Changes to an ecosystem can reach a critical point where they cause dramatic reductions in SPECIES populations or shifts from one biological community to another over a very short period. This THRESHOLD response is the point at which the habitat loses its ability to support species populations at optimum levels. Abrupt declines in populations may be difficult to predict because problems may not be evident until a key threshold is reached or exceeded. Threshold responses can be caused by human-triggered events such as POLLUTION; HABITAT loss, conversion, or FRAGMENTATION; and overuse of land and water resources. Exercising caution in land use decisions is important because approaching thresholds are not always apparent—nor are their triggers.

Five basic scientific PRINCIPLES summarize the essential aspects of healthy, functioning ecosystems: the Time Principle, the Species Principle, the Unique Place Principle, the Ecological Processes Principle, and the Landscape Principle. These principles, which are detailed below, have been adapted from research by the Ecological Society of America.

The Time Principle

Today's species, habitats, and ecosystems developed over thousands of years; therefore, future species, habitats, and ecosystems will be influenced by decisions we make today. Because the full ecological consequences of decisions we make now may not manifest for many years, our land use decisions must consider potential long-term impacts.

The Species Principle

Because species have specific roles in an ecosystem, they can help us understand its function and health. Species are connected through such processes as predation, competition, and pollination. Native species are organisms that have evolved in a particular place as part of an ecosystem. Non-native or exotic species have evolved in other ecosystems and have been introduced here deliberately or accidentally. They can wreak havoc on native ecosystems by disrupting the delicate balance of native species or by spreading diseases.

The Unique Place Principle

Ecosystems, habitats, and species evolve in a specific place. Not only is their evolution related to local climatic, geologic, and hydrologic conditions, but it is heavily influenced by species interactions and natural processes. These factors create distinctive landscapes that are visually recognizable and have unique qualities and conditions-for example, the Colorado Plateau differs distinctly from the Sonoran Desert. Understanding the natural patterns within ecosystems and habitats is critical to the long-term, ecologically sound use of land.

The Ecological Processes Principle

Natural ECOLOGICAL PROCESSES-biotic, physical, disturbance, and cultural-help determine how an ecosystem functions. Biotic processes include the conversion of solar energy into plant material, physical processes include the infiltration of rainwater to underground AQUIFERS, and disturbance processes include natural wildfires and floods. Cultural processes, on the other hand, involve human manipulation of the environment for human benefit, such as managing game species.

The Landscape Principle

Ecosystems occur within landscapes and interact in varying ways depending on their size, shape, and location. Consequently, the landscape context is important to the interactions, connectivity, and diversity of habitats and species. Larger habitats generally support a greater diversity of species than smaller habitats of the same type. Significant increases in the distance between habitats can alter or destroy interactions and cause species loss. Connectivity between habitats is considered a threshold dynamic-that is, gradual changes typically have gradual effects until a certain threshold is passed. At that point, effects are dramatic and may be irreversible.

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The following guidelines, which are adapted from research by the Ecological Society of America, link CONSERVATION science and LAND USE planning. They form the basis of the GOALS and POLICIES that appear in each ELEMENT of the Comprehensive Plan-in fact, many of the plan's policies contain specific references to relevant conservation guidelines, and almost every policy relates to one of these guidelines. For some Elements-Land Use and Growth, in particular-all eleven guidelines apply because their policies address the broadest possible spectrum of planning issues and land use decisions. For the Public Safety Element, which mainly addresses the County's role in providing safety services, only a few guidelines apply because these services typically do not impact natural resources. Some natural resources, such as water, are more subject to cumulative impacts (which conservation guideline K covers), while others, such as ENVIRONMENTALLY SENSITIVE LANDS, are subject to HABITAT FRAGMENTATION (which conservation guideline E covers).

The County's role in implementing the Comprehensive Plan involves applying conservation guidelines A through K to land use decisions, particularly when evaluating the anticipated impacts of proposed developments. While each site and situation requires a unique planning approach, these guidelines offer us a predictable, systematic means to enhancing our environment (both natural and built) and avoiding, minimizing, or mitigating the negative impacts of development. These guidelines are especially useful to County planners when conducting preliminary assessments for proposed projects.

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Although scientific knowledge is useful, it does not always provide clear, certain, and timely answers to important questions about potential environmental impacts. When certain activity threatens human health or the environment, precautionary measures should be taken regardless of whether all cause-and-effect relationships are fully established. This Precautionary Principle recognizes that our understanding of ecosystems is complicated by many factors. Our overall goal is to prevent harm-not to prevent progress. In some instances, we must simply make a "no regrets" decision. In doing so, our decisions should be based not only on the best available scientific information, but also on sound professional judgment and open discussion of both the long-term advantages and consequences.

