Research on Spatial and Temporal Difference of Agricultural Carbon Emission Efficiency and Its Influencing Factors in Hubei Province
TIAN Yun,, WANG MengChenSchool of Business Administration, Zhongnan University of Economics and Law, Wuhan 430073责任编辑: 李云霞
收稿日期:2020-05-4接受日期:2020-07-21网络出版日期:2020-12-16
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Received:2020-05-4Accepted:2020-07-21Online:2020-12-16
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田云, 王梦晨. 湖北省农业碳排放效率时空差异及影响因素[J]. 中国农业科学, 2020, 53(24): 5063-5072 doi:10.3864/j.issn.0578-1752.2020.24.009
TIAN Yun, WANG MengChen.
开放科学(资源服务)标识码(OSID):
0 引言
【研究意义】近年来,气候变化问题已引起了世界各国以及社会各界的广泛关注,并成为了众多****探讨的焦点。其中,联合国政府间气候变化专门委员会(IPCC)发布的第四次评估报告显示,在未来100年内全球地表温度有可能提升1.8—4.0℃,为此抑制全球气候变暖已显得刻不容缓。虽然引起气温上升的原因是多方面的,但人类活动所导致的碳排放在其中扮演极为重要的角色。诚然工业和服务业是产生碳排放的主要源泉,但快速发展的农业所起的助推作用也不容忽视。而作为我国传统农业大省,湖北虽为我国提供了大量的商品粮、棉、油、肉以及水产品,但由于自身对化肥、农药等农用物资的依赖程度过高,客观上也导致了其农业生产相对高碳。为了更好地践行绿色发展战略,加快推进湖北农业低碳发展已迫在眉睫,而厘清其农业碳排放现状及效率特征是实现这一目标的重要前提。【前人研究进展】越来越多的****开始围绕农业碳排放问题展开探究,并涉及到了方方面面。其中,早期主要偏重于农业碳排放测算、时空特征分析以及驱动因素探究。李波等[1]、闵继胜等[2]、TIAN等[3] 的综合研究表明,自20世纪90年代以来,我国农业碳排放量总体处于增长态势而且地区差异明显,农业经济发展是导致其数量变化的关键性因素。而后,随着研究的逐步深入,****们开始聚焦于农业碳排放的效率测度与影响因素探讨,且多立足于国家视角[4,5,6]。研究发现,虽然中国农业碳排放效率总体有较大提高,但区域间存在明显的非均衡性,其变化主要受产业集聚、城镇化水平等因素影响。除此之外,还有不少****围绕农业碳排放与经济发展的互动关系[7,8]、气候变化与低碳农业生产关系[9]、农业碳减排潜力评估与减排成本测度[10,11,12]、农业低碳技术与生产行为[13,14,15]等问题展开深度剖析。与此同时,虽然也有不少****围绕湖北农业碳排放问题展开探究,但主要聚焦于农业碳排放现状测度与驱动因素分解[16]、农业产业化与农村碳排放关系[17]、技术进步与生猪养殖温室气体排放[18]、农业碳排放与农业经济的相互关联[19]等几个领域,而较少涉及其他方面。【本研究切入点】从现有文献来看,农业碳排放效率及其影响因素的研究主要集中于国家层面,多以31个省区作为考察对象,而鲜有****围绕湖北省及各市(州)农业碳效率问题展开深度探讨。所谓农业碳排放效率,即指碳排放约束下的农业生产率水平,在此将农业碳排放作为了非期望产出。【拟解决的关键问题】本文将以湖北省作为研究对象,首先利用DEA-Malmquist分解法完成对其农业碳排放效率的测度并分析其时空差异特征;而后运用Tobit模型探究影响其碳排放效率变化的关键因素。相关研究结论的获取能够为湖北农业低碳生产的切实推进提供必要的参考依据与政策启示。1 研究方法
1.1 DEA-Malmquist指数分解法与变量选取
本文所要探讨的农业碳排放效率属于传统农业生产率的特殊表现形式,唯一的区别在于产出指标还兼顾了非期望产出。由于存在非期望产出,使得Shephard距离函数无法完成对碳排放生产率的准确测度。为此,实际分析中将构造基于SBM方向距离函数的Malmquist-Luenberger生产率指数对湖北省农业碳排放效率进行测度。具体分析中,将基于跨期动态概念,参照Malmquist指数几何平均值思路,构建从t到t+1基于乘除结构和相邻参比的SBM方向性距离函数的全要素生产率指数[21],并定义为碳排放生产效率(CTFP)指数:式中,CTFP代表第t期到t+1期农业碳排放效率的变化率,若CTFP>1时,表明农业碳排放效率有所增长;反之,则下降。进一步,CTFP可分解为技术效率(CEFF)和前沿技术进步(CTECH),其中CEFF表示第t期到t+1期技术效率的变化率,CEFF>1则揭示技术效率提高,反之则下降;CTECH表示第t期到t+1期的技术水平变化,CTECH>1表明技术有所进步,反之即为恶化。需要说明的是,技术效率可以进一步分解为纯技术效率(CPECH)和规模效率(CSECH)。
选择合适的投入与产出变量对于农业碳排放效率测度至关重要,为了确保变量选择的科学性,在此对已有相关研究进行回顾与梳理。其中,关于投入变量的选择,农业劳动力、农业机械总动力、耕地面积与役畜投入得到了较多****[20,21]的认可;而关于产出指标的确定,农业总产值一般被当作期望产出,而农业面源污染、农业碳排放等则通常作为非期望产出[22,23,24]。本文将在参照已有研究成果的基础上,结合数据的可获取性,选取农业投入产出变量具体如下:
农业投入变量包含农业劳动力、土地、农业机械动力、灌溉以及役畜投入等5个方面。其中,农业劳动力反映了人力资本层面的投入,具体将以湖北省各市(州)第一产业年末从业人数作为其衡量标准,单位为万人;土地是农业生产活动得以开展的物质基础,具体以各市(州)年末耕地面积作为衡量指标,单位为khm2;农业机械的广泛使用是促进农业生产力提升的重要手段,故在此也将其作为投入指标,具体以各市(州)历年农业机械总动力作为衡量依据,单位为万kW;随着农田水利等基础设施建设的日趋完善,灌溉在农作物种植过程中扮演着越发重要角色,因此我们不能忽视灌溉投入对农业生产的影响,在此以各市(州)历年有效灌溉面积作为衡量灌溉投入的具体指标,单位为khm2;除此之外,役畜虽然在农业生产中所起作用越来越小,但也不可忽视其存在,仍有必要将其作为投入指标之一,具体以牛(非肉牛、奶牛)、马、驴、骡等的数量作为替代变量,单位为万头。农业产出指标包含两个方面,即期望产出农业总产值,以各市(州)历年农业总产值作为衡量标准,单位为亿元,以及非期望产出农业碳排放量,以各市(州)历年实际农业碳排放数量为准,单位为万t。
1.2 Tobit模型
在厘清湖北省及各市(州)农业碳排放效率之后,为了确保对策建议的针对性,有必要围绕其影响因素展开探讨。具体而言,以历年各地区农业碳排放效率值为因变量,各影响因素为解释变量构建线性回归方程,而后通过自变量系数判断各影响因素对效率值的作用方向及程度。由于DEA方法测算出的效率值一般大于0,直接运用普通最小二乘法实施回归可能会导致参数估计值出现偏向0的情形,为此本文将借鉴一些****[21,25]的已有做法,运用因变量受限制的Tobit模型展开实证分析。其模型基本形式如下:ei~N(0, σ2), i=1,2,3,K,……n
式(5)中,ei为受限因变量,xi为解释变量,β为回归系数。在此基础上,结合本文研究目的,可构建以农业碳排放效率(CTFP)为被解释变量的Tobit模型如下:
式(6)中的CTFP为农业碳排放效率值,i表示各市(州),t表示年份,β0为常数项,β1、β2、βn分别为各个解释变量的回归系数,μ为随机扰动项。
1.3 数据来源及处理
耕地面积、第一产业从业人员、役畜数量、农用机械总动力、有效灌溉面积、农业总产值等投入产出指标的原始数据出自《湖北统计年鉴》《湖北农村统计年鉴》以及各市(州)年鉴。同时,考虑到以实价计算的农林牧业总产值不能进行纵向对比,实际分析中将基于2010年不变价对各市(州)历年农业总产值进行调整。至于各市(州)农业碳排放量,由于目前官方尚无统计,且已有研究成果也较少涉及,为此本文将对其进行有效测度。纵览现有文献可知,一般从农用物资投入、水稻种植以及畜禽养殖等3个维度完成对农业碳排放的测算[26,27],本文也将参照这一做法;但受限于数据的可获取性,在具体指标的选择上有所区别。其中,农用物资投入包含化肥、农药、农膜以及农用柴油,并以各自实际使用量为准;水稻则结合其生长周期的不同分为早稻、中稻和晚稻,均以实际播种面积为准;畜禽养殖主要涉及猪、牛、羊等三大主要牲畜,且考虑到各自饲养周期存在差异,在此参照胡向东等[28]的计算方法对其年均饲养量进行调整。具体测算方法及各自所对应的碳排放系数出自IPCC以及闵继胜等[2]、TIAN等[3]的相关研究,限于篇幅,在此不做过多介绍。另外,鉴于各类基础数据缺失较为严重,鄂州与神农架均不在本次研究的考察范围之内。各市(州)农业投入、产出变量的一般描述性分析如表1所示。Table 1
表1
表1农业投入、产出指标的一般描述性统计结果
Table 1
指标 Indicators | 变量 Variable | 单位 Unit | 极小值 Minimum | 极大值 Max | 均值 Mean | 标准差 St. deviation | |
---|---|---|---|---|---|---|---|
产出指标 Output indicator | 期望产出 Expected output | 农业总产值 Gross agricultural output value | ×108 yuan | 31.86 | 352.19 | 141.75 | 83.32 |
非期望产出 Unexpected output | 农业碳排放量 Agricultural carbon emissions | ×104 t | 25.55 | 212.07 | 98.19 | 60.10 | |
投入指标Input index | 劳动力Labor force | ×104 | 7.81 | 134.35 | 62.09 | 34.82 | |
土地Land | khm2 | 70.22 | 470.34 | 225.3 | 120.87 | ||
农用机械Agricultural machinery | ×104 kW | 72.34 | 646.07 | 264.65 | 149.90 | ||
灌溉Irrigation | khm2 | 30.38 | 423.26 | 151.1 | 101.23 | ||
役畜Beast of burden | ×104 | 0.31 | 108.19 | 29.05 | 30.31 |
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2 结果
2.1 湖北省农业碳排放效率时序比较
