Jaime Pizarro’s research while affiliated with University of Santiago Chile and other places

Understanding the interaction between anthropogenic land use and the rainfall pattern can be crucial to predict changes in total suspended solids (TSS) in streams and rivers. We assessed the effects of land use and annual rainfall on the TSS load of 19 southern Chilean catchments. The results indicated that the concentration of TSS increased in catchments with a rainy regime and greater annual precipitation. TSS load also increased as the surface of open areas increased at the catchment scale and decreased with increasing cover of glaciers and perennial snow. However, we did not find support for models with interaction terms between climate and land use. Results suggest that a regional decrease in annual rainfall accompanied by an increase in the altitude of the zero isotherms, as predicted by climate models, should have multiple effects on TSS. In particular, increased TSS load can be expected from a contraction of glaciers and perennial snow areas as well as the intensification of new crops and urban expansion.

The level of specialization of endemic island birds to their native habitats could contribute importantly to increase their extinction risk. We used abundance obtained from mist-netting and radio telemetry data from one individual to determine the micro-habitat use pattern of Juan Fernandez Tit-tyrants (Anairetes fernandezianus) within native forest. The tracked male tit-tyrant established its home range exclusively in core native forest areas. Regression models of abundance and Resource Utilization Functions showed strong micro-habitat preferences of tit-tyrants. The abundance and utilization probabilities of tit-tyrants declined with distance to exotic shrub and increased with distance to human created gaps. Natural heterogeneity in micro-habitat conditions also affected the micro-habitat selection pattern, with use probabilities and abundance increasing with proximity to the humid sites dominated by Gunnera peltata. These findings demonstrate that tit-tyrants do not use native forest sites at random. Therefore, the conservation and recovery of the declining tit-tyrant population could be improved by incorporating such micro-habitat preferences in habitat management programs.

The level of specialization of endemic island birds to their native habitats could contribute importantly to increase their extinction risk. We used abundance obtained from mist-netting and radio telemetry data from one individual to determine the micro-habitat use pattern of Juan Fernandez Tit-tyrants (Anairetes fernandezianus) within native forest. The tracked male tit-tyrant established its home range exclusively in core native forest areas. Regression models of abundance and Resource Utilization Functions showed strong micro-habitat preferences of tit-tyrants. The abundance and utilization probabilities of tit-tyrants declined with distance to exotic shrub and increased with distance to human created gaps. Natural heterogeneity in micro-habitat conditions also affected the micro-habitat selection pattern, with use probabilities and abundance increasing with proximity to the humid sites dominated by Gunnera peltata. These findings demonstrate that tit-tyrants do not use native forest sites at random. Therefore, the conservation and recovery of the declining tit-tyrant population could be improved by incorporating such micro-habitat preferences in habitat management programs.

Local extinction of native species and colonization of non-native species are commonly invoked as responsible for changes in species similarity among biotas of different regions. In this study we used a model of species similarity between islands to assess the emergent, and unexplored, effects of changes in colonization by native species, extinction of non-native species, and propagule pressure on species similarity among insular communities. The model predicts that extinction probability of endemic species has a positive but asymptotic effect on species similarity, which is exacerbated by increasing colonization and reducing extinction of non-native species. Species similarity tends to increase with increasing colonization probability by non-native species, however this effect may be reduced, or even reverted, when the islands are exposed to an elevated number of non-native species that are prone to extinction, high levels of endemic species loss, and an initially large number of native species shared between islands. Species similarity was positively affected by the propagule pressure rate of non-native species only when their colonization and extinction probabilities were large and small enough, respectively. A negative effect of propagule pressure rate can be caused by an increase in the pool size of non-native species, which involves the introduction of different species into different islands, promoting biotic differentiation between islands. Our results indicate that the interactions between colonization, extinction and species pool lead to nonlinear responses and unexpected scenarios of biotic change. In order to validate model predictions, future research programs should focus on understanding the dynamics on such complex meta-communities where coexist native, non-native and endemic species.

