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pierredv : ecosystems   26

Predicting tipping points in complex environmental systems | Proceedings of the National Academy of Sciences
Ecologists have long recognized that ecosystems can exist and function in one state within predictable bounds for extended periods of time and then abruptly shift to an alternate state (1⇓⇓⇓–5). Desertification of grasslands, shrub expansion in the Arctic, the eutrophication of lakes, ocean acidification, the formation of marine dead zones, and the degradation of coral reefs represent real and potential ecological regime shifts marked by a tipping point or threshold in one or more external drivers or controlling variables within the system that when breached causes a major change in the system’s structure, function, or dynamics (6⇓⇓–9). Large or incremental alterations in climate, land use, biodiversity (invasive species or the overexploitation of species), and biogeochemical cycles represent external and internal drivers that when pushed too far cross thresholds that can could lead to regime shifts (Fig. 1). Seeing the tipping point after the fact and ascribing mechanisms to the change is one thing; predicting them using empirical data has been a challenge. The difficulty in predicting tipping points stems from the large number of species and interactions (high dimensionality) within ecological systems, the stochastic nature of the systems and their drivers, and the uncertainty and importance of initial conditions that the nonlinear nature of the systems introduce to outcomes. In PNAS, Jiang et al. (10) confront these issues using a dimension-reduction framework that uses empirical data from 59 complex multidimensional plant–pollinator mutualistic networks, some of which contain scores of species and interactions, to develop simpler 2D models for studying and predicting tipping points.
PNAS  tipping-points  complexity  ecosystems 
march 2018 by pierredv
Evolution can help head off the next financial crash - opinion - 04 November 2014 - Test - New Scientist
Essay by Eduardo Viegas , Henrik Jeldtoft Jensen and Geoffrey West "We found that financial crises emerge not as the result of specific economic events or regulatory developments, but rather as a result of a long-term evolutionary process that regulates companies' growth – mergers and acquisitions. Inevitably, this process leads to the emergence of imbalanced ecosystems – akin to oligopoly or monopoly – consisting of a few very large, but sluggish "too big to fail" entities, alongside very small, niche entities." "... two mechanisms that act as catalysts for the emergence of a crisis. The first is banks copying the business models of the most (short-term) successful bank, which leads to loss of both diversity and resilience. The second is investors such as fund managers increasing their appetite for risk by trying to outperform competitors."
ecosystems  complexity  finance  economics  NewScientist  opinion 
december 2014 by pierredv
Aliens versus predators: The toxic toad invasion - life - 25 April 2014 - New Scientist
"As the toads invaded Fogg Dam, Shine, who is based at the University of Sydney, got some of the first hard data on their impact. What he has found is that the Australian cane toad invasion is both far worse than anyone thought – and also not nearly as bad. The toads are spreading further and faster than anyone expected, and they do have a devastating impact when they first arrive in a region. But most animals are adapting to their presence surprisingly quickly, and some even benefit."
ecosystems  NewScientist  cane-toad  unintended-consequences 
june 2014 by pierredv
Welcome weeds: How alien invasion could save the Earth - environment - 20 January 2011 - New Scientist
"Far from ravaging threatened ecosystems, non-native species could be powerful allies in the fight to save them"
ecosystems  intuition  invasives  pests  NewScientist 
january 2011 by pierredv
Maximisation, optimisation and all that | openDemocracy
"There’s a compelling notion that, post-financial crisis, economists are turning from ‘physics envy’ to ‘biology envy’. Our economic metaphors have certainly become more vital and ecological: ‘financial contagion’, ‘toxic assets’, ‘systemic risk’. Some have suggested that the regulators of the future will stare at vast fractal diagrams of the financial economy, studying its mutations in real time to assess its overall health."
"Why maximise, and not optimise? Economists will tell you that it is only this implied insatiability that keeps their models nice and tidy. Throw in notions of altruism, reputation, psychology and relationship-building, and neo-classical economics loses its central virtue, which is that it gives straight, unambiguous answers."
