Landscape ecology: Its role as the scientific underpinning of land-use planning
One of the greatest challenges for landscape ecology, and an area of pressing concern, is the incorporation of landscape ecology principles into land-use planning. In Europe, landscape ecology is already well-integrated into land-use planning, and “is presently viewed in Europe as the scientific basis for land and landscape planning, management, conservation, development, and reclamation,” according to Naveh. Indeed, Troll coined the phrase “landscape ecology” when studying problems of land use and development in East Africa, and the discipline emerged from there. Despite it distinct train of thought, the American school of landscape ecology now seeks to encompass the human component of spatial patterning, which has been more characteristic of European landscape ecology.
Development of land and land-use change
The increased rate of land transformation through anthropogenic influences demands attention. As communities throughout the country grapple with growth pressures and environmental degradation brought about by consumptive land use, landscape ecology is considered to provide essential tools for better decision making. Turner remarks,
Estimation of the cumulative impacts of disturbances in a landscape is important for protecting sensitive habitats or environmental quality...impacts of anthropogenic disturbances may have substantial time lags; furthermore, the total areas influenced by both direct and indirect effects can greatly exceed the area of planned development. This suggests a strong need for comprehensive landscape planning through the use of current technologies (e.g. geographic information systems) to address such cumulative or synergistic disturbance effects.
The incorporation of landscape ecology principles into land-use plans may mitigate the effects of land conversion by guiding such transformation in an ecologically appropriate direction. Linehan notes that a “lack of firm theoretical and methodological understanding of landscape ecology within the planning and design professions is partly responsible for the failure to address adequately the role of regional biodiversity within the planning community”. The insight that landscape ecology provides is the spatial perspective that reveals ecological interconnectedness. Presumably referring to the situation in North America, Turner explains that "Ecologists, land managers, and planners have traditionally ignored interactions between the different elements in a landscape - the elements are usually treated as different systems... the landscape (like many ecological systems) represents an interface between social and environmental processes”. Likewise, Forman asserts, “Landscape and regional ecology provides spatial solutions useful in addressing all of society's land-use objectives.” Landscape ecologists recognize the pervasive transformation of land by human activities and work to understand the resulting “mosaic” of natural and human-managed patches varying in size, shape and arrangement. One of the main concerns centers on the effects of habitat fragmentation as both loss of habitat and habitat isolation. Further, due to the interconnectedness of ecological processes, "The long-term maintenance of biological diversity may require a management strategy that places regional biogeography and landscape patterns above local concerns".
Along these lines, landscape ecology has developed an important role in describing and assessing land transformation and the anthropogenic land-use change that causes it. Landscape change obviously affects spatial pattern and ecological processes. The drivers of land transformation—which all increase habitat loss and isolation yet impose their own unique alterations on the landscape—include perforation, dissection, fragmentation, shrinkage, and attrition. Forman explains that:
- Perforation is the process of making holes in a habitat or land type,
- Dissection carves up or subdivides an area using equal width lines,
- Fragmentation breaks an unit into pieces (often widely and unevenly separated),
- Shrinkage obviously decreases the size of landscape, and
- Attrition indicates a subject's disappearance.
These happenings aggregate into a series of events, also known as a mosaic sequence, which is a continuum of spatial patterns over time. Forman describes five sequences that break up spatial patterns. An edge happening occurs when a new land type spreads unidirectionally in parallel strips from the edge, whereas a new corridor bisects initial land types at the outset and expands outward on opposite sides. A nucleus sequence involves a radial spread from a single point and leaves a shrinking ring of original land type. A related occurrence, termed "nuclei", entails growth of land disturbance from a few nuclei, which produces new land type areas expanding radially toward one another. A dispersed series takes place when widely dispersed new patches rapidly eliminate large patches of the initial land type. These processes of change describe how land converts from one state to another. With changes in spatial patterns, ecosystemic structure and function alter. Landscapes are comprised of ecosystems, which themselves are made up of specific structural and functional relationships. Ecological conditions differ between the center and edge of landscape. Landscape boundaries are usually abrupt due to patchiness, natural disturbance, and human activity. Consequently, changes in spatial structure lead to modified ecological processes.
