CARBON FLOW IN INDIAN FORESTS

The present study estimates the net emission of carbon from the forest sector in India. For the reference year (1986), the gross emission from deforestation in that year, plus committed emissions from deforestation in the preceding years, is estimated to be 64 × 10⁶ t of C. The carbon sequestration (or net woody biomass accumulation in trees for long-term storage) from the area brought under tree plantations and the existing forest area under forest succession is estimated to offset the gross carbon emission in India, leading to no net emissions of carbon from the forest sector. Medium-term projections for India (for the year 2011) show that under a business as usual scenario at current rates of afforestation, projected carbon emissions would continue to be balanced by sequestration.     

Tropical deforestation and atmospheric carbon dioxide

Recent estimates of the net release of carbon to the atmosphere from deforestation in the tropics have ranged between 0.4 and 2.5 × 10¹⁵ g yr^–1. Two things have happened to require a revision of these estimates. First, refinements of the methods used to estimate the stocks of carbon in the vegetation of tropical forests have produced new estimates that are intermediate between the previous high and low estimates of carbon stocks. When these revised estimates were used here to calculate the emissions of carbon from deforestation, the new range was 1.0–2.0 × 10¹⁵ g C.Second, the previous range of estimates of flux was based on rates of deforestation in 1980. Myers' recent estimate of the rates of tropical deforestation in 1989 is about 90% higher than the rates just 10 years ago. When these recent rates were used to calculate the current net flux of carbon to the atmosphere, the range was between 1.6 and 2.7 × 10¹⁵ g C.Other uncertainties expanded this range, however, to 1.1–3.6 × 10¹⁵ g C yr^–1. Three factors contributed about equally to the expanded range: rates of deforestation, the fate of deforested lands (permanent or temporary clearing), and carbon stocks of forests, including anthropogenic reductions of carbon stocks within forests (thinning or degradation).     

Deforestation in Russia and its contribution to the anthropogenic emission of carbon dioxide in 1990–2013

The contribution of deforestation in Russia to the anthropogenic emission of carbon dioxide (CO₂) in 1990–2013 is estimated using the methods of computational monitoring. It is found that since 1990 the area of deforestation and forest conversion to other land-use categories is equal to 628.4 x 10³ ha. The respective CO₂ emissions from deforestation in Russia for the whole analyzed period are estimated at 142200 kt CO₂ with the average annual value of 5900 + 2270 kt CO₂/year. The largest contribution to the total losses is made by the changes in soil carbon stock (41.6%) and biomass carbon losses (28.8%). CO₂ emissions from deforestation make an insignificant contribution to the total anthropogenic CO₂ emission in the country (0.2%). Among the CO₂ sources in the land use, land-use change, and forestry sector (LULUCF), the emission from deforestation is the lowest with the average for 1990–2013 contribution of about 0.6%.     

Global Warming and Tropical Land-Use Change: Greenhouse Gas Emissions from Biomass Burning, Decomposition and Soils in Forest Conversion, Shifting Cultivation and Secondary Vegetation

