Andes Research Articles

Using the RedList of Ecosystems andthe Nature-based Solutions Global Standard as an integrated process for climate change adaptation inthe Andean high mountains.

Under anthropogenic pressures and climate change, most ecosystems are showing signs of reduced resilience. Unfortunately, some are more at risk of collapse and, without interventions, they may lose biodiversity, ecological integrity and ecosystem services. Here, we describe two tools that were developed under the auspices of the International Union for Conservation of Nature,the RedList of Ecosystems and the Nature-based Solutions Global Standard, and their capacity to first identify the ecosystems at risk of collapse in a nation and then develop solutions based on nature to improve their resilience. Nature-based solutions include, for example ecosystem-based adaptation, where solutions are developed to meet the needs of the local people while protecting nature to ensure greater resilience of the social-ecological system, not only the natural ecosystem. We discuss through a case study in the Andean high mountains and páramo social-ecological system how these approaches have been used in Colombia. We then discuss lessons learned and challenges that may reduce the capacity of a community to initiate such interventions, such as national policies and funding restrictions. We also discuss through another early case in Ecuador the importance to adapt these types of interventions to the geographical and cultural context of the social-ecological systems. This article is part of the theme issue 'Bringing nature into decision-making'.

Discrimination of tectonic provinces using zircon U-Pb ages from bedrock and detrital samples in the northern Andes

Abstract The northern Andes of southern Colombia contain a rich geologic history recorded by Proterozoic to Cenozoic metamorphic, igneous, and sedimentary rocks. The region plays a pivotal role in understanding the evolution of topography in northwestern South America and the development of large river systems, such as the Amazon, Orinoco, and Magdalena rivers. However, understanding of the basement framework has been hindered by challenging access, security concerns, tropical climate, and outcrop scarcity. Further, an insufficient geochronologic characterization of Andean basement complicates provenance interpretations of adjacent basins and restricts understanding of the paleogeographic evolution of southern Colombia. To address these issues, this paper presents a zircon U-Pb geochronological dataset derived for 24 bedrock samples and 19 modern river samples. The zircon U-Pb results reveal that the Eastern Cordillera of southern Colombia is underlain by basement rocks that originated in various tectonic events since ca. 1.5 Ga, including the accretion of discrete terranes. The oldest rocks, found in the Garzon Massif, are high-grade metamorphic rocks with contrasting Proterozoic protolith crystallization ages. Whereas the SW part of the massif formed during the Putumayo Orogeny (ca. 1.2–0.9 Ga), we report orthogneisses for the NE segment with protoliths formed at ca. 1.5 Ga, representing the NW continuation of the Rio Negro Jurena province of the Amazonian Craton. In contrast, crystalline rocks of the Central Cordillera primarily consist of Permian–Triassic (ca. 270–250 Ma) and Jurassic–Cretaceous (ca. 180–130 Ma) igneous rocks formed in a magmatic arc. In southernmost Colombia, the Putumayo Mountains mainly consist of Jurassic–Cretaceous (180–130 Ma) plutonic and volcanic rocks. Furthermore, we analyzed the heavy mineral abundances in modern river sands in southern Colombia (spanning 1°N–5°N) and found that key minerals such as garnet and epidote can be utilized to trace high-grade metamorphic and igneous lithologies, respectively, in the river catchments. The differentiation of basement ages for separate tectonic provinces, combined with heavy mineral abundances in modern sands, can serve as unique fingerprints in provenance analyses to trace the topographic and exhumational evolution of different Andean regions through time.