Essential Landscape Configuration
Forman argues that there are essential elements for any land-use plan; namely, "Top priority patterns for protection, with no substitute for their ecological benefits, are a few large natural-vegetation patches, wide vegetated corridors protecting water courses, connectivity for movement of key species among large patches, and small patches and corridors providing heterogeneous bits of nature throughout developed areas". According to this viewpoint, large natural vegetation patches constitute the only structures that sustain viable populations of inland species and allow near-natural disturbance regimes. They provide core habitat and escape routes for large home range vertebrates. They constitute such an important part of the landscape, in fact, that Forman states "a landscape without large patches is eviscerated, picked to the bone”. Small patches provide means for species dispersal or recolonization and protect scattered rare species. In other words, small patches offer benefits through provision of heterogeneity but do not replace the fundamental role of large patches. Indeed, Forman presents the "aggregate with outliers" model as a theoretical approach to addressing the problem of patches and spatial heterogeneity. Accordingly, "Land containing humans is best arranged ecologically by aggregating land uses, yet maintaining small patches and corridors of nature throughout developed areas, as well as outliers of human activity spatially arranged along major boundaries". This model promotes the distribution of small patches of all types of human land use as well as small patches of natural vegetation and corridors in order to enhance development of genetic diversity and permit risk spreading across disturbances.
Incorporating ecological design into land-use planning
Calls in the United States for the incorporation of landscape ecology principles into sound, sustainable land-use planning go largely unheeded. Landscape ecologists need to communicate principles of spatial pattern and consequences of heterogeneity to land-use planners, who need to incorporate them into designs. This can happen in several ways, as outlined below.
Greenway corridors have been popular in American landscape design for decades and represent one of the connection points between land-use planning and landscape ecology. As preserved corridors that protect the environment and provide opportunity for outdoor recreation, greenways provide a well-established tool for protecting environments through spatial heterogeneity. Beyond their traditional use by land planners, greenways are now considered important to ecological structure and function. According to Linehan, greenways address the "need...for methods that make the link between ecological structure and function at broad spatial and temporal scales in both basic and applied research". Greenways incorporate conservation measures through elements such as "A wildlife corridor system that protects regional diversity [, which] should be at the forefront of the greenway planning process and could serve as the skeletal framework of a regional greenway system".
Greenways could also help control community development patterns. Municipal zoning regulations often dictate and/or invite fragmented and sprawled development patterns and are usually completed prior to open space planning. This set up fails to protect undeveloped open spaces, community identity, and biodiversity. Greenways offer a means through which to connect undeveloped patches or provide corridors thereby restoring some degree of ecological interconnectedness. Increased population and subsequent land conversion frame one of the most contentious public issues in the intermountain west today. One group of researchers reported on efforts to implement a greenway design project in the Wasatch Front and Snake River Plain as well as land-use planning efforts in the Okanogan Highlands and Greater Yellowstone Ecosystem. The analytical questions asked were: What ecological principles did planners implement (or attempt to)? How do planning efforts based on landscape ecology principles differ from conventional? How do plans based on ecology differ from projected ideal results? What questions could researchers answer to help practitioners more effectively integrate landscape ecology into their work? Such work bridges scientific research and design practice.
Wildlife that move or disperse across landscapes, including large carnivores, face obstacles in the form of human encroachment and habitat fragmentation. These species require large tracts of land, which generally are not available, or corridors through developed areas and transportation networks in order to move from one area to another. Management efforts, though, are rarely in accord with biophysical scales. Most protected areas are not connected with corridors and do not contain intact regional ecosystems. Protection or conservation of these species will depend not only on sound implementation of greenways, but on the incorporation of spatial pattern concepts into development and conservation plans. Good designs will require a regional reserve network of core wilderness areas, multiple-use buffer zones, and connectivity among them.
According to Noss, the use of landscape ecology principles in assessing landscape design results in "old questions about how large a single reserve must be, either to maintain species richness... or to maintain populations of particular target species... giv[ing] way to new questions regarding the optimal scale for the entire network of conservation lands, their relationships to surrounding lands, how lands in all categories are actually managed, and whether the overall management regime is capable of maintaining ecological integrity.” The demands upon land are so great that reserves will not be able to wholly encompass the range of large carnivores. Therefore, planners need to examine and incorporate buffer zones and the landscape matrix as a whole, as Noss describes: “a system of reserves linked by movement corridors will be a whole greater than the sum of its parts because, whereas no single reserve can support a viable population, a network of reserves may do so”. Travel corridors for wildlife increasingly consist of roads. Whether or not individuals of large carnivore populations can move safely through a landscape presents a difficult scientific and practical issue to the incorporation of connectivity. Likewise, wildlife must choose to use the corridors; researchers are studying species’ preferences for various types of corridors, including culverts and overpasses. Obviously, conservation must consider many different scales for assessing the adequacy of corridors.
