East African food security as influenced by future climate change and land use change at local to regional scales

Climate change impacts food production systems, particularly in locations with large, vulnerable populations. Elevated greenhouse gases (GHG), as well as land cover/land use change (LCLUC), can influence regional climate dynamics. Biophysical factors such as topography, soil type, and seasonal rainfall can strongly affect crop yields. We used a regional climate model derived from the Regional Atmospheric Modeling System (RAMS) to compare the effects of projected future GHG and future LCLUC on spatial variability of crop yields in East Africa. Crop yields were estimated with a process-based simulation model. The results suggest that: (1) GHG-influenced and LCLUC-influenced yield changes are highly heterogeneous across this region; (2) LCLUC effects are significant drivers of yield change; and (3) high spatial variability in yield is indicated for several key agricultural sub-regions of East Africa. Food production risk when considered at the household scale is largely dependent on the occurrence of extremes, so mean yield in some cases may be an incomplete predictor of risk. The broad range of projected crop yields reflects enormous variability in key parameters that underlie regional food security; hence, donor institutions’ strategies and investments might benefit from considering the spatial distribution around mean impacts for a given region. Ultimately, global assessments of food security risk would benefit from including regional and local assessments of climate impacts on food production. This may be less of a consideration in other regions. This study supports the concept that LCLUC is a first-order factor in assessing food production risk.     

Assessment of uncertainties in the response of the African monsoon precipitation to land use change simulated by a regional model

Land use and land cover (LULC) over Africa have changed substantially over the last 60 years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties of model simulated response in the African monsoon system and Sahel precipitation due to LULC change using a set of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Although the magnitude of the response covers a broad range of values, most of the simulations show a decline in Sahel precipitation due to the expansion of pasture and croplands at the expense of trees and shrubs and an increase in surface air temperature. The relationship between the model responses to LULC change and the climatologists of the control simulations is also examined. Simulations that are climatologically too dry or too wet compared to observations and reanalyses have weak response to land use change because they are in moisture or energy limited regimes respectively. The ones that lie in between have stronger response to the LULC changes, showing a more significant role in land–atmosphere interactions. Much of the change in precipitation is related to changes in circulation, particularly to the response of the intensity and latitudinal position of the African Easterly Jet, which varies with the changes in meridional surface temperature gradients. The study highlights the need for measurements of the surface fluxes across the meridional cross-section of the Sahel to evaluate models and thereby allowing human impacts such as land use change on the monsoon to be projected more realistically.     

中国近百年来的温度变化

对我国近百年来温度变化的研究工作和结果作了综述，发现我国增温趋势与北半球的情况大致相似，但在具体的变化过程和幅度上又与全球变化存在明显差异，这包括：（１）我国温度出现最高的时期是在４０年代，而不是８０年代以后；（２）我国的西南地区自５０年代以来一直在降温，增暖主要出现在东北、华北和西北西部地区；（３）近百年来中国温度变化出现两次突变，一次在１９１９年，一次在１９５２年。作者还讨论了城市化对温度测量     

The Statistical Significance Test of Regional Climate Change Caused by Land Use and Land Cover Variation in West China

The West Development Policy being implemented in China is causing significant land use and land cover （LULC） changes in West China. With the up-to-date satellite database of the Global Land Cover Characteristics Database （GLCCD） that characterizes the lower boundary conditions, the regional climate model RIEMS-TEA is used to simulate possible impacts of the significant LULC variation. The model was run for five continuous three-month periods from 1 June to 1 September of 1993, 1994, 1995, 1996, and 1997, and the results of the five groups are examined by means of a student t-test to identify the statistical significance of regional climate variation. The main results are： （1） The regional climate is affected by the LULC variation because the equilibrium of water and heat transfer in the air-vegetation interface is changed. （2） The integrated impact of the LULC variation on regional climate is not only limited to West China where the LULC varies, but also to some areas in the model domain where the LULC does not vary at all. （3） The East Asian monsoon system and its vertical structure are adjusted by the large scale LULC variation in western China, where the consequences are the enhancement of the westward water vapor transfer from the east oast and the relevant increase of wet-hydrostatic energy in the middle-upper atmospheric layers. （4） The ecological engineering in West China affects significantly the regional climate in Northwest China, North China and the middle-lower reaches of the Yangtze River; there are obvious effects in South, Northeast, and Southwest China, but minor effects in Tibet.     

