Jonathan Douglas Witten*

Abstract:  Natural and built resources have finite capacities for assimilating growth and associated impacts. The use of analytical tools such as carrying capacity analyses is recommended to assess the cumulative impact of land development upon these resources. Once carrying capacity thresholds have been established, local governments should apply appropriate regulatory controls to ensure that capacities are not exceeded. The application of carrying capacity tools is suggested in all jurisdictions, including states that do not mandate the preparation of comprehensive plans. The adoption of carrying capacity regulations may trigger a regulatory takings analysis. Adoption of legislative actions to preserve carrying capacity limitations, however, are generally entitled to a presumption of validity. This is contrasted with the use of adjudicative permits to assess assimilative capacity thresholds. While adjudicative permits allow for aggressive review of development in relation to cumulative impacts, their ad hoc nature demands precise application by local governments.


This article suggests that local governments use a “cumulative impact”1 or “carrying capacity”2 analysis as a tool to assess the impact [*PG584]of plans, policies and regulations upon built and natural resources.3 A carrying capacity analysis assesses the ability of a built resource (such [*PG585]as roadways, wastewater treatment plants, municipal swimming pools) or natural resource (such as aquifers, surface water bodies, or coastal estuaries) to absorb population growth and related physical development without degradation.4 Without such an analysis, a system could fail to perform as designed,5 or, in the case of a natural resource, diminish in health or productivity.6

[*PG586] Understanding the carrying capacity or constraints of these resources can be an effective method for identifying the areas of the community that are suitable for new or expanded development. The converse proposition is also true: when the carrying capacity of a resource is identified, a local government can revise its plans, policies and regulations to ensure that carrying capacities are not exceeded. Simply put, when municipal residents and officials have a working understanding of carrying capacity limitations, they have the ability to make more rational and defensible decisions regarding the location and density of development.7

However, determining the carrying capacity of a built or natural resource entails a rigorous quantitative analysis.8 Municipalities and local government agencies may avoid this analysis because they believe it requires scientific investigations beyond their financial or technical abilities.9 Nevertheless, by completing a carrying capacity analysis, the government, and local governments in particular, gain a powerful and legally defensible tool with which to make decisions.10 [*PG587]Further, this analysis may also help local governments to resolve conflicts between competing development and preservation goals.11

Whereas previous commentary on this issue has supported carrying capacity approaches to limit or slow municipal growth,12 questioned the substantive basis for use of carrying capacity analysis,13 or discussed only the analytical approaches to carrying capacity,14 this [*PG588]article discusses carrying capacity in a different light: as a way to assess the impact of plans, policies and regulations upon built or natural resources. Local governments have the ability to apply regulatory controls to land development and avoid exceeding the assimilative capacity of a built or natural resource. Further, the tool for ensuring that these carrying capacity controls are effective is the local government’s comprehensive plan.

I.  Analyzing and Assessing Cumulative Impacts and Carrying Capacity

We ought to look at densities in much the same way we look at calories and vitamins. Right amounts are right amounts because of how they perform. And what is right differs in specific instances.15

It is important to remember that all built and natural resources have a carrying capacity.16 When that capacity is exceeded, the resource fails to function as intended or hoped. For example, residents of every major metropolitan region in the nation have experienced carrying capacity failures on freeways leading into and out of these cities.17 Similarly, most residents of urban areas have experienced carrying capacity excesses on mass transit systems, public beaches, and [*PG589]recreational facilities. These systems fail when they simply cannot accommodate the number of residents seeking to use them at the same time.

Solutions to carrying capacity failures for built resources are plentiful. In the examples noted above, a city could solve these problems by building additional roadways, putting additional trains into service, or expanding recreational facilities. There may be financial limitations18 to improve service or expand facilities, but for the most part, built resources can be rebuilt larger, better, and perhaps more accommodating.

On the other hand, natural resource carrying capacities are not as readily improved. Once their carrying capacity is exceeded, it may be impossible to restore.19 The sections below focus in particular on water and wetlands to illustrate and explain how it can be difficult to both “fix” and replicate the carrying capacity of natural resources while still accommodating development.