Tropical forest conversion, shiftingcultivation and clearing of secondary vegetation makesignificant contributions to global emissions ofgreenhouse gases today, and have the potential forlarge additional emissions in future decades. Globally, an estimated 3.1×10⁹ t of biomasscarbon of these types is exposed to burning annually,of which 1.1×10⁹ t is emitted to the atmospherethrough combustion and 49×10⁶ t is converted tocharcoal (including 26–31×10⁶ t C of blackcarbon). The amount of biomass exposed to burningincludes aboveground remains that failed to burn ordecompose from clearing in previous years, andtherefore exceeds the 1.9×10⁹ t of abovegroundbiomass carbon cleared on average each year. Above-and belowground carbon emitted annually throughdecomposition processes totals 2.1×10⁹ t C. Atotal gross emission (including decomposition ofunburned aboveground biomass and of belowgroundbiomass) of 3.41×10⁹ t C year^-1 resultsfrom clearing primary (nonfallow) and secondary(fallow) vegetation in the tropics. Adjustment fortrace gas emissions using IPCC Second AssessmentReport 100-year integration global warming potentialsmakes this equivalent to 3.39×10⁹ t ofCO₂-equivalent carbon under a low trace gasscenario and 3.83×10⁹ t under a high trace gasscenario. Of these totals, 1.06×10⁹ t (31%)is the result of biomass burning under the low tracegas scenario and 1.50×10⁹ t (39%) under thehigh trace gas scenario. The net emissions from allclearing of natural vegetation and of secondaryforests (including both biomass and soil fluxes) is2.0×10⁹ t C, equivalent to 2.0–2.4×10⁹ t of CO₂-equivalent carbon. Adding emissions of0.4×10⁹ t C from land-use category changesother than deforestation brings the total for land-usechange (not considering uptake of intact forest,recurrent burning of savannas or fires in intactforests) to 2.4×10⁹ t C, equivalent to 2.4–2.9×10⁹ t of CO₂-equivalent carbon. The totalnet emission of carbon from the tropical land usesconsidered here (2.4×10⁹ t C year^-1)calculated for the 1981–1990 period is 50% higherthan the 1.6×10⁹ t C year^-1 value used by the Intergovernmental Panel on Climate Change. The inferred (= `missing') sink in the global carbonbudget is larger than previously thought. However,about half of the additional source suggested here maybe offset by a possible sink in uptake by Amazonianforests. Both alterations indicate that continueddeforestation would produce greater impact on globalcarbon emissions. The total net emission of carboncalculated here indicates a major global warmingimpact from tropical land uses, equivalent toapproximately 29% of the total anthropogenic emissionfrom fossil fuels and land-use change.     

An incentive mechanism for reducing emissions from conversion of intact and non-intact forests

This paper presents a new accounting mechanism in the context of the UNFCCC issue on reducing emissions from deforestation in developing countries, including technical options for determining baselines of forest conversions. This proposal builds on the recent scientific achievements related to the estimation of tropical deforestation rates and to the assessment of ‘intact’ forest areas. The distinction between ‘intact’ and ‘non intact’ forests used here arises from experience with satellite-based deforestation measurements and allows accounting for carbon losses from forest degradation. The proposed accounting system would use forest area conversion rates as input data. An optimal technical solution to set baselines would be to use historical average figures during the time period from 1990 to 2005. The system introduces two different schemes to account for preserved carbon: one for countries with high forest conversion rates where the desired outcome would be a reduction in their rates, and another for countries with low rates. A ‘global’ baseline rate would be used to discriminate between these two country categories (high and low rates). For the hypothetical accounting period 2013–2017 and considering 72% of the total tropical forest domain for which data are available, the scenario of a 10% reduction of the high rates and of the preservation of low rates would result in approximately 1.6 billion tCO₂ of avoided emissions. The resulting benefits of this reduction would be shared between those high-rate countries which reduced deforestation and those low-rate countries which did not increase their deforestation over an agreed threshold (e.g., half of “global” baseline rate).     

Assessment of Major Pools and Fluxes of Carbon in Indian Forests

The major pools including phytomass, soil, litter, and fluxes of carbon (C)due to litterfall and landuse changes were estimated for Indian forests. Basedon growing stock-volume approach at the state and district levels, the Indianforest phytomass was estimated in the range of 3.8–4.3 PgC. The totalsoil organic pool in the top 1m depth was estimated as 6.8 PgC, usingestimated soil organic carbon densities and Remote Sensing (RS) based area byforest types. Based on 122 published Indian studies and RS-based forest area,the total litterfall carbon flux was estimated as 208.8 MgCha^–1 yr^–1.The cumulative net carbon flux (1880–1996) from Indian forests(1880–1996) due to landuse changes (deforestation, afforestation andphytomass degradation) was estimated as 5.4 PgC, using a simple book-keepingapproach. The mean annual net C flux due to landuse changes during1985–1996 was estimated as 9.0 TgC yr^–1. For the recentperiod, the Indian forests are nationally a small source with some regionsacting as small sinks of carbon as well. The improved quantification of poolsand fluxes related to forest carbon cycle is important for understanding thecontribution of Indian forests to net carbon emissions as well as theirpotential for carbon sequestration in the context of the Kyoto protocol.     

