’s not good in trees that are soft wood or rotten. You can only go two-thirds up a tree because it’s not strong enough. But what if you want to go up in a collaboration?
So I worked with an ecotourist lodge in Queensland in 1985 and we designed a canopy bridge through the top of the tree so you could sit down or spend the night. Now there are quite a few around the world.
The next chapter is all about aerial surveys and maybe drones. To survey a forest from high up and look down is going to be exciting.
I also used scaffold at one point in time. You can add a layer of scaffold every season to study the growth of trees. Later I used hot air balloons with french biologists.
The most expensive one that we don’t use so much anymore is a construction crane. It’s good for collaborative work, but you have to have a unionized driver of a crane. They’re the Rolls Royce of the tree-studying business.
So nowadays we have a tool kit of four or five good methods. The next chapter is all about aerial surveys and maybe drones. To survey a forest from high up and look down is going to be exciting.
So if you choose to climb a tree to study it how do you do that?
If I have my druthers I go up a set of stairs to the canopy walkway and bring all sorts of equipment and my lunch. But those are only in places where we develop that level of kits.
When climbing, I would go with my backpack and always with a second person for safety. It’s really important to have a spotter on the ground. It’s always a two-person activity.
The first order of business is getting a slingshot out with a fish-sinker weight and some fish line and shoot it. The goal is to try to get it over a strong bridge of the tree.
As a botanist I know which trees produce hardwood and which produce softwood. You can look around and see termite damage or lightning strikes. You can look for die-back and diseases. You have to pick a healthy, strong, vigorous tree. The rule I use is that the branch has to be as big as my thigh to support me.
How do you decide which trees in a forest you’re going to study?
I spend usually a couple of months and weeks designing the questions of my research. So, for example, when I was trying to understand how long leaves live in tropical rain forests (they only live six months in temperate forests) I knew I had to survey at least five species of trees. I basically built this map of what I needed to sample. I ended up surveying coachwood, a common warm temperate tropical forest tree.
Then I picked sassafras because it has a good canopy and a giant stinging tree.
Did you say stinging tree?
I actually did study the giant stinging tree’s deadly stinging surfaces on their leaves. First, because they’re a really big canopy tree and second, because some insects ate the leaves and I wanted to figure out how they did that. To survey them I used to have to climb the next-door tree and then lean in with gloves on.
So how do you find out where all the right trees are in a forest?
I had to map the forest. I’d do cross-section maps that took me sometimes a couple months to find out what was common and what was rare. In the past I’d do drawings because we didn’t have GPS or an ability to do an aerial survey. I’d make grids through the forest to estimate how rare or common different species of trees were and which ones occupied the upper canopy and the mid canopy.
What are the different types of canopies?
The upper canopy is really extreme. The leaves are small and have to be tough to withstand the wind. The mid canopy is shaded, the leaves are bigger and they last longer. In the lower canopy the leaves live the longest and they’re the biggest in size.
So once you identify the trees and the canopy locations what happens next?
So once I had a map then I had to start to measure environmental factors. The light on the tropical forest floor is at one percent. So the leaves in the understory have to a whole different process to gather light and justify their existence.
One of the things I found out is in the tropical forest some understory leaves live over 20 years. So anyway we rig it the fishing line to the climbing rope and pull it up and over a strong branch. Then I put my harness and helmet on and get all of my field equipment into a bucket or backpack.
I use a climbing technique called single rope technique. It’s almost like an inchworm going up a stem. You have what are called jumars, metal ascending devices that mountaineers use. You attach one to your feet and another to your chest and with your hands you slide the chest one up the rope and then slide the feet one up. They have teeth on them that only allow you to go up, so you can stop at any time and rest or take notes and collect data.
What’s inside the bucket of equipment?
A camera, a waterproof magic marker to number leaves and branches, electrician’s waterproof tape to make tags to find permanently marked branches -- every month I’d go back to the same tree to see how things changed. Instruments like acetate paper to trace leaves, rulers, or graph paper to measure how much of the area bugs had eaten. And sometimes I’d take pictures.
The aim of my work was to say how much of the salad bar the insects were eating. The when, where, and how. As well as the toughness, age of the leaf, and its height on the tree.
I’d have to sample at least 30 leaves at each height and three trees at three sites. The essence of field biology is to get averages that give you confidence in your results.
