Chaco Ecoregion Research Articles

Humans seropositive for Trypanosoma cruzi co-infected with intestinal helminths have higher infectiousness, parasitaemia and Th2-type response in the Argentine Chaco

BackgroundThe Gran Chaco ecoregion is a well-known hotspot of several neglected tropical diseases (NTDs) including Chagas disease, soil-transmitted helminthiasis and multiparasitic infections. Interspecific interactions between parasite species can modify host susceptibility, pathogenesis and transmissibility through immunomodulation. Our objective was to test the association between human co-infection with intestinal parasites and host parasitaemia, infectiousness to the vector and immunological profiles in Trypanosoma cruzi-seropositive individuals residing in an endemic region of the Argentine Chaco.MethodsWe conducted a cross-sectional serological survey for T. cruzi infection along with an intestinal parasite survey in two adjacent rural villages. Each participant was tested for T. cruzi and Strongyloides stercoralis infection by serodiagnosis, and by coprological tests for intestinal parasite detection. Trypanosoma cruzi bloodstream parasite load was determined by quantitative PCR (qPCR), host infectiousness by artificial xenodiagnosis and serum human cytokine levels by flow cytometry.ResultsThe seroprevalence for T. cruzi was 16.1% and for S. stercoralis 11.5% (n = 87). We found 25.3% of patients with Enterobius vermicularis. The most frequent protozoan parasites were Blastocystis spp. (39.1%), Giardia lamblia (6.9%) and Cryptosporidium spp. (3.4%). Multiparasitism occurred in 36.8% of the examined patients. Co-infection ranged from 6.9% to 8.1% for T. cruzi-seropositive humans simultaneously infected with at least one protozoan or helminth species, respectively. The relative odds of being positive by qPCR or xenodiagnosis (i.e. infectious) of 28 T. cruzi-seropositive patients was eight times higher in people co-infected with at least one helminth species than in patients with no such co-infection. Trypanosoma cruzi parasite load and host infectiousness were positively associated with helminth co-infection in a multiple regression analysis. Interferon-gamma (IFN-γ) response, measured in relation to interleukin (IL)-4 among humans infected with T. cruzi only, was 1.5-fold higher than for T. cruzi-seropositive patients co-infected with helminths. The median concentration of IL-4 was significantly higher in T. cruzi-seropositive patients with a positive qPCR test than in qPCR-negative patients.ConclusionsOur results show a high level of multiparasitism and suggest that co-infection with intestinal helminths increased T. cruzi parasitaemia and upregulated the Th2-type response in the study patients.Graphical

Water canals may promote large-scale defaunation of the Gran Chaco

In the Gran Chaco, one of the most biodiverse, yet imperiled, arid biomes in the world, open-to-air concrete water canals may threaten wildlife via drowning and habitat fragmentation, although these effects are usually overlooked. We performed field surveys and local people interviews along 250 km of canals in the Gran Chaco ecoregion of Argentina during austral spring and summer (six months). We documented 207 drowned individuals of 35 wildlife species, but more realistic estimations could increase this number to the thousands. Six species of conservation concern drowned in the canal, and eight of the drowned species have decreasing population trends. Drownings in some mammal species decreased with time without any mitigation measures implemented at the canal yet, suggesting an ongoing, large-scale population reduction due to this high mortality rate. Since mitigation measures applied in other regions were not effective to stop drowning and population isolation, these infrastructures should be avoided in arid environments worldwide.

Slow recovery rates and spatial aggregation of Triatoma infestans populations in an area with high pyrethroid resistance in the Argentine Chaco