基于前文所构建公式,利用MAX-DEA软件测度湖北省农业碳排放效率如表2所示。从中不难发现,2011年以来湖北省农业碳排放效率虽年际间存在一定波动但总体处于增长态势,年均增速为2.9%。从驱动源泉来看,农业碳排放综合效率的提升主要依赖于前沿技术进步,其年均贡献率达到了3.6%;农业技术效率则处于恶化状态,年均递减0.3%,进一步分解可知,纯技术效率恶化趋势较为明显,年均递减1.1%,而规模效率得到了轻微改善,年均递增0.7%。Table 2
表2
表2湖北省农业碳排放效率变化情况
Table 2
年份 Year | 前沿技术进步 CTECH | 技术效率 CEFF | 纯技术效率 CPECH | 规模效率 CSECH | 综合效率 CTFP | |||||
---|---|---|---|---|---|---|---|---|---|---|
年际值 Interannual | 累计值 Cumulative | 年际值 Interannual | 累计值 Cumulative | 年际值 Interannual | 累计值 Cumulative | 年际值 Interannual | 累计值 Cumulative | 年际值 Interannual | 累计值 Cumulative | |
2011 | 1.024 | 1.024 | 0.974 | 0.974 | 0.991 | 0.991 | 0.983 | 0.983 | 0.998 | 0.998 |
2012 | 1.007 | 1.031 | 0.951 | 0.926 | 0.944 | 0.936 | 1.008 | 0.991 | 0.958 | 0.956 |
2013 | 1.220 | 1.258 | 0.875 | 0.809 | 0.954 | 0.892 | 0.917 | 0.909 | 1.067 | 1.020 |
2014 | 1.070 | 1.339 | 0.989 | 0.791 | 1.016 | 0.903 | 0.974 | 0.884 | 1.059 | 1.083 |
2015 | 1.133 | 1.497 | 1.165 | 0.919 | 1.062 | 0.961 | 1.097 | 0.968 | 1.320 | 1.428 |
2016 | 0.769 | 1.118 | 1.070 | 1.021 | 1.030 | 0.996 | 1.039 | 1.017 | 0.822 | 1.152 |
2017 | 1.047 | 1.280 | 0.953 | 0.976 | 0.926 | 0.923 | 1.029 | 1.048 | 0.998 | 1.222 |
平均Average | 1.036 | – | 0.997 | – | 0.989 | – | 1.007 | – | 1.029 | – |
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具体到各个年份,2013年、2014年和2015年的农业碳排放综合效率值高于1.0,表明在这3年中湖北省农业低碳发展态势较好;而其他各年综合效率值均在1.0以下,揭示其农业低碳生产面临一定挑战。其中,以2015年综合生产率指数最高,为1.320,表明该年湖北农业碳排放效率较2014年提升了32.0%;与此对应2016年的综合效率值最低,仅为0.822,即较2015年降低了17.8%。进一步剖析历年农业碳排放效率的增长源泉可知,综合效率值高于1.0的3个年份中,2013和2014年碳排放效率的提升完全归功于前沿技术的进步,此时农业技术效率甚至处于下降态势,但所导致的损失要明显小于技术进步带来的贡献;2015年则得益于前沿技术进步与农业技术效率提升的双重贡献,且后者所发挥作用要略大于前者。综合效率值低于1.0的4个年份中,2011年、2012年和2017年碳排放效率的下降完全归结于农业技术效率的恶化,前沿技术虽处于进步状态但却无法弥补技术效率恶化所带来的巨大损失;2016年情形正好相反,其综合效率的下降完全源于前沿技术的大幅衰退,此时农业技术效率虽得到一定提升但却难以抵消技术退化所导致的损失。对各年农业技术效率进行分解可知,纯技术效率与规模效率的作用方向因年而异,作用力度各年情形虽也不尽相同但后者要略大于前者。
2.2 湖北省农业碳排放效率区域比较
接下来,测算湖北省15个市(州)农业碳排放效率如表3所示。从中不难发现,有 8个地区农业碳排放综合效率均值高于1.0,且以武汉最高,达到了1.584;与此对应,其他7个地区综合效率均值低于1.0,且以荆门最低,仅为0.803。结合农业碳排放效率数值差异可将15个市(州)划分为3个组别,即高速增长、低速增长以及下降组。其中,“高速组”包含武汉、宜昌、孝感、随州等4地,其农业碳排放综合效率均在1.10以上。独特的产业结构特点是促使各地效率较高的关键动因,比如武汉经济作物种植比重较高客观提升了其经济产出水平,各地畜牧业占比相对较小或者水稻种植规模偏低也在一定程度上减少了碳排放量。“低速组”包含襄阳、黄冈、仙桃、天门等4地,其农业碳排放综合效率均在1.05以下。黄冈虽为农业大市,但受制于平原面积较少,致使其农业附加值相对较低;襄阳农业产出水平总体尚可,但过高的农用物资投入导致其碳排放量居高不下;仙桃、天门均为省直管县级市,总体处于高排放、高产出状态。“下降组”包含黄石、十堰、荆门、荆州、咸宁、恩施、潜江等6市1州,其农业碳排放综合效率均在1.0以下。其中十堰、恩施以山区地形为主,农业产出水平较低且碳排放处于较高水平,由此导致碳排放效率较低;余下4地主要坐落于平原地区,农作物以水稻种植为主,经济价值较为一般却引发了较高的碳排放量,客观上导致各自碳排放效率较低。Table 3
