Concurrent Climate Change Research Articles

Trends in wheat yields under representative climate futures: Implications for climate adaptation

Underestimating the impacts of climate change on agricultural production could lead to complacency about the potential adaptation challenges. This study used a Representative Climate Futures (RCF) approach to model projected wheat yields under climate change in Australia. It simulated the range of impacts, resulting from a subset of individual Global Climate Models (GCMs), on wheat production in the major wheat regions of Australia. The study used RCFs that represented ‘most-likely’, ‘best’ and ‘worst’ cases across multiple Representative Concentration pathways (RCPs). Median wheat yields modelled for the South West Australia projected declines between 26% and 38%, under a ‘most-likely’ case for RCP 4.5 by 2090, and between 41% and 49%, under a ‘most-likely’ case for RCP 8.5. Median wheat yields declined under RCP 8.5 for the ‘most-likely’ case across the majority of wheat producing regions, with a range of 1% to 49%. Greater declines were projected under the ‘worst’ cases of hottest and driest climates. However, the ‘best’ cases of least warm and wetter climates projected an increase in median wheat yield, a range of 2% to 87%. Variability also changed from the baseline under all projected RCFs and across all regions, with a standard deviation of up to 2.46t/ha under the ‘most likely’ case at a site in south-eastern Australia. These likely shifts in the size and reliability of yields, combined with concurrent climate change impacts on other factors, mean that agriculture faces significant adaptation challenges, particularly under some of the ‘most-likely’ scenarios and all of the ‘worst’ case scenarios. Further work is required to explore how scenarios in one region relate to those in other regions and thus the overall outcome at the continental scale.

Carbon nanotube wools made directly from CO2 by molten electrolysis: Value driven pathways to carbon dioxide greenhouse gas mitigation

A climate mitigation comprehensive solution is presented through the first high yield, low energy synthesis of macroscopic length carbon nanotube (“CNT”) wool from CO2 by molten carbonate electrolysis. The CNT wool is of length suitable for weaving into carbon composites and textiles. Growing CO2 concentrations, and the concurrent climate change and species extinction, can be addressed if CO2 becomes a sought resource rather than a greenhouse pollutant. Inexpensive carbon composites formed from carbon wool as a lighter metal, textiles or cement replacement comprise major market sinks to compactly store transformed anthropogenic CO2. 100×-longer CNTs grow on Monel versus steel. Monel, electrolyte equilibration, and a mixed metal nucleation facilitate the synthesis. CO2, the sole reactant in this transformation, is directly extractable from dilute (atmospheric) or concentrated sources, and the analyzed production cost of $660 per ton CNT is cost constrained only by the (low) cost of electricity. Today's market valuation of >$100,000 per ton CNT incentivizes CO2 removal.

Fire and ecosystem change in the Arctic across the Paleocene–Eocene Thermal Maximum

Fire has been an important component of ecosystems on a range of spatial and temporal scales. Fire can affect vegetation distribution, the carbon cycle, and climate. The relationship between climate and fire is complex, in large part because of a key role of vegetation type. Here, we evaluate regional scale fire–climate relationships during a past global warming event, the Paleocene–Eocene Thermal Maximum (PETM), in order to understand how vegetation influenced the links between climate and fire occurrence in the Arctic region. To document concurrent changes in climate, vegetation, and fire occurrence, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes, from the PETM interval at a marine depositional site (IODP site 302, the Lomonosov Ridge) in the Arctic Ocean.Biomarker, fossil, and isotope evidence from site 302 indicates that terrestrial vegetation changed during the PETM. The abundance of the C29n-alkanes, pollen, and the ratio of leaf-wax n-alkanes relative to diterpenoids all indicate that proportional contributions from angiosperm vegetation increased relative to that from gymnosperms. These changes accompanied increased moisture transport to the Arctic and higher temperatures, as recorded by previously published proxy records. We find that PAH abundances were elevated relative to total plant biomarkers throughout the PETM, and suggest that fire occurrence increased relative to plant productivity. The fact that fire frequency or prevalence may have increased during wetter Arctic conditions suggests that changes in fire occurrence were not a simple function of aridity, as is commonly conceived. Instead, we suggest that the climate-driven ecological shift to angiosperm-dominated vegetation was what led to increased fire occurrence. Potential increases in terrestrial plant biomass that arose from warm, wet, and high CO2 conditions were possibly attenuated by biomass burning associated with compositional changes in the plant community.

