The study, published in PLOS Mental Health, drew on enrollment data collected between March 2019 and August 2021 from adults aged 18 and older living in urban Haiti. Participants completed the Patient Health Questionnaire-9, a widely validated nine-item screening instrument that scores depressive symptoms on a scale from zero to 27. The researchers dichotomized the scores, treating values below 10 as none to mild and values of 10 or above as moderate to severe, a cutoff commonly used in clinical and epidemiological research to flag depression that warrants treatment. Cardiovascular outcomes were not self-reported in a casual sense; instead, cases of angina, myocardial infarction, transient ischemic attack, stroke, and heart failure were adjudicated using epidemiologic definitions aligned with international cohort studies, lending the prevalence estimates a rigor that is often difficult to achieve in settings without routine diagnostic infrastructure.

The scale of psychological distress documented in the cohort was striking. Among the 2,995 participants, who had a mean age of 41.9 years and were 58 percent female, 16.2 percent reported moderate to severe depressive symptoms. That overall figure, however, concealed a sharp gender divide: 22 percent of women screened in the moderate-to-severe range compared with just 8.5 percent of men. This nearly threefold difference in symptom burden echoes patterns seen globally, where women consistently report higher rates of depression, but it takes on particular significance in Haiti, where economic instability, food insecurity, and the aftermath of repeated disasters weigh heavily on household life.

When the researchers cross-tabulated depressive symptoms with adjudicated cardiovascular disease, the association emerged clearly in both sexes. Among men with moderate to severe symptoms, 21.5 percent had prevalent cardiovascular disease, compared with 10.6 percent of men with none to mild symptoms. Among women, the corresponding figures were 23.3 percent versus 15.3 percent. In other words, cardiovascular disease was roughly twice as common among the most symptomatic men and about half again as common among the most symptomatic women, a pattern that persisted across the cohort’s urban neighborhoods.

To move beyond raw prevalence differences, the team employed generalized estimating equation Poisson models with a log link, a statistical approach well suited to estimating prevalence ratios in cross-sectional data where odds ratios can overstate effect sizes for common outcomes. The models adjusted for an unusually comprehensive set of covariates: age, sex, education, income, food insecurity, smoking, alcohol use, physical activity, stress, and body mass index. This adjustment strategy matters enormously in a Haitian context, where food insecurity and material hardship are widespread and could otherwise masquerade as a depression–cardiovascular link. Even after these adjustments, moderate to severe depressive symptoms remained independently associated with a 36 percent higher prevalence of cardiovascular disease, with an adjusted prevalence ratio of 1.36 and a 95 percent confidence interval of 1.08 to 1.71.

Sex-stratified analyses revealed a consistent but nuanced picture. Among women, the adjusted prevalence ratio was 1.38 with a confidence interval of 1.06 to 1.78, indicating a statistically robust association. Among men, the point estimate was somewhat lower at 1.25, but the confidence interval of 0.75 to 1.99 crossed the null, reflecting the smaller number of men in the cohort and the lower prevalence of depressive symptoms among them. The researchers also examined effect modification on the additive scale using the relative excess risk due to interaction, a measure that captures whether the combined burden of being female and depressed exceeds what would be expected from adding the two risks together. The RERI estimate of 0.07, with a confidence interval spanning −0.74 to 0.88, provided limited evidence for additive interaction, and formal tests of multiplicative modification were likewise not statistically significant.

These null interaction findings should not be mistaken for evidence that sex is irrelevant. The point estimates for women were consistently stronger, and the authors describe a stronger pattern among women even while acknowledging that formal significance thresholds were not met. In epidemiological terms, the study was likely underpowered to detect interaction, particularly given the modest number of men with moderate to severe symptoms. The practical takeaway is that depression and cardiovascular disease travel together in both sexes in urban Haiti, with a suggestive but unproven intensification among women that future, larger studies will need to confirm.

The findings carry weight because they emerge from a setting where cardiovascular disease has overtaken infectious disease as the dominant killer, yet mental health remains chronically under-resourced. Haiti has only a handful of psychiatrists for a population of more than eleven million, and depression screening is rarely integrated into routine care, let alone into cardiovascular prevention programs. The study’s authors argue that integrating depression screening into cardiovascular disease prevention could help address the growing dual burden of both conditions in resource-limited settings. Such integration need not be technologically sophisticated; the Patient Health Questionnaire-9 is short, free to administer, and already validated in numerous languages and cultural contexts, making it a realistic addition to community health worker visits and hypertension clinics alike.