[*PG590]A. Drinking Water

Water used for human consumption has a health-related carrying capacity, as consumption in excess of this capacity poses a public health risk. Unlike roads, bridges, or schools, once the carrying capacity of a water supply has been reached, it can no longer be “fixed.” For example, EPA has set the carrying capacity for nitrogen in drinking water at ten parts per million (ppm).20 Once a drinking water supply has exceeded its capacity for nitrogen, the supply no longer meets federal and state health regulations and no longer constitutes potable water. At issue is the “fix.”

Without reducing the sources of nitrogen themselves, there is no existing way to remedy the increased nitrogen levels. In other words, the water at the well cannot be effectively treated to remove nitrogen.21 Thus, the only effective means of re-establishing the potability of well water is to reduce nitrogen levels over time by slowing or ceas[*PG591]ing nitrogen inputs to groundwater. Ironically, this requirement could have been avoided simply by limiting nitrogen inputs to the carrying capacity of the well in the first place.

B. Coastal Waters

The ability of coastal waters to assimilate nutrients such as nitrogen and phosphorus has been the subject of intense research.22 While little doubt remains that coastal systems have carrying capacities,23 an oft-debated issue is whether the coastal waters of different regions have the same carrying capacity. Given their variations in water temperature, flushing, salinity and depth, coastal water bodies are believed to have unique carrying capacities that do not lend themselves to generalities.24

Nevertheless, when the carrying capacities of individual water bodies can be determined, the imposition of regulations can ensure that the capacity will not be exceeded. As in the case of potable drinking water, preventing the carrying capacity from being exceeded requires virtually the same effort as the necessary “fix” required after the carrying capacity has been reached.

C.  Wetlands

Wetlands “replication,” the art and science of creating new or expanded wetlands habitat as a quid pro quo for permission to fill an [*PG592]existing wetland, is a tool for protecting wetlands while simultaneously allowing development.25

At first glance, wetlands replication appears to challenge the proposition that all resources have a carrying capacity. By “re-creating” a resource at the site of development or even at a different locus, it can seem as though the resource has not truly been lost. However, replication and re-creation of a natural resource, even where feasible, does not diminish the importance of understanding carrying capacity thresholds. For example, a land developer seeking to comply with municipal subdivision regulations that require two means of egress from her development may propose to fill several acres of wetlands and replicate the wetland elsewhere on her property. While the proposal clearly complies with the “no net loss” policy for wetland protection,26 replicating the resource should also require the developer to apply carrying capacity principles. For example, she should consider where the replication will occur, the impacts on surrounding land uses, the newly-created resource’s threshold for nitrogen, phosphorus, metals and other contaminants, and the newly-created resource’s potential for survival in the proposed location.27

Wetlands replication assumes that one portion of a resource or region has a greater carrying capacity than another.28 This determination cannot occur, however, until the carrying capacity of each affected built or natural resource has been established.

[*PG593]II.  The Comprehensive Plan and Carrying Capacity

Land use planning and the evolving body of American land use law originates from the notion that cities, towns, and regions must look at the “big picture” to plan adequately for the future. This “big picture” thinking is perceived as visionary and holistic, leading many states to require municipalities to prepare so-called comprehensive, master, or general plans.29 Typically, a municipality must prepare a plan before it may adopt zoning, subdivision control, or health regulations.30

States requiring plans prescribe a process and list of ingredients, or elements, for preparing a comprehensive plan, such as planning for transportation facilities, natural resource management, and affordable housing.31 A second set of states does not require its member local governments to prepare a plan as a precondition for land use regulation.32 These “non-plan” states place their municipalities in a precarious position when local regulations are challenged, because the regulations are arguably arbitrary if not developed in accordance with some plan.33 These two models are discussed in the sections that follow.