Ecophysiological Responses ofTsuga canadensis(Eastern Hemlock) to Projected Atmospheric CO2and Warming

Abstract Tsuga canadensis (Eastern Hemlock) is a keystone tree species currently experiencing high mortality in southeastern US forests due to Hemlock Woolly Adelgid (Adelges tsugae; HWA) invasion. Investigating the impacts of concurrent climate change on Eastern Hemlock is important given its potential direct effects on this species and possible interactions of climatic factors with the continued spread of HWA. We conducted a 2-factorial experiment in controlled-environment growth chambers to test for the main effects and interactions of projected atmospheric CO2 concentrations and transitional-season warming on gas-exchange traits of Eastern Hemlock saplings collected from a northern Georgia field site. We hypothesized that elevated CO2 would increase photosynthesis and that warming would not influence photosynthesis, given the demonstrated capacity for photosynthetic temperature-acclimation in this species. Saplings in elevated CO2 exhibited ∼30% greater leaf-level photosynthesis (A) and ∼35% greater m...

Climate change induced rainfall patterns affect wheat productivity and agroecosystem functioning dependent on soil types

AbstractWheat is a crop of global importance that supplies carbohydrates to more than half of the worlds’ population. We examined whether climate change‐induced rainfall patterns, which are expected to produce less frequent but heavier rain events, will alter the productivity of wheat and agroecosystem functioning on three different soil types. Therefore, in a full‐factorial experiment, Triticum aestivum L. was cultivated in 3‐m2 lysimeter plots, each of which contained one of the following soil types: sandy calcaric phaeozem, gleyic phaeozem and calcic chernozem. Predicted rainfall patterns based on the calculations of a regionalised climate change model were compared with the current long‐term rainfall patterns, and each treatment combination was replicated three times. Future rainfall patterns significantly reduced wheat yield, leaf area index, and plant height at the earlier growth stages; it equally decreased the arbuscular mycorrhizal fungi colonisation of roots and increased the stable carbon isotope signature (δ13C) of wheat leaves. Sandy soils with inherently lower mineralization potential negatively affected wheat growth, harvest index, and yield but stimulated early season root production. The interaction between rainfall and soil type was significant for the harvest index and early wheat development. Our results suggest that changes in rainfall intensity and frequency can significantly affect the functioning of wheat agroecosystems. Wheat production under future rainfall conditions will likely become more challenging as further concurrent climate change factors become prevalent.

Hydroclimatic changes and drivers in the Sava River Catchment and comparison with Swedish catchments.

In this study, we investigate long-term hydroclimatic changes and their possible relation to regional changes in climate, land-use and water-use over the twentieth century in the transboundary Sava River Catchment (SRC) in South Eastern Europe. In a hydropower dominated part of the SRC, unlike in an unregulated part, we find increase in average annual evapotranspiration and decrease in temporal runoff variability, which are not readily explainable by observed concurrent climate change in temperature and precipitation and may be more related to landscape-internal change drivers. Among the latter investigated here, results indicate hydropower developments as most closely related to the found hydroclimatic shifts, consistent with previous such indications in studies of Swedish hydropower catchments. Overall, the present results have quantitatively framed the recent history and present state of hydroclimate in the SRC, of relevance for water resources in several countries and for a majority of their populations. This provides a useful basis for further assessment of possible future hydroclimatic changes, under different scenarios of climate change and land/water-use developments in the region.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-015-0641-0) contains supplementary material, which is available to authorized users.

Declining ozone exposure of European vegetation under climate change and reduced precursor emissions

Abstract. The impacts of changes in ozone precursor emissions as well as climate change on the future ozone exposure of the vegetation in Europe were investigated. The ozone exposure is expressed as AOT40 (Accumulated exposure Over a Threshold of 40 ppb O3) as well as PODY (Phytotoxic Ozone Dose above a threshold Y). A new method is suggested to express how the length of the period during the year when coniferous and evergreen trees are sensitive to ozone might be affected by climate change. Ozone precursor emission changes from the RCP4.5 scenario were combined with climate simulations based on the IPCC SRES A1B scenario and used as input to the Eulerian Chemistry Transport Model MATCH from which projections of ozone concentrations were derived. The ozone exposure of vegetation over Europe expressed as AOT40 was projected to be substantially reduced between the periods 1990–2009 and 2040–2059 to levels which are well below critical levels used for vegetation in the EU directive 2008/50/EC as well as for crops and forests used in the LRTAP convention, despite that the future climate resulted in prolonged yearly ozone sensitive periods. The reduction in AOT40 was mainly driven by the emission reductions, not changes in the climate. For the toxicologically more relevant POD1 index the projected reductions were smaller, but still significant. The values for POD1 for the time period 2040–2059 were not projected to decrease to levels which are below critical levels for forest trees, represented by Norway spruce. This study shows that substantial reductions of ozone precursor emissions have the potential to strongly reduce the future risk for ozone effects on the European vegetation, even if concurrent climate change promotes ozone formation.

