Climate Change Could Expand the Range of a Fern That Mines Rare Earth Elements

A humble fern growing in the evergreen broad-leaved forests of southern China has become one of the most intriguing plants in modern materials science. Blechnopsis orientalis is a confirmed hyperaccumulator of rare earth elements, drawing these strategically critical metals out of the soil and into its tissues at concentrations reaching 1735 to 3850 micrograms per gram. Even more remarkably, the plant can convert the absorbed elements into nanoscale monazite, a phosphate mineral, under ordinary temperature and pressure. Now a new modeling study published in Environmental and Sustainability Indicators has mapped how climate change is likely to reshape the geographic range of this extraordinary species, with direct consequences for both its conservation and the future of green phytomining in China.

The research team, led by Jun Ren and colleagues, assembled 2525 occurrence records of the fern from herbarium databases, the Global Biodiversity Information Facility, and published literature. After removing duplicates and thinning spatially clustered points on a 2.5-arcminute grid, they retained 646 verified distribution records spanning southern China. These points fed into a maximum entropy species distribution model, but with a crucial twist: rather than relying on the software’s default settings, the team systematically tuned the model’s regularization multiplier and feature classes using the ENMeval framework, evaluating candidate configurations with delta AICc and the 10 percent training omission rate.

The optimization mattered. The default parameterization produced a delta AICc of 68.32, far above the threshold of 2 that signals acceptable model fit, indicating pronounced underfitting. The refined configuration, with a regularization multiplier of 1 and a quadratic-hinge-product-threshold feature combination, achieved a delta AICc of zero, slightly reduced the false positive rate, and maintained an outstanding area under the curve of 0.947 across ten cross-validated runs. Because ferns combine powerful long-distance spore dispersal with extreme environmental sensitivity at the gametophyte stage, their responses to climate are often highly nonlinear, and overly complex models risk mistaking spatial noise for ecological signal. The authors argue that parameter optimization should become standard practice in fern distribution modeling.

When the team examined which environmental variables controlled the fern’s distribution, two climatic factors overwhelmed everything else. The mean temperature of the driest quarter alone contributed 52.6 percent of the model’s explanatory power, and annual precipitation contributed another 34.1 percent. Together they accounted for 86.7 percent of the spatial variation in suitable habitat, while topography, vegetation greenness, and the Human Footprint Index contributed less than 1.5 percent each. The response curves revealed sharp thresholds: occurrence probability climbed steeply once the driest-quarter temperature exceeded roughly 5.8 degrees Celsius, and suitability rose markedly once annual precipitation surpassed about 1027 millimeters.

The dominance of the driest-quarter temperature is biologically telling. Fern gametophytes lack a cuticle and are acutely vulnerable to desiccation, so moisture and temperature stress during the driest part of the year plausibly sets the species’ fundamental limits. But the authors propose an additional, more speculative mechanism tied to the fern’s unusual chemistry. Rare earth uptake in Blechnopsis orientalis depends on sustained transpiration-driven water flow and subsequent phosphate precipitation inside leaf cells. Cold snaps and drought suppress stomatal conductance, potentially breaking the chain of element uptake, transport, and mineralization. The team cautions that this rare-earth-related constraint remains a plausible complementary explanation rather than a demonstrated driver, and that disentangling the two effects will require controlled temperature and element-addition experiments alongside comparative modeling of non-hyperaccumulating relatives.

Under present-day climate, the model predicts roughly 1.34 million square kilometers of potentially suitable habitat across China, about 14 percent of the national land area. Yet only a sliver, less than 1 percent of the country, qualifies as highly suitable, concentrated in patches across Taiwan, central and southern Guangdong, and parts of Fujian, Hainan, Yunnan, and Tibet. Strikingly, these high-suitability patches overlap closely with the ion-adsorption rare earth ore belts of southern China, the same geological provinces that supply much of the world’s light rare earth elements. Nine of the twelve rare earth hyperaccumulator plant species reported in China occur within or adjacent to these ore districts, suggesting that climate suitability and geochemical opportunity coincide in a narrow band of subtropical terrain.

