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ABSTRACT: We address whether robust early warning signals can, in principle, be provided before a climate tipping point is reached, focusing on methods that seek to detect critical slowing down as a precursor of bifurcation. As a test bed, six previously analysed datasets are reconsidered, three palaeoclimate records approaching abrupt transitions at the end of the last ice age and three models of varying complexity forced through a collapse of the Atlantic thermohaline circulation. Approaches based on examining the lag-1 autocorrelation function or on detrended fluctuation analysis are applied together and compared. The effects of aggregating the data, detrending method, sliding window length and filtering bandwidth are examined. Robust indicators of critical slowing down are found prior to the abrupt warming event at the end of the Younger Dryas, but the indicators are less clear prior to the Bølling-Allerød warming, or glacial termination in Antarctica. Early warnings of thermohaline circulation collapse can be masked by inter-annual variability driven by atmospheric dynamics. However, rapidly decaying modes can be successfully filtered out by using a long bandwidth or by aggregating data. The two methods have complementary strengths and weaknesses and we recommend applying them together to improve the robustness of early warnings.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 03/2012; 370(1962):1185-204. · 2.77 Impact Factor
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ABSTRACT: We explored systematic patterns in predictability of phytoplankton species from 83 lakes over a gradient
ranging from subpolar to tropical regions in South America. We estimated the explained variance (proxy of
predictability) of the presence and biomass (estimated as biovolume) of species using multiple regressions
from commonly measured environmental variables such as nutrient levels, light, mixing depth, temperature,
and zooplankton biomass. Both the presence and biomass of species occurring at least in 10 lakes were quite
well predicted from the environmental variables, with average values of 35% and 58%, respectively.
Predictability was not systematically related to phylogenetic affiliation or particular functional groups as
defined by morphology. However, biomass predictability decreased with increasing occurrence, and improved
with larger species size (maximum linear dimension). Species that were predictable in terms of biomass (R2 $
0.5, p # 0.05) had, on average, a larger volume, and were relatively more frequent in lakes from warmer
regions, with high water temperature, low chlorophyll a, low nutrient concentrations, and low total
zooplankton biomass. Although we cannot diagnose the mechanisms involved, our finding that the number of
predictable species increases towards warmer regions resembles situations where competition for nutrients and
grazing are likely to be less severe, and may imply that in a future warmer world phytoplankton will be easier
to predict.
Limnol. Oceanogr. 01/2012; 57(4):1126-1135.
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R S Steneck,
T P Hughes,
J E Cinner,
W N Adger,
S N Arnold,
F Berkes,
S A Boudreau,
K Brown,
C Folke,
L Gunderson,
P Olsson, M Scheffer,
E Stephenson,
B Walker,
J Wilson,
B Worm
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ABSTRACT: Unsustainable fishing simplifies food chains and, as with aquaculture, can result in reliance on a few economically valuable species. This lack of diversity may increase risks of ecological and economic disruptions. Centuries of intense fishing have extirpated most apex predators in the Gulf of Maine (United States and Canada), effectively creating an American lobster (Homarus americanus) monoculture. Over the past 20 years, the economic diversity of marine resources harvested in Maine has declined by almost 70%. Today, over 80% of the value of Maine's fish and seafood landings is from highly abundant lobsters. Inflation-corrected income from lobsters in Maine has steadily increased by nearly 400% since 1985. Fisheries managers, policy makers, and fishers view this as a success. However, such lucrative monocultures increase the social and ecological consequences of future declines in lobsters. In southern New England, disease and stresses related to increases in ocean temperature resulted in more than a 70% decline in lobster abundance, prompting managers to propose closing that fishery. A similar collapse in Maine could fundamentally disrupt the social and economic foundation of its coast. We suggest the current success of Maine's lobster fishery is a gilded trap. Gilded traps are a type of social trap in which collective actions resulting from economically attractive opportunities outweigh concerns over associated social and ecological risks or consequences. Large financial gain creates a strong reinforcing feedback that deepens the trap. Avoiding or escaping gilded traps requires managing for increased biological and economic diversity. This is difficult to do prior to a crisis while financial incentives for maintaining the status quo are large. The long-term challenge is to shift fisheries management away from single species toward integrated social-ecological approaches that diversify local ecosystems, societies, and economies.
