a_90can85_snd: 9-second gridded continental Australia composite ecological change for Amphibian 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: AMP_R2_PTS1)

Composite ecological change as a function of three metrics (the potential degree of ecological change and of disappearing and novel ecological environments) shows where change might be greatest and different types of vulnerability using 30-year climate averages between the present (1990:1976- 2005) and projected future (2050:2036-2065) under the CanESM2 global climate model (RCP 8.5), based on a Generalised Dissimilarity Modelling (GDM) of compositional turnover for amphibian (AMP_R2_PTS1). \n\nWherever the Potential degree of ecological change is scored low, ecological environments can neither be novel nor disappearing and minimal change is expected. But when the Potential degree of ecological change is scored high, a variety of possible types of change can occur depending on whether scores for Novel and/or Disappearing ecological environments are also high. \n\nTo create a composite view, we assigned each of the three component measures to a colour band in a composite-band raster: local similarity as shades of green (inverted, 1-0 rescaled 0-255); novel as shades of blue (0-1 rescaled 0-255); and disappearing as shades of red (0-1 rescaled 0-255). The three layers can then be mapped simultaneously (red: band 3; green: band 1; blue: band 2) each scaled 0-255 to show the varying degrees of similar, novel and disappearing ecological environments and their combinations. \n\nThis 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. \n\nData are provided as zipped ESRI tiff grids containing: raster image (*.tif) with associated header (*.tfw) and projection (*.xml) files. After extracting from the zip archive, these files can be imported into most GIS software packages. A readme file describes how to correctly reproduce the colour legend. In ArcGIS, the symbology statistics file can be used: "SND_display.stat.XML". \n\nReproducing RGB composite colours for 3-band raster in ArcGIS: \n1. In file properties in ARCGIS, Symbology tab, Load XML "SND_display.stat.XML"\n2. RED = BAND_3 (Disappearing)\n3. GREEN = BAND_1 (Similarity )\n4. BLUE = BAND_2 (Novel)\n5. Always use min-max legend\n6. Set each band in the custom range 0-255, mean = 126, std = 0\n\nLayers in this 9s series use a consistent naming convention:\nBIOLOGICAL GROUP _ FROM BASE TO SCENARIO _ ANALYSIS\ne.g. A_90CAN85_SND or R_90MIR85_SND\nwhere BIOLOGICAL GROUP is A: amphibians, M: mammals, R: reptiles and V: vascular plants\nand scenario is CAN: CanESM2; MIR: MIROC5\nanalysis, SND refers to – similarity, novel, disappearing\n\nLineage: Ecological similarity ranges between 0 and 1: the closer to zero, the greater the potential for compositional change in biodiversity. Each of the three ecological similarity measures were rescaled between 0 and 255 as integers to match the RGB colour scale, but the Potential degree of ecological change measure was inverted first (1-0 rescaled 0-255). \n\nUsing the Composite Bands tool in ArcGIS 10.2.2, a three-band raster was created with band1 = similarity, S; band 2 = novel, N; and band 3 = disappearing, D. \n\nIn ArcGIS mapping symbology, each of the three component measures are then assigned to a colour band:\nRED channel = BAND_3 (Disappearing)\nGREEN channel = BAND_1 (Similarity)\nBLUE channel = BAND_2 (Novel)\n\nThe gamma stretch legend scaling is not used and the min-max legend stretch is applied with statistics defined from the same custom settings for each band: minimum = 0; maximum= 255, mean = 126, std = 0. \n\nThese settings correctly reproduce the colours. \n\nThe composite ecological change index derives from the following three measures that are elsewhere described: \n\n1. S, similarity: 9-second gridded continental Australia potential degree of ecological change for Amphibians 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: AMP_R2_PTS1)\n2. N, novel: 9-second gridded continental Australia novel ecological environments for Amphibians 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: AMP_R2_PTS1)\n3. D, dissimilarity: 9-second gridded continental Australia disappearing ecological environments for Amphibians 1990:2050 CanESM2 RCP 8.5 (CMIP5) (GDM: AMP_R2_PTS1)\n\nMore detail of the calculations and methods used to derive the individual measures are given in the document “9sMethodsSummary.pdf” provided with the data download.\n\nEach of these three measures use the GDM model that is elsewhere described: Generalised dissimilarity model of compositional turnover in amphibian species for continental Australia at 9 second resolution using ANHAT data extracted 4 April 2013 (GDM: AMP_R2_PTS1)\n\nClimate data. Generalised dissimilarity models were built and projected using climate data that are elsewhere described:\na) 9-second gridded climatology for continental Australia 1976-2005: Summary variables with elevation and radiative adjustment\nb) 9-second gridded climatology for continental Australia 2036-2065 CanESM2 RCP 8.5 (CMIP5): Summary variables with elevation and radiative adjustment\n\nA brief summary of the climate downscaling method is given in the document “9sMethodsSummary.pdf” provided with the data download. \n\nFurther details about the CanESM2 global climate model: \nChylek P, Li J, Dubey MK, Wang M and Lesins G (2011) ‘Observed and model simulated 20th century Arctic temperature variability: Canadian Earth System Model CanESM2’, ATMOSPHERIC CHEMISTRY and PHYSICS DISCUSSIONS 11, 22893—22907 doi:10.5194/acpd-11-22893-2011\n\n

