Climate Change Is Rewriting the Chemistry and Geography of the World’s Medicinal Plants

Medicinal plants have anchored human healthcare for millennia, from the plant-based remedies recorded in ancient Mesopotamia around 2600 BC to the Ayurvedic and Traditional Chinese Medicine systems still practiced today. The World Health Organization estimates that nearly 80 percent of the global population relies on traditional medicine for primary healthcare, and plant-derived compounds remain a cornerstone of modern pharmacology. Yet a new comprehensive integrative review published in Discover Plants warns that this pharmacological inheritance is now under direct threat from climate change, which is simultaneously disrupting how these plants grow, what chemicals they produce, and where they can survive.

The review, authored by Ekperna Dubey, Bhuwal Ram and Rajeev Bhatla of Banaras Hindu University, synthesizes peer-reviewed literature retrieved from Scopus and Google Scholar using structured Boolean searches covering the period from 2000 to 2025. The authors focused on three thematic dimensions: growth and yield, secondary metabolite production, and shifts in geographical distribution. Their central conclusion is that these three dimensions cannot be treated in isolation. The same climatic variables that reduce biomass also alter metabolic pathways and force species to abandon their historical ranges, creating a cascade of effects that ultimately determines whether a medicinal plant remains therapeutically reliable.

The physical backdrop is stark. According to the IPCC Sixth Assessment Report, global surface temperature has already risen by approximately 1.1 degrees Celsius relative to the pre-industrial baseline of 1850 to 1900, and projections show that annual maximum temperatures will continue climbing regionally at warming levels of 1.5, 2, 3 and 4 degrees Celsius. Because plants are sessile organisms that depend directly on temperature, light, precipitation and atmospheric carbon dioxide for their physiology, even slight deviations in these variables can impair growth, metabolism and ecological interactions. At the cellular level, abiotic stress triggers the production of reactive oxygen species such as peroxides and superoxide ions, which damage chloroplast structure, membrane lipids, photosynthetic pigments and proteins, reshaping plant morphology and secondary metabolite profiles in the process.

The consequences for yield are already documented in the field. The review cites documented reductions in harvests of fennel and anise in Hungary following flooding, and the failure of chamomile to reseed in Germany and Poland after hot summers. These anomalies are linked in part to cyclical climatic phenomena such as the El Niño Southern Oscillation, which disrupts normal plant phenology and intensifies existing climatic stress. Phenology, the seasonal timing of events like bud formation, first flowering, leaf emergence and fruit dispersal, is particularly sensitive: when the onset of seasons shifts, these developmental stages can be delayed or fail entirely, reducing both productivity and harvest quality. Heat stress further constrains growth by decreasing stomatal conductance and limiting photosynthesis, while drought directly lowers biomass production and disturbs cellular homeostasis.

Not every response is uniformly negative, however. In studies of four alpine species in the northwestern Himalayas, including the stoloniferous forb Picrorhiza kurrooa and the rhizomatous forb Rumex nepalensis, three growth forms displayed positive responses to elevated carbon dioxide, with increased height, leaf number and leaf area. But the review emphasizes that such short-term gains can be deceptive. Moderate stress may initially act as a biochemical stimulus that activates specific metabolic pathways and boosts phytochemical synthesis, yet prolonged or excessive stress suppresses physiological performance, hampering photosynthesis, biomass accumulation and, ultimately, the concentration of pharmacologically active tissues.

The chemistry of medicinal plants is where climate change produces its most subtle and consequential effects. Secondary metabolites, the alkaloids, flavonoids, terpenoids and related compounds synthesized through the malonic, shikimic and mevalonic acid pathways, are the chemical basis of therapeutic value. More than 2,140,000 plant-derived metabolites have been identified to date, including roughly 29,000 terpenoids, 12,000 alkaloids and 8,000 phenolics. The review shows that their production under stress is highly unpredictable, depending on both the magnitude of the stressor and the duration of exposure. In the beach spider lily, Hymenocallis littoralis, concentrations of the antiviral compounds pancrastistatin, 7-deoxy-trans-dihydronarciclasin and 7-deoxynarciclasine initially rose under elevated carbon dioxide but declined over time. In Ligularia fischeri, drought increased flavones and anthocyanins while decreasing caffeoylquinic acid. Elevated temperature raised root ginsenosides in American ginseng yet increased monoterpenes in the high-altitude aromatic plant Angelica glauca, illustrating how species-specific and even tissue-specific these responses can be.