Ultimately, we need a decision-making framework that minimize risks to people and the environment. Likewise, we can also benefit from a conservation-based planning methodology. Although science cannot always provide definitive answers to land use and development decisions, we can-and should-commit to good planning, collaboration, and foresight. The INTEGRATED CONSERVATION DESIGN methods described below offer us an important set of tools for creating quality developments as communities continue to grow.

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This Comprehensive Plan advocates a system of land use planning that reverses the trend of consumptive sprawl. The best methods for achieving this goal involve INTEGRATED CONSERVATION DESIGN, a conservation-based approach that offers a wide range of options for developments featuring large parcels of land. Integrated conservation design does not negate the rights of private property owners-it simply offers expanded, more flexible options for development.

Conventional Design Differences

Conservation-based planning differs from the "standard development grid" in two key ways. First, it offers protection for ENVIRONMENTALLY SENSITIVE LANDS-WETLANDS, RIPARIAN AREAS, steep slopes, and wildlife HABITAT. The value of such environmental amenities is evident from the high percentage (40 percent) of people who purchase golf-course lots even though they don't play the game ; these buyers want the OPEN SPACE views associated with such properties. Second, conservation-based planning often integrates recreational amenities such as sports fields and playgrounds into new subdivisions, benefiting entire communities. Imagine a property featuring FOREST-LAND and an open meadow that provides important wildlife habitat. Conventional development approaches advocate dividing it into individual lots and scattering houses throughout. Integrated conservation design, on the other hand, advocates tucking the houses into forested areas but leaving the meadow UNDEVELOPED. Likewise, if the property contains a wetland or FLOODPLAIN, conservation-based methods would place any buildings outside of these areas, leaving valuable habitat, open space, or other amenities that all property owners could enjoy.

The process for developing a property using integrated conservation design methods also differs from conventional development processes. In Coconino County, a parcel's ZONING determines its permitted density-that is, the number of units allowed "by right" within in a specified area. Developers and engineers typically begin the design process by drawing roads and lot lines on a map. In contrast, conservation-based planning advocates identifying environmentally sensitive areas before identifying the most suitable building sites based on factors such as the allowable density and the natural features of each parcel. The next design step entails aligning streets and TRAILS. The final step is drawing lot lines.

Options & Incentives

Integrated conservation design methods vary. One approach involves "clustering" development on portions of a property that are not environmentally sensitive and allowing the same net density that would be permitted with a conventional design. This approach not only reduces infrastructure costs, but it also lowers building costs, which are typically more expensive in areas such as floodplains and wetlands.

Another alternative is TRANSFERRING DEVELOPMENT RIGHTS to a portion of the property or to an entirely different property. Yet another design approach features dispersed clusters of home sites each with a designated "building envelope," or the space in which structures are permitted to be built. In this scenario, the land surrounding each site, plus all other undeveloped land, is held in common by all owners for conservation purposes. The home sites are strategically located to minimize impacts on the environment. Many other scenarios are possible; planners should work with property owners and developers to explore creative designs that best apply to a particular area or site.

We also have many possible tools for encouraging the use of integrated conservation design in new subdivisions. One is amending ordinances so they no longer require a zone change when developers want to "cluster" units into a smaller area than what would be permitted under existing zoning. For example, consider a 100-acre parcel with a zoned minimum parcel size of 2½ acres for 40 lots. In this scenario, these 40 lots could be reduced to 1 acre in size and clustered together within an area that takes advantage of a major viewshed or other natural feature, leaving 60 acres of open space.

Another approach for encouraging conservation design is to offer an incentive in the form of a DENSITY BONUS for including open space in a development. If 50 percent of our previous 100-acre example is set aside as open space (preferably for public access and use), perhaps the number of units could be increased by 20 percent; if this conservation setaside covers 60 percent of the property, the density bonus could be increased to perhaps 40 percent. The details of such amendments would be worked out with citizen input through the public hearing process that is requisite for all ordinance amendments.

Design Applications

Integrated conservation design applies to a wide range of development projects, not just to low-density, high-end subdivisions. Two good examples of successful conservation design for moderately priced homes are found in Doney Park, where zoning density was increased to accommodate open space. Integrated conservation design could also work well for manufactured homes. Regardless of the type of development, integrated conservation design lets landowners maximize the use of their properties while offering the fundamental advantage of protecting a network of conservation and open space lands throughout the county.