Funcionarios y políticas sobre el territorio en la Provincia de Buenos Aires : El Departamento de Ingenieros, 1875-1913

En esta ponencia estudiamos la conformación del Departamento de Ingenieros, sus múltiples atribuciones y los cambios que se fueron sucediendo entre su creación en 1875 y su supresión en 1913, un período fundamental para la provincia porque se trata de la época de las últimas entregas de tierra pública (más de 4 millones de hectáreas) y de los infructuosos intentos por controlar las inundaciones en la zona productiva ya ocupada. Nos interesa determinar la relación entre la toma de decisiones, la gestión técnica y económica, los cambios en la política y la economía bonaerense. Estudiamos las relaciones entre las distintas especialidades de la ingeniería y la agrimensura que llevaron a la conformación del Departamento de Ingenieros con muchas más atribuciones, entre las que se encuentran las que tenía el Departamento Topográfico. La creciente especialización de los saberes, evidentemente, estaba impactando no solamente en la disciplina, sino que se expresaba en la especificidad de las agencias estatales, que se iban complejizando para poder abarcar el cúmulo de intereses del estado y de la sociedad civil en torno al territorio

Marine diatoms in deep sea sediments

Long-term evolution is thought to take opportunities that arise as a consequence of mass extinction (as argued, for example, by Gould, 2002) and the following biotic recovery, but there is absolutely no evidence for this being the case. However, our study shows that eutrophication by oceanic mixing also played a part in the enhancement of several evolutionary events amongst marine organisms, and these results could indicate that the rates of oceanic biodiversification may be slowed if upwelling becomes weakened by future global warming. This paper defines three distinct evolutionary events of resting spores of the marine diatom genus Chaetoceros, to reconstruct past upwelling through the analysis of several DSDP, ODP and land-based successions from the North, South and equatorial Pacific as well as the Atlantic Ocean during the past 40 million years. The Atlantic Chaetoceros Explosion (ACE) event occurred across the E/O boundary in the North Atlantic, and is characterized by resting spore diversification that occurred as a consequence of the onset of upwelling following changes in thermohaline circulation through global cooling in the early Oligocene. Pacific Chaetoceros Explosion events-1 and -2 (PACE-1 and PACE-2) are characterized by relatively higher occurrences of iron input following the Himalayan uplift and aridification at 8.5 Ma and ca. 2.5 Ma in the North Pacific region. These events not only enhanced the diversification and increased abundance of primary producers, including that of Chaetoceros, other diatoms and seaweeds, but also stimulated the evolution of zooplankton and larger predators, such as copepods and marine mammals, which ate these phytoplankton and plants. Current thinking suggests new evolutionary niches open up after a mass extinction, but our study finds that eutrophication can also stimulate evolutionary diversification. Moreover, in the opposite fashion, our results show that as thermohaline circulation abates, global warming progresses and the ocean surface becomes warmer, many marine organisms will be affected by the environmental degradation.