Managing forests for climate change mitigation

Forests currently absorb billions of tons of CO2 globally every year, an economic subsidy worth hundreds of billions of dollars if an equivalent sink had to be created in other ways. Concerns about the permanency of forest carbon stocks, difficulties in quantifying stock changes, and the threat of environmental and socioeconomic impacts of large-scale reforestation programs have limited the uptake of forestry activities in climate policies. With political will and the involvement of tropical regions, forests can contribute to climate change protection through carbon sequestration as well as offering economic, environmental, and sociocultural benefits. A key opportunity in tropical regions is the reduction of carbon emissions from deforestation and degradation.     

碳达峰碳中和背景下中国森林碳汇潜力分析研究

[目的]核算我国森林资源碳储量和价值量,摸清我国森林资源家底,了解森林资源状况,合理制定林业发展规划.预测森林碳储量及碳汇潜力,提高森林经营管理水平,为我国实现碳达峰碳中和的林业发展目标提供参考.[方法]利用1973?2018年间9次森林资源清查数据,采用森林蓄积量法核算我国森林资源总碳储量及其变化情况,并按照不同林种...     

Europe's terrestrial biosphere absorbs 7 to 12% of European anthropogenic CO2 emissions

Most inverse atmospheric models report considerable uptake of carbon dioxide in Europe's terrestrial biosphere. In contrast, carbon stocks in terrestrial ecosystems increase at a much smaller rate, with carbon gains in forests and grassland soils almost being offset by carbon losses from cropland and peat soils. Accounting for non-carbon dioxide carbon transfers that are not detected by the atmospheric models and for carbon dioxide fluxes bypassing the ecosystem carbon stocks considerably reduces the gap between the small carbon-stock changes and the larger carbon dioxide uptake estimated by atmospheric models. The remaining difference could be because of missing components in the stock-change approach, as well as the large uncertainty in both methods. With the use of the corrected atmosphere- and land-based estimates as a dual constraint, we estimate a net carbon sink between 135 and 205 teragrams per year in Europe's terrestrial biosphere, the equivalent of 7 to 12% of the 1995 anthropogenic carbon emissions.     

Carbon pools and flux of global forest ecosystems

Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 +/- 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.     

Selective logging in the Brazilian Amazon

Amazon deforestation has been measured by remote sensing for three decades. In comparison, selective logging has been mostly invisible to satellites. We developed a large-scale, high-resolution, automated remote-sensing analysis of selective logging in the top five timber-producing states of the Brazilian Amazon. Logged areas ranged from 12,075 to 19,823 square kilometers per year (+/-14%) between 1999 and 2002, equivalent to 60 to 123% of previously reported deforestation area. Up to 1200 square kilometers per year of logging were observed on conservation lands. Each year, 27 million to 50 million cubic meters of wood were extracted, and a gross flux of approximately 0.1 billion metric tons of carbon was destined for release to the atmosphere by logging.     

基于NbS的北京市乔木林固碳能力分析

[目的]乔木林生物质碳汇是影响森林碳汇的重要组成部分,是一种自然的气候解决方案,在全球气候变化大背景下,森林的固碳潜力一直被广泛关注,本文以北京市为例,分析不同的林业活动对乔木碳储量的影响.[方法]采用北京市森林资源设计调查数据,利用IPCC材积源-生物量法估算北京市乔木林碳储量,分析了2009-2014年北京市在森林...     

Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2

Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of -1.5 petagrams of carbon per year (Pg C year(-1)) and weaker tropical emission of +0.1 Pg C year(-1) compared with previous consensus estimates of -2.4 and +1.8 Pg C year(-1), respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.     

Atmospheric input of carbon dioxide from burning wood

The atmospheric input of carbon dioxide from burning wood, in particular from forest fires in boreal and temperate regions resulting from both natural and man-made causes and predominantly from forest fires in tropical regions caused by shifting cultivation, is estimated to be 5.7 x 10(15) grams of carbon per year as gross input and 1.5 x 10(15) grams of carbon per year as net input. This is a significant amount as compared to the fossil fuel carbon dioxide produced from the utilization of oil, gas, coal, and limestone, and bears on the hypothesis of the enhanced sedimentation of marine detritus as a removal mechanism of excess atmospheric carbon dioxide.     

Land-use allocation protects the Peruvian Amazon

Disturbance and deforestation have profound ecological and socioeconomic effects on tropical forests, but their diffuse patterns are difficult to detect and quantify at regional scales. We expanded the Carnegie forest damage detection system to show that, between 1999 and 2005, disturbance and deforestation rates throughout the Peruvian Amazon averaged 632 square kilometers per year and 645 square kilometers per year, respectively. However, only 1 to 2% occurred within natural protected areas, indigenous territories contained only 11% of the forest disturbances and 9% of the deforestation, and recent forest concessions effectively protected against clear-cutting. Although the region shows recent increases in disturbance and deforestation rates and leakage into forests surrounding concession areas, land-use policy and remoteness are serving to protect the Peruvian Amazon.     

