Nothing Lasts Forever: Environmental Discourses on the Collapse of Past Societies

The study of the collapse of past societies raises many questions for the theory and practice of archaeology. Interest in collapse extends as well into the natural sciences and environmental and sustainability policy. Despite a range of approaches to collapse, the predominant paradigm is environmental collapse, which I argue obscures recognition of the dynamic role of social processes that lie at the heart of human communities. These environmental discourses, together with confusion over terminology and the concepts of collapse, have created widespread aporia about collapse and resulted in the creation of mixed messages about complex historical and social processes

Optimal foraging and community structure: implications for a guild of generalist grassland herbivores

A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47765/1/442_2004_Article_BF00377109.pd

What's the message? Interpretation of an uninformative BRCA1/2 test result for women at risk of familial breast cancer

To test the "false-reassurance hypothesis," which suggests that women who receive an uninformative BRCA1/2 test result may incorrectly conclude that they no longer have an elevated risk, with possible harmful consequences for adherence to breast surveillance guidelines. A prospective questionnaire design was used to compare 183 women with an uninformative BRCA test result (94 affected and 89 unaffected) with 41 proven BRCA mutation-carriers and 49 true negatives before and after BRCA1/2 test disclosure. After DNA-test disclosure, test applicants differed from each other with regard to their perception of the likelihood of carrying a deleterious gene (P <0.0001). The BRCA mutation carriers reported the highest perceived likelihood and the true negatives reported the lowest. Compared to the predisclosure measures, women who received an uninformative DNA test result reported a lower perceived risk after disclosure (P <0.0001), suggesting a relatively high level of reassurance because of the test result. However, after DNA-test disclosure, only 12 women concluded that the risk of carrying a mutation was nonexistent, and perceived likelihood was significantly associated with the pedigree-based risk assessment (P = 0.0001). Moreover, despite the significant decrease in perceived likelihood for uninformative women, intention to obtain mammograms did not change (P = 0.71); it remained at the same almost optimal level as for BRCA mutation carriers. No support was found for the suggestion that the nature of uninformative test results is often misunderstood. Moreover, an uninformative test result did not affect the positive mammography intentions of both affected and unaffected wome

Interactions between climate change, competition, dispersal, and disturbances in a tree migration model

Potentially significant shifts in the geographical patterns of vegetation are an expected result of climate change. However, the importance of local processes (e.g., dispersal, competition, or disturbance) has been often ignored in climate change modeling. We develop an individual-based simulation approach to assess how these mechanisms affect migration rate. We simulate the northward progression of a theoretical tree species when climate change makes northern habitat suitable. We test how the rate of progression is affected by (1) competition with a resident species, (2) interactions with disturbance regimes, (3) species dispersal kernel, and (4) the intensity of climate change over time. Results reveal a strong response of species’ expansion rate to the presence of a local competitor, as well as nonlinear effects of disturbance. We discuss these results in light of current knowledge of northern forest dynamics and results found in the climatic research literature. © Springer