洞庭湖区近百年降水序列构建及其变化特征

采用统计方法结合气象台站历史沿革信息,对1910—2010年洞庭湖区逐月降水量观测资料进行均一化处理,并利用洞庭湖周边气象台站资料对洞庭湖区1951年以前缺测的降水资料进行插补,构成完整均一的降水序列。在此基础上,构建洞庭湖区近百年降水序列并分析其变化特征。结果表明：1910—2010年洞庭湖区年及春、夏、秋三季降水量的变化趋势不显著,冬季降水量呈显著上升的趋势;年降水量存在准3、6、8 a和20 a等多时间尺度的振荡周期;小波分析显示,近百年洞庭湖区年降水量和冬季降水量均存在显著增多的突变。     

环太湖地区土地利用变化的局地气候效应

利用WRF模式和1985年、2005年环太湖区域的土地利用资料,模拟了环太湖区域土地利用变化的局地气候效应,并从陆面过程的角度进行了分析。模拟结果显示：城市扩张区域净短波辐射通量增多,地面温度升高,感热通量增大,潜热通量减小。近地面水平风场在城市化地区风速减小,在城市化带方向上形成狭长的动能衰减区域。湖陆风和城市热岛环流增强,城市化地区向上垂直速度增大,积云性降水增多。老城区和郊区下沉运动增强,对流受到抑制,积云性降水减少。层云降水的改变,集中在层云降水的大值区,且多呈带状分布。总降水在城市化区域增强,在老城区和郊区减少,积云性降水占总降水的比值增大。在土地利用没有变化的区域,降水的改变与地表能量通量的改变在空间分布上大致吻合。     

The role of the land use, land use change and forestry sector in achieving Annex I reduction pledges

Annex I Parties may receive credits or debits from Land Use, Land Use Change and Forestry (LULUCF) activities, contributing to achieving individual emission reduction targets. In the Durban climate negotiations, Parties agreed new LULUCF accounting rules for the second commitment period of the Kyoto Protocol (CP2). By using these new rules, this paper presents key differences among Parties at the minimum (assuming no additional action) and potential (assuming additional actions) contribution of the forest-related LULUCF activities in achieving the pledges for 2020. Overall, the potential contribution of LULUCF is relatively modest (up to about 2 % of 1990 emissions) for the EU, the Annex I Parties likely joining the CP2, and for the Annex I Parties that joined the CP1 as a whole. However, for specific Parties, LULUCF can make a substantial contribution to achieving the pledges. For New Zealand, for instance, the potential contribution of future LULUCF credits may equal 33 % of its 1990 emission level. For Australia, the pledges are expressed relative to 2000 emission levels including LULUCF emissions. Given that LULUCF emissions have strongly declined between 1990 and 2000, and a further decline in foreseen by 2020 (based on Australia’s projections), the minimum contribution of LULUCF to meet the Australian pledges appears to be about 19 % and 7 % relative to its 1990 and 2000 emission level, respectively. A further 3 % potential contribution is estimated from additional actions.     

Numerical simulation of the impact of land cover change on regional climate in China

Land use and land cover change (LUCC) can modify the physical and thermodynamic characteristics of the land surface, including surface roughness, albedo, and vegetation fraction, among others. These direct changes can result in a series of impacts on regional climate. In this paper, the simulated results over China under the scenario of LUCC using weather research and forecasting model are presented. The period for the simulation is from December 2006 to December 2011. Two experiments are initialized by the LUCC datasets derived from the MODIS data of 2001 and 2008, respectively. The results show that the LUCC in most areas of China reduces the surface albedo and increases the surface temperature. Especially in the Hetao Plain, the magnitude of increased surface temperature is above 0.5 °C in winter, and the increase in winter is more obvious than in summer. The precipitation in the Hetao Plain increases. The sensible heat in most parts of East China is reduced, while the latent heat is increased in most areas of China.     