[*PG594]A.  Carrying Capacity and the Comprehensive Plan in Plan States

In addition to the elements traditionally found in the comprehensive plan, the plan should also contain an analysis of the carrying capacity of the jurisdiction’s built and natural resources. Such an analysis should identify and quantify the ability of each resource to withstand the impact of an additional dwelling, retail structure, wastewater treatment plant and so on. The true benefit of the comprehensive plan can be realized only by completing such an analysis.34

For example, plan states require municipalities to prepare a comprehensive plan in accordance with specific criteria and guidelines.35 While the local government generally has broad discretion in expanding the scope of the plan,36 the specific state guidelines are considered to be the mandatory elements of the plan. Yet, while the plan must be both internally and externally consistent,37 states do not [*PG595]impose a carrying capacity requirement. As a result, a comprehensive plan could comply with the state’s planning mandate and consistency requirements, but the effect of incremental or cumulative land use decisions could exceed the assimilative capacity of both the natural resources and built resources.

For example, assume that a city council wishes to designate a portion of the jurisdiction currently zoned for low-density residential use as “light industrial.” Before the zoning ordinance can be amended, the plan must be revised to comport with vertical consistency requirements. Once completed, the city can then ensure horizontal consistency with the plan and land use regulations by rezoning the specific land area light industrial.

To amend the plan and subordinate regulations, the city must determine the impact of the rezoning from residential to light industrial and prove consistency with each required element of the plan. The legislative body can adopt the new zoning designation only after such a determination. However, this otherwise logical process has omitted an important consideration.

While making the vertical and horizontal consistency findings, the city never analyzed the cumulative impact of this plan and regulation change under future build-out38 conditions and never recognized carrying capacity thresholds. The city was required to assess the impacts of the plan change and rezoning on infrastructure, water resources, housing, and open space, for example. But, the alteration was [*PG596]never subjected to a more specific, assimilative capacity test for each element.

Thus, even plan states need to require more from their local governments. Municipalities should articulate definitive statements which enumerate specific goals and policies within their plans. These specific goals and policies should ensure that carrying capacity thresholds will be respected. The relevant legislative and adjudicative bodies can then translate these credible plan goals into enforceable regulations.

B.  Carrying Capacity in Non-Plan States

Local governments in non-plan states are not required to establish a plan before adopting land use regulatory controls. As a result, land use regulations such as zoning and subdivision control do not require consistency with each other or with other regulatory actions such as wetland protection, health codes, or historic and aesthetic regulations.39

For example, suppose a local government in a non-plan state adopts a zoning ordinance allowing development densities such that the carrying capacity of a surface water body relative to nutrients will soon be exceeded. At the same time, it adopts a wetland protection regulation that prohibits disturbance of the wetland habitat within 100 feet of the surface water body. These two regulations are vertically and horizontally inconsistent and will inevitably lead to unintended results. The zoning ordinance ignores the cumulative effect of development on the water resource. In contrast, the wetland regulation seeks to protect wetland habitat but conflicts with the zoning ordinance and will do little except establish a 100-foot buffer around an otherwise lifeless water body. This simple conflict could be avoided if the local government had a comprehensive plan and development was consistent with that plan.40

[*PG597] Perhaps the greatest conflict emerging in all states, but which is magnified in non-plan states, is between the need for affordable housing and the generalized goals of environmental resource protection.41 The shortage of affordable housing for low- and medium-income families has provided the backdrop for a series of recent studies throughout the nation, some aimed at identifying the barriers to affordable housing development.42 One conclusion of these studies is that local regulatory controls, such as zoning, subdivision control, and health-related regulations, are used intentionally as roadblocks in the path of affordable housing development.43 While the issue of affordable housing is beyond the scope of this article, it does highlight an important and related point: without a plan upon which to base regulations, debates over local government priorities become hopelessly confused.

Clearly most urbanized states have affordable housing crises. But they also have crises of wetland loss, open space depletion, and water quality contamination. Their road systems and transportation networks are overtaxed and antiquated. At issue is establishing priorities for subsequent action: without a plan, how do the respective state legislatures or, more importantly, the local government legislatures, prioritize housing over roads, or road development over wetlands protection? In the absence of a plan, how can any priority be anything but arbitrary? The simple answer is that without a plan, the resulting government actions are arbitrary and, if challenged, should fail.