Wood versus fossil fuel as a source of excess carbon dioxide in the atmosphere: a preliminary report

If the amounts of wood consumed in deforestation to increase agricultural land and as firewood in underindustrialized countries are added to the amount consumed by the money economies as forest products, the estimates of the net amount of wood removed from the biosphere in this century should be revised upward. The per capita ratio of the weight of carbon from net wood burned to the weight of carbon from fossil fuel burned in this century has been at least 0.1 and may have approached 1.0.     

Comment on "The incidence of fire in Amazonian forests with implications for REDD"

Arag?o and Shimabukuro (Reports, 4 June 2010, p. 1275) reported that fires increase in agricultural frontiers even as deforestation decreases and concluded that these fires lead to unaccounted carbon emissions under the United Nations climate treaty's tropical deforestation and forest degradation component. Emissions from post-deforestation management activities are, in fact, included in these estimates--but burning of standing forests is not.     

A large terrestrial carbon sink in north america implied by atmospheric and oceanic carbon dioxide data and models

Atmospheric carbon dioxide increased at a rate of 2.8 petagrams of carbon per year (Pg C year-1) during 1988 to 1992 (1 Pg = 10(15) grams). Given estimates of fossil carbon dioxide emissions, and net oceanic uptake, this implies a global terrestrial uptake of 1.0 to 2. 2 Pg C year-1. The spatial distribution of the terrestrial carbon dioxide uptake is estimated by means of the observed spatial patterns of the greatly increased atmospheric carbon dioxide data set available from 1988 onward, together with two atmospheric transport models, two estimates of the sea-air flux, and an estimate of the spatial distribution of fossil carbon dioxide emissions. North America is the best constrained continent, with a mean uptake of 1.7 +/- 0.5 Pg C year-1, mostly south of 51 degrees north. Eurasia-North Africa is relatively weakly constrained, with a mean uptake of 0.1 +/- 0.6 Pg C year-1. The rest of the world's land surface is poorly constrained, with a mean source of 0.2 +/- 0.9 Pg C year-1.     

Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change

Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.     

Net Exchange of CO2 in a Mid-Latitude Forest

The eddy correlation method was used to measure the net ecosystem exchange of carbon dioxide continuously from April 1990 to December 1991 in a deciduous forest in central Massachusetts. The annual net uptake was 3.7 +/- 0.7 metric tons of carbon per hectare per year. Ecosystem respiration, calculated from the relation between nighttime exchange and soil temperature, was 7.4 metric tons of carbon per hectare per year, implying gross ecosystem production of 11.1 metric tons of carbon per hectare per year. The observed rate of accumulation of carbon reflects recovery from agricultural development in the 1800s. Carbon uptake rates were notably larger than those assumed for temperate forests in global carbon studies. Carbon storage in temperate forests can play an important role in determining future concentrations of atmospheric carbon dioxide.     

基于InVEST模型的森林碳储量动态监测

森林碳储量主要通过地面调查数据来估算,存在着统计工作量大,建模复杂度高等难点。如何快捷、准确地估测森林碳储量一直是国内外林业领域研究的热点和难题。结合遥感图像监测尺度大和InVEST模型输入参数少的特点,提出一种基于InVEST模型结合遥感图像估测森林碳储量的方法。该方法根据森林类型碳储量信息和相应的栅格数据,利用InVEST模型估测区域森林碳储量,然后通过比对多期遥感数据估测出的碳储量得出该区域碳储量变化,从而实现森林碳储量的动态监测。对浙江省庆元县2009年的碳储量进行了估算和绘图,根据行政区划图可估算出乡(镇)和村级的碳储量。实验分别对坑西村2009年和2014年的碳储量进行了估算,根据基于碳库差别的方法实现了碳储量动态监测。实验结果表明:①庆元县2009年的森林碳储量为3.274 3×107 Mg;②坑西村2009年到2014年碳储量增加了1.780 3×104 Mg。相比不对森林类型进行细分的森林平均碳密度,将各森林类型平均碳储量和森林类型年度碳汇量引入到森林碳储量监测中,使得森林碳储量的估测精度得到了提升。另外,提出的森林碳储量动态监测可实现对县、乡(镇)和村级的监测,具有模型输入数据量少和输出结果可视化的优点,以及监测手段简单便捷,操作性强等特点。图5表4参32     

Tropical deforestation and habitat fragmentation in the Amazon: satellite data from 1978 to 1988

Landsat satellite imagery covering the entire forested portion of the Brazilian Amazon Basin was used to measure, for 1978 and 1988, deforestation, fragmented forest, defined as areas less than 100 square kilometers surrounded by deforestation, and edge effects of 1 kilometer into forest from adjacent areas of deforestation. Tropical deforestation increased from 78,000 square kilometers in 1978 to 230,000 square kilometers in 1988 while tropical forest habitat, severely affected with respect to biological diversity, increased from 208,000 to 588,000 square kilometers. Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater.     