Rivers of central-northern Chile are exposed to pollution from different sources, including mining activities, natural orogenic process, volcanic activity, and geology. In order to determine the contribution of mining to river pollution, the spatio-temporal dynamics of chemical species dissolved in 12 rivers of central-northern Chile was assessed. Of all the rivers studied, the Elqui showed the highest historical mean concentrations of As, Cu and Pb. The Aconcagua had the highest concentration of Hg and a large Cr concentration, while the Rapel showed elevated concentrations of Cu and Mo. The Elqui and the Aconcagua were clustered as distinct groups by a cluster analysis based on two independent principal components. Hierarchical Bayesian models showed annual trends but no seasonal effects in heavy metal concentrations. As and Cu in the Elqui had positive annual slopes. Sulphate concentration exceeded 100 mg L(-1) in nine rivers, and in seven of them it had positive annual slopes. Our findings suggest that mining pollution is the main process contributing to this increasing annual trend in As, Cu and SO(4)(2-). Therefore, in order to improve the water quality of these rivers it is necessary to identify the main sources of heavy metals associated with mining activities.

The World Wildlife Fund is facilitating a dialogue on impacts of salmon aquaculture. The goal of the dialogue is to establish the state of knowledge in seven subject areas associated with the industry: benthic impacts, nutrient loading, escapees, chemical inputs, diseases, feeds and social issues and to establish international standards for salmon aquaculture practices. Chemical inputs from salmon aquaculture include antifoulants, antibiotics, parasiticides, anaesthetics and disinfectants. The use and potential effects of these compounds are herein summarized for the four major salmon producing nations: Norway, Chile, UK and Canada. Regulations governing chemical use in each country are presented as are the quantities and types of compounds used. The problems associated with fish culture are similar in all jurisdictions, the magnitude of problems is not and the number of compounds available to the fish farmer varies from country to country. Unfortunately, the requirement to publically report chemical use is inconsistent among countries. Chemical use data are available from Norway, Scotland and parts of Canada. The government of Chile and some Canadian provinces, while requiring that farmers report disease occurrence, compounds prescribed and quantities used, do not make this information readily available to the public. The fact that these data are available from regulatory agencies in Scotland and Norway adds pressure for other jurisdictions to follow suit. Data such as these are essential to planning and conducting research in field situations.

Chilean basins have long been exposed to nutrient discharges from human activities and land use changes. A historical seasonal NO(3)(-)-N and PO(4)(3-)-P database of the last 23 years of the main nine rivers of central-southern region of Chile was analysed. Generalized additive models indicated that annual trends in NO(3)(-)-N and PO(4)(3-)-P are nonlinear. River basins such as Bío-Bío, Bueno, Imperial, Maule, Rapel and Valdivia showed a clear increase in NO(3)(-)-N, while PO(4)(3-)-P increased only in the Rapel and Maule basins. Although no seasonal difference in NO(3)(-)-N and PO(4)(3-)-P was found in the analysed basins, there was a negative relation between these nutrients and water flow. Sampling stations with high NO(3)(-)-N concentration were found mostly in sub-basins located in the "central valley" of central Chile, while several PO(4)(3-)-P "over-concentrated" sampling stations were located mostly upstream. If NO(3)(-)-N emissions into Chilean river basins continue at current rates it is probable that the concentration of this nutrient will tend to match that of the most "polluted" rivers around the world.

The Metropolitan Region of Santiago has been declared as nonattainment area for carbon monoxide (CO). The data was based on seven air monitoring stations that do not necessarily represent the real population exposure. Usually, a series of coefficients that relates the concentration of pollutants with health effects (betas of the concentration-response equations) are used. For the calculation of these betas, normally, a city average air pollution concentration is used; nevertheless, these betas do not necessarily represent the real risk of exposure that the inhabitants are experimented. For this reason, this study estimates two aspects that are unknown and that are necessary to policymakers in public health decisions. First, estimate the exposure at a lower spatial resolution level and, second, estimate a concentration-response curve that differs spatially and depends on the proportion of susceptible groups. We followed the Air Pollution and Health, European Approach/Spanish Multicenter Study on the Relationship Between Air Pollution and the Mortality methodology for the determination of the short-term health effect due to CO population exposure at the three spatial levels (city, zone, and county). We found that there are different risks in cardiorespiratory mortality in the group over 64 years old associated to an unequal exposure to CO in Santiago city. The higher risks are in counties located to the south-east of the city. These finding confirm the necessity to face, in a different way, the approach when evaluating control strategies and policy decision to control air pollution in Santiago.