Forests Can’t Keep Up: Adaptation Will Lag Behind Climate Change
Forests are falling behind in the race against climate change, with new research revealing it takes about 150 years for tree populations to adapt — far too slow to keep pace with today’s rapidly warming world. Ecologists are concerned that forest ecosystems will not keep pace with a rapidly changing climate, failing to remain healthy and productive. Before the rapid climate change of the past century, tree populations in the Northern Hemisphere adapted to colder and warmer periods over thousands of years. During the onset of Ice Ages, tree populations migrated south, seeking warmer conditions as global temperatures cooled, their seeds were dispersed by winds and carried by animals. When the climate warmed again, tree species adapted by migrating north to more suitable conditions. Mature trees are long-lived, and their populations cannot migrate quickly. Current climate change is happening faster than many forests can adapt and thrive, creating a mismatch between the pace of warming and the natural adaptation of forests. A new study in the journal Science, co-authored by Professor Moriaki YASUHARA of the HKU School of Biological Sciences, highlights that forests have a lag time of one to two centuries to shift tree populations in response to climate change. Led by first author David FASTOVICH, a postdoctoral researcher at Syracuse University, the research aimed to map the timescales at which tree populations respond to climate change, examining pollen data from lake sediment cores spanning up to 600,000 years ago. David Fastovich led the study exploring how forests react to climate change. ‘We’ve known these time lags have existed, but no one could put a firm number on them,’ says Fastovich. ‘We can intuit how long a tree lives. We can count the rings on a tree and estimate from there. But now we know that after one to two centuries — very close to how long a tree lives on average — entire forest ecosystems begin to turn over as trees die and are replaced in response to climate.’ The research team employed spectral analysis — a statistical technique commonly used in fields such as physics and engineering-to study long-term ecological data. This method allowed the researchers to compare the relationship between tree populations and climate from decades to millennia. One goal was to learn how closely tree population migrations, tree mortality, and forest disturbances, such as those caused by forest fires match climate changes over time. Spectral analysis provides a unified statistical approach to understanding how natural forest adaptation evolves over periods ranging from days to thousands of years. The researchers found that at timescales of years and decades, forests typically change slowly. At longer timescales, centuries and millennia, however, forest changes tend to become larger, tied to natural climate variability. ‘With this new technique, we can think about ecological processes on any timescale and how they are connected,’ says Fastovich. ‘We can understand how dispersal and population changes interact and cause a forest to change from decades to centuries and even longer timescales. That hasn’t been done before.” The workshop where members of our research team first discussed the initial concept for this project. This research project originated from a workshop organised by Professor Yasuhara in Okinawa, aimed at bridging the gap between macroscale biology and palaeobiology. ‘These biological and palaeontological fields share similar research interests, but there are substantial gaps, particularly in the time scales they typically study,’ Professor Yasuhara explained. ‘I am thrilled to see this research come to fruition. This paper provides a unified framework that allows biologists, ecologists, palaeontologists, and palaeobiologists to speak the same language when discussing climatic impact and biotic response regardless of time scales, whether over years, centuries, or millennia, and whether focused on living species or fossils.’ The study also suggests that forests will require more human intervention to remain healthy. Assisted migration might be an effective tool. It is the practice of planting warmer-climate trees in traditionally colder locations to help woodlands adapt and flourish despite the warming of their habitats due to climate change. Forest adaptation to climate will be a slow, complex process requiring nuanced, long-term management strategies, Fastovich notes. ‘There’s a mismatch between the timescales at which forests naturally change to what’s happening today with climate change,’ Fastovich says. ‘Population-level changes aren’t going to be fast enough to keep the forests that we care about around. Assisted migration is one tool of many to keep cherished forests around for longer.’ Lake sediment from Sheelar Lake, Florida.
