Estimated Maize Yield Losses by Stem Borers in Kenya and Tanzania under Current Climatic Conditions (1970-2000) and Different Climate Change Scenarios (2041-2060, 2081-2100)

The research within the scope of which the presented data was generated was part of the funding initiative ‘Knowledge for Tomorrow-Cooperative Research Project in sub-Saharan Africa on Resource, their Dynamics, and Sustainability’ funded by the Volkswagen Foundation. The overall study aimed at investigating the uncertainties in the effectiveness of biological control of stem borers under different climate change scenarios in Kenya and Tanzania. Using the species distribution modelling approach MaxEnt, the research predicts the current and future distribution of three important lepidopteran stem borer pests of maize in eastern Africa, i.e., Busseola fusca (Fuller, 1901), Chilo partellus (Swinhoe, 1885) and Sesamia calamistis (Hampson, 1910), and two of their parasitoids used for biological control, i.e., Cotesia flavipes (Cameron, 1891) and Cotesia sesamiae (Cameron, 1906). Based on these potential distributions and data collected during household surveys with local farmers in Kenya and Tanzania, future maize yield losses are predicted considering three different Global Circulation Models (GCMs) for four different Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP 3-7.0, SSP5-8.5) and two time periods, i.e., 2041-2060 and 2081-2100.
Stem borer-associated maize yield losses (in kg/ha) are extrapolated using data on average maize yield in the study area downloaded from MapSPAM and based on results from a 2018 household survey conducted by researchers from the International Centre of Insect Physiology and Ecology (icipe) under the cooperative project "Adaptation for Food Security and Ecosystem Resilience in Africa” (AFERIA) of icipe, the University of Helsinki and the University of York in which local farmers were asked to quantify losses in maize yield by stem borer infestation. Based on these survey data, 95% confidence intervals (CIs) for maize yield losses were calculated. Yield losses by stem borers for all scenarios are given for mean, lower and upper bound of the CI.

Quality/Lineage: Rasters showing stem borer-associated maize yield losses were calculated in RStudio using the 'raster' package. Three raster layers were multiplied to quantify maize yield losses by the stem borer pests: Y(c,p)= A(c,p)*Mc*Lp
where Yc,p represents yield losses (kg/ha) for each grid cell c and each stem borer species p, Ac,p= {1,0} indicates each stem borer species’ presence or absence for each grid cell, Mc indicates maize yield (kg/ha) for each cell and Lp representing estimated yield losses by each stem borer (%).

本研究生成的相关数据隶属于由大众汽车基金会（Volkswagen Foundation）资助的「明日之知识——撒哈拉以南非洲资源、其动态与可持续性合作研究项目」资助计划。本研究的整体目标为探究肯尼亚与坦桑尼亚境内不同气候变化情景下玉米茎螟生物防治效果的不确定性。

本研究采用物种分布建模方法MaxEnt，预测了东非三种重要的鳞翅目玉米茎螟害虫——即Busseola fusca（Fuller, 1901）、Chilo partellus（Swinhoe, 1885）以及Sesamia calamistis（Hampson, 1910）——以及两种用于生物防治的寄生蜂——即Cotesia flavipes（Cameron, 1891）与Cotesia sesamiae（Cameron, 1906）——的当前与未来分布格局。

基于上述潜在分布数据，以及在肯尼亚与坦桑尼亚开展的农户家庭调研数据，本研究结合三种不同的全球环流模型（Global Circulation Models, GCMs）、四种不同的共享社会经济路径（Shared Socioeconomic Pathway, SSP）情景（SSP1-2.6、SSP2-4.5、SSP3-7.0、SSP5-8.5），以及两个时段（2041-2060年与2081-2100年），对未来玉米产量损失进行了预测。

研究依托从MapSPAM下载的研究区域玉米平均产量数据，结合国际昆虫生理学与生态学中心（International Centre of Insect Physiology and Ecology, icipe）2018年开展的农户家庭调研结果，推算出与茎螟相关的玉米产量损失（单位：kg/ha）。该调研隶属于国际昆虫生理学与生态学中心、赫尔辛基大学与约克大学合作开展的「非洲粮食安全适应与生态系统韧性项目」（Adaptation for Food Security and Ecosystem Resilience in Africa, AFERIA），调研中要求当地农户量化茎螟侵染导致的玉米产量损失。基于上述调研数据，研究计算得到了玉米产量损失的95%置信区间（Confidence Intervals, CIs）。所有情景下的茎螟导致的产量损失均以置信区间的均值、下限与上限值呈现。

数据质量与溯源：与茎螟相关的玉米产量损失栅格数据通过RStudio中的「raster」包计算得到。通过将三个栅格图层相乘，以量化茎螟害虫导致的玉米产量损失：Y(c,p)= A(c,p)*Mc*Lp，其中Y(c,p)代表每个栅格单元c与每种茎螟物种p的产量损失（单位：kg/ha），A(c,p)={1,0}用于标识每种茎螟物种在对应栅格单元中的存在与否，Mc代表对应栅格单元的玉米产量（单位：kg/ha），Lp代表每种茎螟导致的预估产量损失率（单位：%）。