Mechanistically, the depression–cardiovascular connection is thought to run along several converging pathways. Depression is associated with dysregulation of the hypothalamic-pituitary-adrenal axis and elevated cortisol, heightened systemic inflammation, impaired endothelial function, and increased platelet aggregability, all of which promote atherosclerosis and thrombosis. Behavioral channels compound these biological ones: people with depression are more likely to smoke, drink heavily, remain physically inactive, and adhere poorly to medications, while also eating less healthful diets. In Haiti, where the cohort’s own adjustment variables reveal how tightly food insecurity, stress, and poverty are woven into daily life, disentangling these pathways is an empirical challenge that cross-sectional data cannot fully resolve. The authors are explicit on this point, calling for prospective studies to clarify the underlying mechanisms and causal pathways.

What the study establishes is a robust cross-sectional association in a population that has been almost entirely absent from the global cardiovascular literature. Most of what medicine knows about the depression–heart disease link comes from high-income countries, where patients have access to lipid panels, electrocardiograms, and cardiologists. The Haiti Cardiovascular Disease Cohort demonstrates that the same epidemiological tools—validated symptom scales, adjudicated outcome definitions, and carefully adjusted prevalence models—can be deployed in one of the world’s most constrained health systems and yield findings of genuine global relevance. If depression screening becomes a routine part of cardiovascular prevention in Port-au-Prince and cities like it, the payoff could extend beyond Haiti: roughly three-quarters of cardiovascular deaths worldwide occur in low- and middle-income countries, and this study suggests that a treatable mental health condition may be quietly amplifying that toll.

Subject of Research: The association between depressive symptoms and prevalent cardiovascular disease in urban Haiti

Article Title: Depressive symptoms and association with prevalent cardiovascular disease: A cross-sectional analysis in Port-au-Prince, Haiti

Article References: Pierre, D. M., Rasul, R., St. Sauveur, R., Celestin, K., Rouzier, V., Hilaire, E., Deschamps, M. M., Pape, J. W., Yan, L. D., Ogyu, A., Bennett, C., McNairy, M. L., Sufra, R., & Nash, D. (2026). Depressive symptoms and association with prevalent cardiovascular disease: A cross-sectional analysis in Port-au-Prince, Haiti. PLOS Mental Health, 3(8), e0000693. https://doi.org/10.1371/journal.pmen.0000693

Image Credits: AI Generated

DOI: 10.1371/journal.pmen.0000693

Keywords: depression, cardiovascular disease, Haiti, Port-au-Prince, PHQ-9, cross-sectional study, sex differences, global health, mental health, low- and middle-income countries, epidemiology, comorbidity

The scale of the field effort was considerable. Between August 2018 and September 2019, the research team deployed three complementary trap types—Biogents Sentinel traps, CDC Gravid traps, and CDC Light Traps—at 19 study locations across the Ouest Department. Over the thirteen-month sampling window, they captured a total of 22,504 mosquitoes. Two species dominated the catch: Culex quinquefasciatus, which accounted for 53.4 percent of all specimens, and Aedes aegypti, which made up 16.9 percent. These are not incidental species. Cx. quinquefasciatus is the principal vector of lymphatic filariasis in Haiti, while Ae. aegypti transmits the arboviruses responsible for dengue, Zika, chikungunya, and yellow fever. Their numerical dominance underscores how heavily the region’s disease burden is concentrated in a small number of highly adapted urban vectors.

Alongside the two dominant species, the collections included Anopheles albimanus, the country’s key malaria vector, and a broader cast of secondary species, including Psorophora columbiae. All mosquitoes were identified morphologically, and the team then quantified biodiversity using a standard ecological toolkit: species richness measures of alpha diversity, Shannon’s index, and Simpson’s index. Each of these metrics captures a slightly different aspect of community structure—raw species counts, the balance between richness and evenness, and the probability that two randomly drawn individuals belong to the same species, respectively. Applying all three allowed the researchers to distinguish sites that merely hosted many species from those that supported genuinely balanced, multi-species communities.

A crucial methodological finding emerged from this diversity assessment: the metrics varied significantly both by trap type and by month. No single trapping method painted a complete picture of the mosquito community. Biogents Sentinel traps, which target host-seeking container-breeding Aedes, CDC Gravid traps, which attract egg-laying females enriched for Culex, and CDC Light Traps, which sample nocturnal flying insects broadly, each bias collections toward particular behaviors and species. The implication for surveillance programs is direct—reliance on a single trap design risks systematically undercounting the very species that matter most for a given disease system, and the authors emphasize the need for diversified trapping methods in future monitoring efforts.