The future projections deliver a surprise. Whereas climate change studies typically forecast range contractions for rare and specialized plants, Blechnopsis orientalis is projected to expand under every scenario tested. Drawing on the BCC-CSM2-MR global climate model across four Shared Socioeconomic Pathways and three time windows spanning the 2050s to the 2090s, the team found that suitable habitat could grow from the current 1.34 million square kilometers to as much as 1.94 million square kilometers by century’s end, with expansion areas reaching nearly 600,000 square kilometers under the highest emission pathway. Contraction, by contrast, never exceeded 8300 square kilometers in any scenario. The high-suitability zone itself is projected to more than quadruple, spreading into most of Jiangxi, central and southern Hunan, and northwestern Yunnan.

The geography of this growth matters as much as its magnitude. The centroid of suitable habitat, currently located in Quanzhou County in the Guangxi Zhuang Autonomous Region, shifts consistently northwestward under high-emission scenarios, migrating up to about 109 kilometers into southwestern Hunan Province by the 2090s. Under the lowest emission pathway the centroid wobbles, suggesting that internal climate variability dominates when the warming signal is weak, whereas under strong forcing the long-term trend prevails. The authors are careful to note that a moving climate envelope is not the same as a moving population: fern spores can travel tens to hundreds of kilometers on favorable winds, but most settle within a few kilometers of the parent plant, and colonization also demands suitable microhabitats and adequate soil rare earth availability. Transplant experiments show that species performance beyond existing range boundaries typically declines by 40 to 45 percent, so the projected expansion may substantially outpace actual colonization.

These findings translate into concrete spatial strategy. For conservation, the team recommends prioritizing the tri-border region where Guangxi, Guangdong, and Fujian meet, an area that is both climatically stable into the future and close to the species’ current distributional center. For phytomining, they suggest early field trials in near-term expansion zones such as northern Guangdong, western Fujian, and southern Jiangxi, while emphasizing that climatic suitability alone does not guarantee mining suitability, since many projected expansion areas lack the enriched soils the fern needs to accumulate rare earths in commercially interesting quantities. Germplasm banks and ex situ collections, they propose, should be arranged along the projected centroid migration axis through Hunan. Because Blechnopsis orientalis produces less biomass than the related genus Dicranopteris, it may be best deployed where recovering monazite-bound elements is the priority, with the two ferns serving complementary roles.

The study also acknowledges its own limits. High-resolution soil rare earth data for China remain fragmented, so the model could not overlay geochemistry on climate projections; propagule dispersal limitation was not incorporated; soil properties such as pH were excluded; and only a single climate model was used, leaving inter-model uncertainty unquantified. Future work, the authors write, should couple climate projections with digital soil mapping, transplant experiments, and multi-model ensembles. Even with those caveats, the message is striking: one of the planet’s rarest botanical talents, a plant that literally grows critical metals, may find more of China hospitable as the world warms, and where it goes, both new mines without digging and new conservation frontiers may follow.

Subject of Research: Climate-driven distribution shifts of the rare earth element hyperaccumulator fern Blechnopsis orientalis in China

Article Title: Climate-driven shifts in the distribution of the rare earth element hyperaccumulator fern Blechnopsis orientalis : Implications for phytomining and conservation strategies in China

Article References: Ren, J., Li, S., Jiang, L., Yang, Q., Cai, Y., Chen, L., Xiang, Y., Yao, B., & Li, Y. (2026). Climate-driven shifts in the distribution of the rare earth element hyperaccumulator fern Blechnopsis orientalis: Implications for phytomining and conservation strategies in China. Environmental and Sustainability Indicators, 32, Article 101562. https://doi.org/10.1016/j.indic.2026.101562

Image Credits: AI Generated

DOI: 10.1016/j.indic.2026.101562

Keywords: Blechnopsis orientalis, rare earth elements, phytomining, hyperaccumulator, species distribution modeling, MaxEnt, climate change, CMIP6, ferns, monazite, conservation, China