The HIV/AIDS epidemic in South Africa: Convergence with tuberculosis, socioecological vulnerability, and climate change patterns.

Recent assessment reports suggest that climate change patterns are threatening social and ecological vulnerability and resilience, with the strong potential of negatively affecting human health. Persons living with HIV/AIDS (PLWHA) have weakened physiological responses and are immunologically vulnerable to pathogens and stressors in their environment, putting them at a health disadvantage in climate-based rising temperatures, water scarcity, air pollution, potential water- and vector-borne disease outbreaks, and habitat redistributions. These climatic aberrations may lead to increased surface drying and decreased availability of arable land, threatening food/nutrition security and sanitary water practices. Coupled with HIV/AIDS, climate change threatens ecological biodiversity via a larger-scale socioeconomic recourse to natural resources. Corresponding human and environmental activity shape conditions conducive to exacerbating high rates of HIV/AIDS. In South Africa, this epidemic is forming a ‘syndemic’ with tuberculosis (TB), which has come to include multidrug-resistant TB (MDR-TB) and extremely drug-resistant TB (XDR-TB) strains. Because of high convergence rates, one epidemic cannot be addressed without understanding the other. Concurrent climate change mitigation and adaptation strategies are becoming increasingly important to curb changes that negatively affect the biospheres on which civilisation is ultimately dependent – from an agricultural, a developmental, and especially a health standpoint. Mitigation strategies such as reducing carbon emissions are essential, but may be only partially effective in slowing the rate of surface warming. However, global climate assessments assert that these are not sufficient to halt climate change patterns. The roles of regionally specific climate research, socioecologically sustainable industrialisation paths for developing countries, and adoption of health system strengthening strategies are therefore vital.

Combined global change effects on ecosystem processes in nine U.S. topographically complex areas

Concurrent changes in climate, atmospheric nitrogen (N) deposition, and increasing levels of atmospheric carbon dioxide (CO2) affect ecosystems in complex ways. The DayCent-Chem model was used to investigate the combined effects of these human-caused drivers of change over the period 1980–2075 at seven forested montane and two alpine watersheds in the United States. Net ecosystem production (NEP) increased linearly with increasing N deposition for six out of seven forested watersheds; warming directly increased NEP at only two of these sites. Warming reduced soil organic carbon storage at all sites by increasing heterotrophic respiration. At most sites, warming together with high N deposition increased nitrous oxide (N2O) emissions enough to negate the greenhouse benefit of soil carbon sequestration alone, though there was a net greenhouse gas sink across nearly all sites mainly due to the effect of CO2 fertilization and associated sequestration by plants. Over the simulation period, an increase in atmospheric CO2 from 350 to 600 ppm was the main driver of change in net ecosystem greenhouse gas sequestration at all forested sites and one of two alpine sites, but an additional increase in CO2 from 600 to 760 ppm produced smaller effects. Warming either increased or decreased net greenhouse gas sequestration, depending on the site. The N contribution to net ecosystem greenhouse gas sequestration averaged across forest sites was only 5–7 % and was negligible for the alpine. Stream nitrate (NO3 −) fluxes increased sharply with N-loading, primarily at three watersheds where initial N deposition values were high relative to terrestrial N uptake capacity. The simulated results displayed fewer synergistic responses to warming, N-loading, and CO2 fertilization than expected. Overall, simulations with DayCent-Chem suggest individual site characteristics and historical patterns of N deposition are important determinants of forest or alpine ecosystem responses to global change.