To move beyond description and identify the environmental forces structuring these communities, the team turned to boosted regression trees, a machine-learning technique increasingly favored in disease ecology for its ability to model nonlinear relationships and interactions among many predictors simultaneously. The models incorporated both static and temporally varying covariates, including temperature, precipitation, vegetation indices measured through the normalized difference vegetation index (NDVI), and human population density. By relating the diversity indices computed for each collection event to these environmental layers, the BRTs could rank the relative influence of each factor and reveal the shapes of their effects—something classical linear models often obscure.

The results were striking in their consistency. Human population density, temperature, and vegetation indices emerged as the key predictors of mosquito diversity across the study area. This triad tells an ecologically coherent story. Dense human settlement creates the artificial containers, storm drains, and water-holding debris that container-breeding Aedes require, while also supplying the blood meals that sustain high vector populations. Temperature governs mosquito development rates, viral replication within vectors, and seasonal activity windows. Vegetation, as indexed by NDVI, shapes the availability of shaded resting sites, organic-rich larval habitats, and the microclimates that favor some species over others. In a highly urbanized tropical setting, these three forces interact to determine which mosquito species coexist at any given site and in any given month.

Perhaps the most novel component of the study was its use of species co-occurrence networks to describe the relationships among mosquito species. The researchers constructed two types of networks—one based on a cross-product approach and one on a probabilistic framework—to test whether pairs of species occurred together more or less often than expected by chance. The networks revealed significant positive associations between Aedes species and Cx. quinquefasciatus, suggesting that the vectors of arboviruses and lymphatic filariasis frequently share the same habitats and may respond similarly to urban environmental conditions. For control programs, this is a double-edged finding: interventions targeting shared breeding habitats could suppress multiple disease vectors simultaneously, but conditions that favor one dominant species may also be quietly building populations of the others.

Not all relationships in the networks were positive. Psorophora columbiae exhibited negative associations with multiple other species, standing out as the community’s apparent contrarian. Negative co-occurrence patterns can arise from several mechanisms, including competition for larval resources, differing habitat preferences, or predation, although the study’s observational design means the underlying cause cannot be pinned down with certainty. What the pattern does establish is that inter-species dynamics are a real and measurable feature of Haiti’s mosquito communities, not a statistical artifact, and that single-species control strategies may produce ecological ripple effects that are currently poorly understood.

The public health stakes of this work are substantial. Haiti continues to confront endemic malaria transmitted by An. albimanus, recurring dengue outbreaks driven by Ae. aegypti, and lymphatic filariasis sustained by Cx. quinquefasciatus. Ae. albopictus, the Asian tiger mosquito, is also present as an arbovirus vector. By identifying the environmental conditions under which these vectors co-occur, the study provides a foundation for multi-species control measures—interventions designed not against one target insect but against the ecological communities that collectively transmit the country’s major vector-borne diseases. The finding that human population density is a central driver also highlights how urbanization itself functions as a disease ecology variable, concentrating vectors and humans in the same environmental envelope.

The authors are careful to frame their conclusions as a beginning rather than an endpoint. They call for further research on inter-species dynamics to build a more unified understanding of vector ecology in Haiti, and their study design—combining year-round field surveillance, multiple trap types, rigorous biodiversity metrics, machine-learning environmental modeling, and network analysis—offers a template that other resource-limited settings could adapt. The work was funded by the Armed Forces Health Surveillance Branch’s Global Emerging Infections Surveillance section and through a Battelle Memorial Institute contract supporting Navy force health protection efforts, reflecting the strategic importance placed on vector surveillance in the Caribbean region. As climate change alters temperature regimes and urbanization accelerates across the tropics, the environmental levers identified in this study—population density, heat, and vegetation—will only grow in importance for predicting where mosquito biodiversity, and the diseases it carries, will flourish next.