本复合生态变化指标基于三类度量指标（生态变化潜在程度、消失型生态环境与新型生态环境），通过对比当前时段（1990年：1976-2005年）与预估未来时段（2050年：2036-2065年）的30年气候平均值，依托加拿大地球系统模式2（CanESM2）典型浓度路径8.5（RCP 8.5）下的广义相异度建模（Generalised Dissimilarity Modelling, GDM），针对两栖类物种组成周转（AMP_R2_PTS1）开展分析，可识别生态变化最剧烈的区域以及不同类型的生态脆弱性分布。

当生态变化潜在程度评分较低时，区域内既不会出现新型生态环境，也不会有生态环境消失的情况，生态组成仅会发生极小幅度的变化。反之，若生态变化潜在程度评分较高，则会根据新型生态环境与/或消失型生态环境的评分高低，出现多种不同类型的生态变化。

为生成复合可视化结果，我们将三类组分指标分别对应至复合波段栅格的色彩通道：本地生态相似性对应绿色调（经反转处理，将1-0区间重缩放至0-255区间），新型生态环境对应蓝色调（将0-1区间重缩放至0-255区间），消失型生态环境对应红色调（将0-1区间重缩放至0-255区间）。随后可同时绘制三层栅格（红色对应波段3，绿色对应波段1，蓝色对应波段2），各波段均缩放至0-255区间，以展示生态相似、新型与消失型生态环境的变化程度及其组合模式。

本指标与其他相关指标均为配合2014年国际自然保护联盟（IUCN）世界公园大会所开展的研究而开发，旨在评估大陆与全球尺度下气候变化对生物多样性保护区系统的效能。相关方法已刊载于AdaptNRM指南《气候变化对生物多样性的影响：群落级建模方法》，可通过在线链接www.adaptnrm.org获取。

数据集以压缩的ESRI TIFF栅格包形式提供，内含栅格图像文件（*.tif）及其关联的头文件（*.tfw）与投影文件（*.xml）。解压压缩包后，这些文件可导入绝大多数地理信息系统（GIS）软件中。附带的README文件详细说明了如何正确复现色彩图例，在ArcGIS中可直接使用符号系统统计文件"SND_display.stat.XML"。

在ArcGIS中复现三波段栅格的RGB复合色彩步骤如下：
1. 打开ArcGIS中的文件属性窗口，切换至符号系统（Symbology）标签页，加载XML文件"SND_display.stat.XML"
2. 红色通道对应波段3（消失型生态环境）
3. 绿色通道对应波段1（生态相似性）
4. 蓝色通道对应波段2（新型生态环境）
5. 始终使用最小-最大图例缩放模式
6. 将每个波段的自定义范围设置为0-255，均值设为126，标准差设为0

