Catching the Light: Taking the Pulse of Puerto Rico’s Forests 

By Natalia L. Quinteros Casaverde 

After 10 days in southwestern and central Puerto Rico, Petya Campbell and I say, “¡Nos vemos pronto, Boricuas!” (See you soon, Puerto Ricans!) It has been an incredible journey through the island’s intricate landscape where, across fewer than 30 miles (50 kilometers) from the coast into the interior, the environment transforms from a hilly, semi-deciduous tropical dry forest into an evergreen mountainous rainforest, with a patchwork of agricultural land and wilderness in between. The interplay of forests, farms, mountains, and atmosphere welcomed us every morning with spectacular sunrises. 

Petya, a research professor at the University of Maryland Baltimore County and research scientist at NASA Goddard Space Flight Center’s Biospheric Sciences Laboratory in Greenbelt, Maryland, and I, a postdoctoral researcher at the lab and the Southeastern Universities Research Association, had a wonderfully rewarding—and very busy—experience! 

So, what brought us to this beautiful island? 

Our team of scientists from the lab is working to improve how satellites monitor plant health from space. Using specialized instruments that measure the solar radiation reflected and emitted by vegetation, we can turn these signals into useful information about how plants function. 

One particularly exciting signal is solar-induced fluorescence (SIF), a faint glow emitted by plants as they interact with sunlight. By measuring this glow, scientists can gain insights into photosynthetic activity and how efficiently plants use sunlight. 

To make these satellite measurements as accurate as possible, our team is studying how forest canopy signals change throughout the day and across seasons. Over the next two years (2026–2028), a project led by Petya will monitor the fluorescence “glow” of the Guánica Dry Forest canopy.

 

Glowing Guánica 

Guánica is a UNESCO International Biosphere Reserve, the ancestral land of the Taíno people, and one of the most remarkable tropical dry forests in the United States. It is also a very special place for our research. Fluorescence measurements from the forest will be compared with environmental measurements collected by a tower equipped with a suite of scientific instruments. The tower is part of the National Ecological Observatory Network (NEON). 

These ground-based SIF observations provide an essential “reality check” for satellite measurements and will help validate the products from the ESA Fluorescence Explorer (FLEX) mission, which launched September 15, 2026, to map Earth’s plant fluorescence and function from space. 

Two goals, one very busy forest 

Petya and I came to Puerto Rico with two specific field objectives to support FLEX validation. First, we needed more eyes—and more instruments—on the ground. We installed a fluorescence box (FloX) dual spectrometer at the Guánica forest tower. Petya has installed similar instruments on NEON towers in a range of ecosystems, including the tundra and boreal forests of Alaska, the prairie of Kansas, and temperate forests and croplands in Maryland. 

Using this device, we will be able to compare vegetation fluorescence changes at Guánica with patterns observed across these very different ecosystems. Tropical dry forest, meet Alaskan tundra! 

Teaming up  

Installing scientific equipment in a dense tropical forest is no small feat. Fortunately, as always, collaborating with NEON was a fantastic experience, and the Puerto Rican NEON team was no exception. Our local colleagues welcomed us with traditional Boricua warmth and helped with everything from instrument installation to botanical training. 

That botanical training was especially valuable. Despite its relatively small area, the Guánica site contains more than 700 plant species, many of them characteristic of the Caribbean. Armed with our new botanical knowledge—and plenty of enthusiasm—we focused our measurements on the emergent and most abundant tree species. 

NASA hats, hard hats, and a lot of trees 

What did we do with those trees? Well, wearing our NASA hats and the hard hats provided by NEON, we measured tree characteristics, including height, trunk diameter, and crown leaf cover. These measurements help us understand the structure of the forest and will support our second goal: preparing for an upcoming NASA Goddard LiDAR, Hyperspectral & Thermal Imager (G-LiHT) campaign. 

G-LiHT is an airborne imaging system that simultaneously maps the composition, structure, and function of terrestrial ecosystems. It is an important tool for our research, and the information we collected during this visit will help prepare for its upcoming deployment in Puerto Rico. 

From dry forest to mountains to farms 

To accomplish our two goals, we explored sites across southwestern and central Puerto Rico. In addition to the Guánica Dry Forest, we traveled into the mountains to visit the Maricao State Forest and visited several agricultural sites near the coast. 

And, of course, no field campaign would be complete without noticing the wildlife. Between measurements, installations, and botanical lessons, we managed to enjoy some of Puerto Rico’s spectacular and colorful birdlife.  

Finally, after one last mesmerizing sunset over the island, it was time to head back to Greenbelt. 

We left Puerto Rico with preliminary measurements, many new questions, a long list of things to process, and—most importantly—enormous gratitude to our Puerto Rican and NEON colleagues for their hospitality and support. 

Now the real work begins: processing the new FloX data, comparing Guánica with our other ecosystems, and getting ready for the upcoming G-LiHT campaign. 

We’ll follow up with more the next time we return to Puerto Rico to keep supporting NASA’s goal to advance knowledge of the Earth system and its climate.