表3
表3各市(州)农业碳排放效率及其增长源泉比较
Table 3
地区 Region | 前沿技术进步 CTECH | 技术效率 CEFF | 纯技术效率 CPECH | 规模效率 CSECH | 综合效率 CTFP | 排名 Rank | 增长类型 Growth type |
---|---|---|---|---|---|---|---|
武汉Wuhan | 1.398 | 1.133 | 1.000 | 1.133 | 1.584 | 1 | 高速High speed |
黄石Huangshi | 1.012 | 0.984 | 0.987 | 0.996 | 0.995 | 9 | 下降Decline |
十堰Shiyan | 0.827 | 1.000 | 1.000 | 1.000 | 0.827 | 14 | 下降Decline |
宜昌Yichang | 1.191 | 1.000 | 1.000 | 1.000 | 1.191 | 2 | 高速High speed |
襄阳Xiangyang | 1.007 | 1.000 | 1.000 | 1.000 | 1.007 | 7 | 低速Low speed |
荆门Jingmen | 0.803 | 1.000 | 1.000 | 1.000 | 0.803 | 15 | 下降Decline |
孝感Xiaogan | 1.068 | 1.043 | 1.017 | 1.025 | 1.113 | 3 | 高速High speed |
荆州Jingzhou | 0.977 | 1.004 | 1.000 | 1.004 | 0.982 | 11 | 下降Decline |
黄冈Huanggang | 1.051 | 0.989 | 1.000 | 0.989 | 1.040 | 5 | 低速Low speed |
咸宁Xianning | 1.036 | 0.946 | 0.947 | 0.999 | 0.979 | 12 | 下降Decline |
随州Suizhou | 1.106 | 1.000 | 1.000 | 1.000 | 1.106 | 4 | 高速High speed |
恩施Enshi | 1.014 | 0.880 | 0.886 | 0.994 | 0.893 | 13 | 下降Decline |
仙桃Xiantao | 1.027 | 0.979 | 0.998 | 0.981 | 1.006 | 8 | 低速Low speed |
潜江Qianjiang | 1.008 | 0.978 | 0.994 | 0.984 | 0.986 | 10 | 下降Decline |
天门Tianmen | 1.043 | 0.980 | 0.995 | 0.985 | 1.022 | 6 | 低速Low speed |
新窗口打开|下载CSV
从各市(州)农业碳排放效率的增长源泉来看,8个综合效率值高于1.0的地区中,武汉和孝感碳排放效率的提升源于前沿技术进步与农业技术效率改善的双重贡献,且前者作用更为明显;其他6地农业碳排放效率的改善完全依赖于前沿技术进步,其农业碳排放效率或处于不变状态(宜昌、襄阳、随州)、或呈现恶化状态(黄冈、仙桃、天门)。对上述各地技术效率进行分解可知,纯技术效率以不变和恶化状态为主而规模效率三类情形(即改善、不变、恶化)分布较为均衡。7个综合效率值低于1.0的地区中,黄石、咸宁、恩施、潜江等4地的碳排放效率下降主要归结于农业技术效率的大幅恶化,各自前沿技术虽处于进步状态但其幅度有限,无法避免技术效率恶化所带来的效率损失;十堰、荆门、荆州等3地则完全源于前沿技术的退化,各自农业技术效率处于不变或者改进状态。分解7地农业技术效率可知,除荆州之外,其他各地区纯技术效率与规模效率要么同时维持不变、要么均为恶化状态。总体而言,前沿技术进步在推进各地区农业碳排放效率提升上发挥了更为明显的作用,而技术效率改善所起作用相对较小;对技术效率进行分解可知,纯技术效率与规模效率的作用方向因地而异,但后者作用力度要略大于前者。
2.3 湖北省农业碳排放效率影响因素分析
2.3.1 变量确定 分析农业碳排放效率影响因素的关键在于变量的确定,其中被解释变量即为农业碳排放效率值,而解释变量则需在参考已有研究成果的基础上科学选择。近年来,有不少****围绕这一选题展开研究,不过各自在解释变量的选择上却略有差异。纵览文献可知,产业结构、经济水平、城镇化水平、自然灾害等变量得到了广泛认同[29,30,31];除此之外,还涉及到农村用电量[22]、种植规模[32]等变量。基于湖北农业生产的现状特征,并考虑到数据的可获取性,本文拟选取农村经济发展水平、耕地规模、农业产业结构、城镇化水平与农村用电量等5个变量作为潜在的解释变量,并提出如下研究假设。农村经济发展水平。经济发展水平一定程度上决定农业发展高度、反映农民日常生活水准,因此它是呈现农业农村发展水平的重要指标。一般而言,经济水平越高的地区,农业生产会倾向于资本密集型而非劳动力密集型,农用物资投入量相对较高,客观上会导致温室气体排放绝对数量的增加;但同时,农资投入的增加会有助于农业现代化步伐的加快,进而使得农业产出水平得到提升。因此,农村经济发展水平能否促进农业碳排放效率提升将取决于碳增量与农业产出水平各自的作用力大小。在此,以农民人均纯收入作为农村经济发展的替代指标,单位为元,该变量作用方向难以确定,亟待实证检验。