The potential for short-rotation woody crops to reduce U.S. CO2 emissions

Short-rotation woody crops (SRWC) could potentially displace fossil fuels and thus mitigate CO₂ buildup in the atmosphere. To determine how much fossil fuel SRWC might displace in the United States and what the associated fossil carbon savings might be, a series of assumptions must be made. These assumptions concern the net SRWC biomass yields per hectare (after losses); the amount of suitable land dedicated to SRWC production; wood conversion efficiencies to electricity or liquid fuels; the energy substitution properties of various fuels; and the amount of fossil fuel used in growing, harvesting, transporting, and converting SRWC biomass. Assuming the current climate, present production, and conversion technologies and considering a conservative estimate of the U.S. land base available for SRWC (14 × 10⁶ ha), we calculate that SRWC energy could displace 33.2 to 73.1 × 10⁶ Mg of fossil carbon releases, 3–6% of the current annual U.S. emissions. The carbon mitigation potential per unit of land is larger with the substitution of SRWC for coal-based electricity production than for the substitution of SRWC-derived ethanol for gasoline. Assuming current climate, predicted conversion technology advancements, an optimistic estimate of the U.S. land base available for SRWC (28 × 10⁶ ha), and an optimistic average estimate of net SRWC yields (22.4 dry Mg/ha), we calculate that SRWC energy could displace 148 to 242 × 10⁶ Mg of annual fossil fuel carbon releases. Under this scenario, the carbon mitigation potential of SRWC-based electricity production would be equivalent to about 4.4% of current global fossil fuel emissions and 20% of current U.S. fossil fuel emissions.Research sponsored by the Biofuels Systems Division, U.S. Department of Energy, under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc. Environmental Sciences Division Publication number 3952.     

GREENHOUSE GASES FROM DEFORESTATION IN BRAZILIAN AMAZONIA: NET COMMITTED EMISSIONS

Deforestation in Brazilian Amazonia is a significant source of greenhouse gases today and, with almost 90% of the originally forested area still uncleared, is a very large potential source of future emissions. The 1990 rate of loss of forest (13.8 × 10³ km²/year) and cerrado savanna (approximately 5 × 10³ km²/year) was responsible for releasing approximately 261 × 10⁶ metric tons of carbon (10⁶ t C) in the form of CO2, or 274–285 × 10⁶ t of CO2-equivalent C considering IPCC 1994 global warming potentials for trace gases over a 100-year horizon. These calculations consider conversion to a landscape of agriculture, productive pasture, degraded pasture, secondary forest, and regenerated forest in the proportions corresponding to the equilibrium condition implied by current land-use patterns. Emissions are expressed as net committed emissions, or the gases released over a period of years as the carbon stock in each hectare deforested approaches a new equilibrium in the landscape that replaces the original forest. For low and high trace gas scenarios, respectively, 1990 clearing produced net committed emissions (in 10⁶ t of gas) of 957–958 for CO2, 1.10–1.42 for CH₄, 28–35 for CO, 0.06–0.16 for N₂O, 0.74–0.74 for NO_x and 0.58–1.16 for non-methane hydrocarbons.     

The role of soybean production as an underlying driver of deforestation in the South American Chaco

South America’s tropical dry forests and savannas are under increasing pressure from agricultural expansion. Cattle ranching and soybean production both drive these forest losses, but their relative importance remains unclear. Also unclear is how soybean expansion elsewhere affects deforestation via pushing cattle ranching to deforestation frontiers. To assess these questions, we focused on the Chaco, a 110 million ha ecoregion extending into Argentina, Bolivia, and Paraguay, with about 8 million ha of deforestation in 2000–2012. We used panel regressions at the district level to quantify the role of soybean expansion in driving these forest losses using a wide range of environmental and socio-economic control variables. Our models suggest that soybean production was a direct driver of deforestation in the Argentine Chaco only (0.08 ha new soybean area per ha forest lost), whereas cattle ranching was significantly associated with deforestation in all three countries (0.02 additional cattle per hectare forest loss). However, our models also suggested Argentine soybean cultivation may indirectly be linked to deforestation in the Bolivian and Paraguayan Chaco. We furthermore found substantial time-delayed effects in the relationship of soybean expansion in Argentina and Paraguay (i.e., soybean expansion in one year resulted in deforestation several years later) and deforestation in the Chaco, further suggesting that possible displacement effects within and between Chaco countries may at least partly drive forest loss. Altogether, our study showed that deforestation in the Chaco appears to be mainly driven by the globally surging demand for soybean, although regionally other proximate drivers are sometimes important. Steering agricultural production in the Chaco and other tropical dry forests onto sustainable pathways will thus require policies that consider these scale effects and that account for the regional variation in deforestation drivers within and across countries.     

