Eskers are complex geological formations shaped with a linear accumulation of sand and gravel under the glaciers during the last ice age and that provide crucial resources such as drinking water, sand/gravel, outdoor recreational sites, and productive forests. Surrounding sand and gravel and connection with the groundwater influences the physicochemical properties of lakes on esker which can benefit different biotic communities in the food web. The sustainable management of resources provided by eskers requires baseline ecological knowledge of these ecosystems. However, very little information exists about the ecology of freshwater ecosystems on eskers. This study uses a food web approach to identify the environmental variables, biological diversity, and indicator species associated with esker lakes to better understand their ecological functioning and biodiversity patterns to benefit their sustainable management and conservation. Fifty lakes were sampled in the Abitibi-Témiscamingue region (Canada), half on eskers and half on the surrounding boreal clay belt to include the most abundant lake ecosystems of the region. Physicochemical, environmental, and anthropogenic variables measured in the two lake types showed that esker lakes differed markedly from clay lakes. Nutrient concentrations, conductivity, and macrophyte cover were significantly lower in esker lakes than in clay lakes, whereas dissolved oxygen saturation and concentration showed the opposite trend. Three interconnected trophic levels of the esker lake food webs—waterbird, fish, and macroinvertebrate communities—were characterized for biological diversity and the associated species. We found a significantly lower Shannon diversity index for waterbirds (mean ± standard deviation; 0.7 ± 0.2), fish (0.4 ± 0.3), and a tendency for a lower value for macroinvertebrates (0.9 ± 0.3) in esker lakes than the clay lakes (1.1 ± 0.4, 0.9 ± 0.3, and 1.3 ± 0.5, respectively). Common goldeneye (Bucephala clangula) and Canada goose (Bucephala clangula) were associated significantly with esker lakes and identified as indicator species for esker lakes. In contrast, ring-necked duck (Aythya collaris) and hooded merganser (Lophodytes cucullatus) were associated significantly with clay lakes. Perlidae was similarly associated with esker lakes as an indicator for macroinvertebrates. Anthropogenic activities such as forest harvesting have altered the waterbird community, and recreational activities around the lakes have modified the fish and macroinvertebrate communities. We conclude that esker lakes differ from other regional lakes and are associated with specific environmental and biological variables and indicator species. The biological diversity in esker lakes is lower than that of clay lakes for all studied trophic levels of the food web, but these waterbodies provide preferential habitats for some species. This research provides the first baseline ecological information necessary to establish sustainable management and conservation strategies for this vulnerable ecosystem.

Les eskers sont des formations géologiques complexes qui fournissent des ressources cruciales dans les pays nordiques, telles que de l'eau potable, du sable/gravier, du bois et des sites de loisirs en plein air. Cependant, les connaissances sur la biodiversité et le fonctionnement des eskers sont très déficitaires. Les lacs d'esker sont différents des autres lacs boréaux car ils sont principalement alimentés par les eaux souterraines et les précipitations. Ainsi, les lacs d'esker devraient avoir des communautés de poissons réduites ou absentes, ce qui devrait à la fois favoriser l'abondance d'invertébrés aquatiques et une communauté d'oiseaux aquatiques d'eau diversifiée. Ce projet vise à caractériser les communautés d'oiseaux aquatiques associées aux lacs d'esker ainsi que leurs ressources, telles que les poissons et les invertébrés aquatiques, en utilisant une approche de réseau trophique. Cinquante lacs ont été échantillonnés, incluant des lacs situés sur eskers et des lacs sur la ceinture d'argile en Abitibi. Nous avons trouvé un indice de diversité de Shannon significativement plus élevé pour les oiseaux aquatiques dans les lacs d'argile (moyenne ± écart-type = 1,07 ± 0,44) par rapport aux lacs d'eskers (0,72 ± 0,24). L'indice de diversité de Shannon des invertébrés montrait une tendance plus élevée dans les lacs argileux (1,31 ± 0,46), par rapport aux lacs d'esker (1,24 ± 0,36). Pour les poissons, la valeur de l'indice dans les lacs d'argile (0,93 ± 0,29) était significativement plus élevée que dans les lacs sur esker (0,37 ± 0,30). De plus, les concentrations en nutriments, la conductivité et la couverture de macrophytes étaient plus élevées dans les lacs d'argile comparés aux lacs sur esker contrairement à la saturation en oxygène dissous. Les résultats suggèrent que la diversité biologique des lacs d'esker est plus faible à tous les niveaux trophiques du réseau trophique, mais qu'ils fournissent un habitat à quelques communautés rares et importantes. Ce projet représente la première caractérisation de la biodiversité associée aux lacs d'esker et fournira ainsi les informations écologiques de base nécessaires pour établir des stratégies de conservation pour ces écosystèmes vulnérables. 

One of humanity’s most significant challenges in the process of attaining the established sustainability goals is balancing the growing human demand for food and the need to conserve biodiversity. This challenge requires appropriate land uses that are able to conserve biodiversity while ensuring ample food supply. This study compares bird species diversity and abundance in areas undergoing land sharing and land sparing in northeastern Bangladesh (West Bhanugach Reserved Forest). Birds serve as useful biologic indicators because of their presence within different trophic levels and their well-studied ecology. To survey birds, we selected a total of 66 sampling sites within land-sharing (33) and land-sparing (33) land-use areas. Between May and June 2017, we observed and recorded bird calls within a 50-m radius around each sampling site. We counted 541 individuals from 46 species of birds. The Shannon bird diversity was higher in the land-sparing sites (1.52) than in the land-sharing sites (1.23). We found approximately 30% more bird species (39 vs. 30) and 40% more individuals (318 vs. 223) in the land-sparing areas than land-sharing areas. Three bird species, Arachnothera longirostra, Micropternus brachyurus and Copsychus malabaricus, were significantly associated with the land-sparing sites. This study shows that land sharing negatively affects bird diversity, richness and abundance compared to land-sparing. The use of chemical fertilizers and the lack of food, such as insects, for birds can explain the lower diversity, richness and abundance of birds in the land-sharing areas. Although land sharing is an effective means of producing food, land sparing is the most effective land-use practice for preserving bird diversity in northeastern Bangladesh. View Full-Text