耕地规模。耕地规模能较为客观地反映种植业发展态势,规模增加,农作物播种面积就有可能扩大,反之则可能减少。湖北素有“鱼米之乡”美誉,且江汉平原是我国重要的商品粮生产基地并以水稻种植为主,而耕地规模变化一般会对水稻生产产生直接影响。众所周知,除了一般农用物资投入所引发的碳排放外,水稻在其生长过程中还会产生大量甲烷,由此导致其碳排放量处于较高水平,进而对农业碳排放效率产生影响。在此,我们以实际耕地面积作为衡量耕地规模的指标,单位为khm2,并假定耕地规模越大农业碳排放效率越低。
农业产业结构。农业由种植业、林业、畜牧业和渔业等四大产业部门构成,由于各自产业特征存在差异,其碳排放水平必然会有所区别,为此产业结构变化在一定程度上可能也会对农业碳排放效率产生影响。结合湖北农业碳排放特征可知,由于农用物资投入量较大且粮食作物生产以水稻为主,导致种植业是碳排放的主要源头;且与其他产业相比,种植业单位产值所引发的碳排放量明显更高。为此,我们不能忽视农业产业结构对碳排放效率的影响,在此以种植业产值所占农业总产值比重作为衡量指标,并假定其比重越高农业碳排放性效率越低。
城镇化水平。近年来,随着社会经济水平的不断提升,我国城市化进程明显加快,一定程度上也对农业生产部门产生了影响。一方面,城镇化水平的提升意味着二、三产业的不断发展,而制造业、服务业水平的不断进步会反作用于农业生产,促进其机械化、现代化步伐的快速推进,由此也会导致农用能源使用量的增加,进而加剧温室气体排放;但另一方面,城镇化水平的提升必然会导致城市规模的扩大,在这过程中农业用地会受到一定冲击,种植业生产由此受到影响,客观上也会导致碳排放量的减少。为此,有必要将城镇化水平(即城镇人口占总人口的比重)作为解释变量之一,其作用方向目前较难确定,亟待实证检验。
农村用电量。农业农村发展离不开电力的有力支持,如农业灌溉活动在很大程度上就会对电能产生依赖;另外,随着农业现代化步伐的加快,电能也正逐步取代以柴油为代表的农用能源,成为农业生产的重要动力支撑。事实上,虽然电能(尤其是火电)在产生过程中也会导致温室气体排放,但其作用强度可能略低于农用能源的大量使用。考虑到目前有关各地农业用电的统计资料较为缺乏,本文选择农村用电量近似替代,单位为kW·h。之所以如此考虑,是基于当前各个农村家庭的生活用电已趋于稳定而农村用电量的变化主要归结于农业生产活动这一现实情况。在此假定农村用电量越大农业碳排放效率越高。
2.3.2 实证分析 Hausman检验表明对农业碳排放效率的回归分析应选择固定效应的面板数据Tobit模型。在此,利用Stata软件进行估算,回归结果如表4所示。由此可知,农村经济发展水平、农业产业结构、城镇化水平、农村用电量均对农业碳排放性效率产生了显著影响,仅有耕地规模未通过显著性检验。
Table 4
表4
表4农业碳排放效率影响因素的实证分析结果
Table 4
变量Variable | 系数Coefficient | 标准差St. deviation | 检验值Inspection value |
---|---|---|---|
农村经济发展水平Rural economic development level | 0.0078** | 0.7270 | 2.43 |
耕地规模Cultivated land scale | -0.0484 | 0.1016 | -0.48 |
农业产业结构Agricultural industrial structure | -0.7449** | 0.3618 | -2.06 |
城镇化水平Urbanization level | 0.0136*** | 0.1681 | 3.15 |
农村用电量Rural electricity consumption | 0.0025* | 0.4502 | 1.32 |
常数项Constant term | 1.3705*** | 0.2778 | 4.94 |
新窗口打开|下载CSV
具体而言,农村经济发展水平对农业碳排放效率具有显著的正向影响,即在其他条件保持不变的情况下,农民人均纯收入越高,农业碳排放效率越高。可能的解释是,农民收入的提高意味着更多资本投入到农业生产中,由此利于其生产方式改革,加之历年“中央一号”文件均鼓励先进农业生产技术的使用,客观上也有助于农业生产率水平的提升,进而使得农业碳排放效率也得到一定改善。农业产业结构与农业碳排放效率呈现显著的负相关,即在其他条件不变的情况下,种植业产值比重越高越不利于农业碳排放效率的提升。测算结果表明,种植业是各市(州)农业碳排放的主要源头,占比多在80%以上;在既定产出规模约束下,种植业比重的提升显然会导致碳排放量的边际递增,进而导致碳排放效率下降。城镇化水平对农业碳排放效率具有显著的正向影响,即倘若其他条件不变,提升城镇化水平能促进农业碳排放效率的改善。通常而言,城镇化进程的加快必然意味着建设用地的增加,一定程度上会导致农业用地规模的缩减,进而对种植业产生较大影响,客观上也会促使农业碳排放量的减少与碳排放效率的提升。农村用电量与农业碳排放效率呈现显著的正相关关系,即如果其他条件维持不变,农村用电量越大农业碳排放效率越高。虽然电能耗费也会导致碳排放的产生,但其作用强度要低于能源使用,在单位产出一定时,若以电能取代能源(主要为柴油)消耗,将会极大减少碳排放量,进而促使农业碳排放效率的提升。
3 讨论
