9-second gridded continental Australia change in effective area of similar ecological environments (cleared natural areas) for Reptiles 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: REP_r3_v2)

Proportional change in effective area of similar ecological environments for Reptiles as a function of land clearing and change in long term (30 year average) climates between the present (1990 centred) and projected future (2050 centred) under the CanESM2 model (RCP 8.5) based on Generalised Dissimilarity Modelling (GDM) of compositional turnover. This metric describes the combined effects of climate change and land clearing on the area of similar environments to each grid cell as a proportion. Each cell is compared with a sample of 60,000 points in both the present uncleared landscape and an alternative scenario (either present with clearing, or future with clearing), and the pairwise similarities summed (e.g. a completely similar cell will contribute 1, a dissimilar cell 0, with a range of values in between). Only cells which are flagged as uncleared contribute. For each time point, this describes the area of similar environments, which will be low for rare environments and high for widely distributed environments. By dividing the test area by the current area, we are able to quantify the reduction in area as a function of land use/climate change. Values less than one indicate a reduction, values of 1 no change, and values greater than 1 (rare cases in the north) show an increase in similar environments. 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: Mammals, M: mammals, R: reptiles and V: vascular plants

基于成分周转广义相异度建模（Generalised Dissimilarity Modelling, GDM），本数据集表征在CanESM2模式（典型浓度路径8.5, RCP 8.5）下，对比当前（以1990年为中心）与预测未来（以2050年为中心）时段的土地清理与长期（30年平均）气候变化，爬行动物（Reptiles）相似生态环境有效面积的比例变化。该指标以比例形式表征气候变化与土地清理对每个栅格单元的相似生态环境面积的联合影响。

每个栅格单元分别与当前未清理景观及两种替代情景（当前已清理或未来已清理）中的60000个采样点进行比对，将两两相似性求和（例如，完全相似的栅格单元取值为1，完全相异的栅格单元取值为0，中间值对应不同程度的相似性），仅标记为未清理的栅格单元参与计算。在每个时间节点下，该指标反映相似生态环境的面积：稀有生态环境对应数值较低，广布生态环境对应数值较高。通过将测试时段面积除以当前基准面积，可量化土地利用/气候变化导致的面积缩减幅度。数值小于1代表面积缩减，等于1代表无变化，大于1（北半球罕见情况）则表示相似生态环境面积有所增加。

该指标与其他指标一同开发，用于在大陆及全球尺度下评估气候变化背景下保护区系统对生物多样性的保护效能，相关成果曾在2014年国际自然保护联盟（International Union for Conservation of Nature, 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。

数据集以两种形式提供：
1. 压缩的ESRI浮点栅格数据：包含二进制浮点栅格文件（*.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（Geographic Information System, GIS）软件，通过替换对应头文件，也可作为其他二进制格式文件使用。
2. ArcGIS图层包（*.lpk）：该类包可通过ArcGIS软件解压为带有配套图例的栅格图层。此外，文件9sMethodsSummary.pdf中包含简短的方法总结，可供读者获取更多信息。

本9s系列图层采用统一命名规则：生物类群_基准时段_目标情景_分析类型，例如A_90_CAN85_S或R_90_MIR85_L，其中生物类群的含义为：A=哺乳类（Mammals），M=哺乳类，R=爬行动物（Reptiles），V=维管植物（vascular plants）。