Deforestation dynamics and drivers in different forest types in Latin America: Three decades of studies (1980–2010)

Over the last decades there have been a considerable number of deforestation studies in Latin America reporting lower rates compared with other regions; although these studies are either regional or local and do not allow the comparison of the intraregional variability present among countries or forest types. Here, we present the results obtained from a systematic review of 369 articles (published from 1990 to 2014) about deforestation rates for 17 countries and forest types (tropical lowland, tropical montane, tropical and subtropical dry, subtropical temperate and mixed, and Atlantic forests). Drivers identified as direct or indirect causes of deforestation in the literature were also analysed. With an overall annual deforestation rate of −1.14 (±0.092 SE) in the region, we compared the rates per forest type and country. The results indicate that there is a high variability of forest loss rates among countries and forest types. In general, Chile and Argentina presented the highest deforestation rates (−3.28 and −2.31 yearly average, respectively), followed by Ecuador and Paraguay (−2.19 and −1.89 yearly average, respectively). Atlantic forests (−1.62) and tropical montane forests (−1.55) presented the highest deforestation rates for the region. In particular, tropical lowland forests in Ecuador (−2.42) and tropical dry forests in Mexico (−2.88) and Argentina (−2.20) were the most affected. In most countries, the access to markets and agricultural and forest activities are the main causes of deforestation; however, the causes vary according to the forest types. Deforestation measurements focused at different scales and on different forest types will help governments to improve their reports for international initiatives, such as reducing emissions from deforestation and forest degradation (REDD+) but, more importantly, for developing local policies for the sustainable management of forests and for reducing the deforestation in Latin America.     

Isoprene emissions from vegetation and hydrocarbon emissions from bushfires in tropical Australia

Information from a variety of sources, including an airborne field expedition in November 1985, is used to produce estimates of the annual emissions of some hydrocarbons from bushfires, and isoprene from trees, in tropical Australia. For the continent north of 23° S the annual bushfires (biomass burning) input was estimated, in units of Tg carbon, to be 2 TgC (uncertainty range 0.8–5 TgC), emitted predominantly during the May to October dryseason. Isoprene emissions during this period were estimated also to be 2 TgC (uncertainty range 0.5–8 TgC), but were estimated to be an order of magnitude higher during the November to April wet season, at a level of 23 TgC (uncertainty range 6–100 TgC).The large annual emission of isoprene over the tropical part of the Australian continent yields ppbv levels of isoprene measured at the surface in summertime. Isoprene reactivity with hydroxyl radical is such that at these concentrations isoprene must be a dominant factor in controlling the concentration of OH radical in the convective boundary layer. Simple arguments based on the convective velocity scale suggest that the shape of the isoprene vertical profile in November 1985 would be consistent with available data on the OH-isoprene reaction rate if OH concentration in the boundary layer averaged about 2.5×10⁶ cm^-3 over the middle part of the day.Temporarily at the International Meteorological Institute, Stockholm University, S-106 91, Stockholm, Sweden.     

