The patient at the center of the report was a 69-year-old man from Côte d’Ivoire who was residing in France. He had traveled to the Man District in the western part of the country, a region where malaria transmission remains intense. Côte d’Ivoire is among the West African countries where malaria is highly endemic, and repeated exposure to infective mosquito bites means that residents and returning travelers alike face a substantial risk not only of single-species infections but also of mixed infections involving more than one Plasmodium species at the same time. In much of sub-Saharan Africa, Plasmodium falciparum is overwhelmingly the dominant parasite, responsible for the vast majority of acute clinical cases and nearly all of the severe ones. That dominance shapes clinical expectations: when a febrile patient from an endemic region presents with malaria, P. falciparum is the species clinicians and laboratories anticipate.

That expectation is precisely what makes this case instructive. The patient’s initial malarial episodes were attributed to P. falciparum, which was detected and treated in the standard way. But a subsequent episode of illness occurred in the complete absence of re-exposure — the patient had not traveled again, and there was no new mosquito-borne inoculation that could explain a fresh infection. When the laboratory investigated this later episode, the parasite identified was not P. falciparum at all but P. ovale, a species that behaves very differently from its more notorious relative. The temporal dissociation between the two detections, the authors argue, strongly suggests that both species had been acquired during the same period of exposure in Côte d’Ivoire, meaning the patient had likely been carrying a mixed infection from the start, even though only one species was visible to the diagnostic process at the time.

The biology underlying this delayed presentation lies in a feature that separates P. ovale, along with P. vivax, from the other human malaria parasites. P. falciparum is a one-stage parasite in clinical terms: after inoculation, it develops in the liver, floods the bloodstream, and causes disease, and once the blood-stage infection is cleared by treatment, the parasite is gone. P. ovale, by contrast, is capable of forming dormant hepatic stages known as hypnozoites. These hypnozoites can sit quietly inside liver cells for weeks or months, producing no symptoms and no detectable blood-stage parasites, before reactivating to seed a new blood-stage infection. In this patient, the clinical recurrence attributable to P. ovale occurred four months after the primary infection, a timing that, in the absence of any recent travel or new exposure, supports the hypothesis of hypnozoite reactivation rather than reinfection. The late clinical presentation is therefore not an anomaly but a direct consequence of the parasite’s life-cycle strategy.

Why, then, did the P. ovale infection not declare itself alongside the P. falciparum infection in the first place? The authors point to two interacting factors. The first is parasitemia: at the time of the later diagnosis, the P. ovale parasitemia was extremely low, at approximately 0.02 percent of infected red blood cells. Such low-level parasitemia can fall below the detection threshold of routine microscopy and even of some rapid diagnostic tests, particularly when a laboratory is not specifically looking for non-falciparum species. The second factor is plausible interspecies competition. When two Plasmodium species occupy the same host simultaneously, they compete for red blood cells, host resources, and immunological space. P. falciparum, with its explosive replication and high parasitemias, can effectively dominate the host environment, keeping the slower-growing P. ovale population suppressed and subclinical. Only after the falciparum infection was treated and cleared would the ovale parasites have faced reduced competition, allowing the dormant liver stages eventually to reactivate into a clinically apparent relapse.

The diagnostic challenges highlighted by this case are considerable and systemic rather than idiosyncratic. Conventional microscopy, the backbone of malaria diagnosis in most endemic settings, relies on a trained microscopist distinguishing parasite morphologies on stained blood films — a task in which low-density non-falciparum infections are easily missed, especially when the observer’s attention is anchored by an abundant and obvious falciparum population. Rapid diagnostic tests, widely deployed because they are fast and simple, are similarly optimized for the species that matter most epidemiologically, and their sensitivity for low-density P. ovale is limited. The authors emphasize the critical role of sensitive molecular diagnostic tools, including polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP-PCR), which can detect and differentiate Plasmodium species at parasite densities far below what microscopy can achieve. In this case, molecular methods were what allowed the second species to be identified with confidence months after the first.

The clinical implications extend beyond diagnosis to treatment strategy. Blood-stage antimalarial drugs clear parasites circulating in the bloodstream, but they do nothing against hypnozoites hiding in the liver. To prevent relapses from P. ovale or P. vivax, patients require so-called radical treatment — typically a drug such as primaquine, which targets the dormant hepatic stages. The safe use of such drugs depends on the patient’s glucose-6-phosphate dehydrogenase (G6PD) status, because individuals with G6PD deficiency risk hemolysis when exposed to these medications. The report underscores that appropriate radical treatment strategies must target both the blood-stage parasites and the dormant hepatic forms, and that this two-front approach can only be planned rationally when clinicians know which species they are dealing with. A patient treated for falciparum malaria alone, as this one initially was, leaves the liver reservoir untouched and the relapse clock running.

Under-recognition of mixed-species infections is not a marginal problem. Because P. falciparum predominates in the regions where malaria burden is highest, and because co-infections with non-falciparum species produce few distinctive clinical signs of their own, the true frequency of mixed infections is thought to be substantially higher than routine surveillance suggests. Complex interspecies interactions — competition, facilitation, and modulation of the host immune response — can alter the course of disease, the accuracy of diagnostic tests, and the response to therapy. When the co-infecting species is one capable of hypnozoite formation, the consequences can surface months later, often in a setting far from the place of exposure, where the treating physicians may have no reason to suspect malaria at all. For travelers returning to non-endemic countries, as in this case of an Ivorian resident of France, the delayed presentation can easily be mistaken for an unrelated febrile illness unless the travel history is carefully elicited and the laboratory work-up is species-aware.

The report also carries a message for malaria control programs in endemic countries such as Côte d’Ivoire. If mixed infections are systematically under-detected, then treatment policies that focus exclusively on blood-stage clearance will leave a reservoir of relapsing parasites in the population, contributing to recurrent episodes that are misattributed to reinfection and potentially sustaining transmission. The authors argue that variable incubation periods and mixed-species infections deserve a place in diagnostic and clinical management algorithms, and that investment in molecular surveillance would provide a more truthful picture of the parasite landscape. Their study received no external funding and was conducted under ethical protocol 95/99/AVC/ESA approved by the Avicenne Hospital Research Ethics Committee, in accordance with the Declaration of Helsinki, with written informed consent obtained from the patient for participation and publication.

As a single case, the report cannot quantify how often P. falciparum–P. ovale co-infections occur or how frequently they produce this kind of delayed, species-switching presentation. What it does establish is a proof of concept: that a co-infection acquired in a single exposure window can split itself across time, with one species causing acute disease and the other lying dormant in the liver before reactivating four months later. For clinicians, the practical lessons are concrete — consider mixed infections in patients from endemic regions, use species-specific molecular testing when the clinical picture does not fit, and remember that a negative follow-up smear months after treatment for falciparum malaria does not exclude a relapsing non-falciparum infection. For researchers, the case is an invitation to study the interspecies dynamics that keep one parasite quiet while another rages, knowledge that could ultimately refine both diagnosis and treatment for the millions of people living where these parasites overlap.

