Climate change research at UH Hilo: Tree rings and bird song

Professor of Biology Patrick Hart and his research team are studying the endemic māmane tree and palila bird to learn how to predict future environmental changes.

By Anne Rivera. Photos of Hart Lab by Zoe Coffman.
This story is the first in a series on climate change research at UH Hilo.

Prof. Hart and grad student Shea Uehana standing in aisle in lab. Wood samples are stacked on the shelf.
Above, Prof. Patrick Hart with Shea Uehana, a graduate student in the Tropical Conservation Biology and Environmental Sciences Program. Below, some of their work with māmane in Hart Lab. Photos of lab by Zoe Coffman/UH Hilo Stories, click to enlarge.

Climate change is on everyone’s radar and the need to figure out the environmental impacts caused by human consumption has been pushing the scientific community. Several research projects stimulated, conducted, and maintained at the University of Hawai‘i at Hilo are working on this challenge by focusing on innovative methods and ideas that contribute to that field of study and expertise.

There are various research projects around campus that allow students and faculty to work side by side on incredible climate change studies.

Patrick Hart, professor and chair of biology at UH Hilo, has kick-started a few projects in his department that have been ongoing for years.

“We are in a very key place for looking at climate change issues and looking at issues related to biodiversity,” says Hart. “We have this extinction crisis going on in Hawai’i while being in this incredible region of diverse plant and animal species which is fascinating. This dendrochronology research is instrumental in how we will predict future climate shifts on all levels along with being able to prepare for these changes while preserving some of our world’s most amazing plants and animals.”

The dendrochronology project Hart refers to is the study of core samples from indigenous trees on the island of Hawai‘i. His tree ring research project has been in production for almost ten years.

The current research is made possible through the National Science Foundation Centers for Research Excellence in Science and Technology or CREST program now in its fourth year at UH Hilo and funding from the Pacific Islands Climate Science Center.

Tree rings

Various graduate students have worked on this research alongside Hart, contributing to substantial strides in the science community. Shea Uehana is the current graduate student involved on the project—before him, Kainana Francisco and Tishanna Ben also partook in this inquiry.

Tree rings are used in a variety of ways—they are used to calculate the age of a tree, climate conditions throughout the lifespan of the plant, health of the soil, previous precipitation, etc. The rings on a tree develop at the end of an annual year in the life of the plant and tends to be produced in trees that experience a range of the four seasons.

Stack of sliced tree trunk showing rings.
Dendrochronology is the science of dating events in the environment in former periods by comparative study of growth rings in trees and aged wood. These māmane specimens are ready for study in Hart Lab, UH Hilo. Photo credit: Zoe Coffman/UH Hilo Stories.

Until very recently, it was believed that trees native to and living in tropical climates did not produce rings or did not produce them at the same frequency or accuracy as others in non-tropical climates.

However, Uehana and Hart have discovered that some indigenous trees and nonnative trees surviving in Hawai‘i do in fact produce rings in areas of high elevation. According to Hart, the most surprising thing was finding annual rings in a tropical tree in Hawai‘i.

“We thought it was unusual but then found some nonnative trees planted by ranchers a long time ago, like cedar and different kinds of pine, lay annual rings here,” he explains. “They’ve taken that behavior from the continental United States and kept that annual growth behavior.”

The Hart Lab has dozens of core samples to date and evaluate—the research team’s goal is related to climate change but more specifically to prevention and preservation.

“One of our main goals as an ecology lab is to find out how to preserve species,” says Hart. “We are interested in finding out how long it takes to restore certain trees. This study gives us information on how fast they grow, how old they get, and how long it takes them to mature and be useful.”

They are using tree rings to obtain paleoclimatic data because in some areas of Hawai‘i there is only history as recent as the 1960s.

Uehana says, “In order to understand the way climate change will affect things in the future you need to look at things in the past.”

There is no good record of how climate has varied over time in the Pacific so taking the chronology further back to get a better understanding of how climate has been changing will be beneficial to predicting large scale environmental cycles.

Uehana uses the example of El Nino and La Nina.

“If you can more accurately predict how severe an El Nino or La Nina cycle will be then you can better prepare,” he says.

The māmane and the palila

Hart also conducts bird research that uses algorithms to identify bird songs and sounds, which allows scientists and researchers to identify birds in a particular area by just sound alone. The preservation of the endemic palila (Loxioides bailleui) bird is one of the focuses of this research.

Yellow, gray and white bird on tree branch, nibbling at leaves.
Palila (Loxioides bailleui). Photo by Jack Jeffery, USGS Pacific Island Ecosystems Research Center. Click to enlarge photos.

The māmane (Sophora chrysophylla), an endemic tree, provides food and habitat for the palila, hence the spawn of the tree ring research project.

Yellow flowers on tree branch.
Māmane (Sophora chrysophylla). Photo credit Forest and Kim Star.

“This tree ring study has farther reaching impacts beyond environmental, it is also ecological,” says Uehana. “This study can help us learn how to predict things in the future. If we know the next ten years will be drought years and we know that the optimum conditions for the māmane are just the opposite, then we can deduce that it will not only be a bad decade for the māmane but also a bad decade for the palila.”

The usefulness of prediction, Uehana says, is being able to take measures to counteract the bad cycles.

Hart says he loves working and mentoring students as well as watching them go on to be successful after they graduate and over time. He says true joy is seeing them become impactful on some level. The graduate students previously working on the tree ring project have their findings being published—Francisco has been published in the peer reviewed journal Tropical Ecology (“Annual rings in a native Hawaiian tree, Sophora chrysophylla, on Maunakea, Hawaiʻi“), while Ben has a study being published later this year.

This post was updated on Feb. 25, 2017 to include information on funding.


Anne Rivera (junior, communication) is a public information intern in the Office of the Chancellor.

Zoe Coffman (senior, art) is a photography intern in the Office of the Chancellor.

-UH Hilo Stories


Also in this series:

Climate change research at UH Hilo: Near shore water quality

Climate change research at UH Hilo: Fishpond management and restoration

Climate change research at UH Hilo: Collecting data on forests and trees

Climate change research at UH Hilo: Monitoring the coasts for signs of erosion and planning ahead

Share this story