Meeting Europe's climate change commitments: quantitative estimates of the potential for carbon mitigation by agriculture

Under the Kyoto Protocol, the European Union is committed to a reduction in CO₂ emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). The Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere. Thus, land‐use/land‐management change and forestry activities that are shown to reduce atmospheric CO₂ levels can be included in the Kyoto targets. These activities include afforestation, reforestation and deforestation (article 3.3 of the Kyoto Protocol) and the improved management of agricultural soils (article 3.4). In this paper, we estimate the carbon mitigation potential of various agricultural land‐management strategies and examine the consequences of European policy options on carbon mitigation potential, by examining combinations of changes in agricultural land‐use/land‐management. We show that no single land‐management change in isolation can mitigate all of the carbon needed to meet Europe's climate change commitments, but integrated combinations of land‐management strategies show considerable potential for carbon mitigation. Three of the combined scenarios, one of which is an optimal realistic scenario, are by themselves able to meet Europe's emission limitation or reduction commitments. Through combined land‐management scenarios, we show that the most important resource for carbon mitigation in agriculture is the surplus arable land. We conclude that in order to fully exploit the potential of arable land for carbon mitigation, policies will need to be implemented to allow surplus arable land to be put into alternative long‐term land‐use. Of all options examined, bioenergy crops show the greatest potential for carbon mitigation. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the mitigation potential is finite. We suggest that in order to exploit fully the bioenergy option, the infrastructure for bioenergy production needs to be significantly enhanced before the beginning of the first Kyoto commitment period in 2008. It is not expected that Europe will attempt to meet its climate change commitments solely through changes in agricultural land‐use. A reduction in CO₂‐carbon emissions will be key to meeting Europe's Kyoto targets, and forestry activities (Kyoto Article 3.3) will play a major role. In this study, however, we demonstrate the considerable potential of changes in agricultural land‐use and ‐management (Kyoto Article 3.4) for carbon mitigation and highlight the policies needed to promote these agricultural activities. As all sources of carbon mitigation will be important in meeting Europe's climate change commitments, agricultural carbon mitigation options should be taken very seriously.     

Preliminary estimates of the potential for carbon mitigation in European soils through no-till farming

In this paper we estimate the European potential for carbon mitigation of no-till farming using results from European tillage experiments. Our calculations suggest some potential in terms of (a) reduced agricultural fossil fuel emissions, and (b) increased soil carbon sequestration. We estimate that 100% conversion to no-till farming would be likely to sequester about 23 Tg C y^–1 in the European Union or about 43 Tg C y^–1 in the wider Europe (excluding the former Soviet Union). In addition, up to 3.2 Tg C y^–1 could be saved in agricultural fossil fuel emissions. Compared to estimates of the potential for carbon sequestration of other carbon mitigation options, no-till agriculture shows nearly twice the potential of scenarios whereby soils are amended with organic materials. Our calculations suggest that 100% conversion to no-till agriculture in Europe could mitigate all fossil fuel-carbon emissions from agriculture in Europe. However, this is equivalent to only about 4.1% of total anthropogenic CO₂-carbon produced annually in Europe (excluding the former Soviet Union) which in turn is equivalent to about 0.8% of global annual anthropogenic CO₂-carbon emissions.     

The carbon costs of mitigating high‐severity wildfire in southwestern ponderosa pine

