Looking at Lime Hills from Stony River, Alaska
BLM/Alaska Photo by Piia Kortsalo
Looking at Lime Hills from Stony River, Alaska

Yukon Kuskokwim Rapid Ecoregional Assessment (REA)

Status | Location and Setting | Management Questions | Conservation Elements | Change Agents | Data, Maps, and Models | Memos and Reports

REA Status  
The Yukon Kuskokwim REA was initiated in September 2012. It has been completed and peer reviewed and is now available to the public. The Memos and Reports section provide access to the REA data for this ecoregion.

States in the Yukon:

Contact: Project Manager
for more information

  Location Map

Yukon Kuskokwim REA Map

Location and Setting
The Yukon Kuskokwim REA in Interior Alaska encompasses three distinct ecoregions: the Yukon Lowlands, the Kuskokwim Mountains, and the Lime Hills (YKL). Combined, these ecoregions total nearly 41 million acres managed by seven major landowners.

The Yukon Lowlands are part of an extensive wetland system associated with the lower stretches of the Yukon and Koyukuk rivers in the western regions of Interior Alaska. White spruce and balsam poplar line the major rivers. They surround tall stands of alder and willow which grow throughout the floodplains and river bars. Wet sedge meadows and aquatic vegetation fill sloughs and oxbow ponds. Black spruce woodlands, birch-ericaceous shrubs and sedge-tussock bogs cover areas underlain with permafrost.

The Kuskokwim Mountains are old, low, rolling mountains south and east of the Yukon Lowlands. These mountains are underlain with thin to moderately thick permafrost. White spruce, white birch, and trembling aspen cover the uplands and black spruce and tamarack fill the lowlands.

The Lime Hills are glacially dissected mountains descending from the west side of the Alaska Range and south of the Kuskokwim Mountains. This region’s heavy glaciation resulted in sharp mountain ridges with steep headwalls and broad U-shaped valleys. Shrub communities of willow, birch and alder dominate the vegetation. Valley bottoms and mountains slopes are spruce forests and woodlands.

These three ecoregions support large wildlife populations of moose, bear, beavers, furbearers and scattered caribou herds; waterfowl; and, important runs of sockeye, Chinook, chum and coho salmon in the larger rivers. 

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Management Questions
Management questions guide an ecoregional assessment. Successful management questions address specific information needs in order to produce meaningful information for future management actions. Sixty-four management questions were selected for the Yukon Kuskokwim REA that align along these 13 broad themes:

  • Land cover
  • Wildlife
  • Aquatics
  • Soil dynamics
  • Hydrology
  • Climate
  • Fire
  • Invasive species
  • Socioeconomics
  • Subsistence
  • Sport and commercial hunting and fishing
  • Land use
  • Traditional ecological knowledge

See the Memos and Reports section to view Memorandum 1, which outlines the selection process and provides the full list of management questions.

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Conservation Elements
Conservation elements are renewable resources of high conservation interest within an ecoregion. This REA will assess the current condition and forecasted future condition of two types of conservation elements:

  • “Coarse-filter” conservation elements, which typically include all of the major ecosystem types within the assessment landscape, and represent all of the predominant natural ecosystem functions and services in the ecoregions;
  • and “Fine-filter” conservation elements, which complement the first set of elements by including a limited subset of focal species assemblages and individual species.

Thirty conservation elements were selected for assessment in this REA: nine coarse-filter terrestrial elements, five coarse-filter aquatic elements, nine fine-filter terrestrial elements, and seven fine-filter aquatic elements. See the Memos and Reports section to view Memorandum 1, which provides the full list of conservation elements.

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Change Agents
A key purpose of this REA is to understand the influences of significant widespread change agents on the natural resources of the ecoregions in the Yukon Kuskokwim REA. Change agents are features or phenomena that have the potential to affect the size, condition, and landscape context of conservation elements. The following change agents will be assessed:

  • Climate change
  • Fire
  • Invasive species
  • Insect defoliators and disease
  • Anthropogenic uses

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Data, Maps, and Models
In some instances, data may be released in phases for an REA to expedite public access to particular data sets. To learn more about REA data products and determine which REAs have available data, go to the REA Data Portal.

Memos and Reports
For each REA, there is a series of memos which are supplemental documents to the final report.  Memos document the major tasks and decision points made during the assessments and provide pertinent background information necessary to understand the justification and methods used during the assessment.  As memos and the final report are completed, they can be downloaded through the table below.

Yukon Kuskokwim (YKL) REA Memos and Reports


Document Link

Management questions, conservation elements, and change agentsTask 1 Final Memorandum (PDF)
Datasets for analysisTask 2 Final Datasets for Analysis
Analytical models and toolsTask 3 Methods
REA work planTask 4 Final Workplan
Preliminary findings for reviewTask 5 & 6 AMT4 Products Presentation
REA report, maps, and supporting documents 
REA Land Status MapLand Status Map

REA Final Report

Refer to the Table of Contents for detailed descriptions of each Section and Appendix.

Data, maps, and models available through the Data Portal.

YKL Final Report
YKL Appendix A (Introduction)
YKL Appendix B (Change Agents)
YK LAppendix C (Landscape Integrity)
YKL Appendix D (Conservation Elements)
YKL Appendix E (Data Gaps)