Contingencies and compounded rare perturbations dictate sudden distributional shifts during periods of gradual climate change

Harley, Christopher D. G.; Paine, Robert T.

doi:10.1073/pnas.0904946106

Cited by 112 publications

(95 citation statements)

References 21 publications

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“…With the observed gradual increase in water temperature and duration of the ice-free season, we hypothesize a reduction in resilience of the original equilibrium state. Under reduced resilience, environmental perturbations, like an extremely warm winter or an early ice melt, can more easily trigger a regime shift in the benthos by inducing the crossing of a critical threshold (26)(27)(28). We suggest that the Arctic benthic communities in our study have crossed such a critical threshold, tipping the system from an original state (in 1980) with little macroalgae to a new state with relatively high density of macroalgae and a reorganization of benthic community structure.…”

mentioning

confidence: 72%

Climate-driven regime shifts in Arctic marine benthos

Kortsch

Primicerio

Beuchel

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

218

183

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Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years.climate change | community structure | ecological dynamics | ecological interactions | tipping point C limate warming has accelerated over the past 30 y, causing increases in global surface temperatures of about 0.2°C per decade (1). The greatest changes have been recorded in the Arctic, where the temperatures have risen at twice the global average rate and sea ice cover, at the end of the Arctic summer, has declined by 30% (2). These changes modify Arctic marine habitats with respect to light and temperature regimes, which, in turn, impact local biological communities (3, 4). The increasing length of the ice-free season (5), extending the period of primary production, and the increasing seawater temperature, have strong impacts on abundances and distributions of species mediated by changes in demographic and interaction parameters.

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mentioning

confidence: 72%

Climate-driven regime shifts in Arctic marine benthos

Kortsch

Primicerio

Beuchel

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

218

183

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“…Something similar could be affecting the growth of Saccorhiza polyschides but it is difficult to find a straightforward relationship between ecological responses and changes in the abiotic environment. The pattern of change in the distribution and abundance of a species can be gradual or punctuated, depending on the way the abiotic factors change and whether there is a critical threshold or 'tipping point' for species performance (Harley & Paine, 2009). As the period of temperature stress happens in summer, the microscopic stages (from the spore release to the growth of sporophytes to a macroscopic size) that are present from autumn to spring should not be affected (see Table 1), but many other factors influencing the supply and the establishment of propagules need to be investigated (Norton, 1978;Reed et al, 2004;Graham et al, 2007), despite the difficulty of making in situ studies of these microscopic stages (Dayton, 1985).…”

Section: The Case Of Saccorhiza Polyschidesmentioning

confidence: 99%

The retreat of large brown seaweeds on the north coast of Spain: the case ofSaccorhiza polyschides

Fernández

2011

European Journal of Phycology

124

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Recent changes in kelp distribution along the north coast of Spain are described and analysed through a long-term population study focused on Saccorhiza polyschides. The main purpose of this work was to understand which population processes are more sensitive to increased sea surface temperatures and reductions in the intensity of upwelling episodes in the current scenario of global warming. Data on the distribution of kelp species (old and recent data) were obtained from the literature and compared with current species distributions assessed by field sampling between 2007 and 2010 and covering a transition coastline of 200 km. The long-term population study of Saccorhiza polyschides was conducted at a site close to the edge of its current distribution. Data for recruitment, growth and survival, as well as density and supported biomass of populations collected since the 1990s were analysed using data from the late 1970s for comparison. Kelps on the north coast of Spain have shown a westward retreat since the 1980s. Dense populations of Saccorhiza polyschides, the most important species, and Laminaria ochroleuca have been reduced to small patches and isolated individuals east of Pen˜as Cape (43 39.4 0 N; 5 50.8 0 W).The long-term study of Saccorhiza polyschides populations showed a collapse in the growth of the sporophyte and very low recruitment from the beginning of this century. The possible causal factors of this population decline and its consequences are considered, suggesting that long warm summer periods (more than 30 consecutive days of seawater temperature > 20 C) could alter kelp performance.

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“…However much of our knowledge of landscape resilience, albeit sophisticated, is based on studies of singular disturbances (White 1979, Turner 2010. Concern regarding ecological surprises (i.e., non-additive effects) as a result of disturbance interactions, with potentially dramatic impacts on long-term ecosystem structure and functioning, is mounting (Paine et al 1998, Darling and Côté 2008, Harley and Paine 2009; the likelihood of increasing disturbance frequencies resulting from climate change (Dale et al 2001) heightens that concern.…”

Section: Introductionmentioning

confidence: 99%

Disturbance interactions can impact resilience mechanisms of forests

2011

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Abstract. Interactions between multiple disturbances are of special concern in ecology due to their potential for non-linear behavior and long-lasting legacies on landscape structure and function. If multiple disturbances overcome the ecological resilience of a system, alternate stable states are possible. Increases in the frequency and severity of disturbance events as a result of climate change heighten this concern. This study directly addresses the question of ecosystem resilience in the face of multiple disturbances. We investigated a gradient of disturbance interaction severities between two events in a subalpine forest, a 1997 windstorm (variable severity) and a 2002 wildfire (high-severity). A third disturbance, salvage logging of blowdown (1999)(2000)(2001) prior to the fire, served as a de facto experimental treatment. Ninetynine study plots were established across the disturbance gradient, including fire-only areas for a baseline fire response. Modeling indicated that the combination of two severe disturbances created novel conditions which exceeded the resilience mechanisms of the system. Modeled mean fire residence time and temperature (First Order Fire Effects Model, FOFEM), as well as mean distance to potential seed sources, increased as a result of the interaction. Regeneration 8 years post-fire was essentially absent in medium-to high-severity blowdown þ fire plots, whereas low-severity blowdown þ fire and fire-only areas showed strong regeneration. Blowdown þ salvage þ fire had significantly higher regeneration than areas of comparable blowdown, suggesting that fuel loading drove the interaction. CART analysis supported this hypothesis. Multiple disturbances have the potential to create surprising situations and reduce the resilience of an ecosystem. Differential recovery as a result of a ''novel disturbance'' created by compounding events will likely have long lasting legacies across the landscape.

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Contingencies and compounded rare perturbations dictate sudden distributional shifts during periods of gradual climate change

Cited by 112 publications

References 21 publications

Climate-driven regime shifts in Arctic marine benthos

Climate-driven regime shifts in Arctic marine benthos

The retreat of large brown seaweeds on the north coast of Spain: the case ofSaccorhiza polyschides

Disturbance interactions can impact resilience mechanisms of forests

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