Alternative Futures for the Region of Camp Pendleton
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Landscape Ecological Pattern
The focus of landscape ecology is the spatial relationships between structural and functional elements of the land. Any type of landscape at any scale can be described as a mosaic: a background matrix and patches connected by corridors. For instance, a matrix can be uniform to fragmented, continuous to perforated, and aggregated to dispersed. Patches can vary from large to small, elongated to round, and convoluted to smooth. Corridors vary from wide to narrow, and meandering to straight. The edges that separate these spatial elements also vary widely in shape and dimension.
The following elements form the landscape ecological pattern in the study region:
- Contiguous natural vegetation: areas larger than 500ha which currently form the pattern matrix and the principal source of biodiversity;
- Isolated natural vegetation: areas less than 500ha which form natural patches and stepping stones surrounded by disturbed or built landscape;
- Natural edges: a 90m wide band that extends into the contiguous and isolated natural vegetation from disturbed areas;
- Stream corridors: linear features up to 90m across which can connect patch elements;
- Disturbed landscape: primarily agriculture and military impact zones, which have repeatedly disturbed vegetation;
- Built landscapes: all urban land and roads;
- Water.
The evaluation of the landscape ecological pattern presents a hypothesis that there are spatial landscape patterns that will conserve the majority of natural processes in any landscape or major portion thereof. These patterns will not protect every species, every nutrient concentration, or every water body, but conserving the spatial pattern will maintain the most important attributes of the ecosystem. Evidence found over the past several years in the fields of landscape ecology, conservation biology, forestry, and others suggest that spatial pattern is an integral factor in natural processes (Harris, 1984, Franklin, 1993, Soule, 1987, Mefe and Carroll, 1994).
The patch-corridor-matrix model proposes that an ecologically viable landscape must contain four indispensable patterns to provide for critical landscape functions:
- Large patches of natural vegetation which protect the species richness of a landscape;
- Species movement connectivity between large patches in the form of wide corridors or clusters of small natural-vegetation patches;
- Vegetated corridors along major streams and rivers which allow for species movement and a wide range of ecological benefits not otherwise obtained such as erosion control, nutrients, and fish habitat; and,
- Small patches scattered across a less suitable matrix which provide key ecological benefits such as rare species habitats and stepping stones for movement.
The landscape ecological pattern in 1990+ is shown in figure 48. In the region of Camp Pendleton, the matrix is composed of several large natural areas, many of which include the Cleveland National Forest and other public lands. There are large concentrations of "disturbed-urbanized" land as well as areas of "disturbed-natural" land in agriculture and military use. The landscape still retains a set of natural patches and smaller "stepping stones," connected by stream and riparian vegetation corridors. These can (still) be the basis of a conservation pattern with links across the study region.
The landscape ecological pattern of Plans Build-Out is shown in figure 49. There will be two major consequences of this potential change. The first, which can be seen in the change bar chart in figure 50, is the large conversion of natural vegetation habitat into urban uses. About 90,000ha of riparian corridor habitat is threatened, and these are the most significant elements contributing to the connectivity of the landscape ecological pattern. The second consequence, which is perhaps of greater significance to the regionŐs biodiversity, is the inversion of the landscape ecological pattern of 1990+ from one of urban patches in a large well-connected natural matrix to a future pattern of fragmented natural patches in an urbanized matrix. All aspects of biodiversity that currently rely on larger interconnected natural habitat will be diminished.
The natural patches grouped by size for 1990+ and Plans Build-Out are shown in figures 51 and 52. Figures 53 and 54 represent analysis conducted on the entire study area. The changes indicated in the bar charts show a dramatic drop in natural cover, from 65% to 40% of the total area. "Built" areas increased from 10% of the region to 40%.
The structural composition of the natural area has also changed. Significantly, the area of extremely large natural patches (>10000ha) in 1990+ is halved by Plans Build-Out. These large patches, which form the matrix of the landscape, are particularly important to the long term viability of many species. In addition, the remaining natural landscape is much more fragmented, consisting of smaller patches with a greater percentage of human influenced edge. The amount of edge, as expressed as a percentage of the total natural area, has increased, thereby reducing the important interiors of natural patches.
Naturally vegetated stream corridors are also shown to be at great risk. Up to 40% of the corridors present in 1990+ are threatened in the Plans Build-Out. This has important implications both to water quality and to connectivity of the landscape. The changes to the natural landscape in terms of total area, patch size class distribution, fragmentation and edge conditions all have serious negative ecological consequences.
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