9-second gridded continental Australia change in effective area of similar ecological environments (cleared natural areas) for Vascular Plants 1990:2050 MIROC5 RCP 8.5 (CMIP5) (GDM: VAS_v5_r11)

Proportional change in effective area of similar ecological environments for vascular plants 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). The contribution of each cell is scaled by the land condition. 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_ ANALYSISe.g. A_90_CAN85_S or R_90_MIR85_Lwhere BIOLOGICAL GROUP is A: Vascular Plants, M: Vascular Plants, R: Vascular Plants and V: vascular plantsLineage: Proportional change in the area of similar ecological environments was 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. Proportional change was calculated by taking the area of baseline ecological environments similar to each present cell as the denominator and the area of future degraded ecological environments similar to each present cell (with the contribution of each cell scaled by a Natural Areas condition grid 0, degraded to 1 intact) as the numerator. More detail of the calculations and methods are given in the document “9sMethodsSummary.pdf” provided with the data download. GDM Model: \tGeneralised dissimilarity model of compositional turnover in vascular plant species for continental Australia at 9 second resolution using ANHAT data extracted 4 April 2013 (GDM: VAS_v5_r11)Climate data. Models were built and projected using:a) 9-second gridded climatology for continental Australia 1976-2005: Summary variables with elevation and radiative adjustmentb) 9-second gridded climatology for continental Australia 2036-2065 CanESM2 RCP 8.5 (CMIP5): Summary variables with elevation and radiative adjustment Natural Areas Mask (intact/degraded land)Australian Government Department of the Environment (2014) Natural areas of Australia - 100 metre (digital dataset and metadata). Available at http://www.environment.gov.au/metadataexplorer/explorer.jsp and up to date information for Western Australia were provided at 25m Albers projection were reprojected to GDA94, merged and aggregated to a continuous measure of proportion of intact area per grid cell at 9s.

本数据集基于广义不相似性建模（Generalised Dissimilarity Modelling, GDM）的物种组成周转分析，量化了土地开垦与长期（30年平均）气候变化对维管植物（vascular plants）相似生态环境有效面积的比例变化，对比时段为以1990年为基准的当前现状与以2050年为基准的未来情景（基于CanESM2模式的RCP 8.5排放路径）。
该指标表征了气候变化与土地开垦的协同效应对各网格单元对应相似生态环境面积的比例影响。每个网格单元分别与当前未开垦景观及两种替代情景（当前已开垦或未来已开垦）中的60000个采样点进行相似性比对，对两两相似性得分进行求和（例如完全相似的单元得分为1，完全不相似得分为0，中间值对应不同相似程度）。各网格单元的贡献值将依据土地状况进行缩放。
各时间点下，该指标反映的相似生态环境面积，对于稀有环境通常较低，对于广布环境则较高。通过将测试区域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比例。数值小于1代表面积缩减，等于1代表无变化，大于1的情况（澳大利亚北部地区罕见）则表示相似生态环境面积增加。
本指标与其他指标一同开发，用于评估大陆及全球尺度下气候变化对生物多样性保护区系统的有效性，相关成果发表于2014年世界自然保护联盟（International Union for Conservation of Nature, IUCN）世界公园大会。其详细说明见于《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。
数据提供两种格式：
1. 压缩的ESRI浮点栅格文件（ESRI float grids）：包含二进制浮点栅格（"*.flt"）、关联的ESRI头文件（"*.hdr"）与投影文件（"*.prj"）。从压缩包解压后，这些文件可导入多数地理信息系统（Geographic Information System, 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（ArcGIS layer package, "*.lpk"）：该包可由ArcGIS解压为带关联图例的栅格图层。
此外，随数据附带"9sMethodsSummary.pdf"文件，其中包含简短的方法总结以供进一步查阅。
该9s系列图层采用统一命名规则：生物类群_基准时段_情景_分析类型，例如："A_90_CAN85_S" 或 "R_90_MIR85_L"。其中生物类群的取值为：A：维管植物，M：维管植物，R：维管植物，V：维管植物。
计算流程：
相似生态环境面积的比例变化通过高度并行化的定制化CSIRO Muru软件计算完成，该软件运行于Linux高性能计算集群，输入数据为经GDM模型转换的环境栅格。比例变化的计算方式为：以与每个当前网格单元相似的基准生态环境面积作为分母，以与每个当前网格单元相似的未来退化生态环境面积作为分子（各网格单元的贡献值将按自然区域状况栅格进行缩放，该栅格以0表示退化区域，1表示完整原生区域）。详细的计算与方法说明详见数据下载包中的"9sMethodsSummary.pdf"文件。
GDM模型：
针对澳大利亚大陆9秒分辨率的维管植物物种组成周转的广义不相似性模型（Generalised Dissimilarity Model, GDM: VAS_v5_r11），所用ANHAT数据提取于2013年4月4日。
气候数据：
模型构建与投影采用以下数据源：
a) 1976-2005年澳大利亚大陆9秒分辨率栅格气候数据集：包含高程与辐射校正的汇总变量
b) 2036-2065年澳大利亚大陆9秒分辨率栅格气候数据集（CanESM2模式RCP 8.5排放路径，第五次耦合模式比较计划（Coupled Model Intercomparison Project Phase 5, CMIP5））：包含高程与辐射校正的汇总变量
自然区域掩码（完整/退化土地）：
采用澳大利亚政府环境部（2014）发布的《澳大利亚自然区域——100米分辨率数字数据集及元数据》，可于http://www.environment.gov.au/metadataexplorer/explorer.jsp 获取。西澳大利亚州的最新数据以25米Albers投影（Albers projection）提供，已被重投影至GDA94坐标系，经合并与聚合后得到每个9秒网格单元的完整区域比例连续度量值。