|Abstracts on Global Climate Change|
The use of genetic algorithms and Bayesian classification to model species distributions
Termansen, M McClean, CJ Preston, CD
ECOLOGICAL MODELLING 192:3-4 410-424
This paper develops a method to model species’ spatial distributions from environmental variables. The method is based on a search for an optimal identification of environmental niches to match observed species presence/absence data. The identification is based on Bayesian classification and the optimisation is based on a Genetic Algorithm (GA). The algorithm is tested on an artificial “species” and is shown to perform well. We apply the approach to a random sample of 100 plant species native to the British Isles. This enables an identification of the environmental variables that are most important for capturing the species’ spatial distribution. We show that both climate and land use variables are important for modelling the spatial distribution patterns of the sampled species. (c) 2005 Elsevier B.V. All rights reserved.
1851-2004 annual heat budget of the continental landmasses
GEOPHYSICAL RESEARCH LETTERS 33:4 -
Changing climate is accompanied by changing energy in various climate system components including the continental landmasses. When the temperature at ground surface rises, more heat will be deposited to the rocks beneath the ground subsurface, whereas when ground surface temperature falls, certain amount of heat will escape from the ground into the atmosphere. Based on the land-only global meteorological record, I analyze the annual heat budget of the world continents except for Antarctica. I show that between the period from 1851 to 2000 a total of 10.4 ZJ (Zetta-Joules or 10(21) J) of thermal energy had been absorbed by Africa, Asia, Australia, Europe, North America, and South America landmasses. An additional 1.34 ZJ of heat has been stored beneath the ground surface of these continents over the first four years of the 21st century from 2001 to 2004. The recent global climate change has led to an intensified heating in the continental landmasses.
Nest-site selection of endangered cinereous vulture (Aegypius monachus) populations affected by anthropogenic disturbance: present and future conservation implications
Moran-Lopez, R Guzman, JMS Borrego, EC Sanchez, AV
ANIMAL CONSERVATION 9:1 29-37
The cinereous vulture Aegypius monachus is the largest bird of the western Palaearctic, and is threatened over its entire range of distribution. Considering explicitly the influence of human interference, we studied breeding habitat selection in seven breeding colonies using a geographic information system and multivariate statistical models. Steep areas far from human disturbance constituted the preferential breeding sites in all the colonies. The nesting substrate and climatic conditions varied between colonies, but always corresponded to non-extreme climates, and included tree species of adequate size. Since human activities influenced the breeding habitat choice, there is a potential for management policies that can clearly be of benefit for the conservation of this vulture. These would fundamentally be as follows: (1) forestry activity should be oriented to protecting oak (Quercus spp.) and pine (Pinus ssp.) stands, especially individual trees of great height, and to replacing eucalyptus (Eucalyptus spp.) with autochthonous species; (2) activities (recreational, economic, etc.) around the breeding areas should be scheduled and spatially organized to avoid disturbance, particularly those deriving from the proximity of roads and tracks; (3) the expected effects of global warming should be compensated, identifying future sites where the habitat can be managed, supplementary food can be provided and reserves can be designed.
The relationship between phytoplankton diversity and community function in a coastal lagoon
Duarte, P Macedo, MF da Fonseca, LC
HYDROBIOLOGIA 555: 3-18
The decrease of biodiversity related to the phenomena of global climate change is stimulating the scientific community towards a better understanding of the relationships between biodiversity and ecosystem functioning. In ecosystems where marked biodiversity changes occur at seasonal time scales, it is easier to relate them with ecosystem functioning. The objective of this work is to analyse the relationship between phytoplankton diversity and primary production in St. Andre coastal lagoon - SW Portugal. This lagoon is artificially opened to the sea every year in early spring, exhibiting a shift from a marine dominated to a low salinity ecosystem in winter. Data on salinity, temperature, nutrients, phytoplankton species composition, chlorophyll a (Chl a) concentration and primary production were analysed over a year. Modelling studies based on production-irradiance curves were also conducted. A total of 19 taxa were identified among diatoms, dinoflagellates and euglenophyceans, the less abundant group. Lowest diversities (Shannon-Wiener index) were observed just before the opening to the sea. Results show a negative correlation (p < 0.05) between diversity and chlorophyll a (Chl a) concentration (0.2-40.3 mg Chl a m(-3)). Higher Chl a values corresponded to periods when the community was dominated by the dinoflagellate Prorocentrum minimum (> 90% of cell abundance) and production was maximal (up to 234.8 mg C m(-3) h(-1)). Maximal photosynthetic rates (P-max) (2.0-22.5 mg C mg Chl a(-1) h(-1)) were higher under lower Chl a concentrations. The results of this work suggest that decreases in diversity are associated with increases in biomass and production, whereas increases correspond to opposite trends. It is suggested that these trends, contrary to those observed in terrestrial and in some benthic ecosystems, may be a result of low habitat diversity in the water column and resulting competitive pressure. The occurrence of the highest photosynthetic rates when Chl a is low, under some of the highest diversities, suggests a more efficient use of irradiance under low biomass-high diversity conditions. Results suggest that this increased efficiency is not explained by potential reductions in nutrient limitation and intraspecific competition under lower biomasses and may be a result of niche complementarity.