Potential Carbon Flux from Timber Harvests and Management in the Context of a Global Timber Market

This paper presents carbon flux estimates arising from the effect of increasing demand on harvests and management of industrial forests in a global timber market. Results are presented for specific regions and the globe. Harvests and management of forests are predicted to store an additional 184 Tg (1 Tg = 10¹² grams) of carbon per year in forests and wood products over the next 50 years, with a range of 108 to 251 Tg per year. Although harvests in natural boreal and tropical forest regions will cause carbon releases, new plantation establishment in subtropical emerging regions more than offsets these losses. Unlike many existing studies, these results suggest that harvests and management of North American forests will lead to carbon emissions from that region over the next 50 years. The results are quantitatively sensitive to the assumed growth in demand although the results are qualitatively similar in the sensitivity analysis.     

The Australia clause and REDD: a cautionary tale

If a binding agreement can be reached on a post-2012 international climate regime, it is likely to include the phased introduction of a market-linked mechanism for reducing emissions from deforestation and forest degradation in developing countries (REDD). Under such a scheme, countries that reduce net REDD emissions below a pre-set baseline would receive credits that could be sold in carbon markets and used by purchasing nations to meet their international mitigation obligations. This paper draws on the Australian experience with deforestation to identify some of the issues that might obstruct progress on REDD. For the past 20 years, Australia has had the highest rate of deforestation in the developed world; ~416,000 ha of forests were cleared annually between 1990 and 2009, resulting in the emission of almost 80 MtCO₂-e/yr. It is also the only developed country that will rely on reduced deforestation emissions as the primary way of meeting its quantified emissions target under the Kyoto Protocol. Australia’s approach to deforestation issues provides valuable insights into the difficulties an international REDD scheme might encounter.     

Temporal Assessment of Growing Stock, Biomass and Carbon Stock of Indian Forests

The dynamics of terrestrial ecosystems depends on interactions between carbon, nutrient and hydrological cycles. Terrestrial ecosystems retain carbon in live biomass (aboveground and belowground), decomposing organic matter, and soil. Carbon is exchanged naturally between these systems and the atmosphere through photosynthesis, respiration, decomposition, and combustion. Human activities change carbon stock in these pools and exchanges between them and the atmosphere through land-use, land-use change, and forestry.In the present study we estimated the wood (stem) biomass, growing stock (GS) and carbon stock of Indian forests for 1984 and 1994. The forest area, wood biomass, GS, and carbon stock were 63.86 Mha, 4327.99 Mm³, 2398.19 Mt and 1085.06 Mt respectively in 1984 and with the reduction in forest area, 63.34 Mha, in 1994, wood biomass (2395.12 Mt) and carbon stock (1083.69 Mt) also reduced subsequently. The Conifers, of temperate region, stocked maximum carbon in their woods, 28.88 to 65.21 t C ha⁻¹, followed by Mangrove forests, 28.24 t C ha⁻¹, Dipterocarp forests, 28.00 t C ha⁻¹, and Shorea robusta forests, 24.07 t C ha⁻¹. Boswellia serrata, with 0.22 Mha forest area, stocked only 3.91 t C ha⁻¹. To have an idea of rate of carbon loss the negative changes (loss of forest area) in forest area occurred during 1984–1994 (10yrs) and 1991–1994 (4yrs) were also estimated. In India, land-use changes and fuelwood requirements are the main cause of negative change. Total 24.75 Mt C was lost during 1984–1994 and 21.35 Mt C during 1991–94 at a rate of 2.48 Mt C yr⁻¹ and 5.35 Mt C yr⁻¹ respectively. While in other parts of India negative change is due to multiple reasons like fuelwood, extraction of non-wood forest products (NWFPs), illicit felling etc., but in the northeastern region of the country shifting cultivation is the only reason for deforestation. Decrease in forest area due to shifting cultivation accounts for 23.0% of the total deforestation in India, with an annual loss of 0.93 Mt C yr⁻¹.     