[*PG598] The ongoing problems in many states point out the hypocrisy of landuse action in the absence of a plan and planning requirements. Housing advocates argue that local governments use regulatory tools to impede the progress of affordable housing, pointing to large lot zoning and strict subdivision regulations as examples of how local governments are adding too much cost to housing development.44 Yet large lot zoning and subdivision rules and regulations stem from the premise that local governments are empowered to protect the health, safety, and welfare of their residents. A hopelessly circuitous “Catch-22” results: cities and towns are not required to plan as a precondition to adopting land use regulations, but adopted regulations are attacked as being excessive.45

The challenge non-plan states face is how to establish priorities for subsequent action: housing instead of roads or road development instead of wetlands protection. The best way to understand these challenges is to compare the effect of similar statutes on a plan state and a non-plan state. Massachusetts, a non-plan state, adopted the Anti-Snob Zoning Act as a means of increasing affordable housing, particularly in the state’s suburbs.46 In practice, the Act requires municipalities to grant a waiver from any and all locally-based regulations in favor of the development of “affordable housing,” regardless of the regulation’s purpose or intent, if the city or town does not have at least ten percent of its housing stock subsidized by a federal or state [*PG599]subsidy program.47 This requirement, however, conflicts with the readily definable carrying capacity of the region’s water resources for nitrogen and phosphorus.48 Yet, under the Act, an application for affordable housing development that would result in the generation of nutrient levels beyond the carrying capacity of the water resource would nevertheless be entitled to approval. The need for affordable housing has trumped environmental protection, even though there has been no analysis of the impact this sweeping initiative will have upon the state’s environmental resources. Perhaps the greatest indictment against the Massachusetts approach and the approaches of other non-plan states, however, is that by eschewing planning and substituting priorities of political whim, they retard and distort a vision of the future. Ultimately, local residents will lose their voices to their futures when they are lulled with false promises of home rule and self-determination, which are largely irrelevant if local plans and visions are not taken into account.

The example provided by Massachusetts stands in sharp contrast with the approach taken in Rhode Island. Rhode Island has a similar statute to Massachusetts’ Anti-Snob Zoning Act, mandating that local governments have at least ten percent of their housing stock set aside as subsidized for affordability.49 As a plan state, Rhode Island’s Comprehensive Planning and Land Use Regulation Act requires that all local governments prepare and adopt a comprehensive plan, including provisions for housing.50 Local governments in Massachusetts and Rhode Island that do not have the mandated affordability percentages are vulnerable to an appeal to the State Housing Appeals Committee and Housing Appeals Board, respecitively, according to provisions of the Low and Moderate Income Housing Act.51 That is where the similarities end, however, since local governments in Rhode Island are required to adopt a comprehensive plan, they are thereby enabled to devise the most logical means of providing for affordability consis[*PG600]tent with their ability to protect natural and built resources from carrying capacity excess. In contrast, Massachusetts’ mandate for affordability is linked by neither policy nor statute to the other needs of the community.

The conflict stems from an absence of planning goals. Without a plan, the issue du jour makes the headlines and becomes the priority for the moment. The problem, of course, is that this type of knee-jerk action leads to the exact consequences discussed in this article. For example, assume that the housing advocates’ argument is correct: local regulations are largely responsible for the housing crisis in many states. Which regulations should be relaxed? Which regulations should local governments be barred from enforcing? What will be the consequences on all relevant local and state concerns other than affordable housing?52 The failure of some states to require plans as a precondition of regulatory control creates the situation discussed above and prevents governments from acting prudently given the broad responsibilities modern governments have. Moreover, carrying capacities of built and natural resources will forever be at risk when certain government policies trump all others. In the example presented, the need for affordable housing outweighs environmental protection, even though no analysis has been prepared as to the impact of this sweeping initiative upon the states’ environmental resources.

III.  Carrying Capacity Regulations and the Takings Issue

The point at which a land use regulation “goes too far” and thus constitutes a compensable taking, is often debated and is the subject of numerous articles, texts, and weekday planning board and commission hearings across the country. While the subject makes for interesting dialogue, the methodology for assessing when a regulation goes too far, is well accepted.

