On a hot, muggy day in Baton Rouge, Louisiana at the end of August 1992, my aunt who was a nurse at the time patched my broken toe. I was two years old, and the injury had come as the result of a dropped can of corn in an unlit pantry. One might argue though that the cause was somewhat larger. Hurricane Andrew had bombed Louisiana with a wind threat unseen since Hurricane Betsy in 1965, and power restoration in my hometown was more than a week away. In other words, Hurricane Andrew broke my toe.
That’s a story I’ve been told so many times that it is an active memory of my childhood. I’m not sure if I actuallyremember it, or if it’s truly a collective memory of stories told by my family through time. For South Louisiana, the last five days of August hold significant memories for all generations: for those who remember, Hurricane Camille in 1969, the nation-altering Hurricane Katrina in 2005, and most recently Hurricanes Laura (2020) and Ida (2021), to name a few. My own memories of Hurricane Ida will last a lifetime (Figure 1).
Figure 1. Aftermath of Hurricane Ida in Cocodrie, Louisiana (August 31, 2021). Rusty Tucker walks on a flooded Tou Lou Lou Street near our family’s coastal property that was swept from its piling foundation by 150-mph winds on August 26, 2021, the 16-year anniversary of Hurricane Katrina.
A memory of hurricanes past surrounds the identity in my home state, their meteorological numbers are recorded for posterity, and hurricane wind speed in the region has become stronger through time. Climatological observations are useful for as long as we have data, but we only have reliable data for the past 170 years, a period during which humans had substantial influence on Earth’s climate. To assess changes before our influence, we must read the stories of other archives, in my own case through the collective memory of trees.
I first discovered that tree memory in Baton Rouge had similar accounts of local hurricanes during a project with the youth outreach program Coastal Roots in a local city park. Lowest growth in the life of these trees was 1993, the year after Hurricane Andrew (Figure 2). Had Hurricane Andrew broken their toes in an unlit pantry too? Okay, perhaps not the same story, but they had some memory of the storm too. The more pressing question: could the hurricane stories of trees reliably match the hurricane stories of humans, and more importantly, could they tell us stories that nobody had written down? My research since 2013 suggests a definitive “yes!”
Figure 2. Tree-ring chronology of oak (Quercus nigra) at Doyle’s Bayou Park, Baton Rouge, Louisiana (1973–2018).
High winds destroy canopy limbs, storm surge brings desiccating saltwater to coastal trees, and inland rainfallfloods riparian species. These extreme weather events all leave their mark in the physical and chemical composition in trees’ growth rings. Moreover, the most damaging storms in the human stories are often the most memorable in trees too. Remember those trees that had been affected by Hurricane Andrew? They also experienced low growth in 2006 and 2009, the years following Hurricanes Katrina and Gustav, respectively (Figure 2). These three hurricanes alone resulted in 2,013 lives lost and caused an estimated $160 billion in property damages. Understanding long-term trends in hurricane activity is necessary for reducing hurricane-induced catastrophe.
We’re still exploring the utility of tree-ring data as a hurricane proxy, and long-lived species are showing great promise. Baldcypress trees, the longest-lived species in the southeastern U.S., live in low-lying areas where streamflow is affected by vast rainfall produced by hurricanes (Figure 3). We find that 77% of baldcypress false rings are formed during hurricane flooding, and my colleagues Emily Elliott, Jessie Pearl, Josh Bregy, and I aim to produce thousand-year chronologies of hurricane-induced stream floods from baldcypress false rings, latewood, and tree-ring isotopic composition in a recent project funded by the National Science Foundation.
Figure 3. Baldcypress (Taxodium distichum) in Lassiter Swamp at Merchants Millpond State Park, North Carolina. Though frequently flooded throughout the year, baldcypress trees record late-summer flooding from hurricane rainfall in their growth rings.
Though we know the risk from hurricanes in the instrumental climate record, tree memory can tell us stories of hurricanes before we heavily modified our world. We do not yet know the full story of hurricanes through tree memory, but we know they have that memory, and we are exploring the best tree language through which to read that story. I’m excited to see what the past holds and what a future of stories in The Dendro Hub can accomplish!