本文以湖北省作为研究对象,围绕其农业碳排放效率及影响因素展开探讨,这是对现有湖北农业碳排放问题研究体系的有力补充,在一定程度上弥补了现有研究的不足,同时也能为湖北农业低碳生产提供必要的参考依据。研究结果主要揭示两点:一是湖北省农业碳排放效率时空差异明显,其提升主要依赖于前沿技术进步;二是农村经济发展水平、城镇化水平、农村用电量以及农业产业结构是导致湖北碳排放效率变化的关键性因素。这也要求我们在推进湖北农业低碳生产过程中不仅要注重新技术的研发,更需要强化对各类技术的合理运用,以保障技术效率得到提升。同时,还可通过以下举措切实推进湖北省农业低碳生产:一是加大对农业农村的有效支持,进一步促进农村经济繁荣发展;二是制定农业低碳发展战略规划,积极优化农业产业结构;三是各地加快城市化进程,着力实现城乡一体化发展;四是逐步完善农业低碳生产相关立法,强化制度支持与政策保障。与已有研究成果[20,24,31]相比,本文所呈现出来的见解同中有异:从共同点来看,农业碳排放效率总体处于波动上升态势且各地区水平差异明显;农村经济发展水平越高、或者种植业占比越低,越有利于农业碳排放效率的提升。从差异因素来看,农业开放度变量在不少研究中得到运用且通过了显著性检验,但本文却未曾涉及,原因在于其他研究多立足于省域层面进行考察,而本文仅着眼于市级维度,相关数据较为缺乏;城镇化水平在不少研究中并未通过显著性检验,而于本文却表现出了正向作用,这主要是由于城镇化测度方法的不同以及各地实际情况的差异所致。
当然,本研究也存在一定欠缺,主要表现在:第一,由于市级层面的数据极难获取,所采用的是广义农业指标,而农业碳排放测算主要考察的是种植业和畜牧业,渔业和林业涉及较少,由此可能导致农业投入指标与农业碳排放之间存在不匹配问题,进而使得农业碳排放效率指数分解结果存在一定偏差。第二,本文测度农业碳排放效率涉及年限较短,不利于其长期演变轨迹的深度剖析;由于现有年鉴难以搜集到湖北省各市(州)2010年之前的相关原始数据,我们只能通过缩短考察周期来保证研究的顺利开展。而在今后,亟需拓展数据来源渠道以确保分析结果更加客观合理。
4 结论
4.1 湖北省农业碳排放效率总体处于上升态势但伴随着年际波动,各市(州)碳排放效率存在较大差异,无论是湖北省还是各市(州)其农业碳排放效率的提升都更多地依赖于前沿技术进步而非技术效率的改善,这也要求我们在推进湖北农业低碳生产过程中不仅要注重新技术的研发,更需强化对各类技术的合理运用。4.2 考虑到农村经济发展、城镇化水平、农村用电量以及农业产业结构均对农业碳排放效率产生了显著影响的现实境况,实践中我们可以通过繁荣农村经济发展、提升城镇化水平、保障农村用电需求、优化农业产业结构、完善法制建设与制度保障等手段来切实确保农业碳排放效率得到提高。
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基于农地利用、稻田、牲畜养殖三方面17类碳源,测算了湖北省全省1995-2011年及其16个地市(州)2010年的农业碳排放量,并展开时空比较分析;在此基础上,利用LMDI模型对湖北省农业碳排放的驱动因素进行了分解。结果表明:湖北省全省2011年农业碳排放量达到1 544.90万t,较1995年(1 443.56万t)增加了7.02%,年均递增0.43%,呈现较为明显的“上升-下降-上升”的3个阶段变化特征;地市(州)间区域差异明显。根据碳排放的比重差异,将16个地市(州)划分为稻田主导型、农地利用主导型、牲畜养殖主导型、复合因素主导型4种类型;与1995年相比,效率、劳动力、结构因素分别实现了94.13%、41.23%和8.67%的农业碳减排,而经济因素则引发了151.05%的碳增量。??
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基于农地利用、稻田、牲畜养殖三方面17类碳源,测算了湖北省全省1995-2011年及其16个地市(州)2010年的农业碳排放量,并展开时空比较分析;在此基础上,利用LMDI模型对湖北省农业碳排放的驱动因素进行了分解。结果表明:湖北省全省2011年农业碳排放量达到1 544.90万t,较1995年(1 443.56万t)增加了7.02%,年均递增0.43%,呈现较为明显的“上升-下降-上升”的3个阶段变化特征;地市(州)间区域差异明显。根据碳排放的比重差异,将16个地市(州)划分为稻田主导型、农地利用主导型、牲畜养殖主导型、复合因素主导型4种类型;与1995年相比,效率、劳动力、结构因素分别实现了94.13%、41.23%和8.67%的农业碳减排,而经济因素则引发了151.05%的碳增量。??
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DOI:10.3864/j.issn.0578-1752.2019.23.011URL [本文引用: 1]
【Objective】Hubei Province is a large agricultural province, and the carbon emissions from agricultural production account for a large proportion of the total carbon emissions. Environmental problems such as greenhouse effect caused by carbon emission and non-point source pollution caused by agricultural production cannot be ignored. In this study, the co-integration relationship between agricultural economic growth and agricultural carbon emissions was analyzed, and the error correction was carried out, which provided an important theoretical basis and reference for the development of carbon emission reduction in Hubei Province. 