Geographical distribution shifts compound the problem, particularly in mountainous and island regions. In the Himalayas, high-altitude medicinal genera such as Aconitum, Nardostachys and Picrorhiza are moving upward as temperatures rise, becoming confined to progressively narrower alpine zones. Ensemble modelling for Nepal predicts that key traded species such as Nardostachys jatamansi and Neopicrorhiza scrophulariiflora will lose substantial portions of their current range by 2070, with their optimal climatic niches shifting upward by 300 to 500 meters. Once a species reaches the top of a mountain, there is nowhere left to go. In Indonesia, where biodiversity is concentrated on low-lying islands, projections suggest that over half of medicinal plant species may lose up to 80 percent of their suitable habitat by around 2080, especially in the lowland regions of Java, Sulawesi and Papua. Upward migration also creates new competition with species already occupying those scarce high-elevation habitats.

To tie these threads together, the review presents an integrated case study of Picrorhiza kurrooa, an endangered Himalayan herb prized in Ayurveda for its hepatoprotective iridoid glycosides, picroside I and picroside II. Field studies have found that individuals growing at cooler, high-altitude locations contain higher picroside concentrations than those at warmer, lower elevations, and experimental work shows that cooler temperatures enhance the expression of genes involved in picroside biosynthesis. Warming experiments further revealed tissue-dependent effects: both picrosides increased in rhizomes, while in leaves picroside I decreased even as picroside II increased. This means biomass alone cannot serve as a measure of climate impact. A plant may grow vigorously under elevated carbon dioxide while its medicinal chemistry quietly deteriorates, or the reverse. The species thus demonstrates how growth, metabolite stability and range contraction are driven by the same climatic forces and must be assessed together.

Building on this case, the authors propose a conceptual vulnerability framework that groups medicinal plants into four broad exposure categories. High-altitude Himalayan and alpine species such as Aconitum species, Nardostachys jatamansi and Picrorhiza kurrooa face severe range contraction as suitable alpine habitat disappears. Lowland tropical and island species from regions such as Java, Sulawesi and Papua have no higher ground to escape to and are threatened primarily by habitat loss and submergence. Temperate cultivated species such as fennel, anise and chamomile may avoid permanent habitat loss but remain vulnerable to phenological disruption and yield losses from extreme weather. A fourth category, including Picrorhiza kurrooa, Hymenocallis littoralis and Ligularia fischeri, shows tissue-specific metabolite variability that can decouple chemical quality from biomass. The framework is intended as a flexible guide to what evidence matters most for assessing each species, not a rigid classification.

The review also identifies four major gaps in the evidence base. Most experimental studies examine a single stress factor, such as drought, elevated carbon dioxide or temperature, even though plants in nature face multiple stresses simultaneously, and combined-stress responses remain poorly understood. Few studies connect changes in metabolite concentrations to actual pharmacological activity. Regions such as Africa and South America remain largely understudied, and species distribution modelling has been applied to only a handful of traded medicinal plants. On the conservation front, the authors call for multi-scale action, combining ex situ approaches such as seed banks, tissue culture and cryopreservation with in situ habitat protection, supported by digital phenotyping, remote sensing, DNA barcoding and genomic sequencing to track genetic erosion and prevent adulteration in trade. Breeding for heat tolerance through enhanced antioxidant enzyme pathways and osmoprotectant synthesis shows promise, while community-based conservation and the revival of traditional knowledge are framed as the social backbone of any strategy. Ultimately, the authors argue, safeguarding the therapeutic reliability of the world’s medicinal flora will require a multidisciplinary, evidence-based approach that unites genomics, metabolomics, ecological modelling, climate-smart cultivation and the indigenous knowledge systems that have sustained these plants, and the people who depend on them, for thousands of years.

Subject of Research: Impacts of climate change on the growth, secondary metabolite production and geographical distribution of medicinal plants

Article Title: Assessing impact of climate change on medicinal plants through yield decline, metabolite variability and range shifts

Article References: Dubey, E., Ram, B., & Bhatla, R. (2026). Assessing impact of climate change on medicinal plants through yield decline, metabolite variability and range shifts. Discover Plants, 3(1), Article 437. https://doi.org/10.1007/s44372-026-00908-2

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00908-2

Keywords: medicinal plants, climate change, secondary metabolites, yield decline, range shifts, phytochemistry, phenology, Picrorhiza kurrooa, Himalayas, conservation, vulnerability framework, abiotic stress