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Global shifts towards positive species interactions with increasing environmental stress
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The study of positive species interactions is a rapidly evolving field in ecology. Despite decades of research, controversy has emerged as to whether positive and negative interactions predictably shift with increasing environmental stress as hypothesised by the stress-gradient hypothesis (SGH). Here, we provide a synthesis of 727 tests of the SGH in plant communities across the globe to examine its generality across a variety of ecological factors. Our results show that plant interactions change with stress through an outright shift to facilitation (survival) or a reduction in competition (growth and reproduction). In a limited number of cases, plant interactions do not respond to stress, but they never shift towards competition with stress. These findings are consistent across stress types, plant growth forms, life histories, origins (invasive vs. native), climates, ecosystems and methodologies, though the magnitude of the shifts towards facilitation with stress is dependent on these factors. We suggest that future studies should employ standardised defini- tions and protocols to test the SGH, take a multi-factorial approach that considers variables such as plant traits in addition to stress, and apply the SGH to better understand how species and communities will respond to environmental change.
Keywords
Biotic interactions, community ecology, ecosystems and climates, environmental stress, facilitation, invasive species, meta-analysis, plant traits, the stress-gradient hypothesis.
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Global temperature change
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We conclude that global warming of more than 1°C, relative to 2000, will constitute ‘‘dangerous’’ climate change as judged from likely effects on sea level and extermination of species.
climate change El Niños global warming sea level species extinctions
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GLOBAL WARMING AND FISH MIGRATIONS
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Ocean temperatures are expected to rise over the next decades. This is likely to affect the distribution of fish stocks between the exclusive economic zones (EEZs) of different countries. Such changes are likely to be triggered as temperatures rise beyond certain threshold levels, and they are likely to be irregular because temperatures are likely to vary around a rising trend. The paper looks at the case where temperature changes would displace a fish stock out of the EEZ of one country and into the EEZ of another, with a transition period in which the stock is shared. It is examined how this might affect the risk of extinction and degree of overfishing, under different cost scenarios and different assumptions about how countries react to observed changes in the distri- bution of the stock between their economic zones.
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Global warming benefits the small in aquatic ecosystems
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Understanding the ecological impacts of climate change is a crucial challenge of the twenty-first century. There is a clear lack of general rules regarding the impacts of global warming on biota. Here, we present a metaanalysis of the effect of climate change on body size of ectothermic aquatic organisms (bacteria, phyto- and zooplankton, and fish) from the community to the individual level. Using long-term surveys, experimental data and published results, we show a significant increase in the proportion of small-sized species and young age classes and a decrease in size-at-age. These results are in accordance with the ecological rules dealing with the temperature–size relationships (i.e., Bergmann’s rule, James’ rule and Temperature–Size Rule). Our study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.
biological scale body size climate change ectotherms metaanalysis
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Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics
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Many studies suggest that global warming is driving species ranges poleward and toward higher
elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the
shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts.
Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the
potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected
warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition
without parallel at higher latitudes (where range shifts may be compensated for by species from
lower latitudes) and that a high proportion of tropical species soon faces gaps between current
and projected elevational ranges.
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Global Warming: Why Business is Taking it So Seriously.
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Consensus is growing among scientists, governments, and business that they must act fast to combat climate change. This has already sparked efforts to limit CO[SUB 2] emissions. Many companies are now preparing for a carbon-constrained world.
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Global warmth with little extra co2
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Most climate models consider only short-term processes such as cloud and sea-ice formation when assessing Earth’s sensitivity to greenhouse-gas forcing. Mounting evidence indicates that the response could be stronger if boundary conditions change drastically.
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Global water resources affected by human interventions and climate change
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Humans directly change the dynamics of the water cycle through dams constructed for water storage, and through water withdrawals for industrial, agricultural, or domestic purposes. Climate change is expected to additionally affect water supply and demand. Here, analyses of climate change and direct human impacts on the terrestrial water cycle are presented and compared using a multi- model approach. Seven global hydrological models have been forced with multiple climate projections, and with and without taking into account impacts of human interventions such as dams and water withdrawals on the hydrological cycle. Model results are analyzed for different levels of global warming, allowing for analyses in line with temperature targets for climate change mitigation. The results indicate that direct human impacts on the water cycle in some regions, e.g., parts of Asia and in the western United States, are of the same order of magnitude, or even exceed impacts to be expected for moderate levels of global warming (+2 K). Despite some spread in model projections, irrigation water consumption is generally projected to increase with higher global mean temperatures. Irrigation water scarcity is particularly large in parts of southern and eastern Asia, and is expected to become even larger in the future.
ISI-MIP | WaterMIP
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Goetz, Anita
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gogomaju, gogo
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