Subject of Research: Mixed-species Plasmodium falciparum and Plasmodium ovale malaria co-infection with delayed relapse due to hypnozoite reactivation

Article Title: First evidence of plasmodium falciparum-plasmodium ovale co-infection with delayed clinical presentation in an Ivorian patient: observations and diagnostic challenges

Article References: First evidence of plasmodium falciparum-plasmodium ovale co-infection with delayed clinical presentation in an Ivorian patient: observations and diagnostic challenges. (n.d.). https://doi.org/10.1186/s12879-026-14628-1

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14628-1

Keywords: malaria, Plasmodium falciparum, Plasmodium ovale, co-infection, hypnozoites, Côte d'Ivoire, molecular diagnostics, PCR, LAMP-PCR, radical treatment, parasitology, tropical medicine

The origins of the conflict lie in an ambitious housing policy. In 2012, the Ivorian government launched the Presidential Emergency Program, fulfilling a 2010 campaign promise by President Alassane Ouattara to build social and economic housing for low-income households, defined as those earning no more than 400,000 CFA francs per month. The program marked the state’s return to direct housing production after decades of withdrawal; between 1960 and 1980, the state had financed, promoted, and managed more than 90,000 dwellings in Abidjan before stepping back under pressure from international lenders. Annual housing needs around Abidjan were estimated at 22,000 units, roughly 80 percent of them social and economic housing. To secure land for the program’s largest site, the state’s Land Management Agency negotiated directly with the holders of customary rights at Songon-Kassemblé, and in 2013 a contract was signed for the cession of 439 hectares.

The financial architecture of that agreement was precise. Under Decree 2013-224 of March 2013, which regulates the purging of customary land rights for public utility, compensation for the loss of usage rights was set at 2,000 CFA francs per square meter in the Abidjan autonomous district. For the 439.27 hectares in question, the total came to 8.7 billion CFA francs, payable in three installments: 40 percent within two to six months of handing the site to developers, followed by two payments of 30 percent each at three-month intervals, a full settlement within twelve months. Compensation for destroyed crops, including rubber, oil palm, and cassava, added another 1.8 billion CFA francs, calculated by the Ministry of Agriculture under a 1995 scale, bringing the total to more than 10.5 billion CFA francs, roughly 16 million euros.

What followed was a systematic breach of that schedule. Construction began in March 2013 with more than twenty real estate companies, yet between July 2013 and 2015 the landowners received only 20.17 percent of the 8.8 billion CFA francs due, about half of the first installment the state had committed to pay within six months. The state did not settle its accounts in full until October 2020, seven years after signing. As researchers Tonan and Nassa had already observed, the payment schedules established by the state were simply not followed: developers occupied the land while rights-holders waited, sometimes for years, for money owed. The delay ignited a grievance that the Ébrié landowners, drawing on lessons from earlier conflicts in their ethnocultural area, converted into a coordinated strategy of publicization, site blockade, and negotiation.

The protest tactics were direct and disruptive. In May 2015, March 2016, November 2016, and September and November 2019, young villagers whose lineage lands had been sold organized protest marches with chants demanding their money, blocked roads, and occupied the main access route to the construction site, erecting barricades that forced developers to halt work. One young demonstrator explained to fieldworkers in September 2019 that his family had lost about four hectares of cassava and rubber land without being consulted, and that stopping the state’s works was the only way to secure the funds owed. The president of the village youth declared that the site would remain closed until the authorities delivered the second installment, six months overdue, and accused the sub-prefect and officials in Abidjan of making endless empty promises. These were not spontaneous riots but calculated acts of visibility designed to make the landowners audible to the state and to public opinion.

The consequences for the housing program were severe and measurable. The repeated blockages disrupted construction schedules, halted private investment and financing, and pushed delivery dates far beyond the three-year average originally planned. Several real estate companies, unable to absorb the unexpected costs, abandoned the project altogether. The first official handover of homes to subscribers took place only in March 2023, ten years after the program launched. Of an initial target of 60,000 units at the site, only about 15,000 had been built according to the Songon town hall’s technical service, and a February 2024 site visit found scattered clusters of houses interspersed with scrub, unbuilt plots, unfinished structures, and abandoned construction sites. The housing minister himself acknowledged in a 2019 interview that the program had a mixed record, citing the lack of flexibility of customary rights-holders in delaying works and insufficient budgetary resources as two of the major explanations for missing the original 150,000-unit national target.

Beneath the practical disruption, the study identifies a deeper restructuring of power. The negotiation arena at Songon-Kassemblé was dominated by a dyad of the state and the customary landowners, while private developers were sidelined and, remarkably, the village chieftaincy itself was pushed to the margins. The chiefs were excluded from negotiations because the land in question was family property managed by lineage heads under custom, not communal land under chiefly authority, a situation that contrasts sharply with other Ébrié villages such as Anono and Yopougon-Kouté, where chieftaincies signed protocols with the state for major urban projects in 1970 and 1971. The legitimacy of the individual lineage rights-holders gave them a preponderant role, redefining center-periphery relations: decisions were no longer dictated from the capital outward, but renegotiated from the periphery toward the center.

The study frames this reversal through the concept of autochthony capital. The Ébrié, officially recognized as the indigenous people of the Abidjan metropolitan area, have mobilized their identity since the 1970s to defend land rights against urban expansion, and at Songon-Kassemblé that immaterial resource proved decisive, reinforcing their legitimacy in negotiations and their influence over planning decisions. The parallel with Accra is instructive: there, customary actors remain central to land governance, with 80 percent of land held under customary tenure. As the scholar Kobo observed decades ago, the purging of customary rights is far from a mere formality; it is an essential phase of urbanization and one of the focal points of social struggle over land in Côte d’Ivoire and across Africa. At Songon-Kassemblé, the state’s repeated failures over decades of compensation payments placed it in a position of weakness, producing an inversion of roles in which landowners dictated terms through protest.

The resolution of the crisis came through institutionalized bargaining. To contain repeated public disorder, a multiparty working group was created comprising the chieftaincy, landowners, planters, the Ministry of Construction, and the real estate structures, tasked with monitoring both the construction site and outstanding compensation commitments. Community mobilization ultimately secured individual indemnification of the landowners, but without any collective counterpart for the village as a whole, a mechanism that unsettled the internal functioning of the Ébrié community. The monetization of customary land rights, the study concludes, has enabled peripheral actors to assert and price their power in land transactions, even against state authority, transforming a seemingly routine state-landowner dispute into a case study of how urbanization in the Global South can redistribute governance from the center to the fringe.

For scholars of urban land governance, Songon-Kassemblé offers a technically detailed demonstration that peri-urban land production is not a top-down process but a contested arena where customary legitimacy, protest capacity, and state fiscal weakness interact. The case shows that when compensation schedules are breached, the resulting conflict can permanently alter the geography of power, elevating lineage-based landholders into central negotiators and forcing the state to accommodate norms it once sought to supersede. As Abidjan’s expansion continues to absorb villages across the Songon sub-prefecture, whose 627 square kilometers of land capital made it a privileged reservoir for the 1998 Greater Abidjan master plan, the lessons of this decade-long conflict will shape every future negotiation over who pays for the city, and on whose terms.