Phosphorus geochemistry in the Luochuan loess section, North China and its paleoclimatic implications
Rao, WB Chen, J Luo, TY Liu, LW
QUATERNARY INTERNATIONAL 144: 72-83
Total P (P-t) on a carbonate-free basis in an entire loess-paleosol sequence and P-t, organic P (P-o) and inorganic P (P-i) in the S-0-L-1-S-1 sequence were investigated in detail with different resolutions for the Luochuan loess section from northern China. P-t content varies between 393 and 786 ppm throughout the loess-paleosol sequence, and is generally higher in the loess than in interstratified paleosols, showing fluctuation cycles of 100ka in correspondence to loess-paleosol alternations. P-t variations on a carbonate-free basis in the loess-paleosol sequence could indicate variations in atmosphere precipitation resulting in different leaching loss of P from palcosols. P-i has an average value of 499 ppm with a range of 324-560 ppm, accounting for more than 70% of P-t in the S-0-L-1-S-1 sequence, where the minimum of P-i in the Malan loess is higher than the maximum of P-i in S-1. P-o ranges between 59 and 233 ppm with an average of 132 ppm in the S-0-L-1-S-1 sequence. Phosphorus (P) was initially delivered to the Luochuan loess section via influx of aeolian dust from the northern desert and Gobi areas by the East Asian winter monsoon, and then was modified by pedogenesis associated with the East Asian summer monsoon during the last 130 ka. ” Preserved P-t” in the loess L-1 is tightly correlated with grain size without leaching loss of P due to enrichment of P in fine-grained fractions, as well as ” initial P-t”. ” Leaching P-t” data show that paleosol S-1 had lost 15-40% of its ” initial P-t”, and that there was much more precipitation in S-1 than in L-1. P-i subject to slightly weak pedogenesis was completely transformed into P-o without leaching loss of P in loess L-1. By contrast, much P-i disappeared from paleosol S, due to strong pedogenesis, partly through leaching and partly through conversion to organic forms during P cycling processes. P-o variation is similar to those of MS and the < 7.8 mu m fraction in L-1, but contains more information on the East Asian winter monsoon due to weak pedogenesis without leaching of P. P-o in S-1 lower than L1SS1, as a consequence of strong decomposition of the organic matter kept constantly in the middle of S-1 where P-i kept at the lowest of 423 ppm, suggesting that there existed a very warm and humid climate related to the enhanced summer monsoon during that period. The mean organic P/inorganic P ratio (P-o/P-i) is lower in the L1LL1 and L1LL2 than in the S-0, S-1, and L1SS1, indicating that low P-o/P-i ratios coincide with weak weathering-pedogenesis, and higher P-o/P-i ratios correspond to strong weathering-pedogenesis. P-o/P-i ratio can eliminate the effect of grain size on aeolian dust because of chemical uniformity of aeolian dust and enrichment of P-o and P-i in the fine-grained fractions. Thus, P-o/P-i ratio is solely linked to pedogenesis of the Luochuan loess section. Variation in P-o/P-i ratiois similar to those of MS and the Marine Oxygen Isotope composition, indicating the summer monsoon evolution during the last 130 ka and providing the biogeochemical evidence for further understanding the genetic links between the East Asian monsoon and global climate change. (c) 2005 Elsevier Ltd and INQUA. All rights reserved.