Subject of Research: Environmental and demographic drivers of mosquito biodiversity and species co-occurrence in urban Haiti

Article Title: Vegetation, temperature, and human population density influence mosquito biodiversity in Haiti

Article References: Pshea-Smith, I. A., Okech, B. A., Boncy, J., Existe, A., So, J., Hamilton, T., Blanton, J., Matulis, G. A., Metrailer, M. C., Cleary, N. G., Dunford, J. C., Koehler, J. W., Blackburn, J. K., & von Fricken, M. E. (2026). Vegetation, temperature, and human population density influence mosquito biodiversity in Haiti. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07724-3

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07724-3

Keywords: mosquito biodiversity, Haiti, Aedes aegypti, Culex quinquefasciatus, boosted regression trees, species co-occurrence networks, vector ecology, NDVI, urban ecology, dengue, malaria, lymphatic filariasis

The service at the center of the study is EkoLakay, a container-based sanitation system operated in northern Haiti that provides households with a toilet that collects waste in sealed containers, which are swapped out weekly and transported to a treatment facility. In a country where sewer connections are rare and pit latrines often discharge untreated waste into the environment, container-based sanitation is one of the only household-level options that qualifies as safely managed sanitation under international definitions. The service currently costs 350 Haitian gourdes per month, a fee equivalent to less than three US dollars, yet even this modest amount proves prohibitive for some households. That gap between the cost of running the service and what the poorest families can afford is precisely where the question of targeted subsidies enters, and where the study makes its most consequential contribution.

To measure willingness to pay, the researchers used contingent valuation, a survey-based method in which respondents state whether they would pay a specified price for a good or service. It is a technique long used in environmental and development economics to attach values to things that lack market prices, and it requires careful design to avoid inflating or deflating responses. In this study, households were asked about their willingness to pay for EkoLakay service at different price points, and the resulting distribution tells a clear story. Sixty percent of surveyed households said they would pay the current fee of 350 gourdes per month. When the hypothetical price dropped to 250 gourdes, willingness to pay rose to 77 percent, and at 150 gourdes it reached 85 percent. In other words, demand for the service is high but highly price-sensitive, and each reduction in the monthly fee unlocks a substantial additional share of the population.

Those percentages translate directly into policy arithmetic. The authors calculate that a subsidy reducing the effective price to between 150 and 200 gourdes per month could push container-based sanitation coverage in the study area to as much as 80 percent of households. That is a striking figure for a city where safely managed sanitation coverage is otherwise minimal, and it suggests that relatively modest per-household transfers could produce large gains in public health protection. The economics hinge on the fact that the service already functions at scale; the constraint is not the technology or the collection logistics but the affordability of a recurring fee for households living close to the margin. Subsidy design, in this framing, becomes the central lever for expanding coverage rather than an afterthought.

Perhaps the most analytically interesting part of the study is its multivariate regression analysis, which examined which household characteristics were associated with willingness to pay. Three factors stood out: household wealth, the degree of privacy afforded by the household’s current sanitation arrangement, and satisfaction with that current facility. Wealthier households were more willing to pay, which is unsurprising but important, because it means that a uniform price will systematically exclude the poorest, reinforcing the case for targeted rather than universal subsidies. Households whose current toilets offered more privacy, and those who were dissatisfied with what they had, were also more willing to pay for the container-based service, indicating that the perceived quality and dignity of existing arrangements shape demand in measurable ways.

Just as revealing was what did not predict willingness to pay. Whether a household currently owned a private toilet showed no significant association with its willingness to pay for EkoLakay service. At first glance this seems paradoxical: why would families who already have a toilet pay for another one? The focus group discussions, conducted with household members and community leaders, supplied the answer. Participants described the hidden and recurring burdens of pit latrines, including the high cost of emptying a full pit, the persistent smell, and problems with pests. In dense urban neighborhoods where pits are difficult or impossible to empty safely, these costs can be substantial and unpredictable, making a flat monthly fee for a service that removes waste weekly genuinely attractive even to toilet owners.

The focus groups also surfaced contextual factors that a survey alone would have missed. Some participants expressed a desire for multiple toilets within the home, reflecting household sizes and living arrangements that a single facility cannot comfortably serve. Others pointed to the particular value of container-based sanitation in flood-prone areas, where pit latrines can overflow during heavy rains and contaminate yards, wells, and streets. Cap Haitien, like much of coastal Haiti, faces recurrent flooding that turns inadequate sanitation from a chronic nuisance into an acute hazard. In such settings, a sealed container that is removed before it fills offers a form of resilience that conventional on-site systems cannot match, and households appear to recognize and value that difference.

These findings matter well beyond northern Haiti. Container-based sanitation has attracted growing attention in the global sanitation sector as a service model for dense, low-income urban areas where sewers are infeasible and on-site systems fail to protect public health. Operators in Kenya, Ghana, Peru, and elsewhere face the same core dilemma as EkoLakay: the full cost of weekly collection and treatment cannot be recovered from the poorest customers at a price they can afford. The Cap Haitien study provides a template for how operators and governments can estimate the demand curve for such a service and identify the price point at which coverage expands most efficiently. It also demonstrates that willingness to pay is shaped by service attributes, such as privacy and flood resilience, that conventional subsidy formulas based purely on income may overlook.