【Method】Based on six kinds of main carbon sources from the agricultural inputting and production, the agricultural carbon emission load from 1993 to 2017 was calculated, and then the temporal and spatial characteristics of agricultural carbon emission in Hubei Province were analyzed. Furtherly, Kernel density estimation demonstrated that the regional gap of agricultural carbon emissions in Hubei province. Finally, the integrated use of co-order error correction model was discussed as an evidence of Hubei Province's agricultural economic growth and agricultural carbon emissions. 【Result】The total amount and intensity of agricultural carbon emissions in Hubei Province showed a trend of rising first and then later. The average annual growth rate of agriculture carbon emissions was 2.32%, while the average annual growth rate of intensity was 2.21%. The chain growth of which was general in the stage of decline. Fertilizers, pesticides, agricultural film, agricultural diesel, real tillage and agricultural irrigation as a result of carbon emissions, average annual increase rate was 2.23%, 2.44%, 2.40%, 3.32%, 0.44%, and 2.32%, respectively. Kernel density estimation demonstrated that the regional gap of agricultural carbon emissions in Hubei Province was widening. The integrated use of co-order error correction model was discussed as an evidence of Hubei Province's agricultural economic growth and agricultural carbon emissions. The results showed that: for every 1% increase in per capita agricultural output value, the total carbon intensity of pesticides, agricultural film, agricultural diesel, agricultural irrigation and other carbon sources of carbon emission intensity increased by 0.58%, 0.59%, 0.25% and 0.15%, respectively, and the total agricultural carbon intensity increased by 0.19%.【Conclusion】Different agricultural economic development, production conditions and regional development strategies in Hubei Province led to more and more obvious agricultural carbon emission gap between regions. There was a long-term stable relationship between agricultural economic growth and agricultural carbon emission in Hubei Province, which indicated that Hubei Province was also in a critical period of transition from traditional farming mode to green and low-carbon farming mode, and this development mode had existed for a long time.