BackgroundThe emergence of pyrethroid resistance has threatened the elimination of Triatoma infestans from the Gran Chaco ecoregion. We investigated the status and spatial distribution of house infestation with T. infestans and its main determinants in Castelli, a municipality of the Argentine Chaco with record levels of triatomine pyrethroid resistance, persistent infestation over 2005–2014, and limited or no control actions over 2015–2020.MethodsWe conducted a 2-year longitudinal survey to assess triatomine infestation by timed manual searches in a well-defined rural section of Castelli including 14 villages and 234 inhabited houses in 2018 (baseline) and 2020, collected housing and sociodemographic data by on-site inspection and a tailored questionnaire, and synthetized these data into three indices generated by multiple correspondence analysis.ResultsThe overall prevalence of house infestation in 2018 (33.8%) and 2020 (31.6%) virtually matched the historical estimates for the period 2005–2014 (33.7%) under recurrent pyrethroid sprays. While mean peridomestic infestation remained the same (26.4–26.7%) between 2018 and 2020, domestic infestation slightly decreased from 12.2 to 8.3%. Key triatomine habitats were storerooms, domiciles, kitchens, and structures occupied by chickens. Local spatial analysis showed significant aggregation of infestation and bug abundance in five villages, four of which had very high pyrethroid resistance approximately over 2010–2013, suggesting persistent infestations over space-time. House bug abundance within the hotspots consistently exceeded the estimates recorded in other villages. Multiple regression analysis revealed that the presence and relative abundance of T. infestans in domiciles were strongly and negatively associated with indices for household preventive practices (pesticide use) and housing quality. Questionnaire-derived information showed extensive use of pyrethroids associated with livestock raising and concomitant spillover treatment of dogs and (peri) domestic premises.ConclusionsTriatoma infestans populations in an area with high pyrethroid resistance showed slow recovery and propagation rates despite limited or marginal control actions over a 5-year period. Consistent with these patterns, independent experiments confirmed the lower fitness of pyrethroid-resistant triatomines in Castelli compared with susceptible conspecifics. Targeting hotspots and pyrethroid-resistant foci with appropriate house modification measures and judicious application of alternative insecticides with adequate toxicity profiles are needed to suppress resistant triatomine populations and prevent their eventual regional spread.Graphical

Structure of ant assemblages and effect of environmental conditions in gallery forests with different conservation status in the Humid Chaco ecoregion of Argentina

Structure of ant assemblages and effect of environmental conditions in gallery forests with different conservation status in the Humid Chaco ecoregion of Argentina

Phylogeography and ecological niche modelling of the South American cricetid rodent Graomys griseoflavus, with insights into its chromosomal evolution

Abstract The rodent Graomys griseoflavus has a wide geographical distribution in the Arid Diagonal of South America, showing variation in the diploid number (2n = 33–38) caused by three different Robertsonian (Rb) translocations. Two contrasting hypotheses have been proposed to explain the origin and evolution of this polymorphism: (i) unique and sequential events; or (ii) multiple and independent origins of Rb translocations. Here, we combined phylogeography and ecological niche modelling to elucidate the evolutionary history of G. griseoflavus and help to contrast these hypotheses. The results indicated a demographic increase that would have begun ~150 kya from the High Monte ecoregion. The spatial distributions of these populations were coincident with the areas of highest habitat suitability. The palaeoclimatic projections suggested the presence of two main glacial refugia coincident with the main genetic clusters. Graomys griseoflavus underwent two pulses of southward expansion at ~220 and ~210 kya. More recently (~20 kya), there was a secondary contact between the southern populations (Low Monte ecoregion) expanding northwards and the northern populations (High Monte ecoregion) expanding into marginal areas of the Chaco ecoregion. Combined with the cytogenetic evidence, our results support the multiple and independent origins of Rb translocations.

Climatic and soil characteristics account for the genetic structure of the invasive cactus moth Cactoblastis cactorum, in its native range in Argentina.

Knowledge of the physical and environmental conditions that may limit the migration of invasive species is crucial to assess the potential for expansion outside their native ranges. The cactus moth, Cactoblastis cactorum, is native to South America (Argentina, Paraguay, Uruguay and Brazil) and has been introduced and invaded the Caribbean and southern United States, among other regions. In North America there is an ongoing process of range expansion threatening cacti biodiversity of the genus Opuntia and the commercial profits of domesticated Opuntia ficus-indica. To further understand what influences the distribution and genetic structure of this otherwise important threat to native and managed ecosystems, in the present study we combined ecological niche modeling and population genetic analyses to identify potential environmental barriers in the native region of Argentina. Samples were collected on the host with the wider distribution range, O. ficus-indica. Significant genetic structure was detected using 10 nuclear microsatellites and 24 sampling sites. At least six genetic groups delimited by mountain ranges, salt flats and wetlands were mainly located to the west of the Dry Chaco ecoregion. Niche modeling supports that this region has high environmental suitability where the upper soil temperature and humidity, soil carbon content and precipitation were the main environmental factors that explain the presence of the moth. Environmental filters such as the upper soil layer may be critical for pupal survival and consequently for the establishment of populations in new habitats, whereas the presence of available hosts is a necessary conditions for insect survival, upper soil and climatic characteristics will determine the opportunities for a successful establishment.