The study’s implications for targeting are subtle. Because wealth predicts willingness to pay, subsidies aimed at the poorest households would reach those least able to pay the current fee, which is the standard logic of targeted transfers. But because satisfaction with existing sanitation and privacy also predict willingness to pay, a subsidy design that considers the quality of a household’s current facility, not just its income, could allocate resources more effectively. A family with a recently built, well-maintained private toilet may have less to gain from switching than a family using an unimproved shared latrine, even at similar income levels. Incorporating such indicators into eligibility criteria could stretch limited public budgets further, a consideration of acute importance in Haiti, where fiscal capacity is severely constrained and donor funding for water and sanitation is volatile.

The authors are careful to note the limits of what contingent valuation can establish. Stated willingness to pay is not the same as actual payment behavior, and hypothetical responses can diverge from what households do when a real bill arrives. Yet the consistency of the pattern across price points, the plausible direction of the regression results, and the corroborating qualitative evidence give the findings credibility, and the practical payoff is concrete: a quantified estimate that reducing the monthly fee to 150 to 200 gourdes could lift coverage to roughly 80 percent of households in the study area. For basic service providers and government partners in the region, that number converts an abstract debate about equity into a specific, costable policy choice. For the residents of Cap Haitien, it raises the prospect that a safe, dignified, and reliably collected toilet, one of the most fundamental determinants of urban health, could move within reach of the majority of families rather than a fortunate few.

Subject of Research: Willingness to pay for container-based sanitation services and targeted subsidy design in urban Haiti

Article Title: Willingness-to-pay for container-based sanitation and implications for targeted subsidy design in urban Haiti

Article References: Lubeck-Schricker, M., Bauza, V., Felix-Jean, W., Goddard, F. G., Pierre, M. F., Ozeris, B., Schelling, M., & Kramer, S. (2026). Willingness-to-pay for container-based sanitation and implications for targeted subsidy design in urban Haiti. PLOS Water, 5(9), e0000618. https://doi.org/10.1371/journal.pwat.0000618

Image Credits: AI Generated

DOI: 10.1371/journal.pwat.0000618

Keywords: container-based sanitation, willingness to pay, Haiti, Cap Haitien, sanitation subsidies, contingent valuation, EkoLakay, urban sanitation, PLOS Water, public health, pit latrines, flood resilience

The research team, led by Renesky Jean Mary of the Federal University of Latin American Integration in Brazil together with colleagues at the University of São Paulo and the Federal University of Amapá, framed the city not as a set of isolated flood zones but as a single connected hydrogeomorphic system. Water that falls on the high southern uplands near Kenscoff, where elevations climb to roughly 2,159 metres, does not stay there. It moves rapidly through dissected ridges, steep slopes, and confined valleys via rivers such as the Grise and the Froide and the Bois-de-Chêne ravine, arriving within minutes or hours at the low-relief coastal plain occupied by Port-au-Prince, Delmas, Cité Soleil, and Tabarre. Hydrogeological work has already shown that infiltration from these rivers is a principal source of recharge for the Cul-de-Sac alluvial aquifer, confirming that the mountain block and the lowlands function as one hydrological unit.

To capture that connectivity, the researchers used a technique called geomorphon classification, applied to a 30-metre digital elevation model with the r.geomorphon module in GRASS GIS. The algorithm compares terrain visibility in multiple directions and assigns every cell to a local landform class such as ridge, slope, valley, base of slope, or plain. Unlike a simple slope map, this approach distinguishes terrain units associated with runoff generation, transfer, and accumulation. The result is a functional picture of the landscape: ridges and slopes in the south generate runoff, valleys act as transfer corridors, and the flat coastal plain receives and concentrates the flow. When vegetation is stripped from ridges and slopes and replaced with impervious surfaces, the volume and speed of water delivered to the lowlands can increase even if the converted cells themselves are never classified as high-risk terrain.

The land-cover mapping behind the study was unusually rigorous. Landsat 8 classifications for 2015, 2020, and 2025 achieved overall accuracies of 98.44, 95.92, and 94.13 percent, with Kappa coefficients of 0.9704, 0.9362, and 0.9069 respectively. Rather than reporting raw pixel counts, the team applied the area-adjustment method of Olofsson and colleagues, using error matrices to produce corrected class areas with nominal 95 percent confidence intervals. The adjusted built-up estimate rose from 80.79 square kilometres in 2015 to 226.92 square kilometres in 2020, a gain equivalent to 180.9 percent of the starting value, and then to 335.43 square kilometres in 2025, an increase of 315.2 percent over the decade. Vegetation fell from an adjusted 458.08 square kilometres to 277.17 square kilometres, and the remaining green cover became increasingly fragmented along the transition between the coastal plain and the southern uplands.