Subject of Research: Conflict between the Ivorian state and customary landowners over compensation for a peri-urban social housing site in Songon-Kassemblé near Abidjan

Article Title: Logements sociaux et économiques à Songon-Kassemblé: Conflit et recomposition des rapports de pouvoir entre l'État et les propriétaires de droits fonciers coutumiers

Article References: Koffi-Didia, A. M. (2026). Logements sociaux et économiques à Songon-Kassemblé: Conflit et recomposition des rapports de pouvoir entre l'État et les propriétaires de droits fonciers coutumiers. Geographica Helvetica, 81(3), 453-462. https://doi.org/10.5194/gh-81-453-2026

Image Credits: AI Generated

DOI: 10.5194/gh-81-453-2026

Keywords: customary land rights, Côte d'Ivoire, Abidjan, peri-urbanization, social housing, land governance, Ébrié, land conflict, urbanization, compensation, autochthony, Songon

The stakes are considerable. Crop pathogens, pests, and environmental stressors cut annual yields by 21 to 40 percent in major staple crops, with food-deficit regions absorbing a disproportionate share of the loss and a global economic impact estimated above 220 billion US dollars per year. Ground scouting is labor-intensive, covers only a fraction of the production area, and offers no warning before stress symptoms become visible. Reflectance shifts in the 680 to 730 nanometer Red Edge band, by contrast, precede measurable chlorophyll loss, and the normalized difference red edge index has been shown to flag stressed vegetation 13 to 16 days ahead of broadband indices. Capturing those signals routinely, however, has remained out of reach for most of the world’s growers.

The research team, led by Laurensia Simanihuruk of Sepuluh Nopember Institute of Technology together with collaborators in Indonesia and Malaysia, validated their framework on a demanding real-world testbed: ten heterogeneous cocoa agroforestry typologies in Divo, Côte d’Ivoire. The underlying dataset, collected with a DJI Phantom 4 Multispectral flying at 80 meters altitude, comprises 1,272 co-registered RGB-multispectral image pairs spanning 7,632 individual frames. Multi-storey canopies, intercropped shade trees, senescent foliage, and intricate shadow patterns create exactly the kind of spectral complexity that breaks the assumptions of earlier reconstruction methods, which were mostly tuned on laboratory benchmarks with uniform illumination and homogeneous materials.

The architecture’s central insight is biophysical rather than purely computational. Vegetation reflectance follows a causal sequence: pigment absorption shapes the visible bands, the chlorophyll transition defines the Red Edge response around 730 nanometers, and cellular scattering together with water content drives the near-infrared plateau at 840 nanometers. On the Ivorian dataset, the correlation between the RGB input and the near-infrared target is a weak 0.43, while the correlation between Red Edge and near-infrared reaches 0.76, the strongest cross-band relationship in the data. A network that maps RGB directly to near-infrared therefore discards the very band that predicts its target best. TC-SA-UResNet instead routes reconstruction through a Triple Cascaded Decoder: one stream regenerates the visible bands, a second produces the Red Edge band, and a third generates near-infrared using features transferred from the Red Edge decoder through a Learnable Feature Injection module whose transfer gates start at zero and open only when they reduce the loss.

Attention mechanisms refine the cascade at two scales. A Spectral Attention module based on cross-attention lets each location in the near-infrared decoder read every location of the Red Edge decoder, which matters where a shadowed cocoa crown carries weak local evidence. Inside each decoder block, a Channel-wise Dual Attention module weights both channels and spatial locations, while a Global-Local Channel Attention module applies a separate gate per channel at each pixel, allowing fine-grained spectral discrimination. At the bottleneck, an Atrous Spatial Pyramid Pooling module captures context at dilation rates of 6, 12, and 18 pixels, and a Squeeze-and-Excitation block recalibrates the 256 feature channels before decoding begins. A ResNet-50 encoder pretrained on ImageNet supplies the hierarchical features shared by all three decoder streams.

Perhaps the most distinctive contribution is the training objective. Standard pixel losses and structural similarity terms say nothing about whether a reconstructed spectrum is physically plausible for vegetation, and a network can record low error while producing an impossible vegetation index. The authors’ Biophysical Spectral Consistency Loss adds four constraints: it matches the Pearson correlation between reconstructed Red Edge and near-infrared to that of the reference pair, compares the reconstructed NDVI field against the reference, preserves the shape of the spectral curve by matching reflectance steps between adjacent bands, and penalizes any NDVI value straying outside the physical interval from minus one to one. Correlation-guided weighting allocates the largest loss share, roughly 44 percent, to the near-infrared decoder, the band hardest to infer from visible light.

The evaluation was designed to prevent the spatial leakage that plagues many UAV studies. Rather than randomly shuffling frames, which risks near-duplicate images appearing in both training and test sets, the team split the data by plot: six plots for training, two for validation, and two entirely unseen plots for testing, ensuring the model faced canopy structures and illumination conditions it had never encountered. Against three baselines re-implemented from their original publications, a single-decoder U-Net, a dense prediction framework from Zhao and colleagues, and a two-step generative adversarial network, the proposed method achieved the highest structural similarity on the blue and near-infrared bands, the highest near-infrared coefficient of determination at 0.7898, and the smallest spectral angle of any architecture at 3.58 degrees. All 45 pairwise comparisons across bands and baselines reached statistical significance at p below 0.0001.

The ablation study reveals how each component earns its place. Swapping the vanilla encoder for ResNet-50 raised near-infrared R-squared from 0.7154 to 0.7725, and adding the biophysical constraints deliberately reshaped the optimization landscape before the ASPP-SE bottleneck and the full cascade recovered and surpassed all intermediate configurations. The authors are candid about trade-offs: near-infrared structural similarity of 0.7180 trails the blue band’s 0.9540, because near-infrared reflectance depends on internal leaf mesophyll structure that an RGB sensor simply cannot see, bounding the texture the network can recover. Yet the relative error tells a fairer story, with near-infrared at 13.7 percent against 13.4 percent for blue once each band’s error is normalized by its mean reflectance. Since vegetation indices are ratios of band differences to band sums, they depend on magnitude rather than texture, which explains why reconstructed NDVI reached a correlation of 0.9068 with the reference despite the lower structural fidelity.

The agronomic bottom line is nuanced but promising. Reconstructed NDVI achieved a mean absolute error of 0.0342, about 31 percent of one standard deviation of the measured quantity, with every reconstructed pixel falling inside the physical range, supporting vigour zoning within a flight, block ranking on a given date, and directional change detection across dates. The chlorophyll-sensitive indices NDRE and LCI fared less well, with R-squared values of 0.5379 and 0.5873, because both combine the two hardest bands and their uncertainties compound; they remain usable as screening layers to direct ground scouts toward weak zones but cannot support absolute nitrogen inference. The authors caution that the model was trained on one sensor, one crop, and a narrow clear-sky acquisition window, so transfer to other crops or imaging systems will require domain adaptation with paired observations rather than zero-shot deployment. Even with those caveats, the study marks a striking demonstration that the invisible half of the spectrum can be conjured, with measurable fidelity, from the cheap visible light every farmer’s drone already captures.

