Trees in Panama’s tropical forests are growing longer roots in the face of drought

The first time you walk into a Panamanian rainforest in the dry season, you don’t notice the drought at eye level. The canopy above you still looks impossibly lush, a tapestry of greens stitched against a blinding white sky. Birds stitch sound through the branches. A howler monkey complains in the distance. The air is thick enough to drink. If this is drought, you might think, what does normal feel like?

But the true story of the forest isn’t playing out where you can see it. It’s happening underground, in the dark and the quiet, where the roots are slowly rewriting the rules of survival.

Listening to a Thirsty Forest

On a ridge in central Panama, a scientist kneels beside a narrow trench cut into the forest floor. The trench looks almost like a wound—brown soil sliced open to reveal what we never usually see. Fine roots, pale as threads, crisscross the exposed earth. Some are thin as hair, some as thick as pencils, all reaching down and down.

“They weren’t always this long,” she says, brushing loose soil away with a gloved hand. A few years ago, in this same kind of forest, roots tended to gather in the top layers of soil, where decaying leaves drip nutrients like slow rain. But something has changed. The dry seasons are becoming sharper, meaner, and the trees are quietly adapting.

In Panama’s tropical forests, the dry season used to be a pause—three or four months with less rain, a time when streams ran low but rarely silent. Now, some years bring long, relentless stretches without a drop of water. The air bakes. Leaves droop. Streams shrink into a string of disconnected pools. From above, satellites register a stress blush in the forest canopy. From below, the roots respond.

The Hidden Race for Water

To understand why roots are changing, you have to imagine the forest as a crowded city built in three dimensions. Sunlight, water, and nutrients are the currency here, and every tree is hustling. In the wettest months, water is everywhere. Rain hammers the leaves, trickles down the bark, pools in buttress roots, seeps into the soil. Plants can afford to be lazy about it; shallow roots are usually enough.

But in drought, the economy of the forest flips. Water is no longer the background condition of life—it’s the prize in an underground race.

In Panama’s tropical lowlands—particularly in places like the Barro Colorado Island region and the surrounding canal forests—long-term plots of trees are watched year after year. Researchers mark trunks, map crowns, log deaths and new shoots. More recently, they’ve started mapping something else: roots.

What they’re finding is both subtle and profound. Across many species, root systems are reaching deeper than before. Trees that once concentrated their efforts in the first 30 centimeters of soil are now sending more of their fine roots a meter down, sometimes even deeper, where pockets of lingering moisture hide from the harsh surface heat.

The forest doesn’t shout about this shift. There is no sudden drama, no abrupt change in color. But if you could peel the soil back like a curtain and watch in time-lapse, you’d see a slow underground migration: fibers of life diving further into the dark, a patient braid of desperation and ingenuity.

How Trees Learn to Reach Deeper

Of course, trees don’t “decide” to grow longer roots the way we decide to turn on a tap. Their responses are written in chemistry and in time. When the surface soil dries out, the tiny root hairs near the top start to struggle. They sense the drop in moisture—the shift in water pressure—and send hormonal signals up the trunk. Leaves tighten their tiny pores, holding in water. Growth slows. But the tree also shifts investment.

More energy goes into deep roots. In some species, existing deeper roots start branching more intensely, knitting a denser web in the cooler, wetter layers of soil. In others, roots push into unexplored depths, chasing the faint promise of moisture. Over multiple seasons of drought, trees that are better at this game survive and seed the next generation. Little by little, the forest weathers the change by changing itself.

There’s another quiet ally here: fungi. Mycorrhizal fungi wrap around tree roots, forming partnerships so intimate that scientists sometimes call them “wood-wide webs.” In exchange for sugars from the tree, the fungi extend the root network, searching crack by crack for water. In drier years, these underground alliances become even more valuable. A single tree’s thirst is no longer just its own; it’s shared through threads of fungal filaments reaching like nerves through the soil.

This is what adaptation looks like for a forest. Not a sudden heroic leap, but a thousand small adjustments—more roots down here, fewer leaves up there; energy shifting like water in a tilted bowl—guided by the harsh new rhythm of the seasons.

