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Dams are obstructing rivers worldwide, impairing habitat and migration opportunities for many freshwater fish species; however, global data linking dam and fish distributions have been limited. Here, we quantify dam obstruction at the biogeographic scale of freshwater ecoregion, which provides the spatial framework necessary to assess the risk of fish species loss due to dams and allows us to identify both ecoregions and genera at risk. Nearly 50% of the 397 assessed freshwater ecoregions are obstructed by large- and medium-size dams, and approximately 27% face additional downstream obstruction. A synthesis of obstruction data and fish traits indicates that taxa such as lampreys (Lampetra spp.), eels (Anguilla spp.), and shads (Alosa spp.) are at particular risk of species loss. Threatened ecoregions with heavy dam obstruction and above-average counts of total, diadromous, or endemic species are found on all continents and include the Murray—Darling Province, Southern Italy, the Lower and Middle Indus Basin, West Korea, the South Atlantic region of the United States, the Upper Paraná, and Mobile Bay ecoregions.
The current conditions of many seasonally dry forests in the western and southern United States, especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Both prescribed fire and its mechanical surrogates are generally successful in meeting short-term fuel-reduction objectives such that treated stands are more resilient to high-intensity wildfire. Most available evidence suggests that these objectives are typically accomplished with few unintended consequences, since most ecosystem components (vegetation, soils, wildlife, bark beetles, carbon sequestration) exhibit very subtle effects or no measurable effects at all. Although mechanical treatments do not serve as complete surrogates for fire, their application can help mitigate costs and liability in some areas. Desired treatment effects on fire hazards are transient, which indicates that after fuel-reduction management starts, managers need to be persistent with repeated treatment, especially in the faster-growing forests in the southern United States.
On 20 April 2010, the Deepwater Horizon explosion, which released a US government—estimated 4.9 million barrels of crude oil into the Gulf of Mexico, was responsible for the death of 11 oil workers and, possibly, for an environmental disaster unparalleled in US history. For 87 consecutive days, the Macondo well continuously released crude oil into the Gulf of Mexico. Many kilometers of shoreline in the northern Gulf of Mexico were affected, including the fragile and ecologically important wetlands of Louisiana's Mississippi River Delta ecosystem. These wetlands are responsible for a third of the nation's fish production and, ironically, help to protect an energy infrastructure that provides a third of the nations oil and gas supply. Here, we provide a basic overview of the chemistry and biology of oil spills in coastal wetlands and an assessment of the potential and realized effects on the ecological condition of the Mississippi River Delta and its associated flora and fauna.
Legacy effects of past land use and disturbance are increasingly recognized, yet consistent definitions of and criteria for defining them do not exist. To address this gap in biological- and ecosystem-assessment frameworks, we propose a general metric for evaluating potential legacy effects, which are computed by normalizing altered system function persistence with duration of disturbance. We also propose two distinct legacy-effect categories: signal effects from lags in transport and structural effects from physical landscape changes. Using flux records for water, sediment, nitrogen, and carbon from long-term study sites in the eastern United States from 1500 to 2000, we identify gaps in our understanding of legacy effects and reveal that changes in basin sediment dynamics precede instrumented records. These sediment dynamics are not generally incorporated into interpretations of contemporary records, although their potential legacy effects are substantial. The identification of legacy effects may prove to be a fundamental component of landscape management and effective conservation and restoration practice.
Regrettably, the sciences are not untouched by the plagiarism affliction that threatens the integrity of budding professionals in classrooms around the world. My research, however, suggests that plagiarism training can improve students' recognition of plagiarism. I found that 148 undergraduate ecology students successfully identified plagiarized or unplagiarized paragraphs three-quarters of the time. The students' ability to identify plagiarism was not significantly different when the quoted or paraphrased text included complex sentence structure and scientific jargon and when it included only simple sentences that mostly lacked jargon. The students who received plagiarism training performed significantly better at plagiarism detection than did those who did not receive the training. Most of the students, independent of training, identified properly paraphrased, quoted, and attributed material but had much greater difficulty identifying paraphrases that included long strings of copied text—up to 15 words—or proper paraphrases that lacked citations. The misunderstanding of paraphrasing and citation conventions found here could manifest as unintentional plagiarism in these students' later work.
The principles representing the broadest conceptual domains within ecology, which encompasses extremely broad spatial and temporal scales, have been identified in recent work. These broad scales present challenges to maintaining conceptual and theoretical clarity; however, theory development requires a clear understanding of theoretical components. Although researchers often test hypotheses using existing theories, many endeavors could benefit from a formal structure for examining the theoretical underpinnings of the researchers' work. We present a graphical model to organize the theoretical components underlying any particular research effort. We provide an example and suggest that scientists use this framework to present their research in a robust theoretical context. The benefits of this approach include accurately defining the theoretical components used in research; identifying novel questions while avoiding redundancy; and explicitly linking constituent theories, thereby facilitating integration. Many scientists aspire to have an impact on existing theory, and using this approach provides a succinct framework to identify how an individual's research affects ecological theory.
The global change research community needs to renew its social contract with society by moving beyond a focus on biophysical limits and toward solution-oriented research to provide realistic, context-specific pathways to a sustainable future. A focus on planetary opportunities is based on the premise that societies adapt to change and have historically implemented solutions—for example, to protect watersheds, improve food security, and reduce harmful atmospheric emissions. Daunting social and biophysical challenges for achieving a sustainable future demand that the global change research community work to provide underpinnings for workable solutions at multiple scales of governance. Global change research must reorient itself from a focus on biophysically oriented, global-scale analysis of humanity's negative impact on the Earth system to consider the needs of decisionmakers from household to global scales.