Forests provide climate change mitigation benefit by sequestering carbon during growth. This benefit can be reversed by both human and natural disturbances. While some disturbances such as hurricanes are beyond the control of humans, extensive research in dry, temperate forests indicates that wildfire severity can be altered as a function of forest fuels and stand structural manipulations. The purpose of this study was to determine if current aboveground forest carbon stocks in fire‐excluded southwestern ponderosa pine forest are higher than prefire exclusion carbon stocks reconstructed from 1876, quantify the carbon costs of thinning treatments to reduce high‐severity wildfire risk, and compare posttreatment (thinning and burning) carbon stocks with reconstructed 1876 carbon stocks. Our findings indicate that prefire exclusion forest carbon stocks ranged from 27.9 to 36.6 Mg C ha^?1 and that the current fire‐excluded forest structure contained on average 2.3 times as much live tree carbon. Posttreatment carbon stocks ranged from 37.9 to 50.6 Mg C ha^?1 as a function of thinning intensity. Previous work found that these thinning and burning treatments substantially increased the 6.1 m wind speed necessary for fire to move from the forest floor to the canopy (torching index) and the wind speed necessary for sustained crown fire (crowning index), thereby reducing potential fire severity. Given the projected drying and increase in fire prevalence in this region as a function of changing climatic conditions, the higher carbon stock in the fire‐excluded forest is unlikely to be sustainable. Treatments to reduce high‐severity wildfire risk require trade‐offs between carbon stock size and carbon stock stability.     

Co‐benefits of planting species mixes in carbon projects

The carbon market offers a unique opportunity to achieve large‐scale ecological restoration of degraded agricultural landscapes. Here, we outline some of the benefits of planting mixes of native species rather than monocultures in carbon plantings as a step towards creating biodiverse carbon‐rich forests and woodlands in Australia. We highlight the gaps in our knowledge and emphasise the importance of setting benchmarks for carbon projects to maximise their potential to deliver co‐benefits such as habitat provision for wildlife. On the whole, we are optimistic that ongoing refinement of joined biodiversity conservation and carbon credit initiatives will help to develop a carbon market that can drive ecological restoration of Australian agricultural landscapes.     

Costs and benefits of cervical screening. I. The costs of the cervical screening programme

In 1991, the average total Health Service cost of a cervical smear, including follow up at the colposcopy clinic, was almost £22.70 in the Perth and Kinross district of Scotland. The average cost per colposcopy clinic visit was £30. The main cost elements were in general practice (55% of total) and the laboratory (33%), and most of the cost was for staff time.     

Heterotrophic gain of carbon from hosts by the xylem-tapping root hemiparasite Olax phyllanthi (Olacaceae)

Heterotrophic gains of carbon from various host species by the root hemiparasitic shrub Olax phyllanthi (Labill) R.Br. were assessed using techniques based on carbon isotope discrimination (¹³C) on C3 and C4 hosts and C:N ratios of xylem sap and dry matter of host and parasite. Heterotrophic benefits (H) to Olax based on ¹³C values were 30% and 19% from two nonnative C4 hosts (Portulaca oleracea and Amaranthus caudatus respectively) compared with 13% and 15% from these hosts when computed on the basis of C:N ratios of host xylem sap and C and N increments of Olax dry matter. Nitrate was the source of N available to pot cultures of the above species and estimates based on C:N ratios assumed that all N accumulated by Olax had come from nitrate absorbed by the host. Equivalent estimates of H for Olax, grown in nitrogen-free pot culture with the native N₂-fixing host Acacia littorea as its sole source of N, indicated 63% and 51% dependence on host carbon when assessed in terms of xylem sap composition of host parasite respectively. Comparisons of xylem sap solutes of Olax and a range of partner hosts indicated marked selectivity in haustorial uptake and transfer of nitrate, amino compounds, organic acids and sugars. Possible implications of variations between hosts in absolute levels of C and inorganic and organic forms of N in xylem are discussed in relation to evidence of much better growth performance of Olax on Acacia littorea and other N₂-fixing legumes than on non-fixers.     

Exploring the costs and benefits of social information use: an appraisal of current experimental evidence

Research on social learning has focused traditionally on whether animals possess the cognitive ability to learn novel motor patterns from tutors. More recently, social learning has included the use of others as sources of inadvertent social information. This type of social learning seems more taxonomically widespread and its use can more readily be approached as an economic decision. Social sampling information, however, can be tricky to use and calls for a more lucid appraisal of its costs. In this four-part review, we address these costs. Firstly, we address the possibility that only a fraction of group members are actually providing social information at any one time. Secondly, we review experimental research which shows that animals are circumspect about social information use. Thirdly, we consider the cases where social information can lead to incorrect decisions and finally, we review studies investigating the effect of social information quality. We address the possibility that using social information or not is not a binary decision and present results of a study showing that nutmeg mannikins combine both sources of information, a condition that can lead to the establishment of informational cascades. We discuss the importance of empirically investigating the economics of social information use.     