Implications of human–wildlife conflict on the diet of an endangered avian top predator in the northern Andes

Conflicts between rural people and the Endangered Black-and-chestnut Eagle (Spizaetus isidori) are a prominent conservation concern in the northern Andes, as at least 60 eagles were poached between 2000 and 2022 in response to poultry predation. Here, we conducted direct observations to analyze the Black-and-chestnut Eagle diet and evaluated how forest cover affects the feeding habits of the species during nestling-rearing periods in 16 nests located in different human-transformed Andean landscapes of Ecuador and Colombia. We analyzed 853 prey items (46 species) delivered to nestlings. We used Generalized Linear Models to test whether the percent forest cover calculated within varying buffer distances around each nest and linear distances from the nest to the nearest settlement and pasture areas were predictors of diet diversity and biomass contribution of prey. Forest cover was not a factor that affected the consumption of poultry; however, the eagle regularly preyed on chickens (Gallus gallus) (i.e., domestic Galliformes) which were consumed by 15 of the 16 eagle pairs, with biomass contributions (14.57% ± 10.55) representing 0.6–37% of the total prey consumed. The Black-and-chestnut Eagle is an adaptable generalist able to switch from mammalian carnivores to guans (i.e., wild Galliformes) in human-dominated landscapes, and eagles nesting in sites with low forest cover had a less diverse diet than those in areas with more intact forests. Management actions for the conservation of this avian top predator require studies on the eagle’s diet in areas where human persecution is suspected or documented, but also maintaining forest cover for the wild prey of the species, development of socio-economic and psychological assessments on the drivers behind human-eagle conflicts, and the strengthening of technical capacities of rural communities, such as appropriate poultry management.

Variability of the Southern Andes rain shadow

The southern Andes mountain range plays a determinant role in separating humid Chilean climate from dry Argentinian climate. However, there is substantial event-to-event variability in rain shadow strength, such that some precipitation events are able to produce significant spillover precipitation over the Argentinian side. This study investigates the mechanisms modulating the rain shadow strength across the Southern Andes. Rain gauge measurements from Chile and Argentina were used to classify events according to their rain shadow strength, as strong rain shadow (SRS) or weak rain shadow (WRS). ERA5 reanalysis was used to analyze synoptic conditions during these events. Differences between events show that the 0 °C isotherm is higher during SRS events. SRS cases exhibit a larger windward deceleration of cross-barrier wind than WRS events, indicating a blocking signature. Strong mountain wave activity increases precipitation upwind of the Andes and suppresses precipitation on the lee for SRS events, while WRS events exhibit weaker wave activity. Zonal moisture flux offshore is larger for SRS events than for WRS. Analysis of the drying ratio suggests that more water vapor is precipitated out or deflected by the mountains and does not reach the leeside in the SRS events compared to WRS events. The following mechanisms controlling the rain shadow strength are suggested: (1) A higher 0 °C causes more liquid precipitation to fall upstream and over the windward slope of the Andes for SRS events, while WRS cases with a lower 0 °C level allow ice particles and snow at the top of the mountain to be advected to the leeside, decreasing the rain shadow, (2) the low-level impinging flow is blocked by the Andes during SRS events, forcing the flow to rise upstream, increasing precipitation upwind and on the windward slope of the Andes, increasing the rain shadow, (3) leeside descent for SRS events suppresses precipitation on the leeside, while weaker wave activity for WRS cases allows for spillover precipitation decreasing the rain shadow, (4) SRS events that are also characterized by strong orographic enhancement could be produced by the landfall of atmospheric rivers to the area, increasing precipitation upstream and decreasing the rain shadow, as a result of the northerly orientation of the flow in contrast with the more zonal orientation of WRS cases.

Opportunity begets opportunity to drive macroevolutionary dynamics of a diverse lizard radiation.

Evolution proceeds unevenly across the tree of life, with some lineages accumulating diversity more rapidly than others. Explaining this disparity is challenging as similar evolutionary triggers often do not result in analogous shifts across the tree, and similar shifts may reflect different evolutionary triggers. We used a combination of approaches to directly consider such context-dependency and untangle the complex network of processes that shape macroevolutionary dynamics, focusing on Pleurodonta, a diverse radiation of lizards. Our approach shows that some lineage-wide signatures are lost when conditioned on sublineages: while viviparity appears to accelerate diversification, its effect size is overestimated by its association with the Andean mountains. Conversely, some signals that erode at broader phylogenetic scales emerge at shallower ones. Mountains, in general, do not affect speciation rates; rather, the occurrence in the Andean mountains specifically promotes diversification. Likewise, the evolution of larger sizes catalyzes diversification rates, but only within certain ecological and geographical settings. We caution that conventional methods of fitting models to entire trees may mistakenly assign diversification heterogeneity to specific factors despite evidence against their plausibility. Our study takes a significant stride toward disentangling confounding factors and identifying plausible sources of ecological opportunities in the diversification of large evolutionary radiations.