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HKU Geologists Suggest Early Continents Formed through Mantle Plumes, Not Plate Collisions
Geologists from The University of Hong Kong (HKU) have made a breakthrough in understanding how the Earth’s early continents formed during the Archean time, more than 2.5 billion years ago. Their findings, recently published in Science Advances, suggest that early continental crust likely formed through deep Earth processes called mantle plumes, rather than the plate tectonics that shape continents today. Figure 1. An illustration depicting the formation of TTGs in a two-stage mantle plume-sagduction model. Image credit: Adapted from Zhao, D. et al. (2025). Science Advances. DOI: 10.1126/sciadv.adr9513. A New Perspective on Earth’s Early Crust Unlike other planets in our solar system, Earth is a unique planet with continental crust—vast landmasses with granitoid compositions that support life. However, the origin of these continents has remained a mystery. Scientists have long debated whether early continental crust formed through plate tectonics, i.e., the subduction and collision of giant slabs of Earth’s crust, or through other processes that do not involve plate movement. This study, led by Drs Dingyi ZHAO and Xiangsong WANG in Mok Sau-King Professor Guochun ZHAO’s Early Earth Research Group at the HKU Department of Earth and Planetary Sciences, together with international collaborators, has uncovered strong evidence that a distinct geodynamic mechanism shaped the Earth’s formative years. Rather than the plate tectonic processes we see today, the research points to a regime dominated by mantle plumes—towering columns of hot, molten rock ascending from deep within the Earth. It also identifies a phenomenon known as sagduction, wherein surface rocks gradually descend under their weight into the planet’s hotter, deeper layers. These findings shed new light on the dynamic processes that governed the early evolution of Earth’s lithosphere. Studying Ancient Rocks to Understand the Deep Past The team analysed ancient granitoid rocks called TTGs (tonalite–trondhjemite–granodiorite), which make up a large part of the oldest continental crust. These rocks, found in northern China, date back around 2.5 billion years. Using advanced techniques, the researchers studied tiny minerals within the rocks, known as zircons, which preserve chemical signatures from the time the rocks were formed. By measuring the water content and oxygen isotope composition of these zircons, the team found that the rocks were formed in dry, high-temperature environments, unlike those typically found in zones where tectonic plates collide and one sinks below the other (subduction zones). The oxygen signatures also indicate a mixture of molten oceanic rocks and sediments, consistent with rocks formed above mantle plumes rather than subduction zones. The researchers proposed a two-stage model to explain their findings: 1. Around 2.7 billion years ago, a mantle plume caused thick piles of basalt (Fe- and Mg-rich volcanic rock) to form on the seafloor. 2. Then, around 2.5 billion years ago, another mantle plume brought heat that caused the lower parts of these basalts to melt partially. This process produced the lighter TTG rocks that eventually formed continental crust. Figure 2. A group photo of the HKU research team. From the left: Professor Min Sun, Dr Dingyi Zhao, Dr Xiangsong Wang and Professor Guochun Zhao. Implications for Earth and Planetary Science “Our results provide strong evidence that Archean continental crust did not have to be formed through subduction,” explained Dr Dingyi Zhao, postdoctoral fellow of the Department of Earth and Planetary Sciences and the first author of the paper. “Instead, a two-stage process involving mantle plume upwelling and gravitational sagduction of greenstones better explains the geochemical and geological features observed in the Eastern Block.” The study distinguishes between two coeval Archean TTG suites—one plume-related and the other arc-related— by comparing their zircon water contents and oxygen isotopes. Professor Guochun Zhao emphasised “The TTGs from the Eastern Block contain markedly less water than those formed in a supra-subduction zone in the Trans-North China Orogen, reinforcing the interpretation of a non-subduction origin.” “This work is a great contribution to the study of early Earth geodynamics,” co-author Professor Fang-Zhen Teng from the University of Washington added. “Our uses of zircon water and oxygen isotopes have provided a powerful new window into the formation and evolution of early continental crust.” This study not only provides new insights into understanding the formation of Archean continental crust, but also highlights the application of water-based proxies in distinguishing between tectonic environments. It contributes to a growing body of evidence that mantle plumes played a major role in the formation of the early continental crust. Journal paper: A two-stage mantle plume–sagduction origin of Archean continental crust revealed by water and oxygen isotopes of TTGs, by Dingyi Zhao et al., Science Advances (2025). DOI: 10.1126/sciadv.adr9513
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