![]() Abstract Our central paradigm for urban ecology is that cities are emergent phenomena of local-scale, dynamic interactions among socioeconomic and biophysical forces. These complex interactions give rise to a distinctive ecology and to distinctive ecological forcing functions. Kilauea; Mount Etna; Mount Yasur; Mount Nyiragongo and Nyamuragira; Piton de la Fournaise; Erta Ale. Separately, both the natural and the social sciences have adopted complex system theory to study emergent phenomena, but attempts to integrate the natural and social sciences to understand human-dominated systems remain reductionist—these disciplines generally study humans and ecological processes as separate phenomena. Here we argue that if the natural and social sciences remain within their separate domains, they cannot explain how human-dominated ecosystems emerge from interactions between humans and ecological processes. We propose an integrated framework to test formal hypotheses about how human-dominated ecosystems evolve from those interactions. For most of human history, the influence of human beings on biophysical processes, ecological systems, and evolutionary change has been relatively limited, as compared with the influence of “natural” (nonhuman) processes. Ecological and evolutionary change has generally been attributable to natural variation in energy and material flows and to natural selection by parasites, diseases, predators, and competitors. Today, however, humans affect Earth's ecosystems at extraordinary rates through conversion of land and resource consumption (), alteration of habitats and species composition (), disruption of hydrological processes (), and modification of energy flow and nutrient cycles (, ). Humans now use approximately 40% of global net primary production () and more than half of accessible freshwater runoff (). At least half of the world's forests have disappeared as a result of human activity, and three-quarters of that total have disappeared since 1700 (). Human activities fix amounts of nitrogen and sulfur comparable to those fixed by all nonhuman causes (). Humans have radically revamped Earth's carbon cycle () and freed into the environment vast quantities of naturally occurring trace materials (e.g., cadmium, zinc, mercury, nickel, arsenic) and exotic new anthropogenic substances (e.g., polychlorinated biphenyls, chlorofluorocarbons) (). Humans also influence evolutionary processes. Selection is more and more frequently directed by people, or at least by people interacting with other natural processes. For example, humans affect speciation by challenging bacteria with antibiotics, poisoning insects, rearranging and exchanging genes, creating and dispersing thousands of synthetic compounds, and selectively fishing (). By hunting, moving predators and competitors around the globe, and massively reconfiguring the planet's surface, humans have increased extinctions of other species to levels 1000 to 10,000 times higher than those resulting from nonhuman causes (,, ). The combined effect of changing speciation and extinction is rapid evolutionary change (). Despite dominating Earth's ecosystems, humans remain conspicuously excluded as subjects of much ecological thinking and experimentation. Traditional ecological research investigates ecosystems in terms of biophysical, ecological, and evolutionary processes unaffected by human influences. During the last 100 years, formidable strides have been made in the scientific understanding of ecological systems (). Evolutionary theory and population genetics have made fundamental changes in the assumptions underlying ecological research. Ecological scholars no longer regard ecosystems as closed, self-regulating entities that “mature” to reach equilibria. Instead, they see such systems as multiequilibria, open, dynamic, highly unpredictable, and subject to frequent disturbance (). In the newer non-equilibrium paradigm, succession has multiple causes, can follow multiple pathways, and is highly dependent on environmental and historical context. Gloucester mt extra font free download. About Gloucester MT Std Bold Name Gloucester MT Std Bold Type OpenType Category Uncategorized Family Gloucester MT Std Style Bold PostScript GloucesterMTStdBold Glyph Number 253 Units Per em 1000 Ascender 733 Descender -267 Height 1200 Max Advance Width 1146 Max Advance Height 1200 Underline Position -100 Underline Thickness 50 Global BBox (162,225), (1094,977) Has Horizontal yes Has Vertical no Has Kerning no Is Fixed Width no Is Scalable yes Font Size 37.5 KB Downloads Yesterday 0 Total Downloads 358 Rating.
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