Cichlids do not adjust reproductive skew to the availability of independent breeding options

Helpers in cooperatively breeding species forego all or partof their reproduction when remaining at home and assisting breedersto raise offspring. Different models of reproductive skew generatealternative predictions about the share of reproduction unrelatedsubordinates will get depending on the degree of ecologicalconstraints. Concession models predict a larger share when independentbreeding options are good, whereas restraint and tug-of-warmodels predict no effects on reproductive skew. We tested thesepredictions by determining the share of reproduction by unrelatedmale and female helpers in the Lake Tanganyika cichlid Neolamprologuspulcher depending on experimentally manipulated possibilitiesfor helper dispersal and independent breeding and dependingon helper size and sex. We created 32 breeding groups in thelaboratory, consisting of two breeders and two helpers each,where only the helpers had access to a nearby dispersal compartmentwith (treatment) or without (control) breeding substrate, usinga repeated measures design. We determined the paternity andmaternity of 1185 offspring from 47 broods using five to nineDNA microsatellite loci and found that: (1) helpers participatedin reproduction equally across the treatments, (2) large malehelpers were significantly more likely to reproduce than smallhelpers, and (3) male helpers engaged in significantly morereproduction than female helpers. Interestingly, in four broods,extragroup helper males had fertilized part of the brood. Nohelper evictions from the group after helper reproduction wereobserved. Our results suggest that tug-of-war models based oncompetition over reproduction within groups describe best thereproductive skew observed in our study system. Female breedersproduced larger clutches in the treatment compared to the controlsituation when the large helpers were males. This suggests thatmale breeder-male helper reproductive conflicts may be alleviatedby females producing larger clutches with helpers around.     

Radiocollars do not affect the survival or foraging behaviour of wild meerkats

The practice of radiocollaring is increasingly being used in the study of wild animal populations. However, methods of tracking and monitoring are known to affect some species negatively. On a wild population of habituated meerkats Suricata suricatta , we investigated the potential costs and consequences of carrying a radiocollar for small carnivores, focusing on detailed aspects of foraging behaviour and survival. Radiocollared individuals were no more likely to be predated than non-collared individuals in the same social group. We also found that collaring did not affect foraging efficiency, with collared individuals being equally efficient foragers (four measures) while wearing a collar compared with the pre-collaring period. To control for group-specific events, changes in foraging efficiency after collaring were compared with the behaviour of control individuals from the same group and no significant differences were found. In conclusion, we found no evidence to suggest radiocollars impact negatively on the bearer's welfare, survival or foraging ability.     

Agricultural management impacts on soil organic carbon storage under moist and dry climatic conditions of temperate and tropical regions

We conducted a meta-analysis to quantify the impact of changing agricultural land use and management on soil organic carbon (SOC) storage under moist and dry climatic conditions of temperate and tropical regions. We derived estimates of management impacts for a carbon accounting approach developed by the Intergovernmental Panel on Climate Change, addressing the impact of long-term cultivation, setting-aside land from crop production, changing tillage management, and modifying C input to the soil by varying cropping practices. We found 126 articles that met our criteria and analyzed the data in linear mixed-effect models. In general, management impacts were sensitive to climate in the following order from largest to smallest changes in SOC: tropical moist>tropical dry>temperate moist>temperate dry. For example, long-term cultivation caused the greatest loss of SOC in tropical moist climates, with cultivated soils having 0.58 ± 0.12, or 58% of the amount found under native vegetation, followed by tropical dry climates with 0.69 ± 0.13, temperate moist with 0.71 ± 0.04, and temperate dry with 0.82 ± 0.04. Similarly, converting from conventional tillage to no-till increased SOC storage over 20 years by a factor of 1.23 ± 0.05 in tropical moist climates, which is a 23% increase in SOC, while the corresponding change in tropical dry climates was 1.17 ± 0.05, temperate moist was 1.16 ± 0.02, and temperate dry was 1.10 ± 0.03. These results demonstrate that agricultural management impacts on SOC storage will vary depending on climatic conditions that influence the plant and soil processes driving soil organic matter dynamics.     