Deep-seated crustal faults and their role in the thermo-tectonic evolution of an active mountain belt: New evidence from the Northern Andes

Deep-seated structures can exhume deep crustal rocks (>20 km), transmitting the signal of geodynamic processes from the subduction zone to the interiors of the continents. The role of deep-seated structures can be analyzed with low-temperature thermochronological dating techniques. However, studies coupling low-temperature thermochronology with structural geological analyses of the deformational style are not common in the Northern Andes. In this contribution, we present new apatite (AFT) and zircon (ZFT) fission-track data coupled with meso- and microstructural analyses to reveal the deformational and exhumation history of the Santander Massif (SM; Northern Andes) and the related cortical Bucaramanga strike-slip fault (BF). Samples for thermochronological analyses were collected along an elevation profile with a significant elevation difference of 2.4 km across the western flank of the SM, crossing the BF. The time-temperature history modeling of ZFT data reveals phases of prolonged residence in the zircon partial annealing zone from ∼125 to 94 Ma and a cooling phase related to an exhumation episode at around 25 Ma based on samples collected near the BF. Inverse modeling of AFT data reveals structurally-controlled Pliocene exhumation rates of 0.6–0.7 km/Myr mediated by the action of secondary faults. A shift in the deformation style resulting from the oblique interaction of the SM and Mérida Andes domain is interpreted as the main driver of the Pliocene exhumation. This deformation phase is observed in the fault damage zone, where evidence of brittle-ductile deformation was exhumed. Finally, we discuss the geodynamic implications of our thermochronological and structural analyses, contrasting local and more regional competing hypotheses (Pamplona Indenter vs. slab break-off of the Caribbean plate), which may explain the tectonic evolution of the northern part of the Eastern Cordillera and the SM in the Colombian Northern Andes.

Water Quality Index and Health Risks in a Peruvian High Andean River

Water Quality Index and Health Risks in a Peruvian High Andean River

Spatio-temporal evaluation of metals and metalloids in the water of high Andean livestock micro-watersheds, Amazonas, Peru

Cattle ranching is a fundamental economic activity in northern Peru, where proper management of water resources is crucial. This study, a pioneer in the region, evaluated water quality and its suitability for human consumption, vegetable irrigation, and livestock production. It is also the first study to document the presence of metals and metalloids in vulnerable areas because they are located at the headwaters of river watersheds. The spatiotemporal evaluation of physicochemical parameters, metals, and metalloids was performed in five micro-watersheds (Cabildo, Timbambo, Pomacochas, Atuen, and Ventilla) from water samples collected in the dry season (October 2017) and wet season (March 2018). The parameters were analyzed using microwave plasma atomic emission spectrometry. The results were contrasted with international and Peruvian quality standards related to dairy cow production. The highest values of pH, total dissolved solids, and electrical conductivity were reported during the dry season, and the highest turbidity during the wet season. Of the metals evaluated, arsenic (As) was omnipresent in all the micro-watersheds, followed by lead (Pb).In contrast to World Health Organization regulations, concentrations of As, cadmium (Cd), Pb, and iron represent a risk; according to Peruvian regulations, As and Pb exceed the concentrations established for use in animal drinking water and vegetable irrigation, and according to water guidelines for dairy cattle, concentrations of As, Pb, Cd, and Al exceed the permitted limits. The high concentrations of these metals in the study area are attributable to a synergy between natural factors, such as Andean geology and livestock activity. The data reported will allow for proper water resource management, pollution prevention, and the design and adoption of mitigation measures.

