AYESHA RASCOE, HOST:
A century ago, the forests of the Eastern U.S. looked very different. They were packed with towering chestnut trees. But since then, those trees have largely disappeared, and the forests have evolved in a new direction, and relatively rapidly. Science reporter Ari Daniel has this report.
ARI DANIEL, BYLINE: A hundred years ago, botanist Emma Lucy Braun chronicled the forests of Eastern North America.
RICHARD KARBAN: She did all of this work - such a pioneer.
DANIEL: Richard Karban is an ecologist at UC Davis. He says that Braun described forests filled with American chestnut trees.
KARBAN: Oh, the nuts are fantastic. They're a really beautiful tree. They get pretty big around and they reach the canopy.
DANIEL: Or at least they used to. As Braun walked those forests in the 1920s, a fungus from Europe had begun stalking the American chestnut.
KARBAN: The fungus kills the upper portions of the trees so that the tree never reaches the canopy and never reproduces.
DANIEL: And by the mid 20th century...
KARBAN: The fungus has essentially eradicated American chestnut from these eastern deciduous forests.
DANIEL: So Karban wanted to see the forests that Braun had visited a half century earlier for himself. In 1977, after college, he went to Shenandoah National Park in Virginia and walked along a canyon trail.
KARBAN: What I found was that mostly oaks that had been present in the forest with chestnut had just increased, but not much else had changed.
DANIEL: Then a few years ago, at age 66, Karban returned to the same canyon trail. This time, he says the shift was way more dramatic. The oaks had nearly vanished. Birches and maples abounded, trees associated with forests that had been recently cleared or disturbed, Karban says.
KARBAN: That was surprising and frankly, somewhat upsetting because it suggested that changes since 1977 had been far more profound than those that had occurred immediately following the elimination of the chestnut from the forest.
DANIEL: Karban says it's possible the eventual form an ecosystem assumes after the loss of a foundational species like the chestnut might just take a while to play out, but he's concerned that the changes in the forest appear to have accelerated.
KARBAN: We are losing species at an unprecedented rate, and the effects might not become visible for decades.
DANIEL: The research is published in the journal PLOS ONE.
SANDRA ANAGNOSTAKIS: They suggest drastic changes in the forest. Well, of course, there will be.
DANIEL: Sandra Anagnostakis is a retired agricultural scientist from the Connecticut Agricultural Experiment Station who wasn't involved in the research. She calls the study brilliant. She says the fungus no doubt reshaped our forests and adds it's worth considering some of the other forces at play.
ANAGNOSTAKIS: For one thing, there are many new pests and pathogens which are going to impact which species will survive well. And if the climate changes, that will be another factor.
DANIEL: The authors of the paper also acknowledge other reasons behind the forests' current state, like over browsing by deer and a different frequency of fires. Whatever the reason, the conclusion is clear. Today's forests in the East look quite different than they did in the 1920s, or the '70s for that matter. It was hard for Richard Karban to witness such a radical transformation, but he says there was a sweeter side to working on this research project.
KARBAN: So my co-author is my daughter.
DANIEL: She's a PhD student in plant ecology, and the two of them walked the forest trail together, gathering data as they went.
KARBAN: Getting to do this project with her was really quite special. I loved it.
DANIEL: The deciduous forests may have changed, but some saplings can still take root.
For NPR News, I'm Ari Daniel. Transcript provided by NPR, Copyright NPR.
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