A New Species of Cosmocerca Diesing, 1861 (Nematoda: Cosmocercidae) in Elachistocleis haroi Pereyra, Akmentins, Laufer, and Vaira, 2013 (Amphibia: Microhylidae) from South American Chaco.

Cosmocercids are common nematodes that parasitize the digestive tract and lungs of amphibians and reptiles around the world. They are commonly found in leptodactylid and bufonid anurans in South America, primarily in Brazil and Argentina. This paper describes a new species of genus Cosmocerca based on specimens collected in a microhylid from the Dry Chaco ecoregion. A total of 18 specimens of Elachistocleis haroi were collected in October 2011 in Chaco province and in December 2021 and March 2022 in Formosa province, Argentina, both areas of the Dry Chaco ecoregion. The morphology of the nematodes was studied in detail using light microscopy and scanning electron microscopy. One hundred and fifty-one nematodes were collected from the large intestines of E. haroi. Based on the morphology of the caudal papillae (rosette papillae and plectanes), the presence of two spicules and the absence of caudal alae in males, and the presence of two prodelphic ovaries in females, these specimens were allocated to the genus Cosmocerca. However, they presented unique characteristics that differentiate them from all known species. Cosmocerca wichiorum sp. nov. is similar to C. archeyi, C. australis, C. sardiniae, C. zugi, and C. leytensis by having four pairs of plectanes, but can be easily distinguished from all of them by the type, number, and arrangement of the precloacal (non-plectanes), adcloacal and postcloacal papillae, by the length of the spicules and by its different zoogeographical distribution. This is the 14th species of the genus Cosmocerca described in South America and the first one for the microhylid E. haroi from the Dry Chaco ecoregion.

First checklist of the oribatid mites (Arachnida: Oribatida) of the Gran Chaco region (South America) with new records

The South American Gran Chaco ecoregion extends through great areas of Argentina, Paraguay, Bolivia, and Brazil. The region includes vast forests that serve as an important reservoir of tropical and subtropical diversity. In spite of its extent and high biodiversity, it remains an unexplored area regarding Oribatida. We made bibliographic research about the oribatid mites previously registered. In the bibliography of Argentina and Paraguay, a total of 53 species are cited for this region. From our own works in the Argentinean provinces of Santiago del Estero and Chaco, we add some new records of Oribatida in the area. We provide a list of the species registered to date, including 48 firstly recorded in this work, as well as new localities for other 11 species previously known for the area. This paper almost doubles the number of registered species for this highly diverse but poorly known ecoregion, adding information towards the true diversity of Oribatida in the Chaco region.

Pollen from urban flora in the ephemeral nests of solitary Megachile bees in three temperate and subtropical cities of Argentina

Cities are anthropogenic habitats that are home to many taxonomically diverse groups of bees and contribute to their conservation due to the abundance of flowers and nesting substrates. However, the pollen diet composition of nest provisions for most urban bees in South America is poorly studied and therefore the characteristics of the urban flora needed for their survival remains unknown. Pollen analysis was employed to study the diet composition of the wild solitary bees Megachile infima Vachal, M. pusilla Pérez and Megachile spp. that all nest in urban environments in two eco-regions in Argentina. Nests were found in preexisting small holes within human-made structures (walls, hosepipes, water taps), natural substrates (hollow stems) or in semi-exposed spaces within four courtyards of three cities. Pollen from brood provisions from these nests were compared with pollen grains from the available flowering plants surrounding the nests. In the temperate city La Plata from the Pampean eco-region, 23 pollen types from 14 families and five unidentified types were present. The most abundant were Styphnolobium japonicum (Fabaceae, Papilionoideae) and Picris echioides (Asteraceae). In the two subtropical cities from the Chaco eco-region, 15 types from eight families and four unidentified types were present, with Phoenix (Arecaceae) and Punica granatum (Lythraceae) being the most abundant. Although bees were polylectic, the presence of pollen in nests was not evenly distributed, which may be related to resource abundance, pollen attributes, and floral morphology. This study provides evidence of forage versatility of Megachile bees on pollen plants from diverse taxonomic origin and status of naturalization, flowering stratum and city microhabitat.

