Aucklands North Shore - Landscape Ecology Health Assessment

Landscape ecology health assessment

“The study of landscape pattern on process, in heterogeneous landscapes, across a range of spatial and temporal scales”

LANDSCAPE ECOLOGY ASSIGMENT 1

LPSC6401

Ryan Aldrich

12/05/2011

Aucklands North Shore

Ryan Aldrich

Ryan Aldrich

- Introduction Landscape ecology, a case study of ecological health

This report aims to determine the ecological health of an extent of land. It identifies patterns of ecosystems in the landscape, investigates the degree of heterogeneity,

and measures some indicators of processes relating to patterns and heterogeneity as well as the associated assumptions made. This report will estimate the ecological

health of the ecosystems.

The area of study is centred slightly above Albany which is located on the North Shore, Auckland, New Zealand.

This report is an exploration into Landscape Ecology. Therefore as prefix to investigation it is important to explain and define landscape ecology and the

underlying theory to this report. Landscape ecology is the study of the effect of landscape pattern on process. This study ranges across a range of spatial

and temporal scales. Heterogeneous landscapes are the backdrops for the investigations of landscape ecology. Landscape ecology is an interdisciplinary science

incorporating Biophysical and analytical approaches through both holistic and humanistic perspectives. Examples of ecological process are those such as

dispersal, intensification, growth, ect while further explanation of spatial could be space and area. The temporal scale is that of time. Heterogeneous meaning

“composed of unrelated or differing parts or elements” (Collins English Dictionary, 2003) Scales range from coarse grained which views the wide landscape,

region, country. Fine grained scales are also examined; these are small or local examples being a farm or subdivision. Landscape pattern is the relationship

between objects. Landscapes pattern implies that landscapes are heterogeneous or patchy.

“The underlying premise of this discipline is that the explicit composition of, and spatial form of a landscape mosaic affects ecological

systems in ways that would be different if the mosaic compotation or arrangement were different” (Wiens, 1995)

Wines states there are variations on how one can observe spatial pattern. There are two ways to introduce complexity and realism into

views of nature. The first approach is to view space as heterogeneous. This disregards spatial patterns. Another approach is to view

spatial pattern as non-homogeneous. “Perhaps the simplest view of spatial pattern is that of patches set in a background matrix, akin to

island in a featureless sea.” (Wiens, 1995) Rather then conceptualising landscapes as islands in a sea of no habitat. A patch, corridor and

matrix model developed by Forman views nature is a mosaic of homogenous patches that form the basic unit of landscape Ecology.

(Lindenmayer & Fischer, 2006) This model will be adopted for this report.

-Method The presiding text sets out the task and underlying theory of this report. The method for the analysing the

ecological health of the site based in the creation of GIS maps which identify landscape pattern associated with

ecological health. These maps and the connection between map and pattern will be based, and derived from

ecological theory. The theory forming the maps will be explained along with assumptions and limitations being

discussed. The last Map will be an overall health map. This will be formed by compiling and averaging the data

forming the maps previous to it. Discussion and conclusions will follow. While creating maps in GIS field trips

were taken to ground truth the data. These Filed trips involved the collection of data. This data mostly is

related to process. Unfortunately there are many limitations and uncertainty of data. Such as sample sizes not

being broad or large enough. Therefore this data has only been included in the appendix.

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Land Cover

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- land cover

The investigation starts with the creation of a land cover map. Land cover is the physical material draped over the surface of the earth. Examples of land cover are grass, asphalt,

trees, ect.

The land cover map displays distinctly the areas of urban development, native vegetation, pasture, exotic planting including forestry and estuarine water. I Used colour ramps to

display similar types of land cover with similar colours.

This map clearly shows urban build up at the top of Albany and along the coast. As you move west land cover shifts to native plantings, further west and also north is pasture. The

west most region is a hosts large pine forest block.

As percentages the most dominate land cover is grass land, this is followed by built up urban areas, pine forest grouped with regenerating/ed bush, and native vegetation respectively.

+ Land cover GIS data is provided by the Auckland City Council. This data classifies space into a range of land cover categories.

Assumptions and limitations

This data quantifies and averages complex systems before categorising. During this process of simplification data may losses detail which may hold valuable information for

analysis.

Relevant data may get rounded away.