Fracture evaluation of the plutonic basement in the Upper Magdalena Basin: Implications for the development of naturally fractured reservoirs in the Northern Andes

Plutonic rocks typically have negligible matrix porosity and permeability. However, fractures and mineral alterations create storage space and flow pathways that turn plutonic rocks into fluid reservoirs. Despite significant hydrocarbon discoveries, naturally fractured reservoirs in plutonic rocks have been poorly studied. In most Colombian basins, the crystalline basement has undergone multiple deformational events and is thrust over the Cretaceous to Cenozoic source and reservoir rocks of the conventional petroleum system. This structural configuration is ideal for the migration of oil into a fractured basement. A multiscale fracture analysis, including field, petrographical and petrophysical techniques was conducted on the Permian and Jurassic plutonic basement of Upper Magdalena Basin in order to understand the controls on brittle deformation, the development of fracture networks and their potential to form hydrocarbon reservoirs. The results indicate that protolith textures and structures, including magmatic and mylonitic foliation, favours fracturing. Dykes exhibit higher fracture density (7–48 fractures/m), porosity (mean = 0.4%) and permeability (mean = 125,818.75 mD) than the host rock (2–25 fractures/m; 0.23%; 12,066.09 mD). Intersection zones from regional faults, are characterized by the highest fracture and lineament intensity. Our results suggest that dyke swarms and interacting damage zones can significantly enhance the reservoir quality of plutonic rocks by providing storage in fractures and fluid pathways to the host rock.

The political ecology of justice outcomes of lithium mining: The case of Salar del Hombre Muerto, Argentina

Electromobility and lithium-ion batteries are seen as key for the global energy transition, but injustices have been identified in several stages of the life cycle of electric vehicles, particularly in the resource extraction stage. Little is known about the micropolitics driving the acceptance or contestation of lithium mining by communities directly affected by this activity in the highland Andes of South America. In this paper, we explore complaints and demands made by communities living near Salar del Hombre Muerto, a salt flat in the Argentinian province of Catamarca where lithium has been extracted for decades. Having collected ethnographic data from conversations with affected communities and during public meetings and hearings, we applied a coding process using political ecology and energy justice conceptual frameworks. This led to the identification of place-based complaints and demands associated with distributive, procedural, and recognition justice. We further discuss our findings in terms of recent literature on lithium mining to provide explanations of the justice outcomes identified. Although lithium mining may not be the sole cause of (at least some of) these injustices, it nevertheless generates expectations and catalyzes attempts to end marginalization in areas where local and regional institutions are incapable of doing so.

Neogene erosion surfaces and the Andean uplift in northern Peru

The Andean flank in central Peru is characterized by stepped profiles involving up to 20 surfaces and pediments resulting from multiple episodes of uplift and erosion. The study area exhibits the same sequence of surfaces and pediments. The erosional features are also recognized in the Eastern Cordillera in northern Peru. This paper focuses on the seven highest features in the range c. 2800–4700 m. Remnants of the four surfaces higher than 3800 m, which were formed during the interval c. 18–12 Ma, are only found south of latitude 6–6.5° S. The Miocene metallogenic belt associated with the Western Cordillera terminates abruptly at that same latitude. The area north of c. 6° S does not have any features higher than c. 3500 m, which is interpreted as indicating a later initiation of uplift. It also lacks any sign of magmatic activity. On the basis of these factors, the Central Andes are considered to terminate at c. 6° S, the ranges to the north being assigned to the Northern Andes. Once episodic uplift was initiated in the area north of 6° S, it continued at the same rhythm as in the region to the south. There was no apparent change in the pattern of episodic uplift when the normal subduction regime changed to a flat-slab regime at c. 11 Ma, probably as a result of the subduction of the Inca Plateau. The distribution of the erosion surfaces indicates that episodic uplift affected the whole of the Andean Block in northern Peru. It appears that the individual episodes occurred simultaneously and produced the same amount of uplift over the whole width of the cordilleras. There is no sign of any interruption in the process, implying a continuous orogeny from the Mid-Miocene onwards.

