Evaluation of the socio-economic impact of landcover / landuse changes in Owerri Municipal, Imo State, Nigeria using remote sensing and geographic information systems

The study aimed at evaluating the socio-economic impact of landcover / landuse changes in Owerri Municipal, Imo State, Nigeria using remote sensing and GIS with a view to improving the quality of life and social development through its objectives; to identify the changes of the landcover and landuse pattern of the study area for a period of 30 years i.e. 1987 to 2002 to 2017, to evaluate the socio-economic and environmental impact of these changes and to predict future impact of landcover / landuse changes in the study area. The methodology adopted in this study involved sourcing of satellite data from United States Geological Survey (USGS) for the period of years under study, social survey in Owerri Municipal Area for socio-economic impact monitoring. ArcGIS 10.5 and QGIS 2.9 software were used for data processing, analysis and presentation. The study observed a significant increase in built-up area from 1987 (34%) to 2017 (65%), on the contrary, there was a noticeable decrease in the class of bare land (26% to 12%) and vegetation. (37% to 15%) followed by water body which kept fluctuating as result of rainfall. Rapid population growth triggered by rural urban migration coupled with hasty socio-economic development were the main drivers of these changes. Results showed that remote sensing and GIS approach are recommended for further studies as the tools are efficient for landcover/landuse mapping.

A Novel Approach to Asteroid Impact Monitoring

Orbit-determination programs find the orbit solution that best fits a set of observations by minimizing the root mean square of the residuals of the fit. For near-Earth asteroids, the uncertainty of the orbit solution may be compatible with trajectories that impact Earth. This paper shows how incorporating the impact condition as an observation in the orbit-determination process results in a robust technique for finding the so-called virtual impactors, i.e., the regions in parameter space leading to impacts. The impact pseudo-observation residuals are the b-plane coordinates at the time of close approach and the uncertainty is set to a fraction of the Earth radius. The extended orbit-determination filter converges naturally to an impacting solution if allowed by the observations. The uncertainty of the resulting orbit provides an excellent geometric representation of the virtual impactor. As a result, the impact probability can be efficiently estimated by exploring this region in parameter space using importance sampling. The proposed technique can systematically handle a large number of estimated parameters, account for nongravitational forces, deal with nonlinearities, and correct for non-Gaussian initial uncertainty distributions. The algorithm has been implemented into a new impact-monitoring system at JPL called Sentry-II, after undergoing extensive testing. The main advantages of Sentry-II over the previous Sentry system are that Sentry-II can systematically process orbits perturbed by nongravitational forces and that it is generally more robust when dealing with pathological cases. The run times and completeness of both systems are comparable, with the impact probability of Sentry-II for 99% completeness being 3 × 10−7.

An Integrative Approach to Assess the Environmental Impacts of Gold Mining Contamination in the Amazon

As the number of legal and illegal gold mining sites increases in the Andes–Amazonia region, integrative methods to evaluate the effects of mining pollution on freshwater ecosystems are of paramount importance. Here, we sampled water and sediments in 11 sites potentially affected by gold mining activities in the Napo province (Ecuador). The environmental impacts were evaluated using the following lines of evidence (LOEs): water physicochemical parameters, metal exposure concentrations, macroinvertebrate community response (AAMBI), and toxicity by conducting bioassays with Lactuca sativa and Daphnia magna. Dissolved oxygen and total suspended solids were under (<80%) and above (>130 mg/Ls) quality standards 65% of the sites. Ag, Al, As, Cd, Cu, Fe, Mn, Pb, and Zn in water and V, B, and Cr in sediments were detected above quality standards at sampled sites. Nine out of eleven sites were classified as having bad environmental quality based on the AAMBI. L. sativa seed germination in both water (37% to 70%) and sediment (0% to 65%) indicate significant toxicity. In five sites, neonates of D. magna showed a 25% reduction in survival compared to the control. Our integrated LOEs index ranked sites regarding their environmental degradation. We recommend environmental impact monitoring of the mining expansion at the Andes–Amazonia region using multiple LOEs.

Pervasive decline of subtropical aquatic insects over 20 years driven by water transparency, non-native fish and stoichiometric imbalance

Insect abundance and diversity are declining worldwide. Although recent research found freshwater insect populations to be increasing in some regions, there is a critical lack of data from tropical and subtropical regions. Here, we examine a 20-year monitoring dataset of freshwater insects from a subtropical floodplain comprising a diverse suite of rivers, shallow lakes, channels and backwaters. We found a pervasive decline in abundance of all major insect orders (Odonata, Ephemeroptera, Trichoptera, Megaloptera, Coleoptera, Hemiptera and Diptera) and families, regardless of their functional role or body size. Similarly, Chironomidae species richness decreased over the same time period. The main drivers of this pervasive insect decline were increased concurrent invasions of non-native insectivorous fish, water transparency and changes to water stoichiometry (i.e. N : P ratios) over time. All these drivers represent human impacts caused by reservoir construction. This work sheds light on the importance of long-term studies for a deeper understanding of human-induced impacts on aquatic insects. We highlight that extended anthropogenic impact monitoring and mitigation actions are pivotal in maintaining freshwater ecosystem integrity.