Analytical tools and models
Geographic Information Systems (GIS) are the necessary tools for incorporating the scientific principles of landscape ecology into land-use planning. The question, according to Flamm, consists of how to model and measure "spatially explicit stochastic simulation" of land-use and land-cover changes in human influenced landscapes. The study examined pixel-based and patch-based GIS methods to review the difference in which scale change each method simulates.
Another suggested dynamic model, named CLUE (Conversion of Land Use and its Effects), simulates pattern change in space and time from biophysical and human drivers. Currently, modelers only use biophysical approaches, so this model attempts to incorporate social science considerations, which profoundly influence land transformation through land-use change. (Land-use change, in fact, drives land conversion.) The biophysical elements used are: biophysical suitability and fluctuation; land-use history; spatial distribution of infrastructure and land use; and pest and disease occurrence. Human land-use drivers are population size and density; regional and international technology levels; level of affluence; target markets for products; economical conditions; attitudes and values; and applied land use strategies. The model assesses regional needs and then makes final land-use decisions on a grid level GIS.
No conclusions on land-use change can be drawn from these models; they simply represent development of tools to model this change.
Despite it distinct train of thought, the American school of landscape ecology now seeks to encompass the human component of spatial patterning, which has been more characteristic of European landscape ecology. As Linehan explains, landscape ecology principles lend themselves to sound conservation: "Once we change our focus from rescuing isolated critical habitat areas to insuring overall ecological integrity, the connection between patches becomes as important a parameter as patch size, shape, and type. Although a corridor network should not be seen as the end-all solution to conservation problems, it can be a cost-effective complement to the strategy of large multiple reserve systems". Noss notes that some biologists and many politicians are ready to replace all wild lands with open, multiple-use lands, employing the assumption that humans have knowledge and technology to manage ecosystems wisely. While landscape ecology provides many keys to proper land management, it certainly does not yet provide all answers. Those indications the discipline does provide suggest that large patches of natural vegetation cover are necessary to the proper functioning of ecosystems and we would be remiss to let them all suffer conversion to human land use.
- Arnold, G.W. 1995. Incorporating landscape pattern into conservation programs. In: Mosaic Landscapes and Ecological Processes. Chapman & Hall, New York.
- Bienen, L. 2007. Wildlife crossings relink habitat. Frontiers in Ecology and the Environment 5(5): 234.
- Clark, T. P., P. Paquet, and A.P. Curlee. 1996. Large Carnivore Conservation in the Rocky Mountains of the United States and Canada. Conservation Biology 10: 936-939.
- CLUE: Conversion of Land Use and its Effects.
- Flamm, R. O. and M.G. Turner. 1994. Alternative model formulations for a stochastic simulation of landscape change. Landscape Ecology 9: 37-46.
- Forman, R.T.T. 1995. Some general principles of landscape and regional ecology. Landscape Ecology 10: 133-142.
- Linehan, J., M. Gross, and J. Finn. 1995. Greenway planning: developing a landscape ecological network approach. Landscape and Urban Planning 33: 179-193.
- Naveh, Z. and A.S. Lieberman. 1994. Landscape Ecology: Theory and Application. Springer-Verlag, New York.
- Noss, R.F., H.B. Quigley, M.G. Hornocker, T. Merrill, and P. Paquet. 1996. Conservation biology and carnivore conservation in the Rocky Mountains. Conservation Biology 10: 949-963.
- Ryder, B.A. 1995. Greenway planning and growth management: partners in conservation? Landscape and Urban Planning 33: 417-432.
- Saunders, D.A., R.J. Hobbs, and C.R. Margules. 1991. Biological consequences of ecosystem fragmentation: a review. Conservation Biology 5: 18-32.
- Turner, M.G. 1989. Landscape ecology: the effect of pattern on process. In: Annual Review of Ecology and Systematics 20: 171-197.
- Veldkamp, A. and L.O. Fresco. 1996. CLUE: A Conceptual Model of Study- the Conversion of Land Use and its Effects. Ecological Modelling 85: 253-70.