High demand for water is driving potentially unsustainable practices and competition for water resources between various sectors in developing areas. As a result of improved quality of life and population growth, increase in demand for fresh water is anticipated in all African countries in all sectors, over the next 10 years. This study examines the effects of dry season irrigation farming (fadama) on the physical and chemical quality of the River Osin which receives both surface and subsurface flow from irrigated areas in the Upper Osin Catchment, Kwara State, Nigeria. A total of 90 samples were obtained from Upstream (UPS), Irrigated area (IRG) and Downstream (DNS) segments of the river in the dry and rainy seasons. Water samples were analysed for pH, conductivity, total dissolved solids (TDS), suspended solids, dissolved organic matter (DOM), pesticides (ionic basic type), Na+, K+, Mg2+,Cl-, NO3 -, PO4 3-, Ca2+ and HCO3 -. The results indicate that values of agricultural pollutants such as pesticides (CuSO4), NO3 - and PO4 3- were significantly higher at IRG than at UPS, and decreased slightly at DNS, while all other anions and cations except DOM reached peak values at DNS. Agricultural pollutants (NO3 -, PO4 3- and pesticides) contributed significantly to poor water quality observed at IRG and DNS segments but the values are within acceptable tolerance range at UPS. The findings further indicate that irrigation practice degrades the quality of water at IRG and DNS segments. As a result, a holistic approach to agriculture and water resource management is recommended to ensure sustainable water resources development in the catchment.
Systematic observations of Himalayan glaciers over the last few decades provide reliable indications of continuous shrinkage of most of the glaciers. Changes in mass, volume, area and length of glaciers are reported, but an up-to-date regional assessment of glacier changes is lacking. In the present study, satellite data, maps and ground-based measurements have been used to obtain the snout retreat and surface changes of the Tipra Glacier in the Alaknanda river basin of the Garhwal Himalaya for the period 1962–2008. The study reveals that a large part of the glacier has been detached from the main trunk and separated into the Tipra (7.5 km2) and Rataban (7.4 km2) Glaciers as it had one outlet (snout) in 1987. Between 1962 and 2002 estimated surface area reduced by ~18% and snout retreat was ~535 m with an average rate of 13.4 m a-1. Measurement of snout positions of the Tipra and Rataban Glaciers from 2002 to 2008 indicates an enhanced annual retreat of 21.3 and 21.2 m a-1, respectively. Total frontal area vacated during this period was calculated to be 0.084 km2 for Tipra Glacier and 0.028 km2 for Rataban Glacier. The estimated Equilibrium Line Altitude (ELA) rise was 76 m for the Tipra Glacier and 57 m for the Rataban Glacier. Accumulation Area Ratio (AAR) was calculated as 0.47 for the Tipra Glacier and 0.49 for the Rataban Glacier, during the study period. The observations compared with the other studies carried out in the region show a significant reduction in glacier areas. The increased retreat rate of glacier snouts is probably a direct consequence of global warming. The present snouts of the Tipra and Rataban Glaciers are located at altitudes of 3865 and 4120 m, respectively.
Jun 21, 2011; 2009:1-1
Editorial
Jun 21, 2011; 2009:2-2
Article
Clarifying Baker’s Law
Baker's Law states that colonization by self-compatible organisms is more likely to be successful than colonization by self-incompatible organisms because of the ability for self-compatible organisms to produce offspring without pollination agents. This simple model has proved very successful in plant ecology and has been applied to various contexts, including colonizing or ruderal species, islands colonizers, invasive species or mating system variation across distribution ranges. Moreover, it is one of the only models in population biology linking two traits of major importance in ecology, namely dispersal and mating system. Although Baker's Law has stimulated a large number of empirical studies reporting the association of self-fertilization and colonizing ability in various contexts, the data have not established a general pattern for the association of traits.
In this paper, a critical position is adopted to discuss and clarify Baker's Law. From the literature referring to Baker's Law, an analysis made regarding how mating success is considered in such studies and discrepancies with population genetics theory of mating systems are highlighted. The data reporting the association of self-fertilization and colonizing ability are also briefly reviewed and the potential bias in interpretation is discussed. Lastly, a recent theoretical model analysing the link between colonizing ability and self-fertilization is considered.
Evolutionary predictions are actually more complex than Baker's intuitive arguments. It appears that Baker's Law encompasses a variety of ecological scenarios, which cannot be considered a priori as equivalent. Questioning what has been considered as self-evident for more than 50 years seems a reasonable objective to analyse in-depth dispersal and mating system traits.