Different Trees, Different Tactics

Not all trees in Panama’s forests are playing the same game. Walk along a ridge where the soil is thinner and you’ll meet the drought gamblers: species with thick bark, small leaves, and roots that plunge deep in search of the last drops of dry-season water. These are the long-haul survivors, the ones that can sit tight through a brutal dry spell and leaf out again when the rains return.

Down in the valley bottoms and along streams, you’ll find a different cast. These trees grew up counting on more reliable water. Their roots may spread wide rather than deep, feeding on richer, moister soil. In wetter decades, they thrived. Recently, some of them are starting to falter.

In study plots across Panama, researchers are documenting a quiet reshuffling of the forest cast list. Species that can afford deeper roots—either because they evolved that way or learned to invest more in them—are showing higher survival in the harshest dry seasons. Shallow-rooted species are more often the ones found dead and hollow, their trunks slowly returning to soil.

It’s not that every tree is throwing all its bets on depth. Some are experimenting with a mix: slightly deeper roots, a bit more drought-tolerant foliage, better partnerships with fungi or bacteria. But pull back to the whole forest scale, and the pattern is there: on average, root systems are reaching farther down, turning the underground profile of the forest more vertical than it used to be.

What the Numbers Whisper Beneath the Leaves

For all the poetry of long roots searching for water, the story is also a matter of data—years of meticulous measurements in heat and mud. Scientists measure root length, thickness, depth, and density in different forest plots, then track rainfall, temperature, and tree survival. When they stack years of observations on top of one another, a pattern emerges.

Here’s a simplified snapshot of what that underground shift can look like in a typical Panamanian forest plot over time:

The numbers vary from site to site, and the forest doesn’t change as neatly as a chart. But the direction of travel is clear: a greater share of the forest’s root biomass is claiming deeper territory.

These measurements hint at a larger story. When roots grow longer and deeper, trees are not just chasing water— they are reshaping how the entire ecosystem works. Deeper roots can tap older groundwater, stabilizing the forest’s water use when the sky withholds rain. They can also pull up nutrients from layers of soil that used to sit outside the reach of living plants, gradually cycling those elements back to the surface through falling leaves and branches.

On the flip side, that deeper reach can make forests more sensitive in other ways. If long droughts deplete the deeper reserves, or if changing climate patterns alter groundwater, a forest that has learned to lean heavily on deep water may face a new kind of vulnerability. Adaptation, in a changing world, is never a guaranteed win—it’s a moving negotiation.

Climate Change Written in Wood and Soil

In Panama, droughts are not arriving in isolation. They travel with rising temperatures, shifting sea-surface patterns in the Pacific, and human-made climate change that tugs at the strings of rainfall itself. The dry seasons are becoming less predictable—some arriving late, some lingering on, some flashing into intense heat waves that leave even veteran trees gasping.

The deepening of roots is one of the forest’s languages of response. Another is mortality. In extreme drought years linked to El Niño events, certain forests in the region have seen spikes in tree death, especially among large canopy giants. Big trees are paradoxical: they hold enormous amounts of carbon and anchor the forest’s structure, but they can be surprisingly vulnerable when water runs low. Their canopies are vast, their demands high. If their roots can’t keep pace with a deepening drought, they start to fail.

Every fallen giant opens a hole in the canopy, letting light pour to the forest floor. In that sudden brightness, new seedlings race upward, many of them from species more comfortable with stress and scarcity. Deeper-rooted pioneers move in. The forest that regrows is not quite the same forest that fell.

In this way, climate change is being recorded not just in melting ice or rising seas, but in the secret architecture of roots and the slow reshuffling of species. Every longer root in Panama’s forest is like a line of text in a book we are only just learning how to read.

Why Underground Matters Far Beyond the Forest

You might ask: why should we care how deep a tree’s roots go, in a forest many people will never visit? The answer is that those roots are connected, indirectly, to almost everything.

Deep roots help trees keep doing what they do best: pull carbon dioxide out of the air and lock it into wood, bark, and soil. Tropical forests are among the planet’s most powerful carbon vaults. If droughts push them past a tipping point—if trees die faster than they grow back, or if they shift toward shorter-lived, less massive species—the tropical carbon ledger could flip from sink to source, accelerating the warming that started the trouble in the first place.

