Effects of crowding due to habitat loss on species assemblage patterns

Terrestrial animals are negatively affected by habitat loss, which is assessed on a landscape scale, whereas secondary effects of habitat loss, such as crowding, are usually disregarded. Such impacts are inherently hard to address and poorly understood, and there is a growing concern that they could have dire consequences. We sampled birds throughout a deforestation process to assess crowding stress in an adjacent habitat remnant in the southern Brazilian Atlantic Forest. Crowding is expected of highly mobile taxa, especially given the microhabitat heterogeneity of Neotropical forests, and we hypothesized that the arrival of new individuals or species in refuges shifts assemblage patterns. We used point counts to obtain bird abundances in a before-after-control-impact design sampling of a deforestation event. Temporal changes in taxonomic and functional diversity were examined with metrics used to assess alpha and beta diversity, turnover of taxonomic and functional similarity, and taxonomic and functional composition. Over time increased abundance of some species altered the Simpson index and affected the abundance-distribution of traits in the habitat remnant. Taxonomic composition and functional composition changed in the remnant, and thus bird assemblages changed over time. Taxonomic and functional metrics indicated that fugitives affected resident assemblages in refuges, and effects endured >2 years after the deforestation processes had ceased. Dissimilarity of taxonomic composition between pre- and postdeforestation assemblages increased, whereas functional composition reverted to preimpact conditions. We found that ecological disruptions resulted from crowding and escalated into disruptions of species’ assemblages and potentially compromising ecosystem functioning. It is important to consider crowding effects of highly mobile taxa during impact assessments, especially in large-scale infrastructure projects that may affect larger areas than is assumed.     

Coupling check dams with large wood retention structures in clean water

Environmental Fluid Mechanics - The performance of a rake for large wood retention has been analysed in clean water and for the case of a slit check dam. An experimental investigation was conducted...     

Evaluating the impact of extreme temperature based indices in the 2003 heatwave excessive mortality in Portugal

This paper analyses the impact of the 2003 European heatwave on excessive human mortality in Portugal, a country that presents a relatively high level of exposure to heatwave events. A total of 2399 excessive deaths are estimated in continental Portugal, which implies an increase of 58% over the expected deaths. When these values are split by gender, it is seen that women increase (79%), was considerably higher than that recorded for men (41%). The increment of mortality due to this heatwave was detected for all the 18 districts of the country, but its magnitude was significantly higher in the inner districts close to the Spanish border. When we split by gender all districts reveal significant mortality increments for women, while the impact in men's excess deaths is not significant over 3 districts. Several temperature derived indices were used and evaluated in their capacity to explain, at the regional level, the excessive mortality (ratio between observed and expected deaths) by gender. It is shown that the best relationship is found for the total exceedance of extreme days, an index combining the length of the heatwave and its intensity. Both variables hold a linear relationship with r = 0.79 for women and a poorer adjustment (r = 0.50) for men. Additionally, availability of mortality data split by age also allowed obtaining detailed information on the structure of the population in risk, namely by showing that statistically significant increments are concentrated in the last three age classes (45–64, 65–74 and 75 or more). The use of air conditioning systems in some Portuguese hospitals had a major impact on the decrease (up to 40%) in excessive mortality values. A finer approach is relevant for prevention strategies, since it allows to identify better the target population of any preventive strategy regional and national authorities may be interested to implement.     

Effects of Organic Material and Distribution of Fecal Coliforms in Chetumal Bay, Quintana Roo, México

Most wastewater from the city of Chetumal is discharged into the adjoining bay without treatment through a pluvial sewer system. The bay also receives a high volume of vegetal organic material from the River Río Hondo. The average of biochemical oxygen demand (BOD) was 32.26 mg l-1, it was low compared with other reports and should be indicative of self-depuration processes in Chetumal Bay. In the area most used by the public for recreational and fishing activities, concentrations of fecal coliforms above the limit established by Mexican Legislation were shown. The border between Mexico and Belize is Chetumal Bay, which recently was declared a protected area for manatees.     

Effect of initial sulfide concentration on sulfide and phenol oxidation under denitrifying conditions

The objective of this work was to evaluate the effect of the initial sulfide concentration on the kinetics and metabolism of phenol and sulfide in batch bioassays using nitrate as electron acceptor. Complete oxidation of sulfide (20 mg L(-1) of S(2-)) and phenol (19.6 mg L(-1)) was linked to nitrate reduction when nitrate was supplemented at stoichiometric concentrations. At 32 mg L(-1) of sulfide, oxidation of sulfide and phenol by the organo-lithoautotrophic microbial culture was sequential; first sulfide was rapidly oxidized to elemental sulfur and afterwards to sulfate; phenol oxidation started once sulfate production reached a maximum. When the initial sulfide concentration was increased from 20 to 26 and finally to 32 mg L(-1), sulfide oxidation was inhibited. In contrast phenol consumption by the denitrifying culture was not affected. These results indicated that sulfide affected strongly the sulfide oxidation rate and nitrate reduction.     

Agriculture adjustment, land-use transition and protected areas in Northwestern Argentina

Land-use change is the main component of regional environmental change, while protected areas represent a direct land use policy to prevent its potentially negative effects on biodiversity and environmental services. We combined an analysis of trends in land use and human demography with trends in creation of protected areas during the last three decades in northwestern Argentina, a subtropical region including a wide range of environments. The eighty nine administrative analysis units of the region were classified into four ecological groups based on their percentage of cover by the six eco-regions of the study area: (1) "Dry valleys"; dominated by Middle-elevation deserts; (2) "Highlands", dominated by High-elevation alpine zones and plateaus; (3) "Humid ecosystems", dominated by Foggy grasslands and Humid forests, and (4) "Dry forests". Between 1970 and 2002, human population became concentrated in urban areas and land use trends varied greatly among the four ecological groups. Agricultural area decreased in the Highlands and increased in the other regions, particularly in the Dry forests. Domestic animals decreased in Humid ecosystems, Highlands and the Dry valleys; and remained constant in the Dry forests. Several protected areas were created, but most of them were established in regions undergoing a decreasing intensity of land use. Overall, the analysis shows that agricultural production is becoming concentrated in the areas more suitable for modern agriculture while marginal agriculture areas and, particularly, extensive grazing are decreasing. The creation of protected areas reflects the decreasing opportunity costs of marginal areas and is failing to protect the eco-regions most threatened by current land-use trends.     

Inferring episodic atmospheric iron fluxes in the Western South Atlantic

Iron (Fe) and other trace elements such as Zn, Mn, Ni and Cu are known as key-factors in marine biogeochemical cycles. It is believed that ocean primary productivity blooms in iron deficient regions can be triggered by iron in aeolian dust. Up to now, scarce aerosol elemental composition, based on measurements over sea at the Western South Atlantic (WSA), exist. An association between the Patagonian semi-desert dust/Fe and chlorophyll-a variability at the Argentinean continental shelf is essentially inferred from models. We present here experimental data of Fe enriched aerosols over the WSA between latitudes 22°S–62°S, during 4 oceanographic campaigns between 2002 and 2005. These data allowed inferring the atmospheric Fe flux onto different latitudinal bands which varied from 30.4 to 1688 nmolFe m^?2 day^?1 (October 29th–November 15th, 2003); 5.83–1586 nmolFe m^?2 day^?1 (February 15th–March 6th, 2004) and 4.73–586 nmolFe m^?2 day^?1(October 21st–November 5th, 2005).