Partitioning the effects of habitat loss, hunting and climate change on the endangered Chacoan peccary

AbstractAimLand‐use change and overexploitation are major threats to biodiversity, and climate change will exert additional pressure in the 21st century. Although there are strong interactions between these threats, our understanding of the synergistic and compensatory effects on threatened species' range geography remains limited. Our aim was to disentangle the impact of habitat loss, hunting and climate change on species, using the example of the endangered Chacoan peccary (Catagonus wagneri).LocationGran Chaco ecoregion in South America.MethodsUsing a large occurrence database, we integrated a time‐calibrated species distribution model with a hunting pressure model to reconstruct changes in the distribution of suitable peccary habitat between 1985 and 2015. We then used partitioning analysis to attribute the relative contribution of habitat change to land‐use conversion, climate change and varying hunting pressure.ResultsOur results reveal widespread habitat deterioration, with only 11% of the habitat found in 2015 considered suitable and safe. Hunting pressure was the strongest single threat, yet most habitat deterioration (58%) was due to the combined, rather than individual, effects of the three drivers we assessed. Climate change would have led to a compensatory effect, increasing suitable habitat area, yet this effect was negated by the strongly negative and interacting threats of land‐use change and hunting.Main ConclusionsOur study reveals the central role of overexploitation, which is often neglected in biogeographic assessments, and suggests that addressing overexploitation has huge potential for increasing species' adaptive capacity in the face of climate and land‐use change. More generally, we highlight the importance of jointly assessing extinction drivers to understand how species might fare in the 21st century. Here, we provide a simple and transferable framework to determine the separate and joint effects of three main drivers of biodiversity loss.

Flow regulation by dams impacts more than land use on water quality and benthic communities in high-gradient streams in a semi-arid region

In semi-arid regions, water policy has strongly promoted the construction of water reservoirs with little or no consideration for their ecological consequences. In order to quantify the effect induced by flow discontinuity on environmental conditions, water quality, and invertebrate communities at high-gradient streams, we investigated unregulated and regulated reaches at 13 watercourses, located in the Dry Chaco Ecoregion (South America). Dams differed in the dominant land uses (rangeland, agriculture, and urban) of the related catchment area. We assessed on-site hydro-geomorphic features, water quality and bacteriological parameters, habitat condition, chlorophyll a, macrophytes cover, and macroinvertebrate communities. Significant increases in mineral parameters and organic contamination indicators were detected at regulated reaches, such as: conductivity, total solids, turbidity, color, and phosphates. Dams negatively affected habitat condition, and macrophyte cover increased at regulated sites. Macroinvertebrates showed a diminution in most of the metrics analyzed, with a decrease of sensitive groups and an increase in the more tolerant ones. Redundancy Analysis revealed that SWQI (physicochemical based index) and the proportion of coarse gravel were stronger predictors on metrics arrangement. Variance partitioning analyses proved that regulation effects prevailed over land use in explaining metrics variation. Invertebrate community was positively related to better ecological conditions, which suggests that restitution of ecological integrity at regulated reaches should include habitat restoration. These results are relevant for the management of regulated water resources in arid and semi-arid regions in a context of climate change.

Sarcosaprophagous Muscid Fly (Diptera: Muscidae) Assemblages Along an Anthropized Gradient in the Humid Chaco Ecoregion, Chaco Province, Argentina.

Deforestation, agriculture, farmyard animal husbandry, and urbanization are known to be the main causes of biodiversity loss and habitat fragmentation. The present study evaluated the role of anthropization in modulating Muscidae (Diptera) assemblages in the Humid Chaco ecoregion of Argentina, by testing the biotic homogenization and intermediate disturbance hypotheses. The study focused on natural, rural, and urban habitats in San Lorenzo Department, Chaco Province, where sarcosaprophagous muscid flies were surveyed. A total of 1,343 muscid flies were captured and identified to 7 genera and 24 species and morphospecies. We observed the effect of anthropization on the structuring of the assemblages and the presence of exotic species associated with human activity resulting from biotic homogenization. The highest abundance was recorded in the urban habitat, while the highest species richness and diversity (Shannon-Wienner and Hill's numbers) were found in the rural habitat, supporting the intermediate disturbance hypothesis. Several species are classified as indicators of habitat as well as according to their index of synanthropy. Our results provide valuable information about the use of sarcosaprophagous muscids as indicators of disturbance of natural habitats and about possible health risks related to this family of Calyptratae flies previously unsurveyed in northeastern Argentina. This information could be used in the ecological, agronomy, sanitary, and forensic fields.

A methodological approach for the analysis of ecosystem services from the local communities' perspective.