Subject of Research: Deep learning reconstruction of multispectral bands from RGB UAV imagery for cocoa agroforestry monitoring

Article Title: Triple Cascaded Spectral Attention U-ResNet for UAV RGB-to-multispectral reconstruction in cocoa agroforestry

Article References: Simanihuruk, L., Sarno, R., Sungkono, K. R., Putri, R. A., Anggraini, R. N. E., Wiratmoko, D., Larekeng, S. H., & Hitam, M. S. (2026). Triple Cascaded Spectral Attention U-ResNet for UAV RGB-to-multispectral reconstruction in cocoa agroforestry. Journal of Agriculture and Food Research, 31, Article 103333. https://doi.org/10.1016/j.jafr.2026.103333

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103333

Keywords: UAV remote sensing, multispectral reconstruction, deep learning, cocoa agroforestry, vegetation indices, NDVI, near-infrared, precision agriculture, smallholder farming, spectral attention, Côte d'Ivoire, crop stress detection

The research team, led by Mamadou Doumbia of Université Félix Houphouët-Boigny in Abidjan, together with colleagues from Ivorian and French institutions, focused on a deceptively simple question: if you keep everything else in the model the same, how much does the rainfall simulation change when you swap out the schemes that represent convection, cloud microphysics, and the planetary boundary layer? The answer, quantified across thirteen successful simulations, is that the convection scheme alone can swing annual rainfall totals by several hundred percent. In a region where the seasonal monsoon determines planting calendars and reservoir levels, that is not a technical footnote but a headline finding.

To understand why convection matters so much, it helps to know what the scheme actually does. Thunderstorms over West Africa are typically far smaller than the grid cells of a regional climate model, which in this study resolve the watershed at a scale where individual storm systems cannot be explicitly simulated. Instead, the model relies on a parameterization: a set of equations that estimates, on average, how much moisture rises, condenses, and rains out from each grid cell. Four such schemes were tested here: the Emanuel scheme, which bases its calculations on quasi-equilibrium thermodynamics; the Kain–Fritsch scheme, which tracks entrainment and detrainment in rising plumes; the Grell scheme, which treats convection as a stabilizing process between cloud and environment; and the Tiedtke scheme, a mass-flux approach that accounts for both deep and shallow convection.

The team built sixteen possible model configurations by combining these four convection schemes with two cloud-microphysics options, the Subgrid Explicit moisture scheme known as SUBEX and the Nogherotto–Tompkins scheme known as NoTo, and two planetary boundary layer schemes, Holtslag and the University of Washington scheme, or UW. All simulations were driven by the ERA5 reanalysis, a state-of-the-art global dataset that constrains the large-scale atmospheric circulation, and covered the period 2001 to 2009. Thirteen of the sixteen configurations completed successfully and were analyzed, giving the researchers a robust matrix of comparisons over the Bandama watershed.

Evaluating the simulations required trustworthy observations, and in a data-sparse region that is itself a challenge. The researchers turned to two independent satellite-based rainfall products: CHIRPS, the Climate Hazards Group InfraRed Precipitation with Station data, which blends satellite estimates with ground observations, and IMERG, the Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement mission. Against these references, the team applied a battery of statistical measures, including bias, temporal correlation, and distribution- and event-based skill scores. This dual-reference approach matters because satellite rainfall products each carry their own uncertainties; agreement between CHIRPS and IMERG lends confidence that the model rankings reflect genuine differences in physical realism rather than quirks of a single dataset.

The verdict on the convection schemes was unambiguous. The Tiedtke and Emanuel schemes, particularly when paired with the UW boundary layer scheme, performed best. These configurations reproduced the main phases of the seasonal rainfall cycle, from the onset of the monsoon rains in the south to the single-peaked regime of the northern savanna, with moderate annual biases generally below thirty percent. For a watershed-scale climate simulation, that level of agreement is respectable and suggests these configurations could serve as a sound foundation for future climate projections and hydrological studies in the region.

At the other end of the spectrum, the results were sobering. The Grell scheme, in every pairing tested, produced massive overestimates of rainfall, with annual biases exceeding plus 440 percent. The Kain–Fritsch scheme fared poorly as well whenever it was not combined with the UW boundary layer. In practical terms, a modeler who selected Grell without prior calibration would simulate a Bandama watershed drenched by more than five times its actual rainfall, rendering any downstream analysis of floods, soil moisture, or water resources meaningless. The authors’ implicit warning is clear: these schemes should not be used over this region without careful validation, a caution that applies broadly to climate modeling in West Africa, where the interaction between the monsoon circulation, the African easterly jet, and mesoscale convection stresses parameterizations designed elsewhere.

The boundary layer scheme emerged as the second most influential factor. The UW scheme consistently outperformed Holtslag, indicating that how the model represents the turbulent mixing between the surface and the free atmosphere feeds directly into the triggering of convection and hence into rainfall. This finding aligns with earlier work by some of the same authors, who assessed boundary layer parameterization sensitivity over the wider West African domain using RegCM5 and found the choice to be consequential for the mean climate. By contrast, the cloud-microphysics schemes, SUBEX and NoTo, had only a secondary and non-systematic effect on precipitation in this configuration, suggesting that at parameterized-convection resolution the fate of moisture inside resolved clouds matters less than how convection itself is triggered and modulated.

One limitation united all thirteen configurations: a systematic excess of light rainfall, or drizzle. Every simulation produced too many days with small precipitation amounts compared with the satellite references. This drizzle bias is a well-known generic weakness of parameterized convection at these resolutions, arising because the schemes tend to moisten and rain out grid cells too readily, producing frequent weak events instead of the intense, organized squall lines that deliver much of West Africa’s rainfall. The study’s authors note this as a shared limitation rather than a scheme-specific failure, and it points toward the broader trajectory of the field: convection-permitting modeling, in which storms are simulated explicitly at kilometer-scale grid spacing, is increasingly seen as the path forward, and RegCM5 itself has already demonstrated such capability in European-wide experiments.

For Côte d’Ivoire, the practical stakes are considerable. The Bandama watershed feeds agriculture and water infrastructure across the country, and climate change is expected to intensify both drought stress and extreme rainfall in West Africa. Reliable regional projections require a model configuration that can be trusted, and this study provides exactly that kind of evidence-based guidance: favor Tiedtke or Emanuel convection with the UW boundary layer, treat Grell and unpaired Kain–Fritsch with skepticism, and account for the drizzle bias when interpreting simulated rainfall statistics. The work also carries a message for the global modeling community, demonstrating that sensitivity testing at the watershed scale, grounded in independent satellite observations and run on Ivorian supercomputing infrastructure at the Centre National de Calcul de Côte d’Ivoire, can deliver actionable results from the Global South that speak directly to international efforts to improve climate models for the regions that need them most.