Conservation Biology 07/2011; 25(5):904-12. · 4.69 Impact Factor
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B. Moss,
S. Kosten,
M. Meerhoff,
R.W. Battarbee,
E. Jeppesen,
N Mazzeo,
K. Havens,
G. Lacerot,
Z Liu,
L. De Meester,
Hans W. Paerl, M. Scheffer
Inland waters. 01/2011;
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ABSTRACT: Ecosystems are complex systems which can respond to gradual changes of their conditions by a sudden shift to a contrasting regime or alternative stable state (ASS). Predicting such critical points before they are reached is extremely difficult and providing early warnings is fundamental to design management protocols for ecosystems. Here we study different spatial versions of popular ecological models which are known to exhibit ASS. The spatial heterogeneity is introduced by a local parameter varying from cell to cell in a regular lattice. Transport of biomass among cells occurs by simple diffusion. We investigate whether different quantities from statistical mechanics -like the variance, the two-point correlation function and the patchiness-may serve as early warnings of catastrophic phase transitions between the ASS. In particular, we find that the patch-size distribution follows a power law when the system is close to the catastrophic transition. We also provide links between spatial and temporal indicators and analyze how the interplay between diffusion and spatial heterogeneity may affect the earliness of each of the observables. Finally, we comment on similarities and differences between these catastrophic shifts and paradigmatic thermodynamic phase transitions like the liquid-vapor change of state for a fluid like water.
Journal of Physics Conference Series 09/2010; 246(1):012035.
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M Rietkerk,
V Brovkin,
P M Van Bodegom,
M Claussen,
S C Dekker,
H A Dijkstra,
S V Goryachkin,
P Kabat,
E H Van Nes,
A.-M Neutel,
S E Nicholson,
C Nobre,
V Petoukhov,
A Provenzale, M Scheffer,
S I Seneviratne
BGD. 01/2009; 6:10121-10136.
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J. Rockström,
W. Steffen,
K. Noone,
Å. Persson,
F. S. Chapin III,
E. Lambin,
T. M. Lenton, M. Scheffer,
C. Folke,
H. Schellnhuber, [......],
M. Falkenmark,
L. Karlberg,
R. W. Corell,
V. J. Fabry,
J. Hansen,
B. Walker,
D. Liverman,
K. Richardso,
P. Crutzen,
J. Foley
ECOLOGY AND SOCIETY 01/2009; 14(2):32. · 2.52 Impact Factor
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F Berkes,
T P Hughes,
R S Steneck,
J A Wilson,
D R Bellwood,
B Crona,
C Folke,
L H Gunderson,
H M Leslie,
J Norberg,
M Nyström,
P Olsson,
H Osterblom, M Scheffer,
B Worm
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ABSTRACT: Marine resource exploitation can deplete stocks faster than regulatory agencies can respond. Institutions with broad authority
and a global perspective are needed to create a system with incentives for conservation.
Science 04/2006; 311(5767):1557-8. · 31.20 Impact Factor
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ABSTRACT: We studied the effects of different concentrations of decomposing Rhizophora apiculata leaves and their leachates on larvae of the shrimp Penaeus monodon under laboratory conditions. Shrimp mortality was highly dependent on the concentration of oxygen in the water, which in turn was strongly correlated to the amount of decomposing leaves in the same water. Shrimps died after 5min when placed in water containing the highest concentration of mangrove leachates (15gl−1) tested in our experiments. Shrimp survival and biomass decreased significantly when the shrimp were cultured at the relatively higher concentrations of leaves and leachates (10 and 15gl−1); in contrast, moderate amounts of leaves or their leachates (2.5–5gl−1) had positive effects on shrimps. The survival and biomass of shrimps cultured with plastic leaves was lower than those of shrimps cultured with mangrove leaves, indicating that food derived from mangrove leaves contributed to a higher shrimp survival and biomass. These results have important implications for the culture of shrimps in extensive mangrove-shrimp systems. While litter may promote shrimp production, high leaf concentrations may have negative effects due to the drop in the oxygen concentration. Water circulation may help to prevent low oxygen conditions and reduce local accumulations of mangrove leaves.