本9弧秒分辨率系列栅格图层采用统一命名规则：
[生物类群]_[基准时段至情景时段]_[分析类型]
示例：A_90CAN85_SND 或 R_90MIR85_SND
其中：
- 生物类群：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
- 情景模式：CAN代表CanESM2全球气候模式，MIR代表MIROC5全球气候模式
- 分析类型：SND代表相似性（Similarity）、新型（Novel）与消失型（Disappearing）复合分析

指标溯源：生态相似性取值范围为0至1，数值越接近0，代表生物群落组成发生变化的潜在可能性越高。三类生态相似性指标均被重缩放为0-255区间的整数值以匹配RGB色彩标尺，其中生态变化潜在程度指标需先进行反转处理（将1-0区间重缩放至0-255区间）。

使用ArcGIS 10.2.2中的复合波段工具，可创建包含以下波段的三波段栅格：波段1为相似性指标（S），波段2为新型生态环境指标（N），波段3为消失型生态环境指标（D）。
在ArcGIS制图符号系统中，需将三个组分指标分别对应至色彩通道：
- 红色通道对应波段3（消失型生态环境）
- 绿色通道对应波段1（生态相似性）
- 蓝色通道对应波段2（新型生态环境）
无需使用伽马拉伸图例缩放模式，需采用最小-最大图例拉伸方式，并为每个波段设置统一的自定义统计参数：最小值为0，最大值为255，均值为126，标准差为0。
上述参数可正确复现预设色彩。

本复合生态变化指数源自以下三类已在其他文献中详述的指标：
1. S（相似性）：澳大利亚大陆9弧秒分辨率栅格数据，针对两栖类的1990年至2050年生态变化潜在程度，基于CanESM2全球气候模式、RCP 8.5情景（耦合模式比较计划第五阶段，CMIP5），采用广义相异度建模（GDM: AMP_R2_PTS1）
2. N（新型）：澳大利亚大陆9弧秒分辨率栅格数据，针对两栖类的1990年至2050年新型生态环境分布，基于CanESM2全球气候模式、RCP 8.5情景（CMIP5），采用广义相异度建模（GDM: AMP_R2_PTS1）
3. D（相异性，对应消失型生态环境）：澳大利亚大陆9弧秒分辨率栅格数据，针对两栖类的1990年至2050年消失型生态环境分布，基于CanESM2全球气候模式、RCP 8.5情景（CMIP5），采用广义相异度建模（GDM: AMP_R2_PTS1）

各类组分指标的具体计算方法与技术细节已刊载于数据下载包附带的"9sMethodsSummary.pdf"文档中。
三类指标均采用已在其他文献中详述的广义相异度模型：针对澳大利亚大陆9弧秒分辨率栅格的两栖类物种组成周转分析，基于2013年4月4日提取的ANHAT数据，采用广义相异度建模（GDM: AMP_R2_PTS1）。

气候数据：广义相异度模型的构建与投影均采用已在其他文献中详述的气候数据，具体包括：
a) 澳大利亚大陆1976-2005年9弧秒分辨率气候学栅格数据：经高程与辐射校正的汇总变量数据集
b) 澳大利亚大陆2036-2065年CanESM2全球气候模式RCP 8.5情景（CMIP5）下9弧秒分辨率气候学栅格数据：经高程与辐射校正的汇总变量数据集
气候降尺度方法的简要概述已刊载于数据下载包附带的"9sMethodsSummary.pdf"文档中。

关于CanESM2全球气候模式的更多细节可参阅以下文献：
Chylek P, Li J, Dubey MK, Wang M及Lesins G（2011）《观测与模拟的20世纪北极温度变率：加拿大地球系统模式CanESM2》，《大气化学与物理学讨论》11卷，22893—22907，DOI:10.5194/acpd-11-22893-2011