9-second gridded continental Australia need for assisted dispersal (50% similarity) for Vascular Plants 1990:2050 CAN ESM2 RCP 8.5 (CMIP5) (GDM: VAS_v5_r11)

Need for assisted dispersal for Vascular Plants as a function of change in long term (30 year average) climates between the present (1990 centred) and projected future (2050 centred) under the CAN ESM2 model (RCP 8.5) based on Generalised Dissimilarity Modelling (GDM) of compositional turnover.
The distance to the nearest grid cell with ecological similarity of at least 0.5 is given.
This 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.

This 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.

Data are provided in two forms:
1. 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.
2. ArcGIS layer package (*.lpk): These packages contain can be unpacked by ArcGIS as a raster with associated legend.

Additionally a short methods summary is provided in the file 9sMethodsSummary.pdf for further information.

Layers in this 9s series use a consistent naming convention:
BIOLOGICAL GROUP _ FROM BASE_ TO SCENARIO_ ANALYSIS
e.g. A_90_CAN85_S or R_90_MIR85_L
where BIOLOGICAL GROUP is A: amphibians, M: mammals, R: reptiles and V: vascular plants

基于群落更替的通用差异模型（Generalised Dissimilarity Modelling, GDM），本数据集反映维管植物（Vascular Plants）在CAN ESM2模式（RCP 8.5）下，以1990年为中心的当前时段与以2050年为中心的未来预估时段之间的长期（30年平均）气候变化所需的辅助扩散需求。
本数据集给出了与生态相似度至少为0.5的最近网格单元的距离。
该指标用于描述每个9s网格单元在以2050年为中心的未来预估环境条件的特征。借助群落更替的通用差异模型（阐释环境变化对物种组成变化的作用机制），将每个未来点位与当前时段的大陆环境进行对比。针对每个网格单元，该指标会遍历大陆范围内所有其他单元，记录该单元未来环境状态与当前时段最相似单元的生态相似度。相似度值为1时，表示未来环境与当前某一现状点位高度相似，且在澳大利亚境内可找到完全匹配的类似环境；值为0时，则表示当前时段可找到的最相似环境在生态层面差异极大，几乎不存在共有物种，即该环境无当前类似场景，属于全新环境；中间值则体现了最相似单元的生态相似程度。但该指标未考虑最相似单元的空间邻近性——即便环境相似，两个网格单元可能相距数千公里。
该指标与其他指标一同开发，用于在大陆和全球尺度下评估气候变化背景下生物多样性保护地系统的效能，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》，可通过网址www.adaptnrm.org在线获取。
数据集提供两种格式：
1. 压缩后的ESRI浮点网格文件：包含二进制浮点网格文件（*.flt）、配套的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地理信息系统（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）：此类文件可通过ArcGIS软件解压为带配套图例的栅格数据。
此外，文件9sMethodsSummary.pdf中提供了简短的方法概述，以供用户获取更多细节。
本9s系列数据集的图层采用统一命名规则：
生物类群_基准时段_情景_分析类型
示例：A_90_CAN85_S 或 R_90_MIR85_L
其中生物类群的对应关系为：A=两栖类（amphibians）、M=哺乳类（mammals）、R=爬行类（reptiles）、V=维管植物（vascular plants）