Measurement of Carbon Dioxide Emissions Plumes from Prudhoe Bay, Alaska Oil Fields

Large carbon dioxide plumes with concentrations up to 45 ppm aboveambient levels were measured about 15 km downwind of the Prudhoe Bay, Alaskamajor oil production facilities, located at 70° N Lat. above the ArcticCircle. The measured emissions were 1.3 × 10³ metrictons (C) hour^-1 (11.4× 10⁶ metric tons(C) year^-1), six times greater than the combustion emissionsassumed by Jaffe and coworkers in J. Atmos. Chem. 20 (1995), 213–227,based on 1989 reported Prudhoe Bay oil facility fuel consumption data, andfour times greater than the total C emissions reported by the oil facilitiesfor the same months as the measurement time periods. Variations in theemissions were estimated by extrapolating the observed emissions at a singlealtitude for all tundra research transect flights conducted downwind of theoil fields. These 30 flights yielded an average emission rate of1.02 × 10³ metric tons (C) hour^-1 with astandard deviation of 0.33 × 10³. These quantity ofemissions are roughly equivalent to the carbon dioxide emissions of7–10 million hectares of arctic tussock tundra (Oechel and Vourlitis,Trends in Ecol. Evolution 9 (1994), 324–329).     

How the future of the global forest sink depends on timber demand,forest management,and carbon policies

Deforestation has contributed significantly to net greenhouse gas emissions, but slowing deforestation, regrowing forests and other ecosystem processes have made forests a net sink. Deforestation will still influence future carbon fluxes, but the role of forest growth through aging, management, and other silvicultural inputs on future carbon fluxes are critically important but not always recognized by bookkeeping and integrated assessment models. When projecting the future, it is vital to capture how management processes affect carbon storage in ecosystems and wood products. This study uses multiple global forest sector models to project forest carbon impacts across 81 shared socioeconomic (SSP) and climate mitigation pathway scenarios. We illustrate the importance of modeling management decisions in existing forests in response to changing demands for land resources, wood products and carbon. Although the models vary in key attributes, there is general agreement across a majority of scenarios that the global forest sector could remain a carbon sink in the future, sequestering 1.2–5.8 GtCO2e/yr over the next century. Carbon fluxes in the baseline scenarios that exclude climate mitigation policy ranged from −0.8 to 4.9 GtCO2e/yr, highlighting the strong influence of SSPs on forest sector model estimates. Improved forest management can jointly increase carbon stocks and harvests without expanding forest area, suggesting that carbon fluxes from managed forests systems deserve more careful consideration by the climate policy community.     

Deforestation-induced costs on the drinking water supplies of the Mumbai metropolitan,India

The success of incorporating natural capital into resource- and land-use decisions hinges on the ability to quantify the ecosystem services, forecast the returns to the investments, convert these values into effective policy and finance mechanisms, and the presence of well-functioning institutions and infrastructure. However, ecosystem production functions i.e., the relationship between regulatory functions of the ecosystem and the economic activity it protects or supports are often poorly understood. Even with respect to Forest Watershed Services – a service that is widely recognized and even institutionalized through market based mechanisms in some parts of the world – the biophysical relationships between forests and services such as stream flow stabilization, water quality and water quantity are undefined, particularly for the tropics. For this reason, this study through time series data and multivariate analysis characterizes the relationships between Forest Cover (all lands with tree cover of a canopy density of 10% and above when projected vertically on the horizontal ground with minimum areal extent of 1 ha), water quality and cost of water treatment in the Western Ghats of peninsular India. In particular, the recursive relationship between the economic and environmental components is estimated by tracing the effects through the two-stage model. Annual value of impacts (increased ‘treatment cost’, increased ‘water losses due to backwash and desludging’, and changes in ‘water yield’) induced by loss of Forest Cover is estimated as 64.96 Indian rupee/m³ treated water/ha/year ($1.32/m³ treated water/ha/year). At an annual rate of change in the forest cover by −0.0088% (average annual rate of change in the forest cover between the years 1994–2007) the deforestation induced costs translate to 3.73 million Indian rupee/year ($0.075 million/year) according to the 2010–2011 prices for the Panjrapur treatment plant of the Municipal Corporation of Greater Mumbai. Thus, if deforestation is avoided the Municipal Corporation can save significant amount towards recurring costs of water treatment and to some extent mitigate the costs for the development of a new source.     

