Ecoregions as a resource for restoration
At the Native Seed Network, we find ecoregion maps to be a very useful landscape-level framework for organizing ecosystems and addressing native plant materials issues. In the absence of genetic data guiding movement of native plant materials, we consider ecoregions practical seed transfer zone boundaries.
There are 3 major ecoregion classification systems (compared below). Ecoregions for the NSN website are derived from EPA Level III Ecoregions.
1. EPA Ecoregions
- Principal investigator: James Omernik Level III EPA Ecoregion map
- Based on patterns and composition of biotic and abiotic factors, including: geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology.
- Factors weighted most heavily depend on location and scale. Example, precipitation may be more important in one area, while elevation is the most important factor in another area.
- Ecoregions are subdivided into different levels (Level I - Level IV). Level I is the most coarse, while Level IV the finest scale. Map boundary lines may vary depending on what level is used.
2. USDA Forest Service Ecoregions
- Principal investigator: Robert Bailey Ecoregion info page & Ecoregion Map
- Climatology-based. Ecological units are organized by differences in global, continental, and regional climatic regimes and gross physiography. The basic assumption is that climate governs energy and moisture gradients, thereby acting as the primary control over more localized ecosystems.
- Bailey's method is uniform, objective, and nested by design, but as such, may not take into account all of the variability that occurs in natural systems.
- 3 hierarchical levels: Domains (broad scale-subcontinental divisions of broad climatic similarity), Divisions (subdivisions of Domains-named for main climatic regions they delineate), and Provinces (fine scale-climatic subzones)
- Additional reference: Bailey, 2002. Ecoregion-Based Design for Sustainability
3. MLRA (NRCS) Ecoregions
- Contact: Gerald Rouse
- MLRA map and spatial files
- MLRA = Major Land Resource Areas. This system corresponds with EPA (Omernik) Level IV maps, with the addition of soils. Land resource regions are geographic areas that are characterized by a particular pattern of soils, climate, water resources and land uses.