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

Proportional change in effective area of similar ecological environments for Vascular plants as a function of land clearing within the present long term (30 year average) climate (1990 centred) based on Generalised Dissimilarity Modelling (GDM) of compositional turnover. This metric describes the effects of 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 uncleared landscape and degraded landscape (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 then multiplied by a 0 (cleared) to 1 (intact) condition index based on the natural areas layer. 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: amphibians, M: mammals, R: reptiles and V: vascular plants

本指标基于植被组成更替的广义相异模型（Generalised Dissimilarity Modelling, GDM），以1990年为中心的30年平均长期气候现状为基准，表征维管植物（Vascular plants）相似生态环境有效面积的比例变化随土地开垦程度的响应关系。该指标以比例形式量化土地开垦对各网格单元对应相似生态环境面积的影响：每个网格单元将分别与未开垦景观和退化景观中的60000个采样点进行比对，计算两两相似性之和（例如，完全相似的网格单元得分为1，完全不相似的得分为0，中间分值对应不同的相似程度）。随后将每个网格单元的相似性贡献值乘以基于自然区域图层得到的0（已开垦）至1（原生完好）状态指数。通过将测试区域面积除以当前基准区域面积，可量化土地利用/气候变化引发的相似生态环境面积缩减情况。当指标值小于1时，代表相似生态环境面积出现缩减；等于1时代表无变化；大于1时（北部地区仅存在罕见案例）则代表相似生态环境面积有所增加。
该指标与其他多项指标同步开发，用于在大陆与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，相关研究成果曾在2014年世界自然保护联盟世界公园大会（IUCN World Parks Congress 2014）上展示。该指标的详细说明可参阅AdaptNRM发布的《气候变化对生物多样性的影响：群落级建模方法》指南，在线访问地址为：www.adaptnrm.org。
本数据集提供两种格式：
1. 压缩版ESRI浮点栅格数据集：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（GIS）软件，通过替换对应头文件的方式，也可作为其他二进制文件格式调用。
2. ArcGIS图层包（*.lpk）：该类文件可通过ArcGIS软件解压为带有配套图例的栅格图层。
此外，9sMethodsSummary.pdf文件中提供了简要的方法概述，可供用户查阅获取更多细节。本9s系列数据集采用统一命名规则：生物类群_基准时段_情景名称_分析类型，示例为A_90_CAN85_S或R_90_MIR85_L，其中生物类群对应关系为：A代表两栖类（amphibians）、M代表哺乳类（mammals）、R代表爬行类（reptiles）、V代表维管植物（Vascular plants）。