For the purposes of this article, land use regulations are viewed as consisting of either: (1) legislative pronouncements, such as a zoning [*PG601]ordinance establishing minimum lot size for residential development based upon a carrying capacity analysis,53 or (2) adjudicative actions, such as a zoning ordinance that allows an adjudicative board, like a board of appeals, to grant discretionary permits based on established carrying capacity formulas.54

A.  Legislative Actions

The United States Supreme Court succinctly stated the regulatory takings analysis for legislative decisions in Agins v. City of Tiburon.55 The Court explained that a regulatory taking occurs when the legislation (1) does not advance a legitimate governmental interest or (2) denies the landowner economically viable use of his land.56 A regulation adopted in response to a carrying capacity analysis clearly meets the first prong of this test because the analysis upon which the regulation is based indicates that without the regulation, the resource will decline or malfunction.57 The second prong of Agins, based on the principles set forth in Penn Central Transportation Co. v. New York City,58 is violated only where the landowner is left with no reasonable economic value.59 A mere diminution in value has not been held to constitute a regulatory taking.60

[*PG602] Given the rule established in Agins, public health regulations that reduce real property value should not constitute a regulatory taking.61 For example, a regulation adjusted to comport with a carrying capacity analysis so that it deprives a landowner the densities allowed under previous zoning regulations would not result in the total deprivation of economic value. Carrying capacity regulations, then, are not tantamount to a total economic wipeout because they would presumably allow some level of development.62 Therefore, carrying capacity regulations are not regulatory takings under the second prong of Agins because such regulations do not result in a complete diminution of value.63

Landowners, however, may still challenge carrying capacity regulations with a regulatory takings claim. Assume that a carrying capacity regulation is in place to protect a watershed. Will it be a regulatory taking if a landowner seeks to develop her property within the watershed, but the watershed’s carrying capacity for nutrient loading has been exceeded? In other words, previous applicants have developed the watershed to its capacity and the local government will not grant new permits for development within the watershed. The affected landowner, citing the Supreme Court’s holding in Lucas v. South Carolina Coastal Council,64 and Agins,65 will claim that the carrying capacity [*PG603]regulation eliminates all economically beneficial uses of her land and thus requires compensation.66

Local governments have three possible responses to the landowner’s inevitable challenge. First, the local government can compensate the landowner to acquire and preserve the real property.67 The acquisition and protection of real property in a watershed, wellhead protection area, or other natural resource habitat provides the strongest level of protection available.68 Second, local governments can defend the carrying capacity regulation under the holding in Lucas by demonstrating that the regulation, and thus the development prohibition, is supported by common-law nuisance principles found in state law.69 Third, local governments can defend the regulations by asserting that they do not destroy all economically viable property uses.70

The government’s third possible response is perhaps the most important because it focuses on the flexible carrying capacity of natural resources. Unlike built resources that have relatively exact carrying capacity thresholds, natural systems are far more forgiving. When a bridge or water supply conduit has exceeded its carrying capacity for vehicles or flow, the system either breaks or malfunctions. Such built resources are generally sensitive to only one threat: bridges collapse under too much weight and water supply conduits fail under too much water pressure or flow.

Natural resources, however, are more flexible because the limit to carrying capacity depends on the use and location of the resource.71 For example, phosphorus limits fresh water bodies but not coastal es[*PG604]tuaries. Nitrogen limits coastal estuaries, but not fresh water. Finally, nitrogen, but not phosphorus, threatens drinking water supplies.72

Given the flexibility of natural resources, a carrying capacity regulation limiting development within the watershed of a fresh water body need not stipulate that no development is allowed and thus run afoul of Agins and Lucas.73 Rather, the regulation should be tailored to prohibit additional phosphorus loadings within the watershed. The landowner could then propose land uses that do not generate additional phosphorus. Such a carrying capacity regulation would curtail the landowner’s development options, but it is unlikely that the regulation would eliminate all options. Moreover, carrying capacity regulations that are targeted to specific threats should benefit from the highly deferential judicial review given to legislative actions.74

Unfortunately, legislative actions are imprecise in their ability to protect complex natural resources from the negative impacts of development. Legislative action, based on the findings of a comprehensive plan, can ensure appropriate zoning and land use regulatory controls.75 Site-specific analysis, however, is needed to fine tune regula-tions protecting a water body or wetland resource from development impacts. Conditional use and special permits provide this fine tuning through ad hoc and site-specific analysis.76

This illustrates one of the greatest challenges faced by local governments in their protection of natural resources from carrying capacity thresholds. Legislative actions are presumed valid and courts [*PG605]have treated legislative acts with great deference,77 but legislative actions, precisely because they are sweeping and general, are less likely to reflect the particular characteristics or nuances of a natural resource.