Subject of Research: Sensitivity of the RegCM5 regional climate model's physical parameterization schemes for precipitation simulation over the Bandama watershed in Côte d'Ivoire

Article Title: Assessment of the sensitivity of the RegCM5 model to physical parameterization schemes in precipitation simulation in the Bandama watershed (Côte d’Ivoire)

Article References: Doumbia, M., Yoroba, F., Koné, B., Tiémoko, T. D., Kouassi, B. K., Kouadio, K., Diédhiou, A., Salifou, I. T., & Diawara, A. (2026). Assessment of the sensitivity of the RegCM5 model to physical parameterization schemes in precipitation simulation in the Bandama watershed (Côte d’Ivoire). Theoretical and Applied Climatology, 157(10), Article 653. https://doi.org/10.1007/s00704-026-06591-3

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06591-3

Keywords: RegCM5, regional climate modeling, precipitation simulation, convection schemes, Bandama watershed, Côte d'Ivoire, West African monsoon, parameterization, CHIRPS, IMERG, planetary boundary layer, climate model evaluation

The research drew on 393 adults aged 18 to 79 years enrolled in the Côte d’Ivoire dual burden of disease study, known as CoDuBu, which operates within the Taabo health and demographic surveillance system in the south-central part of the country. Roughly half of the participants were women, 55 percent lived in rural settings, and the vast majority were lifetime non-smokers who reported high levels of physical activity. Blood spots collected during health examinations were shipped to a biobank, where DNA was extracted, chemically converted and analyzed on an Illumina EPIC methylation array covering more than 866,000 genomic positions. After rigorous quality control, 841,953 CpG sites remained for the epigenetic age calculations, making this one of the most comprehensive methylation datasets ever assembled from this region of Africa.

From those methylation patterns, the team computed four of the most widely used epigenetic clocks. The first generation, HorvathAge and HannumAge, were trained purely on chronological age and estimate how old a person’s cells appear to be. The second generation, PhenoAge and GrimAge, incorporate clinical markers of disease and mortality, so they aim to capture not just age but the pace of health decline. For each clock, the researchers calculated epigenetic age acceleration, the residual difference between a person’s estimated biological age and their actual calendar age, adjusted where appropriate for the mix of white blood cells circulating in the sample. This acceleration measure is what researchers believe reflects the cumulative wear of environment, behavior and disease on the genome.

The headline result is reassuring: the clocks work. Correlations between epigenetic age and chronological age were strong across all four measures, with Pearson coefficients ranging from 0.83 to 0.93. Concordance statistics, which are stricter because they penalize systematic bias, were somewhat weaker, between 0.73 and 0.85, and the first-generation clocks outperformed the mortality clocks in raw age prediction. HannumAge was the most accurate, deviating from true age by an average of just under two years, while HorvathAge overestimated age by nearly six years on average. Each clock also showed a characteristic sweet spot where its predictions were sharpest: HannumAge performed best around age 32, HorvathAge around 62, and GrimAge around 78. These patterns mirror what has been reported in Ghanaian, South African and high-income cohorts, suggesting that the underlying biology of methylation aging is broadly conserved across human populations.

Yet the clocks are not interchangeable. Correlations between the acceleration measures themselves were surprisingly low, ranging from 0.24 to 0.66, which means each clock captures a partially distinct facet of biological aging. That distinction became vivid when the researchers examined which social and behavioral factors predicted faster aging. Men showed significantly higher acceleration than women on three of the four clocks, by roughly 1.6 to 2.9 years depending on the measure. Participants from the wealthiest households aged more slowly on the extrinsic and phenotypic clocks, an effect of about two years, consistent with the idea that economic security, healthcare access and nutrition buffer the genome against premature aging. High-risk alcohol consumption and smoking both accelerated the mortality-sensitive clocks, with smokers showing GrimAge acceleration of about 3.5 years.

Two of the most striking findings were non-linear. Physical activity and body mass index both showed U-shaped relationships with GrimAge acceleration, meaning that people at the extremes aged fastest. Underweight participants, who made up 7 percent of the sample, showed even stronger acceleration than those with obesity. In a setting where low body weight can reflect undernutrition, chronic infection and psychosocial stress rather than healthy leanness, this result suggests that the methylation clock registers the biological toll of deprivation just as faithfully as it registers the toll of metabolic excess. The authors also note a physical activity paradox: in populations where most activity comes from repetitive manual labor rather than leisure exercise, very high activity levels may promote chronic exhaustion and cardiovascular strain rather than protection, a pattern previously documented in large European studies.

The study then connected biological age to actual disease. About 22 percent of participants met the criteria for metabolic syndrome, and 56 percent had elevated fasting glucose, a strikingly high figure for a predominantly rural cohort. When the researchers regressed these outcomes on epigenetic age acceleration, they found that extrinsic acceleration and PhenoAge acceleration each increased the odds of metabolic syndrome severity by roughly 23 to 26 percent per standard deviation, and both were linked to high blood pressure and impaired fasting glucose. These associations held up after adjustment for demographic, socioeconomic and lifestyle factors, and for body mass index, indicating that the clocks carry information about cardio-metabolic risk beyond what conventional measures provide.

Perhaps the most mechanistically interesting result concerns what drives GrimAge. This clock is built from methylation surrogates of eight plasma proteins plus cumulative smoking exposure, and the team found that one component in particular, a methylation proxy for plasminogen activator inhibitor-1, or PAI-1, largely explained the clock’s associations with both risk factors and metabolic disease. The PAI-1 surrogate was associated with metabolic syndrome, high blood pressure, high triglycerides, central obesity and elevated glucose, and its links with lifestyle risks were robust to adjustment for blood cell composition. PAI-1 is a well-known player in inflammation, coagulation and metabolic dysregulation, and the authors argue that it may serve as a more reliable molecular marker of aging-related metabolic damage than the composite clock itself, a hypothesis they hope future studies will test.

The study has limitations that the authors acknowledge candidly. It is cross-sectional, so it cannot establish whether accelerated aging precedes disease or follows it, and the sample, though carefully characterized, is modest compared with the mega-cohorts of high-income epigenetics. The cohort was originally assembled to study asymptomatic malaria, although sensitivity analyses showed the results were stable when malaria cases were excluded. Even so, the work fills a conspicuous gap. Previous African validations, in Central African hunter-gatherers, South African men and Ghanaian migrants, covered narrow age ranges or specific subgroups; this study spans nearly six decades of adult life in both urban and rural settings and links methylation age to measured clinical phenotypes rather than self-report alone.

The broader implications are considerable. Populations across sub-Saharan Africa are aging rapidly while non-communicable diseases such as diabetes and hypertension rise in parallel with persistent infectious and environmental burdens, a double burden that could compress healthspan and push disease onset into ever-younger ages. If epigenetic clocks can be validated and eventually calibrated with African methylation data, they could become powerful tools for identifying which exposures, from poverty to alcohol to occupational strain, truly accelerate aging in transitioning societies, and for evaluating interventions before clinical disease emerges. The Côte d’Ivoire team argues that future longitudinal studies should fold in the wider exposome, including pollution, stress and sleep, to pinpoint the public health utility of these molecular hourglasses. For now, the message is clear: the clocks tick the same way in a rural Ivorian village as they do in a European clinic, and in both places, they are listening closely to how people live.