Roots also regulate water itself. They help soil act like a sponge, slowing runoff when rains finally return after a harsh dry season. In Panama, this matters in a distinctly practical way. Forests in the canal watershed influence the water levels that ships rely on to pass from ocean to ocean. Prolonged droughts have already forced authorities to restrict ship traffic in some years. Forest health, root depth included, feeds directly into global trade.

Then there’s biodiversity. The web of life in these forests—frogs, orchids, ants, toucans, bats—depends on the stability of the trees that host them. As root strategies shift, so does the cast of plant species. Animals that eat the fruits of a vanishing tree, or nest in its branches, feel those changes in their bones and bellies. Even insects that depend on certain leaf types or bark textures are swept up in the slow underground revolution.

To care about roots, in other words, is to care about a whole chain of consequences that stretches from microscopic fungi to container ships, from the chemistry of the air to the weight of fruit in a monkey’s hand.

What Comes Next Beneath the Canopy

Back on that ridge in Panama, as the scientist climbs out of the trench and wipes soil from her knees, the forest seems briefly to close behind her. The cut into the earth is temporary, soon to be filled in and reclaimed by roots and worms and falling leaves. The data will travel far, to laboratories and climate models and arguments about how the world will change.

What stays behind, though, is the slow work of the trees. Year after year, they play a game of inches in the soil, adding a centimeter of root here, sacrificing a branch there, balancing their books as the climate ledger tips and tilts.

There is resilience in this story, but not the sort that lets us off the hook. Trees in Panama’s tropical forests are not passively waiting for their fate. They are adjusting, improvising, doing what life has always done when the rules grow harsher. Yet even the deepest roots have limits. If droughts grow too frequent, too intense, too prolonged, no amount of underground reach will save every species from the heat.

Still, it is worth pausing to honor what is happening quietly underfoot. In a time when so much of our attention is fixed on what burns, breaks, and disappears, there is also this: a forest digging in, literally, to endure.

The next time you see a picture of a tropical canopy, or fly over a band of green wrapped around the waist of the Americas, remember that much of the real drama is hidden. Picture the roots, lengthening in the dark. Picture them brushing against deeper stones, brushing against old water. Picture a forest learning, in its own slow language, how to reach for life when the rain forgets its name.

Frequently Asked Questions

Are all trees in Panama growing deeper roots because of drought?

No. The trend toward deeper roots is not uniform across every species or every forest. Some species are naturally shallow-rooted and may struggle more as droughts intensify. Others have always had the capacity for deeper roots and are now leaning more heavily on that trait. What researchers are seeing is an overall shift in many communities toward more biomass in deeper soil layers, not a universal change in every single tree.

How do scientists actually measure root depth in a tropical forest?

Researchers use several methods: they dig soil pits or trenches to expose root profiles, extract soil cores at different depths, and sometimes use transparent tubes or cameras to observe roots over time. They then sort, measure, and weigh the roots from different layers. It’s labor-intensive, muddy work, but it reveals how root systems are distributed from the surface downward.

Can deeper roots completely protect forests from climate change?

Deeper roots can help trees survive longer and buffer forests against moderate droughts by tapping hidden water reserves. But they are not a magic shield. Extremely long, repeated, or intense droughts can overwhelm even deep-rooted species, especially when combined with higher temperatures, pests, and human disturbances like logging or fragmentation.

Does deeper rooting affect animals and other plants?

Yes. As trees with deeper roots become more dominant, the species makeup of the forest can change. That can shift which fruits are available, when they ripen, and what kind of canopy structure exists—all of which affect animals. Plants that rely heavily on shallow moisture may be outcompeted, while species better adapted to intermittent or deeper water may gain ground.

What can people do to help these forests cope with increasing drought?

Protecting large, intact forest areas is one of the most important steps. Continuous forest allows a wider variety of root strategies and species to coexist, giving the ecosystem more options to adapt. Reducing deforestation, restoring degraded land, cutting greenhouse gas emissions, and supporting conservation efforts in Panama and beyond all give these forests—and their deepening roots—a better chance to keep doing what they do best: harbor life, steady the climate, and quietly endure.