Gymnetis litigiosa Gory & Percheron, 1833 (Coleoptera: Scarabaeidae: Cetoniinae: Gymnetini): first occurrence of this exotic species in Chile

The subfamily Cetoniinae, the genus Gymnetis MacLeay, and the species Gymnetis litigiosa Gory & Percheron are recorded for the first time in Chile, based on specimens collected in the cities of San Felipe de Aconcagua, Los Andes (Valparaíso Region) and Santiago (Metropolitan Region). This new record increases to four the number of exotic scarab beetles introduced and established in the country and extends the known distribution area of the species to the western slope of the Andes mountain range. A brief diagnosis for recognition of the species, adult photographs, distribution, and natural history data are provided. The possible route of entry of this cetoniid into Chile is discussed.

Identification of priority areas for the restoration of high Andean mountain forests under climate change: a case study using potential distribution models

Paleontological studies in the central Andes have uncovered the vulnerability of Polylepis forests to climate shifts, attributed to limited seed dispersal capabilities and the rugged terrain. Given the ecological significance of these forests‐forming species as biodiversity hotspots and carbon sinks, their restoration is imperative for the preservation of endemic species and ecosystem services. At the extreme south of the genus' range, we find Polylepis australis, a forest‐forming tree species endemic to Argentina and uniquely extending beyond the Andes into the Sierras Grandes of the Córdoba province. This study utilizes potential distribution models to help inform on restoration strategies considering projected future climate scenarios. Employing Maxent 3.4.3 with 453 presence locations, we estimated a present potential distribution spanning 13,923 km2. Our analysis of future climate projections reveals important poleward contractions alongside minor uphill shifts (20 m above sea level), ultimately resulting in a net habitat loss of 4596 km2 (34%). This underscores the critical role of climate simulations in identifying species specific priority sites for restoration efforts and also highlighting Polylepis forests susceptibility to both climate change and anthropogenic impacts.

Association between Gait Speed and Balance Disorders in Older Adults from 12 High Andean Peruvian Communities, 2013-2019.

Gait speed is associated with a higher prevalence of balance disorders in older adults residing at high altitudes. This study investigated this association in older adults from 12 high-altitude Andean Peruvian communities. We performed a secondary data analysis from an analytical cross-sectional study of adults >60 years of age, residing in 12 high-altitude Andean Peruvian communities, enrolled between 2013 and 2019. The exposure and outcome variables were gait speed (categorized in tertiles), and balance disorders (defined as a functional reach value of ≤20.32 cm), respectively. We built generalized linear models of the Poisson family with a logarithmic link function and robust variances, and estimated crude prevalence ratios (cPR) and adjusted prevalence ratios (aPR) with 95% confidence intervals (CIs). We analyzed 418 older adults; 38.8% (n=162) were male, and the mean age was 73.2±6.9 years. The mean gait speed and functional reach were 0.66±0.24 m/s and 19.9±6.48 cm, respectively. In the adjusted regression model, the intermediate (aPR=1.88; 95% CI, 1.39-2.55; p<0.001) and low (aPR=2.04; 95% CI, 1.51-2.76; p<0.001) tertiles of gait speed were associated with a higher prevalence of balance disorders. The intermediate and low tertiles of gait speed were associated with a higher prevalence of balance disorders among older adult residents of 12 high-altitude Andean communities. We recommend further research on the behavior of this association to propose interventions for these vulnerable groups and reduce the impact of geriatric conditions.

Acute hypoxia exposure rapidly triggers behavioral changes linked to cutaneous gas exchange in Lake Titicaca frogs

Ventilation is critical to animal life—it ensures that individuals move air/water across their respiratory surface, and thus it sustains gas exchange with the environment. Many species have evolved highly specialized (if not unusual) ventilatory mechanisms, including the use of behavior to facilitate different aspects of breathing. However, these behavioral traits are often only described anecdotally, and the ecological conditions that elicit them are typically unclear. We study one such “ventilation behavior” in Lake Titicaca frogs (Telmatobius culeus). These frogs inhabit high-altitude (i.e., low oxygen) lakes in the Andean Mountains of South America, and they have become textbook examples of cutaneous gas exchange, which is essentially breathing that occurs across the skin. Accordingly, this species has evolved large, baggy skin-folds that dangle from the body to increase the surface area for ventilation. We show that individuals exposed to acute hypoxic conditions that mirror what free-living individuals likely encounter quickly (within minutes) decrease their activity levels, and thus become very still. If oxygen levels continue to decline, the frogs soon begin to perform push-up behaviors that presumably break the low-oxygen boundary layer around skin-folds to increase the conductance of the water/skin gas exchange pathway. Altogether, we suspect that individuals rapidly adjust aspects of their behavior in response to seemingly sudden changes to the oxygen environment as a mechanism to fine tune cutaneous respiration.