Nature is not static. When analysing through GIS it is important to ground truth information. The landscape changes over time and data may be outdated. An area displayed as native

vegetation may in fact be the new footprint of a subdivision, or motorway. Limitations can be reduced by comparing land cover data and high resolution satellite or Arial

photography. However this has its own limitations.

“The analysis of data from high spatial resolution satellite sensors has potential in land cover monitoring. In this paper, a post-classification method is used to detect land cover

change from multi-temporal satellite data” (Xiuwan)

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Patch Corridor Matrix

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-patch corridor matrix As established in the introduction patch corridor matrix is a way of viewing landscape.

Landscape pattern arises from fragmentation, local uniqueness, and stage of succession, dispersal strategies of organisms, human activities,

disturbance regimes, presence / absence of keystone spices. The patch corridor matrix model is used to analyse pattern.

“The model places focus on geographical composition of landscapes with the different components having different characteristics shapes and functions.” (Wiens, 1995)

There are essential 3 main categories in the model. Patches are different from their surroundings they are relatively homogeneous nonlinear areas. Corridors are links between patches, they relatively

homogeneous differing from the adjacent land on both sides and their surroundings. The final component is the matrix. This is the background land. It is dominant and most extensive. The patch corridor

matrix model has been widely adopted. (Wiens, 1995)

“It is an extension of the island model, which often oversimplifies landscapes into areas of habitat and non habitat.” (Lindenmayer & Fischer, 2006)

There are distinct effects that take place at the edge of patches. The interior of patches not affected are called cores. Effects that take

places on edges are both biotic and a-biotic. (Lindenmayer & Fischer, 2006)

This model was used to create the patch corridor matrix map. The following land cover types were identified for patches; indigenous forest,

broadleaf indigenous hardwoods, Manuka and Kanuka shrub-land, deciduous hardwoods, mixed exotic shrub-land, other exotic forest. The

following rules were applied; patches have a minimum size of 5 ha. Patches must have a core. The core is located 100m in from all boundaries.

If the area is less than 5 ha then the land is a corridor. However corridors must be longer then 200m and be no wider than 200m. The patches

were broken into small and large patches. Small patches having an area between 5 and 25 ha. Large patches have an area larger than 25 ha.

(Janssen, 2006)

Assumptions and limitations

Not all landscapes have sharply defined boundaries. Landscape boundaries are diffuse and differentiating them from the background matrix is not

straightforward. Landscapes with fuzzy geometrics resist Forman’s (1995) model. To deal with these conditions studies are beginning to

emphasize the importance of understanding the pattern of gradients in a landscape. Musick and Grover (1991) subjects that changes in gradient

structure in fuzzy landscapes can be explored using texture measures. (Issues and Perspectives in Landscape Ecology, April 2005)

For this report I have grouped both corridors and steeping stones as one. They are both displayed as corridors. This is as they serve very similar

characteristics. Both corridors and steeping tones aid and enhance ecological connectivity in the landscape. (Lindenmayer & Fischer, 2006)

Models can oversimplify ecological patterns.

Humans view nature and boundaries from a different perspective then different organisms.

Instances arise when creating maps of patch, corridor and matrix when land may easy be cut at different points. Therefore classification into the

basic landscape units will have opinion and perspective in the process. I tried to apply consistent perspective when creating the map.

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Connectivity

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-connectivity

“Good bush connectivity improves food source availability, mating opportunities and allows pollen and seed interchange between bush remnants.” (Janssen, 2006)

Connectivity of bush patches is a result of the distance between patches, the quality of the matrix, the availability of corridors or steeping stones. For example bush patches within

2km of each over present a more likely flight path for native birds. Native birds help with dispersal of plant species. The connectedness of many healthy native bush patches can

restore and maintain native ecosystems process and their long term resilience. To measure the connectedness of bush patches the Janssen’s bush vitality tables were used. In GIS

patches were buffered 2km, 5km, and 10km. Scores are given to patches based on the number of small and large patches within the buffered distances. (Janssen, 2006)

The connectivity map shows that the bush within the reports extent is strongly connected. All the patches scored excellent with a few scoring good according to (Janssen, 2006).

Assumptions and limitations

It is important to realise there is a difference between connectivity for individual species and human defined landscape connectedness of vegetation cover within a landscape.