Morphological Adaptations for Digging and Climate-Impacted Soil Properties Define Pocket Gopher (Thomomys spp.) Distributions

Species ranges are mediated by physiology, environmental factors, and competition with other organisms. The allopatric distribution of five species of northern Californian pocket gophers (Thomomys spp.) is hypothesized to result from competitive exclusion. The five species in this environmentally heterogeneous region separate into two subgenera, Thomomys or Megascapheus, which have divergent digging styles. While all pocket gophers dig with their claws, the tooth-digging adaptations of subgenus Megascapheus allow access to harder soils and climate-protected depths. In a Northern Californian locality, replacement of subgenus Thomomys with subgenus Megascapheus occurred gradually during the Pleistocene-Holocene transition. Concurrent climate change over this transition suggests that environmental factors – in addition to soil – define pocket gopher distributional limits. Here we show 1) that all pocket gophers occupy the subset of less energetically costly soils and 2) that subgenera sort by percent soil clay, bulk density, and shrink-swell capacity (a mineralogical attribute). While clay and bulk density (without major perturbations) stay constant over decades to millennia, low precipitation and high temperatures can cause shrink-swell clays to crack and harden within days. The strong yet underappreciated interaction between soil and moisture on the distribution of vertebrates is rarely considered when projecting species responses to climatic change. Furthermore, increased precipitation alters the weathering processes that create shrink-swell minerals. Two projected outcomes of ongoing climate change—higher temperatures and precipitation—will dramatically impact hardness of soil with shrink-swell minerals. Current climate models do not include factors controlling soil hardness, despite its impact on all organisms that depend on a stable soil structure.

Temperature‐related shifts in butterfly phenology depend on the habitat

AbstractMany species are becoming active earlier in the season as the climate becomes warmer. In parallel to phenological responses to climate change, many species have also been affected by habitat changes due to anthropogenic land use. As habitat type can directly affect microclimatic conditions, concurrent changes in climate and habitat could have interacting effects on the phenology of species. Temperature‐related shifts in phenology, however, have mostly been studied independent of habitat types. Here,Iused long‐term data from a highly standardized monitoring program with 519 transects to study how phenology of butterflies is affected by ambient temperature and habitat type.Icompared forests, agricultural areas and settlements, reflecting three major land use forms, and considered butterfly species that were observed in all three of these habitats. Seasonal appearance of the butterflies was affected both by the ambient temperature and the habitat type. As expected, warmer temperatures led to an overall advancement of the appearance and flight period of most species. Surprisingly, however, phenology of species was delayed in settlement habitats, even though this habitat type is generally associated with higher temperatures. A possible explanation is dispersal among habitat types, such that source–sink effects affect local phenology. When there is little productivity in settlement areas, observed butterflies may have immigrated from forest or agricultural habitats and thus appear later in settlements. My findings suggest that a spillover of individuals among habitats may affect phenology trends and indicate that phenological studies need to be interpreted in the context of habitat types. This becomes especially important when defining strategies to prevent or mitigate effects of climate and land‐use changes on phenology and abundance of species.

Effects of enhanced UV-B radiation on nitrogen fixation in arctic ecosystems

Recent global climate models predict a further significant loss of ozone in the next decades, with up to 50% depletion of the ozone layer over large parts of the Arctic resulting in an increase in ultraviolet-B radiation (UV-B) (280–315 nm) reaching the surface of the Earth. The percentage of total annual ecosystem N input due to biological nitrogen fixation by cyanobacteria might be as high as 80% and the contribution to total annual N uptake by plants up to 20%. A possible reduction of nitrogen fixation raises serious concerns about already nutrient impoverished plant communities. This review shows that nitrogen fixation by moss-associated cyanobacteria in arctic vegetation was dramatically reduced after six years of exposure to enhanced UV-B radiation. In subarctic vegetation, nitrogen fixation activity of moss-associated cyanobacteria was not affected by 6 years of enhanced UV-B radiation. However, a 50% increase of summer precipitation resulted in a 5- to 6-fold increase in activity. Long-term effects of UV-B radiation on nitrogen fixation activity have been examined only in two lichens, giving contrasting results. Peltigera aphthosa (L.) Willd., having external cephalodia, experienced a significant reduction, whereas Peltigera didactyla (With.) J.R. Laudon, having cyanobacteria in the photobiont layer below the upper cortex, did not experience any changes due to radiation regimes. The difference is probably related to the location of the cyanobacteria. While the Nostoc cells are protected by the fungal, melanized upper cortex in P. didactyla, they are exposed and unprotected in P. aphthosa, and their own synthesis of UV-B absorbing compounds appears to be low. Under certain environmental conditions, an increasing UV-B radiation will dramatically affect nitrogen fixation in arctic tundra vegetation, which in turn may have severe influence on the nitrogen budget in these environments. Further long-term studies are necessary to conclude if these effects are temporal and how concurrent climatic changes will influence the nitrogen balance of the ecosystem.