Source terms and source strengths of the carbonaceous aerosol in the tropics

Atmospheric aerosol samples were collected in the Ivory Coast, primarily at Lamto (6°N, 5°W) between 1979 and 1981. The samples were analysed for total particulate carbon concentration and isotopic composition (¹³C/¹²C) by mass spectrometry. Observed concentrations were found high compared to values reported for temperate regions. Fine particulate carbon in the submicrometersize range accounted for 50 to 80% of the reported concentrations. At Lamto, both particulate carbon concentrations and isotopic ratios exhibit a large temporal variability which is shown to reflect the diversity of sources and their seasonal evolution. Natural emissions from the equatorial forest during the wet season, and biomass burning during the dry season, appear to be the major sources. The latter, though active during only a third of the year, is, on an annual basis, the most important source. Based on the data obtained at Lamto, an attempt has been made to estimate the flux of fine particulate carbon emitted from the tropical regions into the global troposphere. This flux, which is of the order of 20×10¹² g C/yr, appears to be equivalent to the flux of fine particulate carbon emitted from industrial sources. These results suggest that the tropospheric burden of fine particulate carbon in lowlatitude regions is dominated by the long-range transport of carbonaceous aerosols originating from the Tropics.     

中国电力行业碳排放达峰及减排潜力分析

推动电力行业低碳发展是中国有效控制CO₂排放和推动尽早达峰的重要抓手。在分别利用学习曲线工具和自下而上技术核算方式分析风电、光伏两类主要的可再生电力和其他各类电源发展趋势的基础上,综合评估了既有政策和强化政策条件下2035年前中国电力行业能源活动碳排放变化趋势。研究发现,既有政策情景下电力行业碳排放在2030年左右达到峰值,届时非化石能源在发电量中比重为44%,而通过强化推动能源绿色低碳发展的相关政策,2025年前即可达到电力行业碳排放峰值,2030年非化石电力在发电量中比重可以提升至51%,其中可再生电力加速发展将分别贡献2025、2030和2035年当年减排量（相对于既有政策情景）的45%、54%和62%。尽管从保障电力稳定安全供应角度,煤电装机仍有一定增长空间,但考虑到电力行业绿色低碳和可持续发展的长期需求,仍应加强对煤电装机的有效控制,“十四五”期间努力将煤电装机控制在11亿kW左右的水平。     

Amazon forest biomass density maps: tackling the uncertainty in carbon emission estimates

As land use change (LUC), including deforestation, is a patchy process, estimating the impact of LUC on carbon emissions requires spatially accurate underlying data on biomass distribution and change. The methods currently adopted to estimate the spatial variation of above- and below-ground biomass in tropical forests, in particular the Brazilian Amazon, are usually based on remote sensing analyses coupled with field datasets, which tend to be relatively scarce and often limited in their spatial distribution. There are notable differences among the resulting biomass maps found in the literature. These differences subsequently result in relatively high uncertainties in the carbon emissions calculated from land use change, and have a larger impact when biomass maps are coded into biomass classes referring to specific ranges of biomass values. In this paper we analyze the differences among recently-published biomass maps of the Amazon region, including the official information used by the Brazilian government for its communication to the United Nation Framework on Climate Change Convention of the United Nations. The estimated average pre-deforestation biomass in the four maps, for the areas of the Amazon region that had been deforested during the 1990–2009 period, varied from 205?±?32 Mg ha^?1 during 1990–1999, to 216?±?31 Mg ha^?1 during 2000–2009. The biomass values of the deforested areas in 2011 were between 7 and 24 % higher than for the average deforested areas during 1990–1999, suggesting that although there was variation in the mean value, deforestation was tending to occur in increasingly carbon-dense areas, with consequences for carbon emissions. To summarize, our key findings were: (i) the current maps of Amazonian biomass show substantial variation in both total biomass and its spatial distribution; (ii) carbon emissions estimates from deforestation are highly dependent on the spatial distribution of biomass as determined by any single biomass map, and on the deforestation process itself; (iii) future deforestation in the Brazilian Amazon is likely to affect forests with higher biomass than those deforested in the past, resulting in smaller reductions in carbon dioxide emissions than expected purely from the recent reductions in deforestation rates; and (iv) the current official estimate of carbon emissions from Amazonian deforestation is probably overestimated, because the recent loss of higher-biomass forests has not been taken into account.