Stability and change within indigenous land use in the Ecuadorian Amazon

In the Amazon basin and other tropical forest regions, many forested landscapes are inhabited by indigenous peoples who are increasingly exposed to infrastructure expansion, large-scale natural resource extraction, and development programs. How indigenous land use evolves in this context will be a critical determinant of the future of these forests. To date, few studies have had access to longitudinal, large-sample and field-based data that enables the measurement of indigenous land use change and its correlates in these contexts. To address this lacuna, we make use of a unique multi-ethnic household survey conducted in 32 indigenous communities of the Northern Ecuadorian Amazon in 2001 and again with the same households in 2012. We analyze these data to measure land use and land use change as well as their determinants. This reveals that the overall household agropastoral footprint has remained close to constant over time, but with important changes within particular land uses and ethnicities. Notably, cacao has largely replaced coffee (tracking commodity price changes), and Kichwa and Shuar households have intensified production on increasingly subdivided plots, with the Shuar specializing in cattle. In contrast, Waorani and Cofán households have maintained small footprints, while Secoya households largely abandoned cattle ranching. Taken together, the results emphasize ethnic heterogeneity in indigenous land use change, a pattern which is only visible through the use of a longitudinal, large-sample, field-based design.     

近百年丹东气温变化特征分析

对1906—2005年丹东气温资料序列进行分析,得到近百年丹东气温变化特征。结果表明:在近百年丹东逐月平均气温变化趋势中,除夏季7月和8月呈线性递减趋势外,其他月份均呈线性递增趋势。在近百年丹东年代际和年际变化中,逐年代平均气温线性递增率为1.13℃/100 a,逐年演变过程中的年平均递增率为0.12℃/10 a。在各季的平均气温变化中,冬季(12月—翌年2月)线性增温最显著,平均线性递增率为0.30℃/10 a;春季(3—5月)次之,线性增长率均为0.12℃/10 a;秋季(9—11月)平均气温线性增温最小,线性增长率为0.06℃/10 a;夏季除6月几乎没有变化外,7—8月均呈递减趋势,整个夏季(6—8月)总线性增减率为0.03℃/10 a。近20 a年线性增暖趋势异常显著,逐年线性递增趋势为0.36℃/10 a。     

Integrating global and regional analyses of the effects of climate change: A case study of land use in England and Wales

The purpose of this paper is to exemplify a means by which an integrated assessment can be made of global and regional effects on land use of climate change. This is achieved by use of data on the effects of climate change on world food prices as inputs to a regional land use allocation model.Data on world prices are drawn from a recent global study of climate change and crop yields. In a case study of England and Wales a land allocation model is used to infer changes of land use that are the product of the integrated effect of climate-induced global price changes and climate-related changes of yield in England and Wales. This combination of changed prices and yield potential is used to calculate the land use providing the highest returns for each of 155,235 1 km² cells of land in England and Wales for a future assumed for the year 2060 (without climate change) and then for that same environment with climate change. The difference between these two is then treated as an estimated effect resulting from climate change.     

Toward Bayesian uncertainty quantification for forestry models used in the United Kingdom Greenhouse Gas Inventory for land use, land use change, and forestry

The Greenhouse Gas Inventory for the United Kingdom currently uses a simple carbon-flow model, CFLOW, to calculate the emissions and removals associated with forest planting since 1920. Here, we aim to determine whether a more complex process-based model, the BASic FORest (BASFOR) simulator, could be used instead of CFLOW. The use of a more complex approach allows spatial heterogeneity in soils and weather to be accounted for, but places extra demands on uncertainty quantification. We show how Bayesian methods can be used to address this problem.     

大兴安岭地区近30a大风天气变化的特征分析

本文利用大兴安岭地区1979-2008年6个县(区)的气象资料,对大兴安岭地区大风天气发生的地理分布和月、季、年代的变化分布特征进行了统计分析,并对其大风天气的地理分布特征及变化规律从地形、地理环境条件及大气环流转换等方面作了进一步的研究,以便更好的为大风天气的预报提供气候背景。     