Structural geology of El Peñón karst system along an anticlinorium of the northern Andes, Colombia

Structural control is one of the most important factors in developing the karstic system since the fractures facilitate the infiltration and circulation of groundwater. This accelerates the mineral dissolution processes responsible for the formation of endo and exokarstic geomorphological features, such as sinkholes and underground cavities, among other landforms that characterize this environment. This study provides information on the structural geology of the El Peñón karstic system, considered one of the most significant and extensive karstic regions in Colombia. The karst is tectonically controlled by joints with a preferential NW-SE orientation and cleavage planes with an NE-SW trend, guiding the development of drainage systems, closed depressions, and underground cavities. The stress tensor obtained with a NW-SE direction (127°) explains the deformation in the area and its influence on the development of the karstic system. It was also established that the potential groundwater flow occurs through open fractures with a direction of 120°–130° (parallel to the stress tensor) and along the cleavage planes (40°–50°). The fracture patterns are characterized by intermediate intensity values, predominantly low fracture density, minimal lengths, and good connectivity between fracture planes.

Oligocene to Miocene magmatic and hydrothermal evolution in the Maricunga belt (Región de Copiapó, Chile): A new look to a long known metallogenic belt

The Maricunga metallogenic belt, herein defined to encompass the region from 25° S to 28° S along the Cordillera Frontal of northern Chile, is known for hosting a series of gold-copper and lesser copper-molybdenum porphyries and gold-silver epithermal systems that are hosted in a segment of the late Oligocene-Miocene Andean calc-alkaline magmatic arc. Based on an up-to-date geochronological database, four episodes of magmatism and related hydrothermal deposits are proposed to characterize intensity and style of volcanism and hypabyssal intrusive rocks over time. The late Oligocene episode (26-21 Ma) is characterized by stratovolcanoes, dome complexes, pyroclastic sequences, and hypabyssal intrusives of andesitic to dacitic composition that host gold-rich porphyry systems such as Caspiche, Maricunga, and La Pepa. The early Miocene episode (21–17 Ma) has similar rock types but is volumetrically reduced, hosting epithermal and porphyry deposits like La Coipa and Caserones, respectively. A reinvigoration of volcanism occurred during the third stage between 17 and 11 Ma, giving rise to large volcanic complexes and intra-to extra-caldera ignimbritic deposits that host several gold-rich porphyry deposits such as Lobo-Marte, Luciano, and Cerro Casale; as well as epithermal deposits such as Fenix. Some of the 17 to 11 Ma and younger igneous rock belong to the high-K calc-alkaline series, showing a higher alkali content compared to previous periods. The last magmatic episode, from 11 to 5 Ma, coincides with the shallowing of the subduction angle and is characterized by an eastward migration of volcanism, and more heterogeneous rocks including trachytic compositions. During this period mineralization was emplaced at the Salares Norte epithermal deposit and El Volcan porphyry Au–Cu deposit.Porphyry and epithermal systems formed throughout the evolution of the Maricunga belt. Overprint of advanced argillic alteration on porphyry style alteration is widespread albeit commonly devoid of significant addition of epithermal Au–Ag mineralization. The Au-rich nature of the majority of the porphyry systems is attributed to the shallow crustal depths of emplacement compared to Cu- and Mo-rich porphyry systems. Conversely, high-sulfidation epithermal Au–Ag deposits such as La Coipa and Nueva Esperanza are not known to be telescoped on coeval porphyry gold deposits.The location of the mineralized centers was favored by crustal weaknesses expressed by intersection of oblique- and parallel-to arc structures, the former inherited from the construction of the continent before to the formation of the Andean range. The arc oblique structures also segment the Maricunga belt into domains with unique magmatic and hydrothermal styles.