One of the study’s most technically interesting results concerns the choice of satellite sensor. For 2025, the team produced a parallel classification from Sentinel-2 at 10-metre resolution, which achieved 99.35 percent overall accuracy and a Kappa of 0.9908. Yet the two sensors disagreed dramatically on class shares: Landsat 8 allocated 42.6 percent of the area to built-up land, while Sentinel-2 allocated only 17.9 percent, a ratio of 2.38. The authors are careful to explain that this is not sensor bias but a consequence of spatial support. A single 30-metre Landsat pixel in a dense informal settlement typically mixes rooftops, roads, bare soil, and sparse vegetation, and the whole pixel gets assigned to one class, often built-up. The finer Sentinel-2 grid resolves that sub-pixel structure, separating exposed soil, which received 34.7 percent under Sentinel-2 versus 18.7 percent under Landsat 8, from genuinely impervious surfaces. For planners deciding where drainage investments should go, that distinction matters enormously.

Combining the 2025 Sentinel-2 land cover, slope, and flow accumulation into a weighted flood-susceptibility index, with weights of 40, 25, and 35 percent respectively, the study found that moderate and high susceptibility concentrates overwhelmingly in Tabarre, Delmas, and Cité Soleil. These communes occupy low-relief coastal and alluvial surfaces where modeled flow convergence, extensive urban sealing, and restricted drainage coincide. High susceptibility is not spread evenly but follows drainage axes and geographically confined depressions. Gressier, Kenscoff, and Carrefour show predominantly low susceptibility at the commune scale because of their steeper upland terrain, yet moderate and high classes persist locally along valley bottoms and downslope outlets, a reminder that commune averages can hide sharply confined hazards. An overlay of historical flood and rainfall disaster records from humanitarian and local sources showed broad spatial agreement with the susceptibility map, with the largest documented event counts in Cité Soleil and Port-au-Prince, though the authors stress this comparison is a qualitative plausibility check rather than statistical validation, since official georeferenced disaster records in Haiti remain fragmented.

The precipitation analysis added a troubling temporal dimension. Drawing on five daily gridded products for 1983 to 2024, including CHIRPS, ERA5, ERA5-Land, AgERA5, and PERSIANN-CDR, the team computed standard climate extremes indices and tested trends with the two-sided Mann-Kendall test, complemented by Benjamini-Hochberg and Benjamini-Yekutieli corrections for the many repeated cellwise tests. The most consistent signal across products was an increase in consecutive dry days, the longest run of days with less than one millimetre of rain. During the December-to-February season, the median statistically significant area reached 81.5 percent and was fully retained after false-discovery adjustment, with the strongest drying trends, exceeding 0.40 days per year, in northeastern and eastern cells. Annual total precipitation on wet days showed predominantly negative but non-significant slopes, indicating no uniform wetting or drying tendency.

At the same time, the frequency of very heavy rainfall events showed geographically restricted increases. During June to August, the count of days exceeding 60 and 80 millimetres rose significantly across large portions of the arrondissement, with a median significant area of 70.5 percent that survived Benjamini-Hochberg adjustment almost intact at 69.1 percent. Positive tendencies also appeared in August one-day maximum rainfall and precipitation above the 99th percentile, though little or no significant area remained after conservative multiplicity control. The authors interpret this combination, longer dry spells alongside occasional intense downpours, as greater rainfall irregularity acting on a landscape whose runoff pathways and vulnerable receiving areas are already established. They explicitly caution that the analysis does not show dry spells causing subsequent flooding, and that the absence of a continuous quality-controlled local rain-gauge record prevents direct validation of the gridded products.

Interpreted through the Pressure and Release framework, the study treats urban expansion and vegetation loss as dynamic pressures, occupation of steep terrain and flood-prone plains as unsafe conditions, and intense rainfall as the immediate trigger. That framing keeps the physical susceptibility analysis separate from social vulnerability while allowing both to inform the same risk picture, an important distinction in a city where access to drainage, secure housing, and protective infrastructure is deeply unequal. The authors recommend prioritizing drainage rehabilitation and maintenance in Tabarre, Delmas, Cité Soleil, and coastal Port-au-Prince, protecting and restoring vegetation on ridges, steep slopes, valley margins, and river corridors, using Sentinel-2-class imagery for current planning while retaining Landsat for long-term monitoring, and expanding rain-gauge coverage and georeferenced disaster inventories. The susceptibility map, they emphasize, is a screening tool for field investigation and community-informed planning, not a calibrated prediction of inundation depth. What the evidence supports, cautiously but clearly, is that a decade of breakneck construction across hydrologically connected terrain has raised the potential for rapid runoff delivery toward the densely occupied lowlands, and that greater rainfall irregularity may magnify the consequences of that transformation for millions of residents.

