There is a growing body of evidence suggesting that vegetation mortality during drought or periods of high temperatures is rising across the globe. Research regarding the mechanisms of vegetation mortality has grown dramatically in the last five years, as has research on the consequences of mortality on climate forcing. This new research has also stimulated valuable debate regarding how universal or variable mortality mechanisms may be globally, and how much feedback there is upon climate. Resolving these questions is essential for improving global climate models due to the inherent land-climate feedbacks. I will review the evidence for the variety of hypothesized mechanisms of death and the subsequent potential climate forcing. I will conclude by outlining a vision towards resolving these scientific questions, with the ultimate goals of improving our understanding and modeling of climate-terrestrial impacts and feedbacks.
Greg Asner is an ecologist with the Carnegie Institution for Science and Stanford University. Here he presents new insights from the CAO program, shedding light on ways in which 3-D studies of ecosystems can improve scientific knowledge and accelerate natural resource and climate-change policy actions.
For many years, we have been making use of the Hawaiian Islands as models for understanding how soils and ecosystems develop and function. Results of this research show that the properties of soils exhibit sharp thresholds in both space and time, places where soil properties change abruptly with a small additional change in forcing. We have identified three major thresholds in Hawaiian soils – one associated with the accumulation of carbonate in dry soils, a second associated with the depletion of primary minerals in the rooting zone, and a third associated with iron reduction and phosphorus mobility.
Asbestos fibers were exploited commercially beginning in the early 20th century, with 50 million metric tons used between 1920-1970. Inhalation of asbestos fibers is associated with pulmonary fibrosis (asbestosis), lung and laryngeal cancers, and malignant mesothelioma, with a long latent period of 20-40 years. The 15-year cumulative mortality from malignant mesothelioma from 1994-2008 is 175,000 deaths.
The physical and chemical properties of asbestos fibers related to carcinogenicity include fiber dimensions, surface reactivity, and biopersistence following inhalation into the lungs. Long, rigid fibrous materials trigger incomplete or frustrated phagocytosis by target cells in the lungs, resulting in impaired clearance and persistent release of reactive oxygen species and proinflammatory mediators. Direct intraperitoneal injection of carbon nanotubes has also been shown to induce malignant mesothelioma in mice. Carbon nanotubes have shapes and dimensions similar to asbestos fibers; however, their graphenic surface is hydrophobic, while crystalline mineral fibers are hydrophilic. Asbestos fibers and carbon nanotubes are biopersistent; however, carbon nanotubes can be chemically modified to accelerate their degradation by oxidants.
Carbon nanotubes are a rapidly growing worldwide market, and production is projected to exceed 12,000 metric tons in 2016. At this early stage in commercialization, it should be possible to engineer less toxic, biocompatible, and biodegradable carbon nanotubes to minimize potential adverse health impacts.
In response to general interest in the events associated with the recent Fukushima disaster in Japan, the Division has scheduled Dr. Robert Budnitz as our speaker. Bob brings considerable expertise to the topic, having spent most of his scientific career involved with nuclear-reactor safety and radioactive-waste safety. Bob’s talk will describe (technically, but in laymen's terms) what happened at the Fukushima reactors during and after the disastrous March 11 earthquake and tsunami, what the radioactive releases have been and what they mean, and what the path forward seems to be at the site. The potential implications that these events might have upon the future of nuclear power in general will also be discussed.
Distinguished Scientist Seminar Series
The ESD Distinguished Scientist Series is a monthly seminar featuring eminent individuals from various disciplines in the scientific community whose research is outstanding, interdisciplinary, and of broad interest to strategic interest initiatives in the earth sciences. Speakers normally spend a full day with researchers at Earth Sciences Division, LBNL, and the University of California, Berkeley.