Domain of space credits

It does not make sense to compensate space loss in New York with space preservation in Alaska or Patagonia. Space credits generated in one area should be valid only within that area. How does one go about defining boundaries of an area of space credit validity?

Defining an area of space credit validity

The purpose of space credits is to couple space filling in an area to compensating space preservation in a similar setting somewhere nearby. recommends that area-of-validity determinations be based as much as possible on uniformity of geography and ecology.No two tracts of land are exactly alike, so the question is this: how similar do the filled space and the preserved space have to be? This can be a thorny issue, particularly if multiple jurisdictions would like to have some land included in their area and, by implication, excluded from their competitor’s area1. recommends that area definitions be made as much as possible by geographic and ecological analysis, with a goal of maximizing uniformity within an area of validity. Administrative matters will intrude on this ideal, as described below.

Larimer County in Colorado, the county that is home to,  provides a good example for definition of areas of uniform geography and ecology. Larimer County straddles the eastern side of the Rocky Mountains; its eastern part is on the Great Plains, and its western edge is on the Continental Divide—the ridge that separates rivers flowing to the Atlantic Ocean from those flowing to the Pacific Ocean. Elevations below 6,000 ft (2,000 m) in the eastern part of the county are relatively flat, with natural vegetation cover of short grass; higher elevations in the western part have steep terrain and forest cover2. Owing to these significant differences in terrain and natural vegetation, it makes sense for Larimer County to be divided into two areas of space preservation, one on the plains and one in the foothills and mountains.

There is a branch of the sciences of geography and landscape ecology that is devoted to definition of ecoregions. Maps3 prepared by scientists working in these fields can be useful in defining domains of space credit validity.

Administration matters

The next county to the south, Boulder County, has geography similar to that of Larimer County. Based only on geographic and ecological uniformity, it could make sense to merge the plains areas of the two counties into one space credit domain, and also to merge their mountainous areas into a second domain. Such mergers could, however, introduce difficulties in the administrative arena.

The most obvious way to maintain records of space credits is to harness the land records systems that already exist in county governments in the United States. It is most practical to honor county boundaries in defining domains of space credit validity.These systems record and track land ownership, values (for taxation), liens, and easements—including conservation easements. When a conservation easement is established and it protects space within a county, the records of the easement and of the space credits that it creates will most naturally be certified and recorded within that county. From an administrative perspective, therefore, it is easiest to honor county boundaries in establishing domains of validity of space credits.

Cross-jurisdiction domain mergers

Imagine that two adjacent counties have established comparable systems of space credit administration. This means that each county has functions in place that are described under Some Implementation Details. If each county is confident in the system of its neighbor, then the kind of merging of domains described above under Administration matters can be done by agreement between the two jurisdictions. In the example discussed above, this might mean that space credits created by conservation easements in the plains region of Boulder County would be valid for compensation of space filling in the plains region of Larimer County and vice versa. This would require reliable communication and coordination between the counties’ land recording systems as to the validity, ownership, and termination of space credits across county boundaries4.

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Some Implementation Details

A number of functions relating to the creation, administration, and utilization of space credits depend on local institutions.

Ecoregions (external link)

Ecoregions are areas of similar terrain and natural biology. Ecoregion units are useful to combine with administrative boundaries in defining domains of space credit validity.

1 This situation can happen wherever growth areas are contested or negotiated. In Colorado, cities and towns control development within their urban growth areas, and boundaries between these areas are negotiated among neighboring jurisdictions. While some space preservation will occur within growth management areas, open land outside these growth areas can be managed as a common pool of space available for protection—and for compensation for development within the growth areas.
2 Above about 11,000 ft elevation, forest gives way to alpine tundra.
3 Two ecoregion maps, using slightly different methodologies,  have been made for the United States. This page shows the maps developed originally by James Omernik, and this page shows the maps originally developed by Robert Bailey. The page for Bailey’s maps contains links to ecoregion maps for other continents.
4 This is an example, not a recommendation for these two counties.