Aquaculture International 01/2006; 14(5):467-477. · 0.91 Impact Factor
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Journal of Applied Ecology 03/2005; 42(2):251 - 260. · 5.05 Impact Factor
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ABSTRACT: The characteristic ecology of floodplain lakes is in part due to their relatively strong water-level fluctuations. We analyzed the factors determining water-level fluctuations in 100 floodplain lakes (during non-flooded conditions) in the active floodplains of the Lower Rhine in the Netherlands. Furthermore, we explored the relationship between water-level fluctuations and macrophyte species richness, and analyzed the suitability of artificially created lakes for macrophyte vegetation. During non-flooded conditions along the Rhine, lake water-level fluctuations are largely driven by groundwater connection to the river. Hence, water-level fluctuations are largest in lakes close to the main channel in strongly fluctuating sectors of the river and smallest in isolated lakes. Additionally, water-level fluctuations are usually small in old lakes, mainly due to reduced groundwater hydraulic conductivity resulting from accumulated clay and silt on the bottom. Species richness of floating-leaved and emergent macrophytes was reduced at both small and large water-level fluctuations, whereas species richness of submerged macrophytes was reduced at small water-level fluctuations only. In addition, species richness of submerged macrophytes was higher in lakes that experienced drawdown, whereas no similar pattern was detected for floating-leaved and emergent macrophytes. The decline in amplitude of lake water-level with lake age implies that the number of hydrologically dynamic lakes will decrease over time. Therefore, we suggest that excavation of new lakes is essential to conserve the successional sequence of floodplain water bodies including conditions of high biodiversity. Shallow, moderately isolated, lakes with occasional bottom exposure have the highest potential for creating macrophyte-rich floodplain lakes along large lowland rivers. The water-level regime of such lakes can in part be designed, through choice of the location along the river, the distance away from the river and the depth profile of the lake.
Hydrobiologia 01/2005; 539(1):239-248. · 1.78 Impact Factor
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ABSTRACT: SUMMARY 1. We analysed the vegetation structure of 215 lakes in the flood plain of the river Lower Rhine in relation to environmental variables related to hydrological connectivity, lake morphometry, lake age and land use on adjacent land.2. The frequency distribution of the cover of submerged macrophytes was not normal, implying that submerged macrophytes in any one lake were either scarce or abundant.3. We observed clear water lakes with submerged macrophyte dominance over a wide range of total P concentration (0.020–0.40 mg total P L−1).4. Multiple logistic regression indicated that the probability of dominance by submerged macrophytes decreased markedly with the surface area, depth and age of the lakes. The surface area effect occurred independently of the depth. Further, there was a negative relationship between submerged macrophyte dominance and the long-term annual duration of inundation by the river.5. Nymphaeid cover showed a distinct optimum with respect to mean lake depth, being almost absent in lakes shallower than 0.5 m. In contrast to what was found for submerged plants, the probability of occurrence of nymphaeids increased with lake age.6. The probability of helophyte occurrence increased with lake age, and decreased with the presence of trees, cattle grazing, surface area, use of manure and mean lake depth.7. In all cases the critical level of one factor (e.g. mean lake depth) depended on other factors (e.g. surface area or age of lake). Thus, in the present study, small lakes tended to remain dominated by submerged macrophytes up to a greater depth than large lakes, and helophytes colonised smaller lakes in an earlier phase.8. The effect of inundation by the river was modest. This could be because most of our lakes are rarely inundated during the growing season and experience only moderate current velocities while flooded.9. The results have practical implications for future management of flood plains for conservation purposes. In new water bodies, macrophyte domination will be promoted if many small shallow lakes, rather than few large deep ones, are excavated.
Freshwater Biology 02/2003; 48(3):440 - 454. · 3.29 Impact Factor
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ABSTRACT: All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.