Subject of Research: Validation of DNA methylation epigenetic clocks and their cardio-metabolic risk associations in adults in Côte d'Ivoire

Article Title: Validity and cardio-metabolic risk profiles of DNA methylation clocks among adults in south-central Côte d’Ivoire

Article References: Validity and cardio-metabolic risk profiles of DNA methylation clocks among adults in south-central Côte d’Ivoire. (n.d.). https://doi.org/10.1186/s43682-022-00008-8

Image Credits: AI Generated

DOI: 10.1186/s43682-022-00008-8

Keywords: epigenetic clocks, DNA methylation, biological aging, Côte d'Ivoire, metabolic syndrome, GrimAge, PhenoAge, HorvathAge, HannumAge, non-communicable diseases, Africa, PAI-1

The study, published in the journal Discover Geoscience, was led by Vincent Tchimou Assoma of the University of Félix Houphouët-Boigny in Abidjan, together with colleagues from the University of Jean Lorougnon Guédé. Their goal was deceptively simple to state but notoriously difficult to achieve: find the open fractures in hard crystalline rock that can supply enough water to justify the cost of drilling a production borehole. In basement terrain, a misplaced borehole is not merely a disappointment; it is an expensive hole in the ground that can cripple the budget of a rural water programme. Across the region, 65.3 percent of villages rely on inadequate water points, each serving an average of 1,518 inhabitants against the national standard of one point per 500 people.

The conceptual foundation of the work rests on a paradigm shift that has reshaped hydrogeology over the past two decades. For much of the twentieth century, groundwater in crystalline rock was assumed to flow through tectonic fractures, and prospectors targeted the largest visible faults. Modern research has overturned that view: it is weathering, not tectonics alone, that creates the fracture networks through which water moves. As biotite minerals in granite oxidise and swell, and as differential stress is released during the breakdown of the rock, a zone of micro-fracturing develops at the base of the weathering profile. This so-called Stratiform Fractured Zone, typically 10 to 30 metres thick, provides the primary transmissivity of hard-rock aquifers across West Africa, and the highest borehole yields consistently come from intersections with it.

To see through the vegetation and regolith, the team turned to the European Copernicus programme’s Sentinel-1 radar satellites. Unlike optical sensors such as Landsat or Sentinel-2, whose views are routinely blocked by clouds and canopy, the C-band radar wave penetrates vegetation and responds to micro-topography and soil roughness. The researchers processed two Sentinel-1B scenes acquired in January 2019 in dual VV and VH polarisations, applying orbit correction, radiometric calibration, terrain correction against a digital elevation model, and a Lee speckle filter. Sobel edge-detection filters oriented along four azimuths then accentuated linear discontinuities, which the team extracted manually using standard photo-geological criteria before discarding anthropogenic features such as roads and plantation boundaries.

The result was a structural map of remarkable density: 458 major lineaments, some stretching up to 33.5 kilometres in length, and 1,442 lineaments in total across all azimuths. The dominant orientations tell a deep geological story. East-west trends between N82° and N97° are the most frequent, followed by northwest-southeast directions of Liberian age (N120° to N160°) and northeast-southwest directions of Eburnean age (N30° to N60°). Together they confirm the intensity of the tectonic deformation that has racked this fragment of the West African craton. When the researchers overlaid 26 boreholes with yields of 5 cubic metres per hour or more onto the lineament map, every single one sat on or within 100 to 500 metres of a mapped structure, a statistical association that strongly suggests many of these lineaments mark open, water-bearing fractures.

Radar images, however, only hint at what lies below. To validate the structures on the ground, the team conducted electrical resistivity profiling with a Schlumberger array at seven sites in the Agboville department, using a Syscal Junior resistivity meter with a 200-metre current electrode spread and 10-metre station spacing. In total, four profiles comprising 90 measurement stations and 860 linear metres of surveying were completed, each run perpendicular to the presumed strike of the target anomaly. The apparent resistivity curves revealed characteristic conductive anomalies in three shapes: sharp V-shaped minima indicating narrow conductive compartments, and broader U- and W-shaped troughs indicating wide compartments. One V-shaped anomaly at the Ery Makoudjié site bottomed out at just 800 ohm-metres, while paired U- and W-shaped anomalies at another site registered around 1,200 ohm-metres. Such lows are classically interpreted as open fractures or thickened weathered material saturated with water, though the authors caution they could also represent clay-filled palaeochannels or lithological contacts that would need vertical electrical soundings to discriminate.

The third pillar of the integrated approach was a statistical dissection of the region’s drilling archive. From a national database, the team retained 307 village water supply boreholes with complete records on depth, lithology, static water level and air-lift yield. The boreholes ranged from 20.6 to 111.8 metres deep, with a mean of 57.7 metres, and penetrated weathered profiles varying from zero to 100 metres thick, averaging around 35 to 40 metres. Air-lift yields spanned 0 to 21.6 cubic metres per hour, with a mean of 4.2 and a median of 2.5, a strongly skewed distribution typical of fractured aquifers where a few lucky holes tap transmissive structures while most scrape by. Classified by the Inter-African Committee for Hydraulic Studies scheme, the region’s boreholes split into 16.9 percent very low, 31.9 percent low, 21.8 percent medium, 17.6 percent high and 11.8 percent very high yield categories.

The productivity analysis yielded concrete siting criteria that could transform future drilling campaigns. The best yields, above 2.5 cubic metres per hour, cluster in granitic and volcano-sedimentary schist terrains where the regolith is between 15 and 80 metres thick and total borehole depths run from 30 to 90 metres. The single highest recorded yield of 19.8 cubic metres per hour came from granite at roughly 50 metres of alterite thickness and 58 metres of total depth. Yields of 10 cubic metres per hour or more occurred systematically where boreholes penetrated the Stratiform Fractured Zone at depths of 50 to 80 metres below ground. Granite hosted 62.5 percent of the region’s boreholes and volcano-sedimentary schists 36.8 percent, with migmatites and gneisses playing a negligible role. Box plots across the five yield classes showed interquartile ranges widening from 0.2 to 0.7 cubic metres per hour in the low classes up to 12.0 to 15.8 in the very high class, underscoring the extreme spatial heterogeneity of fracture permeability.

The authors are candid about the limits of their method. Electrical profiling is a qualitative, first-order reconnaissance tool vulnerable to interpretation artefacts, and a resistivity minimum can as easily mark an impermeable clay pocket as a productive fracture. The geophysical survey covered only seven sites, and the borehole database suffered from inconsistent geological descriptions, forcing rigorous pre-processing that retained just 27 percent of the original records. Spatial correlation between high-yield boreholes and lineaments, moreover, implies statistical association rather than proven causation. The team recommends that future work deploy vertical electrical soundings or full 2D and 3D electrical resistivity tomography to resolve the geometry of conductive bodies at depth, alongside systematic pumping tests and hydrochemical analyses. They also point to emerging tools, including InSAR time series that track aquifer deformation and deep learning networks such as U-Net that could automate lineament extraction with more objectivity than human interpreters.

Even with those caveats, the study delivers a practical framework at a moment when it is urgently needed. The Agnéby-Tiassa Regional Council has a funding proposal pending that would use these findings to site new water supply boreholes, and the quantitative criteria on regolith thickness, depth and lithology offer a reference for campaigns across similar basement terrains in humid tropical Africa. By demonstrating that free Copernicus radar data, low-cost electrical profiling and existing drilling archives can be woven into a coherent targeting strategy, the research offers a path to lower failure rates, better investments and, ultimately, safer drinking water for communities whose hidden aquifers have waited beneath the forest canopy all along, in line with the United Nations Sustainable Development Goal 6 on clean water and sanitation.

