Chapter 2.1
Floodplain and River Corridor Land Use

• ALL
• Remove Code Barriers
• Create Incentives
• Fill Regulatory Gaps

Development Restrictions to Protect Prime Soils

INTRODUCTION

Limiting development based on soil quality can preserve and support land suitable for farming, while discouraging other uses on high-quality soil.[1] Every hour, 180 acres of farm and ranch are lost to development for other uses.[2] This equates to over 30 million acres since 1982 – about the size of Mississippi.[3] In addition, 1.7 billion tons of topsoil are lost every year through erosion.[4] The American Farmland Trust (AFT) predicts that the U.S. will lose another 6 million acres of viable farmland in the next several years.[5] A significant contributor to the loss of farmland is sprawling and, at times, inefficiently planned housing and commercial development.[6]

Prime soil helps create efficient farmland.[7] The type of soil “composition and breakdown rate affect: the soil structure and porosity; the water infiltration rate and moisture holding capacity of soils; the diversity and biological activity of soil organisms; and plant nutrient availability. Nutrient exchanges between organic matter, water and soil are essential to soil fertility and need to be maintained for sustainable production purposes. When the soil is exploited for crop production without restoring the organic matter and nutrient contents, the nutrient cycles are broken, soil fertility declines and the balance in the agro-ecosystem is destroyed.”[8] Local governments must understand the value of the soil to determine whether to discourage nonagricultural development on prime soils or to  preserve the farmland upon which they are situated for agricultural use.[9]

Ordinances seeking to preserve farmland based on the quality of soil can be effective measures to preserve prime soil for agricultural uses.^[10] As evidenced by the local government ordinance examples below, such an ordinance generally functions by explicitly limiting the percentage of prime soil or farmland on any lot in a predominantly agricultural district on which nonagricultural development is allowed. Ordinances may also include classifications of which soils are considered prime or unique, and can require developers to explain why they are unable to develop mostly or entirely on land that is non-prime farmland or that is set back from agricultural lands before they are allowed to encroach on prime farmland.[11] To increase the ordinances’ effectiveness, some local governments expand the traditional definition of prime soil and farmland to include areas that do not contain prime soils, per se, but which “lie within, or are surrounded by contiguous areas” that have prime soils.[12] This helps to preserve the integrity and productivity of farmlands with prime soils nearby.[13]

Another common measure taken to preserve prime soil and its agricultural use is to restrict nonagricultural uses and associated development to a small portion of a lot.^[14] This allows “landowners to preserve large pockets of valuable soils” (for more information about this type of zoning ordinance see our brief on Cluster/Conservation Subdivision in Rural/Urban Area).^[15] However, on its own, this approach does not necessarily prevent one of the largest concerns associated with urban development on farmland. Namely, it does not prevent the misuse of prime soil. Development may still occur within prime soil areas, resulting in the loss of efficient farmland. Supplementing zoning ordinances with explicit regulations concerning the amount of prime soil that is allowed on a development site ensures prime soil is saved for its best use. Such an approach may also be supplemented with an ordinance limiting soil compaction (for ordinances discussing this see Reduce Soil Compaction during Construction).

Enacting a prime soil ordinance may limit the amount of development on prime farmland. Reducing development on farmland with prime soil can help maintain those areas that are most efficient and suitable for agricultural use. Limiting development in this way may help the economic viability of farms.^[16] Finally, open space will be preserved and urban sprawl will be limited, as soil composition will prevent large scale development from encroaching on prime farmland. This encroachment might not be stopped by more conventional zoning ordinances.

An additional option for local governments to preserve prime soil is the enactment of ordinances focused on mitigation. Such ordinances seek to “mitigate the loss through the purchase or donation of easements providing permanent protection from development on [other] land with comparable soils” within a reasonable distance of the development site.[17] This can be similar to a Purchase of Development Rights program, focused on soil conservation; to find out more about such programs generally, see our brief on Purchase of Development Rights. Alternatively, local governments can require direct offsets; for our brief discussing these ordinances see Offsetting Agricultural Land Loss Stemming from New Development.

Like many ordinances, to make sure there is not a regulatory takings issue with such an ordinance, local governments must be careful to leave some economically reasonable use of a property in question and/or comply with specific jurisdictional requirements concerning regulatory takings. Finally, in conjunction with these ordinances, local government may seek to provide additional regulations to ensure the health of the soil. While these ordinances may protect soil health from development, they do not address soil health as impacted by a variety of agricultural practices and do not encourage regenerative or sustainable practices that optimize soil health, such as no-till, cover cropping, and perennial cropping systems.

