Controlling a pest species raises questions about the harmful effects its eradication could cause in ecosystems. Currently, in Uruguay are being analyzed strategies to eradicate the New World Screwworm (NWS), Cochliomyia hominivorax (Diptera: Calliphoridae), an obligatory ectoparasite that causes myiasis in warm-blooded vertebrates, including humans. The loss of a species implies a risk of secondary extinctions and cascading effects that depend on the ecological function of the species and the capacity of the rest of the species with which it interacts to compensate for its loss. To assess the ecological impact of the NWS eradication, we analyzed its ecological redundancy, its effect as an indirect regulatory agent for other species, and its participation in critical ecosystem functions. We conclude that the NWS presents high functional redundancy in most ecological interactions. It does not play an essential role as a regulatory agent of other species and does not play an important role in critical ecosystem functions. Without ignoring the information gaps that certainly exist about the ecological interactions network of the NWS in Uruguay, we estimate that its eradication is unlikely to cause secondary extinctions or cascading effects in the networks it integrates. In order to timely detect possible impacts during the course of the program, it is recommended to monitor the ecosystems using indicators related to direct and indirect partners in the ecological interactions of the NWS.

Hudson's Canastero, Asthenes hudsoni (Furnariidae) is a secretive passerine from the Rio de la Plata grasslands of South America. It is considered near threatened, but little is known about its distribution and seasonal movements. We performed a thorough revision of historical and recent records of the species and estimated its original and current geographic distribution using niche modeling based on climatic and land cover information. We found that A. hudsoni is not widespread across the Rio de la Plata grasslands but mostly restricted to the humid pampas in Argentina, with isolated populations in central Argentina and SE Brazil. Most records north of the humid pampas in Argentina and Uruguay correspond to wintering individuals, revealing that the species is a partial seasonal migrant. Our distribution models indicate that its original area of occupancy may have been reduced by 65% to a current similar to 50,000 km(2), with a stronghold in the flooding Pampas in eastern Buenos Aires province. However, because of the specific microhabitat requirements of the species, we suspect that this figure underestimates the extent of appropriate habitat available, and that A. hudsoni could be very close to the threshold of area of occupancy for vulnerable species under IUCN criteria. Further research on habitat requirements, distribution, and population trends are urgently needed.

The palaeolimnological conditions of Mirim Lagoon, a large coastal shallow lagoon under the influence of historical human impacts related to the development of the primary sector of the economy were reconstructed. The first significant human impact consisted of locking the estuarine system to induce the transition from brackish to freshwater conditions. During this transition, the sedimentation rate consistently increased from pre-disturbance values of 0.25 cm yr-1 to >1 cm yr-1. A concomitant increase in nitrogen and carbon values was recorded indicating a related eutrophication process. The highest nutrient levels were achieved during the 1990s after the incorporation of cutting-edge technologies for agricultural production such as high-yielding varieties of rice resistant to climate variability and pests, and the use of inorganic fertilisers, pesticides and water supply controlled by irrigation. After 2011, the soybean production boosted and the area cultivated with this oilseed equalled the area of rice paddies, i.e., 2 × 105 ha. A sharp decrease in δ13C from -19 to -24‰ and in δ15N from 6 to 2‰ were observed in the sedimentary record, indicating a major shift in the composition of the organic matter after the agricultural intensification. Trace elements Cr, Cu, Ni and Zn showed a high positive correlation with Al and Fe, and enrichment factors near 1, indicating a natural and terrigenous source of these elements and also unpolluted conditions. However, the increase of As after 1990 and the positive correlation with Pb was associated with agricultural practices. All elemental ratios (K/Al, Ti/Al and V/Cr) showed constant pre-disturbance trends and a turning point ca. the 1990s. Microplastics were detected from the beginning of the 1990s and increased towards recent sediments, thus corroborating an anthropogenically impacted scenario. Therefore, the development of the primary sector of the economy exerted clear impacts on the environmental quality of the system.

The Río de la Plata (RdlP) mud depocenter is an outstanding centennial ultra-high-resolution information source of hydroclimatic variability and terrigenous export because sedimentation attains values of 13 mmyr−1. Thus, our main objective was to inter-compare and correlate the direct hydroclimatic observations to the proxy record from the RdlP mud depocenter. We correlated continental input and marine productivity proxies to the instrumental historical hydroclimatic observations, and determined the associated periodicity and coherences of such environmental processes by means of wavelet analyses. We discuss the results in the context of both natural climate variability and anthropogenic impacts within the RdlP drainage basin. To this end, we performed a 210Pb and 14C mixed age-depth model and μXRF scanning (every 2 mm), and used Ti/Al and Ba/Al as proxies for continental input and marine productivity changes. We incorporated instrumental observations, i.e., rainfall, river discharges and climate variability modes (CVM) such as: El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). The statistical correlation analyses indicated a consistent correspondence between both proxies and rainfall anomalies for the warm season within the lower Paraná drainage basin. Such rainfall anomalies are dominated at inter-annual, decadal and multi-decadal scales by ENSO, PDO and AMO modes of variability, respectively, which together modulated river flow. Thus, centennial hydrological and proxy variability appear to be mainly modulated by the CVM. In this sense the present study is in close agreement and complementary to previous worldwide studies by showing similar results for RdlP drainage basin. We further identified a strong change in the proxy data after 1970s; i.e., the highest continental input and marine productivity record, and we related it to the combined effect of climatic variability and anthropogenic impact. Such a period is related to a dominance of positive ENSO (El Niño events) and PDO, and negative AMO, leading to increased rainfall and runoff over the drainage basin, together with intensified agricultural practices. The strong intensification of agricultural activities, mostly soy beans, together with increasing rainfall and runoff led to increased soil erosion and sediment transport, whose final fate is the RdlP mud depocenter.