From the forest to a leaf

The 5 million specimens of pressed and dried plants, algae, and fungi in the Harvard University Herbaria’s collection — among the world’s largest — must be celebrated and protected for their own sake, and for their role in deepening our understanding of a changing planet, says newly appointed Director Jeannine Cavender-Bares. 

“Biodiversity collections house the knowledge we have about organisms, their taxonomies, their names, and the whole histories of their discovery,” said Cavender-Bares, a plant ecologist and professor in the Department of Organismic and Evolutionary Biology.

The new director has spent her career studying plant biology from the smallest physiological features to sweeping habitats made visible by advances in satellite-based remote sensing. Solving the related crises of climate change and biodiversity loss requires discovery at many different scales, she said.

Cavender-Bares points to a research project she led that mapped swaths of diseased oak trees so they could be culled to prevent spread. On the cellular level, her teams examined tissue of trees stricken with oak wilt disease to understand immune response. Using aircraft, they measured electromagnetic information from affected forests, detecting sick and healthy canopies.

“This is an example of how we’re moving from cells and details of the anatomy of a plant to large, regional remote sensing for management,” she explained.

This and other projects fall under a National Science Foundation-funded Biology Integration Institute based at the University of Minnesota that Cavender-Bares leads, called ASCEND, aimed, in part, at training the next generation of leaders in spectral biology and its many applications.

As a leading expert in spectral biology, Cavender-Bares uses the interaction between light and plant matter to reveal unique, fingerprint-like information about plants’ chemistry, structure, and cellular function. Such information can be gathered from handheld spectroradiometers measuring how leaves reflect light; also from aircraft and satellite sensors, like those planned for NASA’s Surface Biology and Geology mission and the European Space Agency’s CHIME mission, which will capture sweeping hyperspectral information over landscapes for monitoring agriculture practices and soil health. 

Cavender-Bares is initiating an effort toward spectral digitization of herbarium specimens, not only at Harvard but among a network of academic and institutional herbaria worldwide.

“We’re working with other herbaria to get all the protocols worked out and figure out the right way to do this, so that we don’t have 10 different herbaria doing this 10 different ways,” she said.

The Herbaria will soon mark the 100-year anniversary of one of its largest and most important collections, the Farlow Herbarium of Cryptogramic Botany, which contains 1.4 million specimens of lichenized and non-lichenized fungi, bryophytes, and algae. Luminaries in mycological sciences and botany will gather at Harvard to reflect on the collection’s history, and share knowledge about everything from the foundational importance of fungi in ecosystems to the latest science of rusts, which are pathogens that cause plant fungal diseases.

Cavender-Bares hopes events like the Farlow celebration will give the Herbaria a forward-facing outlook and underscore for the public its significance as a hub of scientific knowledge. Biodiversity collections show us where we’ve been and what we could lose, she noted.

“We’re facing choices about converting our forests into solar panels,” she said. “But if we’re not simultaneously thinking about all these other organisms for the functions they provide, for the water they clean, for erosion control, for carbon sequestration — we’re going to lose them, and the potential they harbor for regenerating healthy ecosystems in the face of global change.”

Learn more about the Harvard Herbaria and the Farlow Herbarium anniversary celebration on Nov. 1.