North America Terrestrial Ecoregions Level 3

This data set shows Level III ecological regions (ecoregions) of North America and is an update and revision of terrestrial ecoregions released by CEC in 2009. This current cartographic layer consists of an integration of updated ecoregions in Mexico, United States and Canada by the National Institute of Statistics and Geography, the Environmental Protection Agency, and the Government of Canada; Agriculture and Agri-Food Canada, respectively. Ecoregions are areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. The ecoregions in this data set are based on the premise that a hierarchy of ecological regions can be identified through the analysis of the patterns and the composition of both living and non-living phenomena, such as geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology, that affect or reflect differences in ecosystem quality and integrity. All the characteristics are considered when determining ecoregions, but the relative importance of each characteristic may vary from one ecoregion to another. Different levels of ecological regions are identified with a Roman numeral hierarchical scheme. Level I is the coarsest level, dividing North America into 15 broad ecological regions. The 50 level II North American ecological regions provide a more detailed description of the large ecological areas nested within the level I regions and are useful for national and sub-continental overviews of ecological patterns. The 182 level III ecological regions, smaller ecological areas nested within level II regions, enhance regional environmental monitoring, assessment, and reporting, as well as decision-making. The challenging task of determining North American ecoregions has been the result of research and consultation between federal, state, provincial, and territorial agencies, as well as nongovernmental groups, universities, institutes, and the CEC. This data set represents an update of North American ecoregions derived from national agencies from Canada, the United States and Mexico, aligned with CEC terrestrial ecoregions classification scheme. CEC terrestrial ecoregions classifications represent the working group’s best consensus on the distribution and characteristics of major ecosystems at all three levels across North America. Files Download本数据集展示了北美洲三级生态区域（ecoregions），是对北美环境合作委员会（CEC）2009年发布的陆地生态区域的更新与修订。当前的制图图层整合了墨西哥国家统计与地理研究所、美国环境保护署、加拿大联邦政府以及加拿大农业与农业食品部分别更新的本国境内生态区域。生态区域是指在生态系统类型、环境资源的种类、质量与数量上具有总体相似性的区域。本数据集所收录的生态区域基于如下前提：通过分析影响或反映生态系统质量与完整性差异的生物与非生物现象（如地质、地貌、植被、气候、土壤、土地利用、野生动物与水文）的格局与组成，可以识别出生态区域的层级结构。在划定生态区域时需综合考量所有上述特征，但各特征的相对重要性会因生态区域的不同而有所差异。生态区域的不同层级采用罗马数字层级体系进行标识。一级生态区域为最宏观层级，将北美洲划分为15个宽泛的生态大区。北美洲的50个二级生态区域则对嵌套于一级生态大区下的大型生态区域进行了更细致的划分，适用于国家级及次大陆尺度的生态格局概览。嵌套于二级生态区域之下的182个三级生态区域尺度更小，可助力区域级的环境监测、评估、报告工作与决策制定。划定北美洲生态区域是一项富有挑战性的工作，其成果源自联邦、州、省与地区级机构，以及非政府组织、高校、科研院所与CEC之间的研究与磋商。本数据集是对加拿大、美国与墨西哥国家机构所提供的北美洲生态区域的更新，契合CEC陆地生态区域分类体系。CEC陆地生态区域分类体系代表了工作组就北美洲三级生态系统的分布与特征达成的最优共识。文件下载