EFFECTS

Prime soil and farmland are threatened by the continuing spread of urban sprawl and continual developer demand for new land.[18] As more undeveloped land is sought by developers, farmland containing prime soil becomes valuable for the sake of its open space and for other qualities that often make such soil more desirable for construction purposes.[19] Though it may not be considered the most efficient use of the land, this has not historically held developers back, and without local government protections, such prime farmland will continue to be lost.[20] With the land utilized for development, the community loses the benefits, economic and otherwise, of the land itself, such as food production, open space, and associated ecosystem services.[21]

In addition, soils are crucial to providing healthy food. “Food availability relies on soils: nutritious and good quality food and animal fodder can only be produced if our soils are healthy living soils.  Over the last 50 years, advances in agricultural technology and increased demand due to a growing population have put our soils under increasing pressure.  In many countries, intensive crop production has depleted the soil, jeopardizing the soils productive capacity and ability to meet the needs of future generations.”[22]

Urban development of prime soil areas can have significant impacts. For example, in Indiana an estimated 20.2 million acres were under the control of farmers in 1950.[23] Since then, there has been a loss of nearly 5 million acres, part of which is attributable to non-farming development.[24] Data covering the entire U.S. shows that development has increased in areas containing soil with few or no limiting factors, with slightly higher rates on land with second-best rated soil (still very farmable soil) compared to areas with the very highest rated soil.[25] Developers appear to be choosing this land for development.[26] In areas with soil that generally is not highly rated, such as California, developers still appear to be choosing areas with soil that is comparatively highly rated for that area.[27]

The obvious effect of this is the loss of farming potential for those lands.[28] In addition, the indirect effect on the remaining agricultural uses in the area is also detrimental. As the number of nonagricultural uses in an area increases, complaints against agricultural uses increases.[29] And, with this increase in disruption, come rules and regulations (and potentially nuisance lawsuits) to reduce the impact of the agricultural uses on non-farming residents and businesses.[30] As new nonagricultural uses are brought into the area, not only is farmland with prime soil developed away from agricultural uses, but the remaining agricultural uses are stifled to lessen their impact on the newer urban development. As the area becomes less agricultural, there is also the potential for increasing the chance that the agricultural use will be deemed unsuitable for the location through nuisance law.[31] This puts the economic viability of farming in jeopardy, which is problematic for states where agriculture is a vital part of the economy.[32]

EXAMPLES

Whitman County, WA

The Whitman County, Washington, zoning code has a provision that allows for the development of residential areas within its Agricultural District.[33] As opposed to developing on a single lot, these Planned Residential Developments would create large, multi-lot residential developments that take advantage of the natural features of the area.[34] Not only are these developments intended to highlight and utilize the natural features of the site, but they are also intended to provide additional protection for the natural habitats in the area.[35]

These Planned Residential Developments are a special conditional use within the district.[36] As such, they are subject to a variety of requirements in order to receive approval from the board.[37] One of these requirements restricts the amount of prime farmland that can be present on a development site.[38] A Planned Residential Development cannot have more than 25 percent of the proposed parcel classified as prime farmland.[39] The ordinance goes on to define prime farmland as land that has a consistently above average crop yield.[40] In addition to placing a limit on the amount of prime farmland that may be present at the site, the ordinance also requires that the soil at the site be comprised of at least 51 percent non-tillable soil types.[41] With this restriction in place, Whitman County preserves its best farmland from development, while encouraging and accelerating the development of land that has less agricultural value.

To view the provision see Whitman County, WA, Code of Ordinances §19.10.110 (2015).

Clinton County, IN

Clinton County, Indiana, has adopted a zoning ordinance that limits the amount of prime soil on a development site. The relevant ordinance applies to development in A-1 districts, that is, districts where the predominant usage of the land is agricultural in nature.[42] Furthermore, agricultural land use will be favored above other uses, with conflicting uses discouraged.[43]

Dwellings in the A-1 district use a point system to determine approval.[44] The relevant factors are listed in a chart, along with the associated positive or negative scaled score. For example, as large lots are encouraged for agricultural use in these districts, parcels with 20 to 39 acres receive four points.[45] Plans that fall below ten points total must appeal to the Zoning Board of Appeals in order to receive approval.[46] Clinton County classifies its soil types, with non-prime soil classified as permitted to build on, and with prime soil requiring additional approval for construction.[47] With their scoring system, the greater the percentage of permitted soils that are present on the development lot, the more points the plan receives.[48] Land that only has 25 percent of permitted soil or less and a high percentage of protected soil receives zero points, while land with a low percentage of protected soil receives three points.[49] Though the protected soils are not all considered prime soils, prime soils are included in the protected categories.[50]

To view the provisions see Clinton County, IN, Unified Development Ordinance §§ 302.01, 513, & app. A (2015).

ADDITIONAL EXAMPLES

Tewksbury Township, NJ, Development Code § 723.3 (2004) (promoting agricultural preservation while creating subdivisions, and protecting prime soil from exploitation, with at least 75 percent of each tract designated as open land, and providing within those open lands “[at] least 65% . . . shall be non-critical areas and prime agricultural soils, soils of Statewide importance, or tillable soils”).

Hamilton Township, NJ, Land Development Code § 550-73 (B)(14)(b)(7) (2012) (requiring a certain percentage of open space to consist of prime soil, with at least 60 percent of designated “open lands” some combination of prime soils or other soils of statewide importance, and aiming towards the preservation of agricultural lands and soils).

Elk Township, PA, Zoning Ordinance § 702(b)(4)(a-c) (2012) (preferring subdivisions that do not build on prime soil or that are contiguous with previously developed land. Though the town does not bar development on prime soil, developers must prove that development on non-prime soils is not feasible).

Island County, WA, Code of Ordinances § 17.03.180 (2018) (excluding numerous development uses from being built on prime soil).