Natural and anthropogenic changes threatening the ecological and limnological integrity of Lake Baringo, Kenya: A Review

Lakes are characterized by dynamic responses to ecological and limnologic disturbances that occur within a constrained timeframe. Some endorheic lakes in the Kenyan Rift valley are presently regarded as environmental hotspots because of complex changes that are revealed through multiple proxies; changing lake levels and surface area, turbidity and sedimentation, proliferation of macrophytes and loss of aquatic biodiversity. Lake Baringo is characterized by widespread catchment degradation accompanied by high levels of turbidity during erratic and decline of native fishery based on Oreochromis niloticus baringoensis. A careful analysis implicates potential natural factors such as catchment topography and increasing anthropogenic pressure as the main causes of lake ecosystem degradation. This paper recommends several strategies for restoration of Lake Baringo based on an integrated multi-faceted approach which combines catchment rehabilitation, pollution control and provision of alternative livelihoods such as agriculture to the riparian communities.

RIVERBED, BANKS AND BEYOND: AN EXAMINATION OF ROMAN INFRASTRUCTURE AND INTERVENTIONS IN RESPONSE TO HYDROLOGICAL RISK IN THE PO–VENETIAN PLAIN

Water poses a particular challenge to the cities and settlements of the Po–Venetian plain. The region has some of the highest levels of precipitation in Italy and is criss-crossed by dozens of rivers, including the Po, Adige and Tagliamento. Throughout history, there was considerable hydrological risk to the well-being of riparian communities from hazards such as flooding and lateral channel movement, yet local residents did not sit idly by. This article synthesizes the available evidence for Roman responses to hydrological risk in the Po–Venetian plain from the first century BC to the sixth century AD, examining their workings and the hazards they sought to counteract, integrating them into wider discussions on risk in the Roman world. The responses are divided into the categories of defensive works (embankments and dykes) and channel interventions (channel rectification, channel diversion and dredging). While the effectiveness of these methods is questioned, in particular their potential to cause unintended changes to the watercourse, the decision by riparian communities to undertake them suggests a degree of local success. Nevertheless, an examination of the archaeological and palaeoclimatic evidence suggests a discrepancy between peak intervention and peak risk, implying increasing vulnerability and risk acceptance amongst riparian communities during late antiquity. L'acqua pone una particolare sfida alle città e agli insediamenti della pianura padano-veneta. La regione è caratterizzata da alcuni tra i più alti livelli di precipitazioni in Italia ed è attraversata da molti fiumi, tra cui il Po, l'Adige e il Tagliamento. Nel corso della storia, le comunità rivierasche hanno dovuto affrontare un notevole rischio idrologico legato a inondazioni e instabilità dei canali laterali. Gli abitanti dell'area non sono certamente rimasti a guardare. Questo articolo propone una sintesi delle evidenze disponibili relativamente alle risposte romane al rischio idrologico nella pianura padano-veneta dal I secolo a.C. al VI secolo d.C., esaminando il loro funzionamento e i pericoli che hanno cercato di contrastare, integrandole in più ampie discussioni sul rischio nel mondo romano. Le soluzioni individuate per arginare il rischio idrogeologico sono suddivise nelle categorie di opere difensive (argini e fossati) e interventi di canalizzazione (modifiche e deviazioni dei canali e dragaggio). Sebbene l'efficacia di questi metodi sia stata messa in dubbio, in particolare la loro possibilità di causare cambiamenti non intenzionali al corso d'acqua, la decisione delle comunità rivierasche di adottarli suggerisce un certo grado di successo locale. Tuttavia, un esame delle testimonianze archeologiche e paleoclimatiche suggerisce una discrepanza tra il picco di intervento e il picco di rischio, implicando una crescente vulnerabilità e un'accettazione del rischio tra le comunità rivierasche durante la tarda antichità.