DOI:10.3864/j.issn.0578-1752.2019.23.011URL [本文引用: 1]
【Objective】Hubei Province is a large agricultural province, and the carbon emissions from agricultural production account for a large proportion of the total carbon emissions. Environmental problems such as greenhouse effect caused by carbon emission and non-point source pollution caused by agricultural production cannot be ignored. In this study, the co-integration relationship between agricultural economic growth and agricultural carbon emissions was analyzed, and the error correction was carried out, which provided an important theoretical basis and reference for the development of carbon emission reduction in Hubei Province. 【Method】Based on six kinds of main carbon sources from the agricultural inputting and production, the agricultural carbon emission load from 1993 to 2017 was calculated, and then the temporal and spatial characteristics of agricultural carbon emission in Hubei Province were analyzed. Furtherly, Kernel density estimation demonstrated that the regional gap of agricultural carbon emissions in Hubei province. Finally, the integrated use of co-order error correction model was discussed as an evidence of Hubei Province's agricultural economic growth and agricultural carbon emissions. 【Result】The total amount and intensity of agricultural carbon emissions in Hubei Province showed a trend of rising first and then later. The average annual growth rate of agriculture carbon emissions was 2.32%, while the average annual growth rate of intensity was 2.21%. The chain growth of which was general in the stage of decline. Fertilizers, pesticides, agricultural film, agricultural diesel, real tillage and agricultural irrigation as a result of carbon emissions, average annual increase rate was 2.23%, 2.44%, 2.40%, 3.32%, 0.44%, and 2.32%, respectively. Kernel density estimation demonstrated that the regional gap of agricultural carbon emissions in Hubei Province was widening. The integrated use of co-order error correction model was discussed as an evidence of Hubei Province's agricultural economic growth and agricultural carbon emissions. The results showed that: for every 1% increase in per capita agricultural output value, the total carbon intensity of pesticides, agricultural film, agricultural diesel, agricultural irrigation and other carbon sources of carbon emission intensity increased by 0.58%, 0.59%, 0.25% and 0.15%, respectively, and the total agricultural carbon intensity increased by 0.19%.【Conclusion】Different agricultural economic development, production conditions and regional development strategies in Hubei Province led to more and more obvious agricultural carbon emission gap between regions. There was a long-term stable relationship between agricultural economic growth and agricultural carbon emission in Hubei Province, which indicated that Hubei Province was also in a critical period of transition from traditional farming mode to green and low-carbon farming mode, and this development mode had existed for a long time.
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Agriculture is one of the important greenhouse gas (GHG) emission sources. Based on People’s Republic of China Initinal National Communications on Climate Change, the GHG emission from agricultural sources contributed to 17% of China’s total greenhouse gas emissions in 1994. The methane emission from agricultural activities amounted for 50.15% of China’s total methane, the nitrous oxide emission from agricultural sources accounted for 92.47% of China’s total. Analysis of published papers and documents suggested that following technologies have the potential to mitigate GHG emission from agricultural activities. Improvement of ruminant nutrient is estimated to reduce CH4 emission from individual yellow cattle by 16%~30%; Intermittent irrigation of rice paddy field could reduce CH4 emissions flux by 30% in comparison with flush irrigation; Maximum GHG emission reduction per household biogas digesters could be 2.0~4.1 t CO2 equivalent per year. Application of release-controlled nitrogen fertilizer to crop land reduced N2O emission flux by 50%~70% against regular fertilizers. It is suggested that demonstration and assessment of identified mitigation technology are definitely necessary.
URL [本文引用: 1]
Agriculture is one of the important greenhouse gas (GHG) emission sources. Based on People’s Republic of China Initinal National Communications on Climate Change, the GHG emission from agricultural sources contributed to 17% of China’s total greenhouse gas emissions in 1994. The methane emission from agricultural activities amounted for 50.15% of China’s total methane, the nitrous oxide emission from agricultural sources accounted for 92.47% of China’s total. Analysis of published papers and documents suggested that following technologies have the potential to mitigate GHG emission from agricultural activities. Improvement of ruminant nutrient is estimated to reduce CH4 emission from individual yellow cattle by 16%~30%; Intermittent irrigation of rice paddy field could reduce CH4 emissions flux by 30% in comparison with flush irrigation; Maximum GHG emission reduction per household biogas digesters could be 2.0~4.1 t CO2 equivalent per year. Application of release-controlled nitrogen fertilizer to crop land reduced N2O emission flux by 50%~70% against regular fertilizers. It is suggested that demonstration and assessment of identified mitigation technology are definitely necessary.
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To preliminarily explore livestock greenhouse gas emissions and trends, and assess the amount of greenhouse gases emitted by China’s livestock industries, using the calculation methodology and livestock industry gas emission parameters published by the In
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To preliminarily explore livestock greenhouse gas emissions and trends, and assess the amount of greenhouse gases emitted by China’s livestock industries, using the calculation methodology and livestock industry gas emission parameters published by the In
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