In this paper, we developed an innovative and plural methodology for a socio-cultural assessment of ecosystem services (ES). This methodology was performed using diverse and interdependent tools applied within the framework of ethnoecology and post-normal science, with the aim of identifying ES from the perspective of local communities that inhabit different socio-ecosystems, highlighting the relevance of Indigenous and Local Knowledge (ILK). As examples of how this methodology works, we analyzed a multiple case study performed in three peasant communities of the Dry Chaco eco-region, Argentina. We identified ES in all the categories and their fundamental contributions to the particular way of life in this area. The method is flexible enough to be used in other socio-ecosystems with different environmental and social features.

First record of the Delicate Salt Flat Mouse, Salinomys delicatus Braun & Mares, 1995 (Rodentia, Cricetidae) in a xeric environment of northwestern Córdoba (Argentina), with comments on its conservation status

Salinomys delicatus Braun & Mares, 1995 is a sigmodontine rodent endemic to perisaline environments in west-central Argentina. It is currently considered to be a Vulnerable species due to its patchy distribution and the loss of optimal habitats caused by intensive anthropogenic activities. In this work, we document the first record for this species in the Dry Chaco ecoregion of northwestern Córdoba province (Argentina), enlarging the geographic distribution of this species by approximately 115 km to the east of previously known occurrences. Our new record highlights the need to strengthen conservation policies in the Dry Chaco of Córdoba province.

Chagas Disease: Seroprevalence and Associated Factors in Indigenous Communities of the Southern Limit of Argentine Chaco.

Chagas disease is more prevalent in socially vulnerable communities in the Gran Chaco Eco-region. The study evaluated the seroprevalence of Chagas disease and associated factors between May 2014 and September 2015, in indigenous communities of Santa Fe, Argentina, in the southern Chaco. Lysate ELISA and indirect hemagglutination tests were used to detect antibodies against Trypanosoma cruzi, and recombinant ELISA was used in the case of disagreement. Household surveys were conducted with the head of household about risk factors for the disease. Serological tests were conducted on 298 people from three indigenous communities, 127 male and 171 female. Seroprevalence was 18.5%. A total of 64 surveys were conducted; 82.8% of the heads of household were male, with a median age of 39 years, and 61.0% had not completed primary school. In 35.9% of the households, there was at least one member of the cohabiting group infected with T. cruzi. The level of education of the head of household showed a statistically significant association with Chagas disease (OR = 3.43), among all the risk factors studied. The prevalence of infection is lower than that of other indigenous communities of the Gran Chaco, probably because environmental conditions are moderating and disfavoring the establishment of the insect vector in homes, but also because of socioeconomic differences with the rest of the eco-region. Beyond this, serological controls are needed to prevent vertical transmission.

Mieles del Chaco Húmedo: origen botánico y geográfico de la provincia de Formosa (Argentina)

The Humid Chaco Ecoregion of Formosa Province is characterized by a variety of native plant species with long flowering periods, some of which are used by bees for honey production. The objective of this work is to characterize the honeys by botanical and geographical origin through the palynological analysis of samples collected in 14 apiaries. Ninety six honey samples were obtained during three beekeeping periods from 2009 to 2012. The conventional methodology was used, taking into account the acetolysis technique. The pollen spectrum of the honeys allowed us to recognize 126 pollen types, belonging to 57 families of Angiosperms and comprising 65% of the floristic survey. Monofloral honeys were obtained in spring with dominant pollen of Eugenia uniflora (dominant pollen range: 45% - 85%), Neltuma sp. (45% - 61%), Geoffroea decorticans (52%) and Sarcomphalus mistol (47%). At the end of spring and beginning of summer, monofloral honeys were identified with the dominant pollen of Copernicia alba (50% - 98%), while at the end of summer with the pollen of Schinopsis balansae (45% - 68%) and Tessaria integrifolia (52%). The botanical families most represented in the honeys were: Anacardiaceae, Arecaceae, Myrtaceae, and Rhamnaceae. The pollen spectrum of Formosa honeys showed the diversity and floristic richness that characterizes the vegetation of the native forest and wetland areas.