Characterization of Riparian Tree Communities along a River Basin in the Pacific Slope of Guatemala

Ecosystem conservation in Mesoamerica, one of the world’s biodiversity hotspots, is a top priority because of the rapid loss of native vegetation due to anthropogenic activities. Riparian forests are often the only remaining preserved areas among expansive agricultural matrices. These forest remnants are essential to maintaining water quality, providing habitats for a variety of wildlife and acting as biological corridors that enable the movement and dispersal of local species. The Acomé river is located on the Pacific slope of Guatemala. This region is heavily impacted by intensive agriculture (mostly sugarcane plantations), fires and grazing. Most of this region’s original forest is now restricted to forest remnants concentrated along the riverbank. However, the botanical composition and species diversity of the riparian communities has not been characterized. This baseline information is essential to develop restoration strategies and management plans. This study aimed to characterize the riparian tree communities along the Acomé riverbank by systematically collecting herbarium specimens and photographic material for trees over 10 cm DBH (diameter at breast height). Cluster analysis was used to identify the main riparian communities, and diversity indices were calculated for each community. A total of 115 tree species were identified, belonging to 91 genera and 43 families. The cluster analysis suggested the presence of four riparian tree communities along an altitudinal gradient. Rhizophora mangle, Cecropia obtusifolia, Guazuma ulmifolia, and Brosimum costaricanum were the dominant species of the identified communities. This research will support ongoing restoration efforts and biological connectivity plans in this region.

Evidence of Range Shifts in Riparian Plant Assemblages in Response to Multidecadal Streamflow Declines

Riparian corridors are thought to form hydrological refugia that may buffer species and communities against regional climate changes. In regions facing a warming and drying climate, however, the hydrological regime driving riparian communities is also under threat. We examined recruitment in response to streamflow declines for species inhabiting the riparian zone in southwest Western Australia, testing the extent to which the riparian system has buffered riparian communities from the drying climate. We stratified 49 vegetation transects across the >600 mm per annum regional rainfall gradient encompassed by the Warren River Catchment. Local hydrological conditions were estimated over two 10-year periods; 1980–1989, and 2001–2010, to quantify changes in the flood regime. Mixed effects models tested the relationship between rainfall and flooding on the relative frequency of immature to mature individuals of 17 species of trees and shrubs common to the riparian zones. At the low-rainfall extent of their geographic range, the relative frequency of immature riparian species decreased with declining flow, whereas at the high-rainfall extent of their geographic range the relative frequency of immature individuals increased with declining flow. These results suggest that the geographic ranges of riparian species may be contracting at the low-rainfall margin of their range, while at the high-rainfall margin of their geographic range, reduced flooding regimes appear to be opening up new habitat suitable for recruitment and narrowing the river corridor. No such patterns were observed in upland species, suggesting the river may be buffering upland species. We discuss these findings and their implications for ongoing management and species conservation in a region projected to face further, significant rainfall declines.

The Impacts of Hydropower Dams in the Mekong River Basin: A Review

The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams and groupings of dams and the geographies of their impacts. Specifically, we examined the 3S (Sesan, Sekong Srepok) river system in northeastern Cambodia, the Central Highlands of Vietnam, and southern Laos; the Khone Falls area in southern Laos; the lower Mun River Basin in northeastern Thailand; and the upper Mekong River in Yunnan Province, China, northeastern Myanmar, northern Laos, and northern Thailand. Evidence shows that these dams and groupings of dams are affecting fish migrations, river hydrology, and sediment transfers. Such changes are negatively impacting riparian communities up to 1000 km away. Because many communities depend on the river and its resources for their food and livelihood, changes to the river have impacted, and will continue to negatively impact, food and economic security. While social and environmental impact assessments have been carried out for these projects, greater consideration of the scale and cumulative impacts of dams is necessary.

Studies on riparian communities in eastern Morocco: coastal dayas at the mouth of the Moulouya River

This paper aims to study the riparian community of coastal dayas at the mouth of the Moulouya River in the northeast of Morocco. We carried out a monthly sampling of riparian fauna on two dayas (EMDI & EMDII) on the Mediterranean coast. Banks of these dayas are an ecotone where terrestrial, riparian, and aquatic species mix. Riparian species dominate the population in richness and abundance: most species are either sporadic (EMDI) or accidental (EMDII). The dominant species are halophilous. Interesting species have been collected from these dayas: Gonocephalum yelamosi, new species for Morocco, Blaps nitens, Dyschirius tensicollis, and Dyschirius africanus, which dayas is a new distribution in the region. Species with the same ecological niches that can compete with each other seem to share the occupation of this environment. The same phenomenon seems to occur for species of the genus Pogonus and Pogonistes, which have populations that reach their maximum expansion at different periods.