Quantifying relationships between bird and butterfly community shifts and environmental change
Debinski, DM VanNimwegen, RE Jakubauskas, ME
ECOLOGICAL APPLICATIONS 16:1 380-393
Quantifying the manner in which ecological communities respond during a time of decreasing precipitation is a first step in understanding how they will respond to longer-term climate change. Here we coupled analysis of interannual variability in remotely sensed data with analyses of bird and butterfly community changes in montane meadow communities of the Greater Yellowstone Ecosystem. Landsat satellite imagery was used to classify these meadows into six types along a hydrological gradient. The northern portion of the ecosystem, or Gallatin region, has smaller mean patch sizes separated by ridges of mountains, whereas the southern portion of the ecosystem, or Teton region, has much larger patches within the Jackson Hole valley. Both support a similar suite of butterfly and bird species. The Gallatin region showed more overall among-year variation in the normalized difference vegetation index (NDVI) when meadow types were pooled within regions, perhaps because the patch sizes are smaller on average. Bird and butterfly communities showed significant relationships relative to meadow type and NDVI. We identified several key species that are tightly associated with specific meadow types along the hydrological gradient. Comparing taxonomic groups, fewer birds showed specific habitat affinities than butterflies, perhaps because birds are responding to differences in habitat structure among meadow types and using the landscape at a coarser scale than the butterflies. Comparing regions, the Teton region showed higher predictability of community assemblages as compared to the Gallatin region. The Gallatin region exhibited more significant temporal trends with respect to butterflies. Butterfly communities in wet meadows showed a distinctive shift along the hydrological gradient during a drought period (1997-2000). These results imply that the larger Teton meadows will show more predictable (i.e., static) species-habitat associations over the long term, but that the smaller Gallatin meadows may be an area that will exhibit the effects of global climate change faster.
Niche breadth, competitive strength and range size of tree species: a trade-off based framework to understand species distribution
Morin, X Chuine, I
ECOLOGY LETTERS 9:2 185-195
Understanding the mechanisms causing latitudinal gradients in species richness and species range size is a central issue in ecology, particularly in the current context of global climate change. Different hypotheses have been put forward to explain these patterns, emphasizing climatic variability, energy availability and competition. Here we show, using a comparative analysis controlling for phylogeny on 234 temperate/boreal tree species, that these hypotheses can be included into a single framework in an attempt to explain latitudinal gradients in species range size. We find that species tend to have larger ranges when (i) closer to the poles, (ii) successionally seral, (iii) having small and light seeds, and (iv) having short generations. The patterns can simply be explained by energy constraints associated with different life-history strategies. Overall, these findings shed a new light on our understanding of species distribution and biodiversity patterns, bringing new insights into underlying large-scale evolutionary processes.
Wind generation, power system operation, and emissions reduction
Denny, E O’Malley, M
IEEE TRANSACTIONS ON POWER SYSTEMS 21:1 341-347
With increasing concern over global climate change, policy makers are promoting renewable energy sources, predominantly wind generation, as a means of meeting emissions reduction targets. Although wind generation does not itself produce any harmful emissions, its effect on power system operation can actually cause an increase in the emissions of conventional plants. A dispatch model was developed that analyzes the impact that wind generation has on the operation of conventional plants and the resulting emissions of carbon dioxide (CO2), sulphur dioxide (SO2), and oxides of nitrogen (NOX). The analysis concentrates on a “forecasted” approach that incorporates wind generation forecasts in the dispatch decisions. It was found that wind generation could be used as a tool for reducing CO2 emissions but alone, it was not effective in curbing SO2 and NOX emissions.
Top-down herbivory and bottom-up El Nino effects on Galapagos rocky-shore communities
Vinueza, LR Branch, GM Branch, ML Bustamante, RH
ECOLOGICAL MONOGRAPHS 76:1 111-131
We evaluated the effects of marine iguanas, sally lightfoot crabs, and fish on rocky-shore sessile organisms at two sites at Santa Cruz Island, Galapagos Islands, Ecuador, for 3-5 years during and after the 1997-1998 El Nino, using exclusion cages to separate the effects. Plots exposed to natural grazing were dominated either by encrusting algae or by red algal turf and articulated corallines. Algae fluctuated in response to El Nino in the following way. During an early phase, crustose Gymnogongrus and/or red algal turf were dominant. In the heart of El Nino, grazers had limited effects on algal cover but influenced algal sizes substantially. Most algae (particularly edible forms) were scarce or declined, although warm-water ephemeral species (notably Giffordia mitchelliae) flourished, increasing diversity and overgrowing crusts. Iguana mortalities were high, and crab densities low. When normal conditions returned, warm-water ephemerals declined, crab densities rose, and grazers had significant but site-specific effects on algae. At one site, any combination of grazers diminished most erect species, reducing diversity and restoring dominance of competitively inferior grazer-resistant crusts. At a second site, only the combined effect of all grazers had this effect. Laboratory experiments confirmed that crabs could control erect algae and promote crustose forms, and crustose Gymnogongrus developed into an erect form in the absence of crabs. Differences between sites and large-scale temporal changes associated with El Nino indicate that tropical shores are not all as constant in time and space as previously suggested. Mobile grazers did affect algal communities, but over the period of our observations far greater effects were attributable to intersite differences and temporal shifts in oceanographic conditions. El Nino events reduce nutrients, intensify wave action, and raise sea levels, affecting food availability for intertidal herbivores and their influence on benthic algae. Thus, the dramatic transformations of communities during El Nino presage the impacts of global climate change.