Human-induced climate change is disrupting the familiar temperature and rainfall patterns that California’s coastal redwoods and oaks have long adapted to, pushing these and other native trees to the brink of their tolerance limits. The urgent task of identifying new habitats for these iconic California species now takes center stage, according to Professor Lawren Sack, an expert in ecology and evolutionary biology at UCLA. However, the question remains: if these trees could communicate, where would they want to call home?
In a groundbreaking study, a team led by Sack and fellow UCLA biologists has decoded a clandestine language concealed within leaves and woody stems, providing valuable clues to each species’ ideal habitats. This newfound knowledge could revolutionize the ability to pinpoint suitable new locations for these plants, ensuring their continued existence, and enhance the preservation of their existing ecosystems.
Remarkably, scientists and conservationists have lacked a reliable method to determine the optimal environment for individual plant species, often relying on their current geographical distribution. However, for many plants, their current habitats fall short of ideal conditions.
California is home to numerous species exclusive to specific climate niches, found nowhere else in the world. Unfortunately, urbanization, agriculture, and industrial expansion have driven many of these species to the fringes of their habitats, exacerbated by the looming threat of climate change. Therefore, while it might appear logical to relocate species to areas resembling their current habitat or solely protect their existing homes, both approaches could jeopardize their future survival.
The recently published research in Functional Ecology introduces a statistical model that calculates each species’ preferred temperature and precipitation levels, considering factors such as height, leaf size, wilting point, leaf anatomy, leaf chemical composition, and wood density.
Using this data, the scientists developed a model that predicts not only what temperatures and rainfall amounts a species can tolerate but also what they genuinely prefer. Furthermore, the model allows for an estimation of how far a plant’s current location deviates from its native climate.
Lawren Sack, the senior author of the study, explained, “Plant species can directly reveal to us their climate preference and their vulnerability to potential climate change in the ‘language’ of their leaves and wood. Now that we know this, if you give us a leaf and a piece of wood, we can provide a scientifically informed prediction of the plant’s ideal habitat.”
Sack collaborated with UCLA postdoctoral scholar Camila Medeiros and an international team to analyze ten distinct leaf and wood traits from over 100 species across various environments, predominantly within the University of California Natural Reserve System. These ecosystems encompassed desert, coastal sage scrub, chaparral, montane wet forest, mixed riparian woodland, and mixed conifer broadleaf forest—covering roughly 70% of California’s land area.
Camila Medeiros, the study’s first author, noted, “The alignment of leaf and wood traits with species’ climates is remarkable. For instance, species native to warmer, drier climates tend to be shorter, possess thicker and denser leaves, and lower wilting points—traits that enable them to continue photosynthesis during water scarcity and grow more rapidly when water is abundant.”
Medeiros added, “The correlation between a species’ preferred climate and its leaves and wood traits has evolved over millennia, perfectly adapting plant physiology to California’s diverse climate conditions.”
Furthermore, the study unveiled that many plants were residing in locations with climates differing from their estimated optimal niches. As climate change accelerates, this mismatch could exacerbate the vulnerability of numerous species, including common trees like the California buckeye and shrubs like the purple sage and California lilacs.
For years, scientists have debated whether functional plant traits could accurately predict climate preferences. This study, which employed advanced measurement technologies and comprehensive statistical modeling, marks a significant breakthrough.
Medeiros emphasized, “Our study was unique in simultaneously applying all of these methods, granting us unprecedented predictive power.” Additionally, this approach has the potential to assist in prioritizing the conservation efforts for threatened species most in need of protection.