The Andes–Amazon–Atlantic pathway: A foundational hydroclimate system for social–ecological system sustainability

The Amazon River Basin’s extraordinary social–ecological system is sustained by various water phases, fluxes, and stores that are interconnected across the tropical Andes mountains, Amazon lowlands, and Atlantic Ocean. This “Andes–Amazon–Atlantic” (AAA) pathway is a complex hydroclimatic system linked by the regional water cycle through atmospheric circulation and continental hydrology. Here, we aim to articulate the AAA hydroclimate pathway as a foundational system for research, management, conservation, and governance of aquatic systems of the Amazon Basin. We identify and describe the AAA pathway as an interdependent, multidirectional, and multiscale hydroclimate system. We then present an assessment of recent (1981 to 2020) changes in the AAA pathway, primarily reflecting an acceleration in the rates of hydrologic fluxes (i.e., water cycle intensification). We discuss how the changing AAA pathway orchestrates and impacts social–ecological systems. We conclude with four recommendations for the sustainability of the AAA pathway in ongoing research, management, conservation, and governance.

Atmospheric black carbon observations and its valley-mountain dynamics: Eastern cordillera of the central Andes of Peru

Glacial bodies in the Peruvian Andes Mountains store and supply freshwater to hundreds of thousands of people in central Peru. Atmospheric black carbon (BC) is known to accelerate melting of snow and ice, in addition to contributing to air pollution and the health of people. Currently there is limited understanding on the sources and temporal variability of BC in valley and mountain environments in Peru. To address this problem, this study combined surface observations of BC collected during 2022–2023 with WRF model simulations and HYSPLIT trajectories to analyze the dispersion and sources of BC in valley and high elevation environments and the associated local atmospheric circulations. Results show high BC concentrations are associated with the valley-mountain wind system that occurs on both sides of the Huaytapallana mountain range. A pronounced circulation occurs on the western slopes of Huaytapallana when concentrations of BC increase during daylight hours, which transports atmospheric pollutants from cities in the Mantaro River Valley to the Huaytapallana mountain range. Low concentrations of BC are associated with circulations from the east that are channeled by the pronounced ravines of the Andes-Amazon transition. On average, during the season of highest BC concentrations (July–November), the relative contributions of fossil fuels are dominant to biomass burning at the valley observatory and are slightly lower at the Huaytapallana observatory. These results demonstrate the need to promote mitigation actions to reduce emissions of BC and air pollution associated with forest fires and local anthropogenic activity.

Reproductive behavior of Erythrodiplax abjecta (Rambur, 1842) from Andean Mountains

Research about the behavior of Neotropical species is crucial to understand how the rapid environmental changes in the Neotropics affect the reproduction of various organisms. The reproductive behavior of insects in tropical ecosystems, such as those belonging to the order Odonata, is as yet scarcely known. In this article, the reproductive behavior of Erythrodiplax abjecta is described from several localities in the Colombian Andean Mountains. Playing out between 10:00 and 14:30 h, male individuals of this species may exhibit either territorial or satellite behavior. Sexually mature males and females engage in tandem and copulation behaviors, which are brief and may occur either perched or in flight. Females of E. abjecta oviposit directly in the water at various times, alternating with periods of rest. During oviposition, males stand guard over females, perched or hovering, in a quest to protect them against other males. Conspecific males have been observed to engage in sieges of perching or ovipositing females, as well as mating pairs. Following a siege, either the female or the original pair flees, or the besieging male will succeed in outcompeting the original male, take the female in tandem, copulate with her, and then guard her while she oviposits. If the female flees, she may perch elsewhere, continue ovipositing, or may be taken by another male. The intense male guarding behavior during oviposition could represent an adaptation to temporarily high male densities at oviposition sites and a high level of competition during the short period in which active copulation takes place.