Subject of Research: Hydrogeological characterization of fractured basement aquifers in southern Côte d'Ivoire using satellite radar, geophysics and borehole data

Article Title: Hydrogeological characterization of fractured basement aquifers using an integrated analysis in the Agnéby-Tiassa region of southern Côte d’Ivoire

Article References: Assoma, V. T., Koudou, A., Youan, M. T., Diaby, M., & Oularé, S. (2026). Hydrogeological characterization of fractured basement aquifers using an integrated analysis in the Agnéby-Tiassa region of southern Côte d’Ivoire. Discover Geoscience, 4(1), Article 361. https://doi.org/10.1007/s44288-026-00733-w

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00733-w

Keywords: hydrogeology, basement aquifers, Sentinel-1, lineaments, electrical resistivity, borehole productivity, fractured rock, Côte d'Ivoire, groundwater, remote sensing, weathering profile, water supply

A team of researchers led by Bi Irie Ghislain Tré of Nangui Abrogoua University, working with colleagues in Côte d’Ivoire and France, measured 550 mahogany trees across three natural stands spanning the country’s major agro-ecological zones. The sites could hardly be more different in character. Pouniakele, in the northern Sudanian savanna, receives about 1,200 millimetres of rain a year and is the driest and most disturbed of the three, with pastures and agricultural exploitation pressing in on the trees. Kouassi-N’Dawa, in the east, is a sacred forest on a hill where human activity is deliberately limited by cultural tradition. Koumokro, in the centre-east, is a community forest sitting in the climatic transition zone between subtropical and humid tropical conditions, receiving roughly 1,300 millimetres of annual rainfall. Measurements were collected between January 2022 and June 2024, all on standing trees in their natural habitat, using non-destructive techniques.

The methodological design is what gives the study its power. Rather than treating all trees as a single population, the researchers sorted them into three diameter-based cohorts that serve as proxies for developmental stages: young trees between 5 and 25 centimetres in diameter, non-exploitable adults from 25 to 40 centimetres, and exploitable adults of 40 centimetres or more, the size class targeted by selective cutting for charcoal. On every tree, eleven traits were recorded, ranging from the classic dendrometric measures of trunk diameter, total height, bole height and crown spread to a suite of foliar characters including leaf length and width, petiole length, the number of leaflets per leaf, and the length and width of individual leaflets. This dual focus on architecture and foliage allowed the team to track how different parts of the tree’s form respond to different pressures across the lifespan.

The statistical treatment was equally rigorous. After standardisation, the data were subjected to analysis of variance to detect differences among sites within each cohort, then to hierarchical cluster analysis to group trees with similar morphology, and finally to discriminant function analysis to identify which traits did the best job of separating those groups. Bartlett’s test of sphericity and the Kaiser-Meyer-Olkin measure confirmed the datasets were suitable for multivariate work. The results were strikingly consistent: at every developmental stage, and again when all 550 trees were pooled, the analyses resolved three distinct morphological groups, and leaf length and leaflet length emerged as the most discriminating traits across all stages of life.

Some of the site-level patterns were unexpected. Pouniakele, despite being the driest and most degraded site, produced trees with the largest mean diameters in every cohort. Kouassi-N’Dawa and Koumokro, by contrast, yielded trees with significantly larger leaves. In the young cohort, ten of the eleven measured variables differed highly significantly among sites, with juveniles at Kouassi-N’Dawa reaching the greatest total heights, an apparent response to light competition in the shaded sacred forest. Among non-exploitable adults, Koumokro dominated seven variables, posting the tallest mean height at 13.54 metres and the widest crown spread at 8.5 metres, while Pouniakele trees paradoxically combined the thickest trunks, averaging 33.12 centimetres, with the lowest values for six other traits.

Perhaps the most intriguing result is a reversal in the ontogenetic trajectory of diameter. Among juveniles, the gradient ran from thickest at Koumokro to thinnest at Pouniakele. By maturity, that order had flipped, with Pouniakele trees topping the rankings. The researchers interpret this inversion as evidence that the survivors at the harsh northern site prioritise radial growth to enhance mechanical stability and resource storage after episodes of water stress and pruning. Supporting this reading, the coefficient of variation for crown spread surged from 25.6 percent in young trees to 51.9 percent in exploitable adults, a signature of individual trees each following their own adaptive path through a mosaic of microhabitats and human disturbances.

The pooled analysis of all trees crystallised the picture into three site-scale morphotypes. Group 1 contained the giants of the sample, with a mean diameter of 42.9 centimetres, a total height of 14.37 metres and a crown spread of 9.53 metres, but the shortest leaves at 28.3 centimetres. Group 3 sat at the opposite pole: small trees averaging just 10 centimetres in diameter and 6.6 metres in height, yet bearing the largest leaves, up to 37.7 centimetres long. The geographic distribution of these morphotypes was anything but random. At drought-prone Pouniakele, 60.5 percent of trees belonged to the big-trunk, small-leaf Group 1, a combination that favours water conservation and mechanical resilience. At Kouassi-N’Dawa and Koumokro, where regeneration is denser and competition for light fiercer, the small-stature, large-leaf Group 3 dominated, reflecting an investment in foliar area to fuel rapid height growth in crowded stands. At Pouniakele, that morphotype was almost entirely absent, accounting for just 1.2 percent of trees.

The study’s two founding hypotheses fared differently. The first, that morphological heterogeneity would be greatest at the juvenile stage, was confirmed: coefficients of variation showed young trees to be the most variable, consistent with high initial phenotypic plasticity. The second, that natural selection would progressively filter this diversity into a converged adult form, was refuted. Even the exploitable adults remained strongly differentiated, with seven of eleven parameters differing significantly among sites. This persistence of structure into old age suggests that savanna mahogany maintains multiple viable adaptive strategies simultaneously rather than marching toward a single optimal body plan. The authors frame this as an evolutionary bet-hedging strategy, a reservoir of resilience against environmental fluctuation, though they caution that the coexistence of several phenotypic groups could also represent a transitional phase before a stable adaptive optimum emerges under recurrent disturbances such as bushfires and pruning.

The practical implications reach well beyond evolutionary theory. Because leaf length and leaflet length proved reliably discriminant at every stage, foresters now have simple, measurable phenotypic criteria for selecting superior mother trees for seed collection, a critical step for plantation development that could relieve pressure on natural stands. The identification of vulnerable growth stages also helps target protection efforts. At the same time, the authors are candid about the limits of their work. The study relies exclusively on morphology, so it cannot yet say whether the observed morphotypes reflect genetic differentiation between populations or purely environmental plasticity, and the cohort design compares different individuals rather than following the same trees over time. Combining the morphometric approach with neutral genetic markers, and mounting long-term monitoring of marked cohorts, are the obvious next steps. What is already clear, however, is that conserving this species means conserving its diversity of forms, not just its count of individuals, and that a sacred forest, a community woodland and a battered northern savanna each preserve a different chapter of the mahogany’s adaptive story.