How long do you usually spend up a tree?
Sometimes a couple hours. With the original leaves that I marked and mapped over time, eventually every single bud would burst. So an area where I started with 15 leaves would turn into 45 or 50 leaves by the end of the season. By the end of a tree season I’d have 300 marked leaves turn to 3,000. Or at the end of the season an entire branch would be destroyed
I’m looking at all variables of temporal and spatial variation of the canopy. That would be height, light, elevation, location of the forest. And then I needed to replicate temporal variation: young vs. old leaves, new foliage vs mid foliage, if it leafed out in March or September. Activities of the insects 12 months a year, year to year, or decade to decade. That gives a complete picture -- a huge snapshot of the forest canopy in terms of how the foliage is being impacted.
How do you keep track of all that data?
I go nuts. And that’s a huge challenge for all of science. Especially back in the 80s working in remote Australia most of my data was in notebooks and then I’d come back home and do analyses using a calculator.
Now I have all that data in a computer. But way back then I spent hours and hours pouring over the data, creating graphs of where insects were feeding and what kinds of trees they preferred.
Then I had to do a separate study of capturing, identifying, and recognizing the different kinds of insects and what damage they did. I never expected to study insects.
What are you working on right now?
I have a long term database of insects feeding on foliage in canopies around the world. Citizen scientists help me, but my passion right now is just conserving the forest. More than collecting the data I’m doing conservation biology.
Right now I’m working in Ethiopia with Coptic priests to help them understand that the only remaining trees in all of Northern Ethiopia are in their little church yards. Everything else has been cleared for farming because they’re starving.
Wait, ALL the trees in Ethiopia have been cleared?!
The church yards are these little dots of green surrounded by barren brown soil. The priests at first thought I was some kind of kook. The only white female for miles around. But the priests stay in their little church forests and people come to them and worship. So they don’t know that outside there aren’t any trees and over the next valley it’s all barren and desert. So I have a local colleague and he translates and together we have been fundraising in the US for the simple task of building stone walls around the edges of these trees so cattle don’t get in and eat seedlings or the kids don’t come in and chop them down for firewood.
They’re really precious. They’re the source of fresh water and medicine. These little tiny islands of trees are the future of Ethiopia and we can’t connect them yet because they need better agricultural processes. But we can save them.
How many trees are left in Ethiopia?
There are 3,500 and we have a study of the 25 most diverse forests sites there. We’re trying to wall them off so they’ll be the future genetic heritage.
It begs an interesting question because in science we all tend to study areas where our friends are because they have air conditioned labs. But right now nobody is working in Somalia, or Ethiopia, or Saudi Arabia. We need to work in these urgent-need zones but there’s no funding.
So where are most interesting and important forests to study right now?
The most amazing interesting forest is still the Amazon because it’s so complex and our last big forest left. I do a lot of long term research there understanding how so many people live in that forest sustainably. Conserving it is very important to everybody in the world.
After that other important forests are island forests like Samoa or Madagascar. In a valley on the mainland a forest can be regrown, but on an island it has grown from seeds floating to shore or coming in on birds legs. To recreate it is impossible.
And Africa. It’s the least researched part of the world and doesn’t have enough universities with high-tech field stations. For a little effort our technology can go a long way.
That being said, it’s amazing how much of your work is still so low-tech.
It’s true. People are still climbing. With the exception of this new really expensive technology like NASA and Stanford have invested in called LIDAR [editor’s note: LIDAR uses lasers to analyze surfaces by measuring light reflection] or aerial satellite surveying. With that you gather a very different kind of information. But you don’t see insects or know if they’re eating an orchid and a vine or a tree and if what you’re looking at is actually three different insects. It’s a whole different data set.
We just can’t let go of ground-truthing. Just like research in space: we can take a picture of the moon but we still want to go there and sample the soil.
Photos courtesy Meg Lowman
Not all science is done in a lab by guys in white coats staring into microscopes. Lots of discoveries require brave men and women to put their boots on the ground and get down and dirty in dangerous environments. Every month we’ll profile one of these field scientists, tell you how they do their job, and explain the science behind what they do. If there’s a scientist or field of science you’re dying to hear more about shoot us an email or a tweet: erin at erinbiba dot com, @erinbiba