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In arctic Alaska, air temperatures have warmed 0.5 degrees Celsius (°C) per decade for the past 30 years, with most of the warming coming in winter. Over the same period, shrub abundance has increased, perhaps a harbinger of a conversion of tundra to shrubland. Evidence suggests that winter biological processes are contributing to this conversion through a positive feedback that involves the snow-holding capacity of shrubs, the insulating properties of snow, a soil layer that has a high water content because it overlies nearly impermeable permafrost, and hardy microbes that can maintain metabolic activity at temperatures of −6°C or lower. Increasing shrub abundance leads to deeper snow, which promotes higher winter soil temperatures, greater microbial activity, and more plant-available nitrogen. High levels of soil nitrogen favor shrub growth the following summer. With climate models predicting continued warming, large areas of tundra could become converted to shrubland, with winter processes like those described here possibly playing a critical role.
We evaluated possible changes to current farming practices in two Minnesota watersheds to provide insight into how farm policy might affect environmental, social, and economic outcomes. Watershed residents helped develop four scenarios to evaluate alternative future trends in agricultural management and to project potential economic and environmental outcomes. We found that environmental and economic benefits can be attained through changes in agricultural land management without increasing public costs. The magnitude of these benefits depends on the magnitude of changes to agricultural practices. Environmental benefits include improved water quality, healthier fish, increased carbon sequestration, and decreased greenhouse gas emissions, while economic benefits include social capital formation, greater farm profitability, and avoided costs. Policy transitions that emphasize functions of agriculture in addition to food production are crucial for creating change. We suggest that redirecting farm payments by using alternative incentives could lead to substantial environmental changes at little or no extra cost to the taxpayer.
Female birds incur costs associated with increased egg production, including reductions in chick provisioning ability, in future fecundity, in survival, and in egg and chick viability. It should be possible to identify the components of the physiological system underlying reproduction, or the specific reproductive traits themselves, that explain these costs, but this has proved to be difficult, in part because of marked, but unexplained, individual variation in these traits. Resolving the physiological and evolutionary consequences of this individual variation represents an exciting challenge for the future. Several mechanisms have been proposed for the cost of egg production (e.g., protein depletion and impaired flight muscle function; immunosuppression), which assume relatively simple resource-allocation trade-offs. I argue that such mechanisms provide an unsatisfactory explanation for costs that can occur over months or even years. A more productive approach for future research will be to focus on hormonally mediated, non-resource-based costs of egg production caused by pleiotropic effects of reproductive hormones that can operate over the longer time scales at which costs of reproduction are expressed.
Only tiny remnants of unploughed natural meadows remain in the eastern part of the state of North Dakota, and in Canada from eastern Saskatchewan to Manitoba. Those west of Lake Manitoba and the Red River Valley are characterized by their distinctive fauna of insects, principally leafhoppers and planthoppers (Homoptera: Auchenorrhyncha). These true bugs include hundreds of species invariably associated with North American grasslands. The distributions of those with the most limited dispersal abilities reflect long-term patterns of dominance and contiguity of native grass stands in prairies. These bug distributions indicate that bluestem-dominated grasslands in Canada, which usually are under 0.5 meter (20 inches) in height, are equivalent to tallgrass prairie from Illinois. This prairie once extended as much as 400 kilometers (250 miles) northwest of its previously known distribution. These bugs help differentiate tallgrass prairie from sites in southwestern Manitoba and adjacent North Dakota, which are more arid, and from sites east of Lake Manitoba and southward in the Red River Valley, which were formerly oak savanna.
I review new species of birds described from 1993 to 2002, comparing the methods used to diagnose (identify) new bird species with those used for other classes of vertebrates. Birds are described and subsequently identified using a far more restrictive set of criteria than other organisms, with field diagnosability being the ultimate criterion of distinctiveness. This has led to a large number of evolutionarily distinct bird taxa that are not recognized as distinct taxonomic units. This disparity has important consequences for ornithology and for other disciplines that use birds as biodiversity measures.
Sufficient quality and quantity of science education at the elementary-school level is the key to developing science literacy and inspiring students about potential careers in science. We collaborated with a school district to develop 5E (engage, explore, explain, elaborate, evaluate) teaching cycles that matched the state and district curriculum guidelines. The 5E teaching cycle is a hands-on/minds-on, inquiry-based method that is effective at any level of instruction, especially for challenging misconceptions. Teams of teaching fellows (graduate students in the sciences) and teachers implemented the instructional units. Their training was fine-tuned, for example, by using a classroom teaching-observation rubric and information about the teachers, teaching fellows', and students' attitudes toward science education. The most significant result was that, in addition to the teachers becoming more comfortable with and adept at teaching science and the fellows improving their communication skills, the fellows understood the value of linear conceptual development in science curricula and their ability to facilitate that as teachers.