Subject of Research: Ontogenetic variation in morphological traits of Khaya senegalensis across three savanna sites in Côte d'Ivoire

Article Title: Ontogenic dynamics of phenotypic diversity in savanna mahogany (Khaya senegalensis) across three sites in Côte d’Ivoire

Article References: Tré, B. I. G., Koffi, K. G., Kouonon, L.-C., Yao, Y. E. P., Pereda-Loth, V., & Sié, R. S. (2026). Ontogenic dynamics of phenotypic diversity in savanna mahogany (Khaya senegalensis) across three sites in Côte d’Ivoire. Discover Plants, 3(1), Article 408. https://doi.org/10.1007/s44372-026-00883-8

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00883-8

Keywords: Khaya senegalensis, savanna mahogany, phenotypic plasticity, ontogeny, Côte d'Ivoire, morphological variability, tree conservation, CITES, mother tree selection, drought adaptation, leaf morphology, sustainable forestry

The team’s starting point was a practical gap. Ecotoxicological risk assessment tools have been built and validated largely in temperate Europe, where the garden snail Cantareus aspersum serves as a standardized test organism enshrined in ISO guidelines. Tropical West Africa, with its distinct soils, climates and faunas, has had no equivalent sentinel. Yet the giant Achatininae snails are ideal candidates. They are large, abundant, sedentary, easy to sample, and they occupy a central place in local food culture, where they are traditionally eaten whole. Any metal that accumulates in their tissues therefore travels directly into the human food chain, making these animals simultaneously an ecological indicator and a public health concern.

To quantify the pressure that contamination exerts on each site, the researchers applied a Toxic Pressure Index, or TPI, an integrative metric previously developed for managing polluted sites, which aggregates the concentrations of multiple metals relative to reference values. Crucially, they computed the TPI twice: once for the soil at each site and once for the snail tissues collected there. If external contamination drove internal burden in a straightforward way, the two indices should rise and fall together. They did not. Across every tissue-species combination, the study found no significant relationship between soil TPI and tissue TPI, a systematic decoupling between what is in the ground and what ends up inside the animal.

The scale of soil contamination itself was striking. Zinc dominated the toxic pressure at every one of the thirteen sites, and pseudo-total zinc concentrations reached as high as 37,656 milligrams per kilogram of soil, a figure far exceeding typical background levels. Such values reflect the diffuse loading that peri-urban tropical soils receive from industrial emissions, vehicle traffic, waste burning and agricultural inputs. But pseudo-total concentrations measure everything that strong acid digestion can extract from the soil, not the fraction that an animal’s gut can actually dissolve and absorb. The study’s central result is precisely that this distinction matters enormously, and that it matters in a patterned, quantifiable way.

That pattern emerged from the bioconcentration factors, or BCFs, calculated for every combination of metal, tissue and species. The BCF expresses the ratio of a metal’s concentration in snail tissue to its concentration in the soil, and values above one indicate bioconcentration, while values below one indicate biodilution. For iron and zinc, the verdict was unambiguous: biodilution occurred universally, in every tissue and in both species. Even more telling, log-log regression slopes for zinc in the flesh of both species approached minus one, a mathematical signature of strict homeostatic regulation. In practical terms, as soil zinc concentration increased, the snails’ internal zinc concentration barely moved, as though a physiological ceiling capped how much of the metal their bodies would tolerate regardless of external loading.

Copper told a different story. It was the only element consistently bioconcentrated above unity, and only in the hepatopancreas, the snail’s equivalent of a liver and digestive gland combined. This occurred at eight of the thirteen sites for Achatina achatina and eleven of thirteen for Archachatina ventricosa. The explanation is physiological rather than toxicological: copper is an essential trace element, required for respiratory pigments and enzymatic functions, and the hepatopancreas actively accumulates and stores it. The finding echoes decades of work on temperate helicid snails, in which metallothionein proteins and organ-specific storage have long been shown to separate essential metals, which are regulated and sequestered, from non-essential ones, which are more passively handled. The Abidjan study extends that framework to a tropical lineage for the first time with field data.

Tissue identity proved to be the strongest single determinant of accumulation. For all three metals and both species, BCF values were significantly higher in the hepatopancreas than in the flesh, with Wilcoxon tests returning p-values below 0.01 throughout. Hepatopancreas-to-flesh ratios ranged from threefold to twenty-twofold, meaning that the organ responsible for detoxification can carry an internal burden an order of magnitude greater than the muscle tissue that people typically eat. Yet the two compartments are not independent. The study detected a significant positive correlation between hepatopancreatic and flesh BCFs for copper in both species, which matters directly for consumer exposure: because these snails are traditionally consumed whole, including the hepatopancreas, the organ that concentrates metals the most is also on the plate.

Perhaps the most sobering result is what the researchers could not find. Using multivariate regression modelling, they attempted to build ecologically coherent models that combined soil metal concentrations with soil physicochemical properties, such as pH, texture and organic matter, as joint predictors of bioconcentration. The models failed. No combination of measured soil characteristics reliably predicted how much metal ended up in the snails. This null result carries a pointed message for risk assessment practice: knowing a soil’s total metal content, and even its chemistry, is not sufficient to forecast biological uptake. Bioavailability, governed by processes that pseudo-total digestion cannot capture, remains the critical and stubbornly site-specific variable. It also suggests that temperate-derived predictive models cannot simply be transplanted into tropical contexts without recalibration.

Encouragingly for the use of these snails as sentinels, the two species behaved remarkably similarly. No significant interspecific differences in BCF were detected, suggesting that Achatina achatina and Archachatina ventricosa employ broadly comparable metal regulation strategies. For monitoring programs in West Africa, this means either species could serve as a bioindicator, and results from one may be cautiously generalized to the other. Given that both are harvested from the wild and sold in local markets, the convergence also simplifies the task of translating ecological measurements into dietary exposure estimates for communities living along contamination gradients.

The broader implications reach well beyond Abidjan. Peri-urban soils across rapidly expanding West African cities face mounting metal inputs from the same mix of industrial, urban and agricultural sources, while formal ecotoxicological infrastructure remains scarce. This study supplies both a warning and a method. The warning is that soil contamination maps alone cannot identify which animals, and therefore which meals, carry the greatest internal burdens, and that homeostatic regulation can mask exposure in ways that total soil chemistry never reveals. The method is a paired index approach, comparing external toxic pressure with internal tissue burden, that can be replicated wherever large, edible, sedentary gastropods occur. As cities like Abidjan continue to grow into their surrounding landscapes, the humble giant snail may prove to be one of the most informative, and most consequential, sentinels of environmental health in the tropics.

Subject of Research: Bioaccumulation of iron, copper and zinc in tropical land snails across a peri-urban contamination gradient in Abidjan, Côte d'Ivoire

Article Title: From Soil Contamination to Internal Metal Burden: Drivers of Fe, Cu and Zn Bioaccumulation in Tropical Achatininae Across a Peri-Urban Contamination Gradient (Abidjan, Côte d’Ivoire)

Article References: Kouadio, G. A., Louzon, M., Memel, J.-D., & Katta, E. L. (2026). From Soil Contamination to Internal Metal Burden: Drivers of Fe, Cu and Zn Bioaccumulation in Tropical Achatininae Across a Peri-Urban Contamination Gradient (Abidjan, Côte d’Ivoire). Archives of Environmental Contamination and Toxicology, 91(3), Article 21. https://doi.org/10.1007/s00244-026-01222-4

Image Credits: AI Generated

DOI: 10.1007/s00244-026-01222-4

Keywords: land snails, bioaccumulation, heavy metals, soil contamination, Abidjan, Côte d'Ivoire, ecotoxicology, copper, zinc, iron, peri-urban, food safety