Impact of sinking carbon flux on accumulation of deep-ocean carbon in the Northern Indian Ocean

The export of carbon through the biological pump from the surface to the deep ocean has a direct influence on the removal of CO₂ from the atmosphere. This is because the carbon is sequestered for only a few days to months in the surface while the carbon removed from the surface to deep waters takes hundreds of years to re-enter the atmosphere. The highest dissolved inorganic carbon (DIC) is expected in the deep waters of the North Pacific due to longer age of waters. On contrary, the higher deep water DIC is found in the northern Indian Ocean than elsewhere in the World Oceans. The sinking fluxes of particulate organic (POC) and inorganic carbon (CaCO₃) are found to be the highest in the northern Indian Ocean. The rates of bacterial respiration, organic carbon regeneration and inorganic carbon dissolution are also found to be the highest in the northern Indian Ocean than elsewhere. A most efficient biological pump appears to be operating in the northern Indian Ocean that transports surface-derived organic/inorganic carbon to deeper layers where it is converted and stored for longer times in dissolved inorganic form.     

Cold and carbon dioxide used as multi-hurdle preservation do not induce appearance of viable but non-culturable Listeria monocytogenes

AIMS: To study whether the exposure to cold (4 degrees C) and carbon dioxide which results in the elongation of Listeria cells, induces a viable but nonculturable (VBNC) state. METHODS AND RESULTS: When cold and CO2 stressed L. monocytogenes were observed under a fluorescence microscope, using the LIVE/DEAD BacLight bacteria viability kit (Molecular Probes, Eugene, OR, USA), the healthy, mildly injured, and the putative VBNC cells accounted for 31.0% of the stressed cell population. By using the selective plate count, 31.4% of the same stressed cell population was found to be healthy and mildly injured (putative VBNC cells not included). If there were VBNC state cells present, we should have observed a significant difference between the above two numbers. In fact, there was no significant difference between the results obtained from those two methods. CONCLUSIONS: There were no VBNC state cells observed in the stressed cell population. We conclude that cold and CO2 do not induce L. monocytogenes to enter a VBNC state. SIGNIFICANCE AND IMPACT OF THE STUDY: Cold and modified atmospheres are widely used in fresh muscle food and fruit preservation. Whether they would induce L. monocytogenes into a VBNC state is of a great concern for microbial food safety.     

Utilization of the cyanobacteria Anabaena sp. CH1 in biological carbon dioxide mitigation processes

Before switching totally to alternative fuel stage, CO₂ mitigation process has considered a transitional strategy for combustion of fossil fuels inevitably. In comparison to other CO₂ mitigation options, such as oceanic or geologic injection, the biological photosynthetic process would present a far superior and sustainable solution under both environmental and social considerations. The utilization of the cyanobacteria Anabaena sp. CH1 in carbon dioxide mitigation processes is analyzed in our research. It was found that an original developed photobioreactor with internal light source exhibits high light utilization. Anabaena sp. CH1 demonstrates excellent CO₂ tolerance even at 15% CO₂ level. This enables flue gas from power plant to be directly introduced to Anabaena sp. CH1 culture. Double light intensity and increased 47% CO₂ bubble retention time could enhance CO₂ removal efficiencies by 79% and 67%, respectively. A maximum CO₂ fixation rate of 1.01 g CO₂ L⁻¹ day⁻¹ was measured experimentally.     