Formicidae (Hymenoptera) from the Humid Chaco ecoregion: inventory of species, new records, and pictorial keys for subfamilies and genera identification

Formicidae (Hymenoptera) from the Humid Chaco ecoregion: inventory of species, new records, and pictorial keys for subfamilies and genera identification

Diet and Habitat of the Scorpion Mud Turtle (Kinosternon scorpioides scorpioides) in the Southern Limit of the Species' Distribution (Argentina)

In this study we describe some ecological features of Kinosternon scorpioides scorpioides from a section of the Argentina's Chaco ecoregion encompassing the provinces of Salta, Chaco, and Formosa, including the description of the capture sites and an analysis of the feeding ecology of the species. Six field trips were made during the spring and summer months from 2016 to 2020. We captured 23 turtles: 8 in Salta, 8 in Chaco, and 7 in Formosa; all corresponding to the dry portion of the Chaco ecoregion. They were found in a variety of aquatic environments (including those with considerable waste and human disturbance), and they also seemed to tolerate some fragmentation of the forest matrix. The analysis of 20 stomach contents and 14 fecal samples corroborated that K. s. scorpioides is predominantly an opportunistic omnivore, capable of feeding upon a diverse variety of invertebrates, some small vertebrates, and large volumes of vegetal material. The present study provides some baseline information about habitat requirements and feeding habits of the southernmost known populations of K. s. scorpioides.

Influence of Prey Availability in the Dissimilarity of Predator–Prey Interactions

Photo 1. Majority of anurans feed on arthropods, like the Oval Frog (Elachistocleis matogrosso), an ant specialist. Photo credit: Karoline Ceron. Photo 2. But there are some exceptions, such as the Cranwell's horned frog (Ceratophrys cranwelli), a voracious predator, attempting predation upon a Pigmy Toad (Rhinella bergi) in Brazilian Chaco. Photo credit: Karoline Ceron. Photo 3. Anuran diet can vary throughout space, for example, between ecoregions. Nhecolândia, a subregion of the Pantanal, is characterized by the coexistence of thousands of lakes called baías (freshwater) and salinas (waters of alkaline composition; upper panel), in contrast, the Chaco ecoregion has a flat topography, a semiarid climate, and distinct plant formations (lower panel). Photo credit: Karoline Ceron. Photo 4. Also, the anuran diet can vary throughout time, for example, between seasons. Brazilian Cerrado, a seasonal ecoregion, at the RPPN Estância Mimosa, Mato Grosso do Sul, Brazil, during the rainy season (upper panel) and the dry season (lower panel). Photo credit: Karoline Ceron. Photo 5. Studying these variations in time and space, we found that the dissimilarity of the anuran-prey network between ecoregions and seasons is primarily driven by interaction rewiring, which is determined by the variation in prey availability. A waxy monkey frog (Phyllomedusa sauvagii) in the RPPN Estância Mimosa, Mato Grosso do Sul, Brazil. Photo credit: Karoline Ceron. These photographs illustrate the article “Differences in prey availability across space and time lead to interaction rewiring and reshape a predator–prey metaweb” by Karoline Ceron, Diogo B. Provete, Mathias M. Pires, Andrea C. Araujo, Nico Blüthgen, and Diego J. Santana published in Ecology. https://doi.org/10.1002/ecy.3716

Talking about trees: the territorial classification of native forests in the Argentinian Chaco

Deforestation represents an important contributor to climate change. For this reason, identifying conditions that enable the adoption of policies halting or reversing this process is crucial to avoid catastrophic climate change. The Argentinian Gran Chaco is a hotspot of deforestation, mainly due to the expansion of capital-intensive agriculture. In Argentina, the introduction of the national forest law (NFL) represents an important step to protect the remaining forests. However, in the Chaco ecoregion, the implementation of the NFL by the different provinces is extremely heterogeneous. Previous research has provided rich descriptions of the dynamics behind the implementation of the NFL. Yet this research, mainly based on qualitative approaches, does not allow for a systematic analysis of the conditions leading to more or less stringent implementations of the NFL. To address this gap, we first combine the socio-ecological systems framework with historical materialism to generate a plausible hypothesis for the heterogeneous implementation of the NFL across the 12 different provinces of the Argentinian Chaco. Specifically, we hypothesise that it is the differences in contextual factors (i.e. differences in forest cover), material/economic conditions (i.e. presence and extent of capital-intensive agriculture) and the strength of pro- and anti-deforestation coalitions, which lead to a heterogeneous territorial classification of native forests across the various provinces. Subsequently, we test the hypothesis by developing thorough case studies via qualitative comparative analysis. This approach allows us to study in a more systematic way the reasons for the observed institutional heterogeneity. The results show that the proportion of native forests characterised as of low conservation value reflects both the environmental context (i.e. the extent of native forests) as well as the material/economic conditions (i.e. the extent of capital-intensive agriculture) and the presence of strong pro-deforestation cultures, expressed via pro-deforestation coalitions.