河北张家口坝上地区退化林修复碳排放估算

基于河北张家口坝上地区退化林修复各机械设备的燃料品种、基本燃料消耗量,肥料种类、肥料施用量等活动水平数据,以及相应的排放因子等参数,采用IPCC法（一种以详细技术为基础的部门方法）,分别估算了油锯伐木、油锯造材、汽车运材、机械整地、汽车运苗、汽车运肥、洒水车运水和复合肥等各排放源的碳排放量,然后相加得出碳排放总量。再由碳排放总量除以修复面积,得出单位面积碳排放量。结果表明,河北张家口坝上地区退化林修复项目CO₂排放总量为182 315.1 t,单位面积CO₂排放量为2.2 t/hm²。研究成果有助于森林经营活动的碳汇计量与监测,以及省级乃至国家级温室气体清单的编制。通过研究,建议各地在退化林修复过程中应充分利用自然,选择自然恢复为主的修复方式开展修复。在辅以补植等人工措施时,还要采取科学设计栽植密度、选择更为节水的灌溉方式等措施,以减少对化石燃料的消耗,降低碳排放量,促进节能减排工作。     

安徽碳排放特征及"十三五"碳排放对策

"十二五"时期,安徽碳排放呈现总量逐年上升,行业高度集中,区域差异明显,强度不断下降,人均水平较低等趋势和特征。"十三五"安徽正处在工业化和城市化加快发展的关键时期,经济结构高碳特征显著,碳减排工作面临较大挑战。实现碳减排目标,关键是要加快建设以低能源消耗和低碳排放为特征的产业体系和消费方式,逐步构建创新型绿色发展模式。     

江苏省农业碳排放时序特征与趋势预测

为探讨江苏省农业碳排放时序特征及未来碳排放趋势,利用排放因子法对江苏省2000—2019年农业碳排放进行估算,并运用STIRPAT模型对2020—2030年全省农业碳排放趋势进行预测。结果表明：江苏省2000—2019年的CO₂排放当量（CO₂e）整体呈现降低-升高-降低的趋势,并在2005年达峰,估算为8 361.77万t,其中种植业、畜牧业则分别在2010年、2003年达峰,种植业排放量远高于畜牧业。农业CO₂e排放强度呈先升高后降低的趋势,2003年后排放强度逐年递减,到2019年已降至1.31 t·万元^-1;在各碳源中,水稻种植是全省农业碳排放的最大排放源,而在主要畜禽中,猪养殖过程中造成的碳排放远高于其他畜禽;预计2020—2030年,伴随城镇化发展、农业人均GDP提高和农业碳排放强度的进一步降低,全省农业CO₂e排放量仍将呈下降趋势,在减碳的同时可以兼顾农业经济高效发展。研究表明,江苏省农业已实现碳达峰,未来农业碳排放的持续降低将有利于加速全省碳中和目标的实现。     

Global deforestation: contribution to atmospheric carbon dioxide

A study of effects of terrestrial biota on the amount of carbon dioxide in the atmosphere suggests that the global net release of carbon due to forest clearing between 1860 and 1980 was between 135 x 10(15) and 228 x 10(15) grams. Between 1.8 x 10(15) and 4.7 x 10(15) grams of carbon were released in 1980, of which nearly 80 percent was due to deforestation, principally in the tropics. The annual release of carbon from the biota and soils exceeded the release from fossil fuels until about 1960. Because the biotic release has been and remains much larger than is commonly assumed, the airborne fraction, usually considered to be about 50 percent of the release from fossil fuels, was probably between 22 and 43 percent of the total carbon released in 1980. The increase in carbon dioxide in the atmosphere is thought by some to be increasing the storage of carbon in the earth's remaining forests sufficiently to offset the release from deforestation. The interpretation of the evidence presented here suggests no such effect; deforestation appears to be the dominant biotic effect on atmospheric carbon dioxide. If deforestation increases in proportion to population, the biotic release of carbon will reach 9 x 10(15) grams per year before forests are exhausted early in the next century. The possibilities for limiting the accumulation of carbon dioxide in the atmosphere through reduction in use of fossil fuels and through management of forests may be greater than is commonly assumed.