Explore the vast range of titles available.

The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L−1), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue.

The Sirex woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae), a widespread invasive pest of pines in the Southern Hemisphere, was first detected in North America in 2004. This study assessed the impacts of life history traits, host resistance and species interactions on the demography of S. noctilio in New York, Pennsylvania and Vermont, then compared key metrics to those found in the native range in Galicia, Spain. Many trees naturally attacked by S. noctilio in North America produced no adult woodwasps, with 5 of 38 infested trees (13%) sampled across six sites yielding 64% of emerging insects. Reproductive success was highest in the introduced host scots pine, Pinus sylvestris , but native red pine, Pinus resinosa , produced larger insects. Sirex noctilio required one or sometimes two years to develop and sex ratios were male biased, 1:2.98 ♀:♂. Body size and fecundity were highly variable, but generally lower than observed in non-native populations in the Southern Hemisphere. Hymenopteran parasitoids killed approximately 20% of S. noctilio larvae and 63% of emerging adults were colonized by the parasitic nematode Deladenus siricidicola , although no nematodes entered eggs. Demographic models suggested that S. noctilio in the northeastern USA have a higher potential for population growth than populations in the native range: estimated finite factor of increase, λ, was 4.17–4.52 (depending on tree species colonized), compared to λ = 1.57 in Spain.

Resolving the relative contributions of top-down versus bottom-up drivers of vegetation dynamics is a major challenge in drylands. In the coming decades, growing livestock populations and shifts in water availability will simultaneously impact many arid systems, but a lack of empirical data on plant responses to these pressures limits understanding of how plants will respond. Here, we combine ground and drone observations from an herbivore exclosure experiment to identify ungulate visitation patterns and their impacts on the cover and melon production of !nara (Acanthosicyos horridus), a large, long-lived desert plant in the hyper-arid Namib Desert. !Nara are of key ecological, social, and economic importance to Namib ecosystems and to the local Topnaar people. At our study site, we find that among native and domestic herbivores, free-ranging donkeys have the largest impact on !nara cover and melon production. !Nara cover was negatively affected by herbivores close to the desert-ephemeral river ecotone during a dry period, whereas !nara cover increased on all plants across the landscape during a wetter period, regardless of herbivore access. !Nara near the river channel and those protected from herbivores had more mature melons, particularly during the wetter period. At this site, the potential for conflict between Topnaar !nara melon harvesting and pastoral practices varies with a plant’s distance from the river and prevailing abiotic conditions. This work advances monitoring approaches and adds empirical support to the understanding that top-down and bottom-up regulation of plant dynamics varies with spatiotemporal context, even within landscapes.

There is increasing interest in using “real-world pedagogy” to train students in ways that make them better able to contribute toward a more sustainable society. While there is a robust body of literature on the competencies that students need as sustainability professionals, there is a lack of specific guidance in the literature on how to teach for competency development or on how to structure a program or course to support competency development. Our research addresses this gap in the literature through a description and autoethnographic reflection on the design and early implementation of a “real-world” course. The course is from the Environmental Studies Program at Dartmouth College (Hanover, NH, USA), but it takes place in the environs of the Gobabeb Research and Training Centre in the Namib Desert of Namibia and in nearby Topnaar settlements. Our research objective was to articulate strategies to address the primary pedagogical challenges that we faced during the design and first five iterations of the course. These include: How do we frame this course and communicate it to students in a way that is understandable and works within the particular context and constraints of the course? Can we provide students with a coherent framework that helps them to understand the approach and also provides a platform for thoughtful consideration, acquisition, and retention of appropriate competencies? How do we develop collaborations with our community partners that are ethical and effective? How do we frame these real-world experiences in a way that allows for students to integrate their experience with the theory and broader empiricism they learn on campus? To address these pedagogic challenges, we framed the course as a research-based course, more specifically community-based research (CBR), conducted in a social-ecological system (SES). We developed lower-level strategies for implementing this framing, including preparing students for collaborative research, encouraging student ownership of their learning, linking theory to research, and thoughtfully navigating time constraints. Furthermore, program-level and student-level engagement with community have been critical for avoiding becoming “helicopter researchers.” Drawing on our personal reflections and those of our community partners, we conclude with a discussion of emergent outcomes and the next steps for continual improvement and adaptation.

Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future.