Subject of Research: Urban expansion, flood susceptibility, and precipitation extremes across the mountain-to-coastal gradient of the Port-au-Prince Arrondissement, Haiti

Article Title: Urban expansion across a mountain-to-coastal gradient and its implications for hydrogeomorphic risk in Port-au-Prince, Haiti

Article References: Mary, R. J., de Bodas Terassi, P. M., da Silva Scheer, M. A. P., Palhares, J. M., & Rauber, A. L. (2026). Urban expansion across a mountain-to-coastal gradient and its implications for hydrogeomorphic risk in Port-au-Prince, Haiti. Natural Hazards, 122(18), Article 622. https://doi.org/10.1007/s11069-026-08384-3

Image Credits: AI Generated

DOI: 10.1007/s11069-026-08384-3

Keywords: Port-au-Prince, Haiti, urban expansion, flood susceptibility, land-use change, remote sensing, Landsat 8, Sentinel-2, geomorphons, precipitation extremes, hydrogeomorphic risk, runoff connectivity

Locke’s central contention is that the world’s smallholder farmers have been framed for too long as beneficiaries of development assistance when they should instead be recognized as architects of the next great agricultural transformation. The world population is projected to rise by roughly 1.5 billion by 2050, with nearly all of that growth concentrated in developing countries where smallholder dominance is greatest. Conventional thinking has often treated increased food production and environmental restoration as competing goals, implying that feeding more people necessarily requires more land, more synthetic inputs and more ecological sacrifice. Locke’s proposition inverts that trade-off. He argues that the same investment needed to raise smallholder productivity — training, financing, research, market access and extension support — can simultaneously convert agriculture from an extractive activity into a regenerative one, producing measurable gains in soil health, biodiversity, water resources, carbon storage and farmer livelihoods at the same time.

Much of the empirical grounding for this argument comes from Haiti, where Locke and Haitian agronomist Timote Georges co-founded the Smallholder Farmers Alliance in 2010. The organization now works with roughly 10,000 member farmers, and the results offer a working model of what broader support could achieve. When participating smallholders receive basic agricultural services built on sustainable practices, their yields increase by an average of about 40 percent, while household incomes rise between 50 and 100 percent depending on local conditions. Alliance members also plant approximately one million trees every year. The organization pioneered what it calls a tree currency model: farmers plant and care for trees in exchange for agricultural services, training, seeds and other inputs. This mechanism directly links increased farm productivity with environmental restoration, ensuring that ecological gains and economic gains reinforce one another rather than compete.

The Haiti experience shaped one of the book’s central conclusions: hundreds of millions of smallholder farmers are producing well below their potential not because of any inherent limitation of small farms, but because agricultural policies, research priorities, financing systems and extension services have disproportionately favored large-scale industrial agriculture for decades. Locke is careful to distinguish his vision from nostalgia. This is not, he insists, a call to return agriculture to some idealized past. It is about recognizing where one of the greatest opportunities for the future of food now exists. Smallholders are particularly well positioned to lead a regenerative transformation because many retain traditional agricultural knowledge, operate diversified farming systems, and have adopted industrial methods far less extensively than producers in wealthier countries — meaning they have less to undo and more to build upon.

Regenerative agriculture, as the book frames it, goes beyond merely reducing the damage farming causes. It is a holistic approach designed to improve the natural systems on which agriculture depends. The methodology draws on three streams of knowledge: Indigenous and ancestral farming traditions, decades of experience with organic farming, agroecology, permaculture and other sustainable approaches, and contemporary science, including advances in soil biology, ecosystem science and impact measurement. Depending on local conditions, regenerative farmers may employ crop rotation, cover crops, intercropping and diverse cropping systems, composting and other methods of building soil organic matter, reduced tillage, agroforestry and the integration of livestock. The objective is not adherence to a universal checklist of practices but measurable improvement in outcomes such as soil health, biodiversity, water quality and availability, carbon storage, food production, farmer livelihoods and community resilience.