Modelling the response of net primary productivity (NPP) of boreal forest ecosystems to changes in climate and fire disturbance regimes

This study reports on the use of the process-based ecosystem model CENTURY 4.0 to investigate the patterns of net primary productivity (NPP) along a transect across the boreal forests of central Canada and the influence of climate change, CO 2 fertilization and changing fire disturbance regimes on changes in NPP over time. Simulated NPP was tested against observed NPP data from northern sites near Thompson (Manitoba) and southern sites near Prince Albert (Saskatcheuan) and shown to be consistent with the data. The temporal dynamics of NPP were very different for the southern, central and northern sites, consistent with the hypothesis that different climate-driven processes regulate forest growth in the various regions of the boreal forest transect case study (BFTCS). The simulations suggest that climate change would result in increased NPP for most sites across the transect. According to the model results, increases in atmospheric CO 2 also show increased NPP. The combined influence of climate change and elevated CO 2 appear to interact in a positive, but non-linear manner. Statistical analysis of the simulation results indicate that changes in NPP are also positively correlated with changes in net N mineralization ( R 2=0.89). This supports the conclusion that feedback via N cycling — a coupling of aboveground production with changes in belowground decomposition — is very important for understanding the NPP dynamics of the boreal forest under a changing climate. It was also found that NPP increases with greater fire frequency under current climate conditions, at least over the range of fire return intervals considered (50–200 years). The influence of other changes in disturbance regimes (e.g. altered fire severity and concurrent changes in climate or CO 2 fertilization), however, were not considered.

Long-Term Response of an Arctic Sedge to Climate Change: A Simulation Study.

It appears that polar regions of the Earth will bear the brunt of global temperature increases. Because of the ecological importance of the sedge Eriophorum vaginatum in the arctic and the large amount of data available on its growth and physiology, we chose this species as a test case to model the potential long-term response of arctic plants to global climate change. Our simulation model utilizes a mechanistic framework and includes the effects of light, temperature, season length, nitrogen availability, and CO2 concentration on E. vaginatum growth dynamics. The model was parameterized based on a series of published studies of the growth responses of E. vaginatum to nutrients and validated using (1) field studies on the growth responses of E. vaginatum to temperature and shading, and (2) the effects of elevated CO2 and temperature on E. vaginatum photosynthesis. The effect of a 50-yr period of climate change on peak biomass (overwintering biomass plus seasonal production) in E. vaginatum was explored. We use climate change here to refer to linear increases over a 50-yr period in temperature (from 8° to 13°C), season length (from 100 to 120 d), and atmospheric CO2 (from 340 to 680 @mL/L). Similarly, a wide range of nitrogen availabilities (from 9 to 18 g°m -2 °yr-1 ) was also examined because of its importance in productivity. The model predicts that a simultaneous increase in the direct effects of temperature, season length, and CO2 , with no change in nitrogen availability, will result in a slight decrease in peak biomass. A simulated long-term doubling of nitrogen availability results in an °70% increase in peak biomass, whereas with concurrent changes in climate and nitrogen availability, the model predicts a slight decline in peak biomass compared to increases in nitrogen alone. In essence, the model predicts that climate change will have substantial effects on E. vaginatum only indirectly through changes in nitrogen availability. Simulated peak biomass responds linearly up to a doubling of current nitrogen availabilities. Therefore, at low-to-moderate increases in nitrogen availability, the predicted response of E. vaginatum to climate change is linearly (and almost exclusively) dependent on our ability to predict the effects of climate change on nitrogen cycling. At nitrogen availabilities >2x current availabilities, the relationship flattens out very rapidly because the plant becomes limited by carbon uptake. Thus, if nitrogen availabilities more than double in the future, E. vaginatum may shift from being a nutrient-limited to a carbon-limited system and, consequently, increased season length and elevated CO2 concentrations may play an important role in controlling E. vaginatum productivity.