区域气候模式对温室效应引起的中国地区气候变化的数值模拟

利用基于 ＲｅｇＣＭ２的区域气候模式并单向嵌套澳大利亚 ＣＳＩＲＯ Ｒ２１Ｌ９全球海－气耦合模式，进行了温室气体二氧化碳浓度倍增对中国气候变化影响的数值试验研究。控制试验结果表明：区域模式由于具有较高的分辨率，因而对中国区域地面气温和降水的模拟效果较全球模式有了较大提高；模式对 ２×ＣＯ２敏感性试验结果表明了在 ＣＯ２浓度倍增情况下，由于温室效应，中国区域的地面气温将有明显升高，降水也将呈增加趋势。     

百年来上海、北京气候突变的初步分析

本文应用Mann-Kendall方法对1873—1989年上海、北京的气温、降水时间序列进行了突变检验。其结果表明,上海、北京的百年气温分别在1932年和1919年出现冷转暖的气候突变。同时,还判别出上海降水在1906年发生突变,其后进入一个相对多雨时段。北京降水突变在1903年,而后进入一个相对少雨时段。另外,还用其它方法对突变点加以验证说明。     

The role of land surface processes in regional climate change: a case study of future land cover change over south western Australia

Summary Using a high resolution regional climate model we perform multiple January simulations of the impact of land cover change over western Australia. We focus on the potential of reforestation to ameliorate the projected warming over western Australia under two emission scenarios (A2, B2) for 2050 and 2100. Our simulations include the structural and physiological responses of the biosphere to changes in climate and changes in carbon dioxide. We find that reforestation has the potential to reduce the warming caused by the enhanced greenhouse effect by as much as 30% under the A2 and B2 scenarios by 2050 but the cooling effect declines to 10% by 2100 as CO₂-induced warming intensifies. The cooling effect of reforestation over western Australia is caused primarily by the increase in leaf area index that leads to a corresponding increase in the latent heat flux. This cooling effect is localized and there were no simulated changes in temperature over regions remote from land cover change. We also show that the more extreme emission scenario (A2) appears to lead to a more intense response in photosynthesis by 2100. Overall, our results are not encouraging in terms of the potential to offset future warming by large scale reforestation. However, at regional scales the impact of land cover change is reasonably large relative to the impact of increasing carbon dioxide (up to 2050) suggesting that future projections of the Australian climate would benefit from the inclusion of projections of future land cover change. We suggest that this would add realism and regional detail to future projections and perhaps aid detection and attribution studies.     

Simulation of regional temperature change effect of land cover change in agroforestry ecotone of Nenjiang River Basin in China

Currently, US forests constitute a large carbon sink, comprising about 9 % of the global terrestrial carbon sink. Wildfire is the most significant disturbance influencing carbon dynamics in US forests. Our objective is to estimate impacts of climate change, CO₂ concentration, and nitrogen deposition on the future net biome productivity (NBP) of US forests until the end of twenty-first century under a range of disturbance conditions. We designate three forest disturbance scenarios under one future climate scenario to evaluate factor impacts for the future period (2011–2100): (1) no wildfires occur but forests continue to age (S_aging), (2) no wildfires occur and forest ages are fixed in 2010 (S_{fixed_nodis}), and (3) wildfires occur according to a historical pattern, consequently changing forest age (S_{dis_age_change}). Results indicate that US forests remain a large carbon sink in the late twenty-first century under the S_{fixed_nodis} scenario; however, they become a carbon source under the S_aging and S_{dis_age_change} scenarios. During the period of 2011 to 2100, climate is projected to have a small direct effect on NBP, while atmospheric CO₂ concentration and nitrogen deposition have large positive effects on NBP regardless of the future climate and disturbance scenarios. Meanwhile, responses to past disturbances under the S_{fixed_nodis} scenario increase NBP regardless of the future climate scenarios. Although disturbance effects on NBP under the S_aging and S_{dis_age_change} scenarios decrease with time, both scenarios experience an increase in NBP prior to the 2050s and then a decrease in NBP until the end of the twenty-first century. This study indicates that there is potential to increase or at least maintain the carbon sink of conterminous US forests at the current level if future wildfires are reduced and age structures are maintained at a productive mix. The effects of CO₂ on the future carbon sink may overwhelm effects of other factors at the end of the twenty-first century. Although our model in conjunction with multiple disturbance scenarios may not reflect the true conditions of future forests, it provides a range of potential conditions as well as a useful guide to both current and future forest carbon management.