"As I explore in Reinventing the Firm, businesses that are not subject to the pressure of external shareholders or private equity funds can be considered profit-making, but not profit-maximising."
via:andrewcurry  complexity  ecosystems  economics 
april 2010 by pierredv
Self-referential systems
Focuses on W B Arthur's El Farol bar problem; references term "ecosystem" used by Holland to refer to the mix of predictors
complexity  emergence  ecosystems 
march 2010 by pierredv
French beach toxic enough to kill a horse | Seattle Times Newspaper
"There had been signs of a crisis for years in this idyllic corner of Brittany. But scaring away tourists was in no one's interest, including the farming industry — the region's economic backbone — whose nitrate-packed fertilizers power algae blooms."
ecosystems  complexity  politics  France  EU 
august 2009 by pierredv
The ecology of crisis | The Australian
summary of paper by Andrew Haldane (Executive Director, Financial Stability, Bank of England), "Rethinking the Financial Network" on how financial systems resemble fragile ecosystems
via Tren
finance  regulation  complexity  ecosystems 
july 2009 by pierredv
Saving the Galapagos means rebuilding nature | - Sara Miller Llana
Good feature on restoration
Ecosystem definition that made me think about "business ecosystems":
"If an ecosystem is a community of life forms that have evolved together and achieved equilibrium, then the restoration of that ecosystem begins with the removal of everything that upsets the balance."
complexity  ecosystems 
april 2009 by pierredv
As beetle invasion rages, a debate over logs |
reasons: "The beetles are nothing new to the region, and every few decades their population explodes. This current outbreak is being fueled by drought conditions, the fact that earlier logging homogenized the age of the trees, and the lack of long winter cold spells that kill the beetles"
csmonitor  ecosystems  beetles 
january 2009 by pierredv
Heat sends Southwest climate back in time |
Includes survey of fire practice, resilience, and water: "Until around 1910, wildfires had burned through Southwestern eco­­systems about every five to 15 years locally, according to tree-ring records – apparently for millennia. Fires continually burned back encroaching juniper and pinyon trees, leaving only those trees mature and strong enough to withstand a burning understory. Absent the fires, young trees moved in unchecked. During the 20th century, areas that were once predominantly grassy ... became scrubby, erosion-prone pinyon-juniper forest." "Ecosystems are shaped by extremes of hot and cold, wet and dry. If those extremes are pushed even a little further away from the mean, the effect can be drastic, especially when relatively slow-growing trees are involved." "in Arizona in 2000, agriculture used four times as much water as everything else combined. But farming contributed less than 1 percent of the state’s GDP"
ecosystems  policy  fire  csmonitor  factoids  resilience 
january 2009 by pierredv
Management and restoration of dynamic ecosystems, John E Gross
ecosystem responses to perturbations, including restoration efforts, can be highly nonlinear and lead to management surprises. . . further complicated by social-ecological interactions emerging from biophysical dynamics and the institutional framework
complexity  ecosystems 
august 2008 by pierredv
What's killing the elk in Yellowstone? -
interaction of elk populations, hunting, wolves, bear, trees - lots of management challenges
january 2008 by pierredv
Chaos in Eden - 14 October 1995 - New Scientist
trenchant critique of the long-discredited but still current notion of ecological communities, succession, and the island-based mass extinction predictions of EO Wilson and Co
also right at the end useful references to elk case in Yellowstone, and effect
gardening  ecosystems 
january 2008 by pierredv
Product Puts Beekeepers, Lawn Growers at Odds - from Time Warner Cable
imidacloprid, used to control grubs in lawns and crops, may be causing bee hives to collapse across North America
unintended-consequences  ecosystems  complexity 
november 2007 by pierredv
"Revolt" and "Remember" - Panarchy theory
mechanisms and importance of cross-scale interactions
complexity  policy  ecosystems 
october 2007 by pierredv
introduction to terminology, with link to download first chapter of the Holling et al book
complexity  ecosystems 
october 2007 by pierredv

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