Origin and cycling of riverine inorganic carbon in the Sava River watershed (Slovenia) inferred from major solutes and stable carbon isotopes

The Sava River and its tributaries in Slovenia represent waters strongly influenced by chemical weathering of limestone and dolomite. The carbon isotopic compositions of dissolved inorganic carbon (DIC) and suspended organic carbon (POC) fractions as well as major solute concentrations yielded insights into the origin and fluxes of carbon in the upper Sava River system. The major solute composition was dominated by carbonic acid dissolution of calcite and dolomite. Waters were generally supersaturated with respect to calcite, and dissolved CO₂ was about fivefold supersaturated relative to the atmosphere. The δ¹³C of DIC ranged from −13.5 to −3.3‰. Mass balances for riverine inorganic carbon suggest that carbonate dissolution contributes up to 26%, degradation of organic matter ∼17% and exchange with atmospheric CO₂ up to 5%. The concentration and stable isotope diffusion models indicated that atmospheric exchange of CO₂ predominates in streams draining impermeable shales and clays while in the carbonate-dominated watersheds dissolution of the Mesozoic carbonates predominates.     

The human carbon budget: an estimate of the spatial distribution of metabolic carbon consumption and release in the United States

Carbon dioxide is taken up by agricultural crops and released soon after during the consumption of agricultural commodities. The global net impact of this process on carbon flux to the atmosphere is negligible, but impact on the spatial distribution of carbon dioxide uptake and release across regions and continents is significant. To estimate the consumption and release of carbon by humans over the landscape, we developed a carbon budget for humans in the United States. The budget was derived from food commodity intake data for the US and from algorithms representing the metabolic processing of carbon by humans. Data on consumption, respiration, and waste of carbon by humans were distributed over the US using geospatial population data with a resolution of ~450 × 450 m. The average adult in the US contains about 21 kg C and consumes about 67 kg C year⁻¹ which is balanced by the annual release of about 59 kg C as expired CO₂, 7 kg C as feces and urine, and less than 1 kg C as flatus, sweat, and aromatic compounds. In 2000, an estimated 17.2 Tg C were consumed by the US population and 15.2 Tg C were expired to the atmosphere as CO₂. Historically, carbon stock in the US human population has increased between 1790 and 2006 from 0.06 Tg to 5.37 Tg. Displacement and release of total harvested carbon per capita in the US is nearly 12% of per capita fossil fuel emissions. Humans are using, storing, and transporting carbon about the Earth’s surface. Inclusion of these carbon dynamics in regional carbon budgets can improve our understanding of carbon sources and sinks.     

Terrestrial carbon stocks across a gradient of urbanization: a study of the Seattle,WA region

Most of our global population and its CO₂ emissions can be attributed to urban areas. The process of urbanization changes terrestrial carbon stocks and fluxes, which, in turn, impact ecosystem functions and atmospheric CO₂ concentrations. Using the Seattle, WA, region as a case study, this paper explores the relationships between aboveground carbon stocks and land cover within an urbanizing area. The major objectives were to estimate aboveground live and dead terrestrial carbon stocks across multiple land cover classes and quantify the relationships between urban cover and vegetation across a gradient of urbanization. We established 154 sample plots in the Seattle region to assess carbon stocks as a function of distance from the urban core and land cover [urban (heavy, medium, and low), mixed forest, and conifer forest land covers]. The mean (and 95% CI) aboveground live biomass for the region was 89±22 Mg C ha^?1 with an additional 11.8±4 Mg C ha^?1 of coarse woody debris biomass. The average live biomass stored within forested and urban land covers was 140±40 and 18±14 Mg C ha^?1, respectively, with a 57% mean vegetated canopy cover regionally. Both the total carbon stocks and mean vegetated canopy cover were surprisingly high, even within the heavily urbanized areas, well exceeding observations within other urbanizing areas and the average US forested carbon stocks. As urban land covers and populations continue to rapidly increase across the globe, these results highlight the importance of considering vegetation in urbanizing areas within the terrestrial carbon cycle.     