For example, the city council could pass a city-wide carrying capacity regulation that limits nitrogen contributions to groundwater to five parts per million. But this broad action is likely to ignore unique attributes of one portion of the city’s aquifer system or ignore specific land uses within one wellhead protection area versus another. Site-specific issues should not be addressed by sweeping legislative action; they should be resolved through adjudicative proceedings because conditional use and special use permits allow for specific variations in geology or land use proximate to the natural resource.

B.  Adjudicative Actions

As discussed above, local governments can use legislative actions to establish appropriate use requirements and minimum lot sizes, but legislative actions are generally too “clumsy” to both protect natural resources and ensure that carrying capacity thresholds are not exceeded.78 Adjudicative permits79 cure this shortcoming because a municipal board or agency can fine tune a development application to ensure that the carrying capacity of an affected resource will not be exceeded.80

Adjudicative permits must be used with caution and in accordance with rules clarified by a recent host of cases. First, permit con[*PG606]ditions, known as extractions, must relate to the harm posed by the new or expanded development.81 A nexus between the permit and the harm has always been an integral piece of substantive due process requirements and was last reaffirmed by the Supreme Court’s decision in Nollan v. California Coastal Commission.82 Under Nollan, the permit granting authority must ensure that the permit’s conditions directly relate to the harms posed by the new development to an identified built or natural resource.83

Second, the permit conditions must also be proportional to the harm posed by the new or expanded development.84 As with the nexus requirement, proportionality has been historically based on substantive due process.85 It received renewed public attention in Dolan v. City of Tigard when the Supreme Court required the permit granting authority to ensure that a regulation satisfies the nexus requirement and that a regulation imposes conditions proportional to the likely impacts.86

Finally, these tests will always apply when real property is surrendered and may apply when public benefits are required in addition to fee simple (or less than fee simple) dedication of real property.87 As a conservative recommendation, adjudicative boards should apply the standards developed in Nollan and Dolan to all extractions under a carrying capacity regulation.88 For example, if the carrying capacity of a water resource will be exceeded unless the development density of a proposed project is reduced by 15%, the adjudicative body could re[*PG607]quire that the proposed development be reduced by 15% of its housing units without violating the standards in Nollan and Dolan.89 First, the required reduction has a substantive basis, as required by Nollan, because the reduction is directly related to the harm posed by the development to the water resource.90 Second, the 15% reduction mandate is based upon analytical and defensible findings and represents no less than the reduction needed to preserve the resource. Thus, the requirements are proportional to the harm.91

Some commentators may argue that the nexus and proportionality requirements do not apply because an extraction is not real property. That argument, however, is risky.92 It would be safer to analyze the relationship and extent of the extraction to the carrying capacity regulation relative to the harm the community seeks to minimize, rather than focusing on whether the extraction was land, money, or off-site improvements.93


This article asserts that all built and natural resources have definable carrying capacities beyond which the resource degrades to an unacceptable level. In the case of built resources, the road, treatment plant, or facility fails to function as designed. In the case of natural resources, the environmental system exhibits substantially adverse effects from human activities.94

[*PG608] Local governments have the ability to ensure that their built and natural systems do not exceed their respective assimilative capacities. A variety of both regulatory95 and non-regulatory96 tools are available to municipalities to implement carrying capacity regulations. If properly adopted and applied, these tools will be both legally defensible and extremely valuable in the protection of built and natural resources.

Perhaps the most important characteristic of carrying capacity limitations, however, is that they reflect the admission by local government residents and officials that their resources have limits. A corollary admission is that once the carrying capacity of certain resources has been exceeded, financial investments may not provide an adequate remedy.97 The “fix” has come too late and was clearly avoidable. It was avoidable by adhering to a plan for growth, which matched the limitations to growth, in the municipality and region.

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