9-second gridded continental Australia change in effective area of similar ecological environments (intact) for Amphibians 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: AMP_r2_PTS1)

Proportional change in effective area of similar ecological environments for Amphibians as a function of 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 effects of climate change on the area of similar environments to each grid cell, expressed as a proportion of original area. Each cell is compared with a sample of 60,000 points in both the present and the future, 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). For each time point, this describes the area of similar environments, which for the present will be low for rare environments and high for widely distributed environments. By dividing the future area by the current area, we are able to quantify the proportional reduction in area as a function of 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

基于物种组成周转的广义相异性建模（Generalised Dissimilarity Modelling, GDM），本数据集展示了以1990年为基准的当前气候，与以2050年为基准的未来气候（采用CanESM2模式下的RCP 8.5情景）间的长期（30年平均值）气候变化为自变量时，两栖类相似生态环境有效面积的比例变化。

该指标用于描述气候变化对每个栅格单元对应相似生态环境面积的影响，以原始面积的比例形式呈现。研究分别在当前与未来气候情景下，将每个栅格单元与6万个采样点进行两两比对，并累加相似性得分（例如完全相似的栅格得分为1，完全相异的得分为0，取值范围介于二者之间）。在任一时间节点下，该指标表征相似生态环境的面积：当前情景下，稀有生态环境对应的面积值较低，广布生态环境对应的面积值较高。通过将未来情景下的面积除以当前面积，可量化气候变化驱动下的面积比例变化：取值小于1代表面积缩减，等于1代表无变化，大于1的情况（北半球罕见）则表示相似生态环境面积有所扩张。

该指标与其他同类指标一同开发，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》，可通过网址www.adaptnrm.org在线获取。

本数据集提供两种格式：
1. 压缩版ESRI浮点栅格：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）：该类文件可通过ArcGIS软件解压为带配套图例的栅格图层。

此外，附带的9sMethodsSummary.pdf文件提供了简要的方法学概述，可供读者查阅更多细节。

本9s系列数据集的图层采用统一命名规范：
生物类群_基准年份_情景_分析类型
示例：A_90_CAN85_S 或 R_90_MIR85_L
其中生物类群的代码含义为：A代表两栖类，M代表哺乳类，R代表爬行类，V代表维管植物。