Nature 11/2001; 413(6856):591-6. · 36.28 Impact Factor
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M Scheffer
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ABSTRACT: Ponds and shallow lakes can be very clear with abundant submerged plants, or very turbid due to a high concentration of phytoplankton and suspended sediment particles. These strongly contrasting ecosystem states have been found to represent alternative attractors with distinct stabilizing feedback mechanisms. In the turbid state, the development of submerged vegetation is prevented by low underwater light levels. The unprotected sediment frequently is resuspended by wave action and by fish searching for food causing a further decrease of transparency. Since there are no plants that could serve as refuges, zooplankton is grazed down by fish to densities insufficient to control algal blooms. In contrast, the clear state in eutrophic shallow lakes is dominated by aquatic macrophytes. The submerged macrophytes prevent sediment resuspension, take up nutrients from the water, and provide a refuge for zooplankton against fish predation. These processes buffer the impacts of increased nutrient loads until they become too high. Consequently, the response of shallow lakes to eutrophication tends to be catastrophic rather than smooth, and various lakes switch back and forth abruptly between a clear and a turbid state repeatedly without obvious external forcing. Importantly, a switch from a turbid to a stable clear state often can be invoked by means of biomanipulation in the form of a temporary reduction of the fish stock.
TheScientificWorldJOURNAL 08/2001; 1:254-63. · 1.66 Impact Factor
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ABSTRACT: New studies are showing that the El Niño Southern Oscillation (ENSO) has major implications for the functioning of different ecosystems, ranging from deserts to tropical rain forests. ENSO-induced pulses of enhanced plant productivity can cascade upward through the food web invoking unforeseen feedbacks, and can cause open dryland ecosystems to shift to permanent woodlands. These insights suggest that the predicted change in extreme climatic events resulting from global warming could profoundly alter biodiversity and ecosystem functioning in many regions of the world. Our increasing ability to predict El Niño effects can be used to enhance management strategies for the restoration of degraded ecosystems.
Trends in Ecology & Evolution 03/2001; 16(2):89-94. · 15.75 Impact Factor
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nat. 01/2001; 413:591--596.
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M L. Meijer,
E. Jeppesen,
E. Donk,
B. Moss, M. Scheffer,
E. Lammens,
E. Nes,
J. A. Berkum,
G. J. Jong,
B. A. Faafeng,
J. P. Jensen
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ABSTRACT: The effects of fish stock reduction have been studies in 3 Dutch lakes (Lake Zwemlust, Lake Bleiswijkse Zoom and Lake Noorddiep) and 1 Danish lake (Lake Vng) during 4–5 years. A general response id described. The fish stock reduction led in general to a low fish stock, low chlorophyii-a, high transparency and high abunuance of macrophytes. Large Daphnia became abundant, but their density decreased, due to food limitation and predation by fish. The total nitrogen concentration became low due to N-uptake by macrophytes and enhanced denitrification. In Lake Bleiswijkse Zoom the water transparency deteriorated and the clear water state was not stable. The fish stock increased and the production of young fish in summer was high. lear water occurred only in spring. Large daphnids were absent in summer and the macrophytes decreased.In Lake Zwemlust, Lake Vng and Lake Noorddiep the water remained clear during the first five years. In summer of the sixth year (1992) transparency decreased in Lake Zwemlust (with high P-concentration of 1.0 mg P l-1). Also in Lake Vng (with a low nutrient concentration of 0.15 mg P.-1) a short term turbid stage (1.5 month) occurred in summer 1992 after a sudden collapse of the macrophytes. Deterioration of the water quality seems to start in summer and seems related to a collapse in macrophytes. At a low planktivorous fishstock (e.g. Lake Vng)thhe duration of the turbid state is shorter. than in presence of a high planktivorous fish biomass (e.g. Lake Zwemlust, and later years of Lake Bleiswijkse Zoom).
Hydrobiologia 01/1994; 275-276(1):457-466. · 1.78 Impact Factor
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ABSTRACT: The turbidity of lakes is generally considered to be a smooth function of their nutrient status. However, recent results suggest that over a range of nutrient concentrations, shallow lakes can have two alternative equilibria: a clear state dominated by aquatic vegetation, and a turbid state characterized by high algal biomass. This bi-stability has important implications for the possibilities of restoring eutrophied shallow lakes. Nutrient reduction alone may have little impact on water clarity, but an ecosystem disturbance like foodweb manipulation can bring the lake back to a stable clear state. We discuss the reasons why alternative equilibria are theoretically expected in shallow lakes, review evidence from the field and evaluate recent applications of this insight in lake management.
Trends in Ecology & Evolution 08/1993; 8(8):275-9. · 15.75 Impact Factor
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Archiv für Hydrobiologie 160 (2004) 3.