Locke describes this dual character as regenerative agriculture’s dual revolution: it is simultaneously a farming methodology and a framework for determining whether farming is actually producing regenerative results. The distinction matters because practices appropriate to a smallholder in Haiti, India or Kenya may be very different from those suitable for a large farm in Canada or the United States. The critical question, he argues, is not simply whether a farmer is using regenerative practices, but whether the land, the ecosystem and the farming community are measurably better as a result. This represents a fundamental shift from agricultural practices designed to do less harm toward practices engineered to deliver net positive outcomes, and it places verification and evidence at the heart of the regenerative movement.

The climate implications are substantial. Healthy soils and growing plants remove carbon dioxide from the atmosphere and store carbon in soil organic matter and biomass, while regenerative systems also reduce emissions associated with the manufacture and transportation of synthetic fertilizers. Drawing on peer-reviewed research, Locke estimates that approximately 240 million smallholder farms making the transition to regenerative agriculture across an estimated 480 million hectares could remove up to 0.72 gigatons of CO2 from the atmosphere annually during the period in which soil carbon is actively accumulating. Reduced reliance on synthetic fertilizer could add roughly 0.1 gigatons of CO2 equivalent per year in avoided emissions, bringing the estimated combined benefit to approximately 0.6 to 0.85 gigatons per year at mature adoption — a figure roughly comparable in scale to the annual CO2 emissions of the entire global aviation industry.

Locke is careful not to overstate the climate case. Soils cannot absorb carbon indefinitely; soil carbon generally accumulates over one to three decades before approaching a new equilibrium, and outcomes vary substantially with soil types, climate, farming practices and farmers’ starting conditions. Regenerative agriculture, he stresses, is not a license to keep emitting carbon elsewhere. Its climate potential is important precisely because it arrives alongside other urgently needed benefits: healthier soil, greater biodiversity, more resilient farms, increased food production and stronger rural communities. This framing guards against the growing tendency to reduce regenerative agriculture to a carbon accounting exercise, and it underpins the book’s argument that a farming system which sequesters carbon while degrading biodiversity, water resources or farmer livelihoods cannot meaningfully be called regenerative.

The book arrives at a moment when regenerative agriculture is moving rapidly into the mainstream yet still lacks a universally agreed definition, making credible measurement especially important. Rather than allowing a farm or company to be deemed regenerative simply because it has adopted a favored technique, Whole Earth Farming advocates assessing a broad range of environmental and social outcomes. Locke highlights the emerging Regen10 Outcomes Framework, developed through more than two years of global consultation, as an important step toward a common reference for assessing regenerative agriculture while allowing farmers to choose methods appropriate to local circumstances. The framework encompasses ecological health, farmer livelihoods, food quality, community resilience and other dimensions, providing a template for accountability as the movement scales.

Locke calls the broader opportunity a Great Regenerative Transformation, comparable in ambition to the Green Revolution that dramatically raised agricultural production in the second half of the twentieth century, but with a crucial difference. Where the Green Revolution relied on improved crop varieties, irrigation, synthetic fertilizers, pesticides and standardization, this transformation would combine traditional agricultural knowledge with ecological science, locally adapted practices and modern measurement systems. The book carries a foreword by Roy Steiner, Senior Vice President of the Food Initiative at The Rockefeller Foundation, who describes the world’s 475 million smallholder farming households as not a measure of the problem but a measure of the possibility, and emphasizes that regenerative transformation cannot succeed without farmers themselves acting as agents of change. Endorsements have come from figures including former U.S. President Bill Clinton and chef and humanitarian José Andrés. The book, which includes 21 farmer stories from 18 countries and was launched during Climate Week NYC, rests on a deceptively simple proposition: the world need not choose between feeding more people and restoring the planet, provided the hundreds of millions of farmers who have long operated at the margins of agricultural policy are finally given the means to lead.

Subject of Research: The potential of smallholder farmers adopting regenerative agriculture and agroforestry to meet global food demand by 2050 while restoring soils, biodiversity and sequestering carbon.

Article Title: Just half the world's 475 million smallholder farmers could meet all of humanity’s additional food needs in 2050 while restoring soils and biodiversity

Article References: Just half the world's 475 million smallholder farmers could meet all of humanity’s additional food needs in 2050 while restoring soils and biodiversity. (n.d.). Original publication

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Keywords: smallholder farmers, regenerative agriculture, agroforestry, food security, soil carbon, biodiversity, climate change, sustainable farming, Haiti, Global South, Regen10 Outcomes Framework, agricultural transformation