9-second gridded continental Australia need for assisted dispersal (50% similarity) for Mammals 1990:2050 MIROC5 RCP 8.5 (CMIP5) (GDM: MAM_r2)

Need for assisted dispersal for Mammals as a function of change in long term (30 year average) climates between the present (1990 centred) and projected future (2050 centred) under the MIROC5 model (RCP 8.5) based on Generalised Dissimilarity Modelling (GDM) of compositional turnover. \nThe distance to the nearest grid cell with ecological similarity of at least 0.5 is given.\nThis metric describes the nature of the projected 2050 centred future environmental conditions for each 9s grid square. Using a Generalised Dissimilarity Model of compositional turnover (the effects of changing environment on changing species), each future location is compared with the continent in the present. For each cell, the metric looks out to all other cells in the continent, and records the ecological similarity of the future state of the cell to the most similar cell in the present. A value of 1 indicates that the future environment is similar to a current location in the present, and perfect analogue can found somewhere in Australia. A value of 0 indicates that the most similar environment to be found in the present is ecologically so different that we would expect no species in common, i.e. there are no current analogues for this environment; it is novel. Intermediate values show how ecologically similar the most similar cell is. However, no weight is given to the proximity of the most similar cell. The environment may be similar, but the cells thousands of kilometres apart.\n\nThis metric was developed along with others for use in an assessment of the efficacy of the protected area system for biodiversity under climate change at continental and global scales, presented at the IUCN World Parks Congress 2014. It is described in the AdaptNRM Guide “Implications of Climate Change for Biodiversity: a community-level modelling approach”, available online at: www.adaptnrm.org. \n\nData are provided in two forms:\n1. Zipped ESRI float grids: Binary float grids (*.flt) with associated ESRI header files (*.hdr) and projection files (*.prj). After extracting from the zip archive, these files can be imported into most GIS software packages, and can be used as other binary file formats by substituting the appropriate header file.\n2. ArcGIS layer package (*.lpk): These packages contain can be unpacked by ArcGIS as a raster with associated legend.\n\nAdditionally a short methods summary is provided in the file 9sMethodsSummary.pdf for further information.\n\nLayers in this 9s series use a consistent naming convention:\nBIOLOGICAL GROUP _ FROM BASE_ TO SCENARIO_ ANALYSIS\ne.g. A_90_CAN85_S or R_90_MIR85_L\nwhere BIOLOGICAL GROUP is A: amphibians, M: mammals, R: reptiles and V: vascular plants\n\nLineage: Need for assisted dispersal was calculated calculated using the highly parallel bespoke CSIRO Muru software running on a LINUX high-performance-computing cluster, taking GDM model transformed environmental grids as inputs. The distance to the nearest future cell with an ecological similarity > 0.5 to the present cell was calculated. More detail of the calculations and methods are given in the document “BiodiversityModellingMethodsSummary.pdf” provided with the data download. \nGDM Model: \nGeneralised dissimilarity model of compositional turnover in mammal species for continental Australia at 9 second resolution using ALA data extracted 27 February 2014 (GDM: MAM_r2)\nClimate data. Models were built and projected using:\na) 9-second gridded climatology for continental Australia 1976-2005: Summary variables with elevation and radiative adjustment\nb) 9-second gridded climatology for continental Australia 2036-2065 MIROC5 RCP 8.5 (CMIP5): Summary variables with elevation and radiative adjustment\n \n

本数据集围绕哺乳动物辅助扩散需求展开，该需求以当前（以1990年为中心）与MIROC5模型（RCP 8.5）下预测的未来（以2050年为中心）气候的长期（30年均值）变化为函数，基于物种组成周转的广义相异模型（Generalised Dissimilarity Modelling, GDM）构建。
数据集提供了各格网单元到生态相异性至少为0.5的最近格网单元的距离。

该指标描述了每个9秒格网单元对应的以2050年为中心的未来环境特征。通过构建物种组成周转的广义相异模型（即环境变化对物种变化的影响机制），将每个未来位置与当前时期的大陆进行比对。对于每个格网单元，该指标会检索大陆范围内所有其他格网单元，并记录该单元未来状态与当前最相似格网单元的生态相异性。相异性值为1时，表示未来环境与当前某一位置的环境相似，且在澳大利亚境内可找到完美匹配的类似环境；值为0时，表示当前所能找到的最相似环境在生态上差异极大，以至于可以认为二者不存在共有物种，即该环境无当前类似物，属于全新环境；中间值则体现了最相似格网单元的生态相似程度。但该指标未考虑最相似格网单元的空间距离，即便环境相似，两个格网单元之间可能相距数千公里。

该指标与其他指标一同开发，用于评估大陆及全球尺度下保护区系统在气候变化背景下对生物多样性的保护效能，相关成果曾在2014年世界自然保护联盟（IUCN）世界公园大会上展示。该指标的详细说明见于《AdaptNRM指南：气候变化对生物多样性的影响：群落级建模方法》，可在线获取：www.adaptnrm.org。

数据集以两种形式提供：
1. 压缩的ESRI浮点格网数据：包含二进制浮点格网文件（*.flt）、关联的ESRI头文件（*.hdr）与投影文件（*.prj）。从压缩包解压后，这些文件可导入绝大多数GIS软件，也可通过替换对应头文件的方式作为其他二进制文件格式使用。
2. ArcGIS图层包（*.lpk）：此类包可由ArcGIS解压为带有关联图例的栅格数据。

此外，数据集中附带了简短的方法概述文件9sMethodsSummary.pdf，以供进一步参考。

本9秒格网系列图层采用统一命名规则：
生物类群_基准期_情景_分析类型
例如：A_90_CAN85_S 或 R_90_MIR85_L
其中生物类群的对应关系为：A=两栖动物，M=哺乳动物，R=爬行动物，V=维管植物。

数据谱系：本数据集的辅助扩散需求指标通过运行于LINUX高性能计算集群的高度并行化定制CSIRO Muru软件计算得到，以经过GDM模型转换的环境格网数据作为输入。计算了当前格网单元与未来最相似（生态相异性>0.5）格网单元的距离。更详细的计算方法与流程可见随数据下载一同提供的《BiodiversityModellingMethodsSummary.pdf》文档。

GDM模型说明：
针对澳大利亚大陆9秒分辨率的哺乳动物物种组成周转广义相异模型（GDM: MAM_r2），其数据源自2014年2月27日提取的ALA（澳大利亚生物多样性图集）数据。
气候数据：模型构建与投影使用以下数据：
a) 1976-2005年澳大利亚大陆9秒格网气候数据集：包含经海拔与辐射校正的汇总变量
b) MIROC5模型RCP 8.5情景下2036-2065年澳大利亚大陆9秒格网气候数据集（CMIP5）：包含经海拔与辐射校正的汇总变量。