环境因子对农业土壤有机碳分解的影响

为研究环境因子对有机C在农业土壤中分解的影响 ,在不同温度、水分及土壤质地下进行小麦和水稻秸秆及其根培养实验 ,结果表明 ,在同样的水热条件下 ,秸秆有机C的分解量大于根的分解量 .在温度较低情况下 ,升高温度促进了有机C的分解 ;而在温度较高的情况下 ,升高温度对有机C分解的促进作用降低 .在非淹水条件下 ,温度对有机C分解的影响随着时间的延长而逐步减小 .淹水条件下培养一周后 ,温度对有机C分解的影响不随时间而变化 .当含水量为 30 0 g·kg-1和 5 0 0 g·kg-1时 ,有机C分解较快 ,而在 2 0 0 g·kg-1和淹水条件下则分解较慢 ,空白对照培养结果的趋势是分解速率随水分含量的增加而加快 .培养实验的第一个月内 ,小麦秸秆有机C的分解量与土壤粘粒含量呈负相关     

Temporal dynamics of the carbon isotope composition in a Pinus sylvestris stand: from newly assimilated organic carbon to respired carbon dioxide

The (13)C isotopic signature (C stable isotope ratio; delta(13)C) of CO(2) respired from forest ecosystems and their particular compartments are known to be influenced by temporal changes in environmental conditions affecting C isotope fractionation during photosynthesis. Whereas most studies have assessed temporal variation in delta(13)C of ecosystem-respired CO(2) on a day-to-day scale, not much information is available on its diel dynamics. We investigated environmental and physiological controls over potential temporal changes in delta(13)C of respired CO(2) by following the short-term dynamics of the (13)C signature from newly assimilated organic matter pools in the needles, via phloem-transported organic matter in twigs and trunks, to trunk-, soil- and ecosystem-respired CO(2). We found a strong 24-h periodicity in delta(13)C of organic matter in leaf and twig phloem sap, which was strongly dampened as carbohydrates were transported down the trunk. Periodicity reappeared in the delta(13)C of trunk-respired CO(2), which seemed to originate from apparent respiratory fractionation rather than from changes in delta(13)C of the organic substrate. The diel patterns of delta(13)C in soil-respired CO(2) are partly explained by soil temperature and moisture and are probably due to changes in the relative contribution of heterotrophic and autotrophic CO(2) fluxes to total soil efflux in response to environmental conditions. Our study shows that direct relations between delta(13)C of recent assimilates and respired CO(2) may not be present on a diel time scale, and other factors lead to short-term variations in delta(13)C of ecosystem-emitted CO(2). On the one hand, these variations complicate ecosystem CO(2) flux partitioning, but on the other hand they provide new insights into metabolic processes underlying respiratory CO(2) emission.     

The active uptake of carbon dioxide by the marine diatoms Phaeodactylum ticornutum and Cyclotella sp.

Mass spectromelry has been used to investigate the uptake of CO₂ by two marine diatoms, Phaeodactylum tricornutum and Cyclotella sp. The time course of CO₂ formation in the dark after addition of 100 mmol m^?3 dissolved inorganic carbon (DIC) to cell suspensions showed that external carbonic anhydrase (CA) was not present in cells of P. tricornutum but was present in Cyclotella sp. In the absence of external CA, or when it was inhibited by 5 mmol m^?3 acetazolamide, cells of both species preincubated with 100 mmol m^?3 DIG rapidly depleted almost all of the free CO₂ (3·2mmol m^?31 at pH7·5) from the suspending medium within seconds of illumination and prior to the onset of steady-state photosynthesis. Addition of bovine CA quickly restored the HCO₃^?–CO₂ equilibrium in the medium, indicating that the initial depletion of CO₂ resulted from the selective uptake of CO₂ rather than uptake of all DIG species. Transfer of cells to the dark caused a rapid increase in the CO₂ concentration in the medium, largely as a result of the efflux of unfixed inorganic carbon from the cells. The measured CO₂ uptake rates for both species accounted for 50% of the total DIG uptake at HCO₃^?–CO₂ equilibrium, indicating that HCOHCO₃^? was also being taken up. These results indicate that both Phaeodactylum tricornutum and Cyclotella sp. have the capacity to transport CO₂ actively against concentration and pH gradients.