Department of Energy and Technology, Swedish University of Agricultural Sciences (SLU), Uppsala SE750 07, Sweden.
Sci Total Environ. 2022 Aug 20;835:155455. doi: 10.1016/j.scitotenv.2022.155455. Epub 2022 Apr 23.
Agricultural land use and management practices affect the global climate due to greenhouse gas (GHG) fluxes and changes in land surface properties. Increased albedo has the potential to counteract the radiative forcing and warming effect of emitted GHGs. Thus considering albedo could be important to evaluate and improve agricultural systems in light of climate change, but the albedo of individual practices is usually not known. This study quantified the albedo of individual crops under regional conditions, and evaluated the importance of albedo change for the climate impact of current crop production using life cycle assessment (LCA). Seven major crops in southern Sweden were assessed relative to a land reference without cultivation, represented by semi-natural grassland. Crop-specific albedo data were obtained from a MODIS product (MCD43A1 v6), by combining its spatial response pattern with geodata on agricultural land use 2011-2020. Fluxes of GHGs were estimated using regional data and models, including production of inputs, field operations, and soil nitrogen and carbon balances. Ten-year mean albedo was 6-11% higher under the different crops than under the reference. Crop-specific albedo varied between years due to weather fluctuations, but differences between crops were largely consistent. Increased albedo countered the GHG impact from production of inputs and field operations by 17-47% measured in GWP, and the total climate impact was warming. Using a time-dependent metric, all crops had a net cooling impact on global mean surface temperature on shorter timescales due to albedo (3-12 years under different crops), but a net warming impact on longer timescales due to GHG emissions. The methods and data presented in this study could support increasingly comprehensive assessments of agricultural systems. Further research is needed to integrate climatic effects of land use on different spatial and temporal scales, and direct and indirect consequences from a systems perspective.
农业土地利用和管理方式会通过温室气体（GHG）通量和地表特性变化影响全球气候。反照率增加有可能抵消排放 GHG 的辐射强迫和变暖效应。因此，考虑反照率对于评估和改善气候变化下的农业系统可能很重要，但通常不知道个别措施的反照率。本研究在区域条件下量化了个别作物的反照率，并通过生命周期评估（LCA）评估了当前作物生产中反照率变化对气候影响的重要性。相对于未耕作的土地参考（半自然草地），评估了瑞典南部的七种主要作物。通过将其空间响应模式与 2011-2020 年农业土地利用的地理数据相结合，从 MODIS 产品（MCD43A1 v6）中获得了作物特定的反照率数据。使用区域数据和模型估算了 GHG 通量，包括投入生产、田间作业以及土壤氮和碳平衡。与参考相比，不同作物下的 10 年平均反照率高出 6-11%。由于天气波动，作物特定的反照率在不同年份有所不同，但作物之间的差异基本一致。增加的反照率抵消了投入生产和田间作业的 GHG 影响，在 GWP 中占 17-47%，总气候影响是变暖的。使用时变指标，由于反照率（不同作物下 3-12 年），所有作物在较短时间内对全球平均地表温度都有净冷却影响，但由于 GHG 排放，在较长时间内有净变暖影响。本研究中提出的方法和数据可以支持对农业系统进行越来越全面的评估。需要进一步研究以整合不同时空尺度上土地利用的气候效应，以及从系统角度来看的直接和间接后果。