There are barriers for animals that are not accounted for with a model based only on proximity. For example two patches may be close enough to score excellent however a multiple

lane motorway may run between them. This would severally limit connectivity for flightless organism. If this was taken into consideration perhaps my patches would score lower

for connectivity.

“Higher levels of landscape connectivity as perceived by humans will not always directly correspond to higher levels of habitat connectivity for a given individual species or vice

versa.” (Lindenmayer & Fischer, 2006)

This report has an extent to the study area. When assessing how many patches fall within a certain proximity patches on the edge of the extent are disadvantaged as no patches

outside the extent were studied. For example an edge patch might have poor connectivity with patches inside the extent however it may have excellent connectivity with patches

just beyond the extent which are not visible. My data however indicates that most patches scored excellent so this should not considerably affect the overall outcome of the report.

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This project will investigate ecological health by combing 5 sets of data. This data comprises of GIS maps of the

following topics connectivity, matrix health, patch hydrology, core ratio and patch heterogeneity. The following pages will

display these maps except the already mapped connectivity.

The ecological health maps and assessment is based on the large patches. Therefore smaller cores have been omitted

from the following maps unless they directly relate.

Connectivity + Matrix Health

+ Patch Heterogeneity

+ Patch Hydrology

+ Core Ratio

=

Ecological health

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Matrix Health

Ryan Aldrich Patch Heterogeneity

Heterogeneity

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Patch Hydrology

Ryan Aldrich Core Ratio

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-Prefix maps ecological health Matrix Health

The matrix health map was created by buffering the large patches by 200m. The matrix was examined within this constraint. Higher scores were awarded for bush surrounded by waterways, bush

corridors, small patches, and a high level of vegetation within the matrix. No or very little residential or urban development should be within the matrix. This concept is based on reasoning that

residential and urban environments have increase predication from domestic animals. They also severely fragment the landscape exposed open land is not suitable habitat for many species. An

example being small organisms on an exposed concrete site are vulnerable predators. More obstacles are introduced to connectivity with urban development. Property fences obstruct movement of

flightless organisms. Cars may be a danger to connectivity. Louder noises generated by people and our machines might scare organisms from certain areas (A scarecrow effect).

Patch Heterogeneity The patch heterogeneity map was created by examining the variety of land cover on each patch. Patches with more variation of land cover received higher scores. Emphasis was also placed on native

spices which received higher scores then patches of mostly exotic spices. Have a heterogeneous landscape provides more resilience. There is a wider range of habitat for organisms, adding to greater

biodiversity.

Patch Hydrology The patch hydrology map was created to analyse the water network connectivity to the sites. Patches formed along or patches with many

intersecting rivers or estuaries scored highest. This was based on Kichner (2003) he states riparian corridors offering effective habitat

connectivity for many species as well as contributing to ecological connectivity. (Lindenmayer & Fischer, 2006)

“riparian corridors may also act as dispersal routs for some terrestrial animals and facilitate seed dispersal in plants.” (Lindenmayer & Fischer, 2006)

Core Ratio The core to patch ratio map examines the quality of the patch of bush. A patch of bush has a core which features

different qualities then its edge. A-biotic effects on patch edges such as macrobiotic changes are evident. An example

could be changes in weather conditions such as humidity and light. Biotic edge effects are also evident. Examples of

this is weeds, and predators penetration a certain distances into the patch. (Lindenmayer & Fischer, 2006)

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-Ecological health The patch health map was created to summarise the ecological health of the extent in one

graphic. The health of the large cores is scored 1 to 5. This is achieved by compiling the large

patch data from the previous 5 maps. The previous 4 maps had rated their specific data on a

scale of 1 to 5. The scale placed a score of one as poor and 5 as excellent. The connectivity map

using the (Janssen, 2006) bush vitality assessment model used a score system between 1 and 14.

This was adjusted to be 1 to 5 so that data could be averaged from the last 5 maps with equal

waiting. This data was then displayed as a map using GIS

The patch health clearly shows the large patches within the extent of the report. The patches

all display ecological health scores that fall between 3 and 5 or between fair and excellent

respectively. Without considering the limitations or assumptions associated with this map it can

be stated that the ecological health of the extent is in a good condition.

However there are many limitations and assumptions to this investigation. The previous 4 maps

are very subjective. They are assessed visually rather than using an objective system.

There is also no waiting placed on particular maps. They all have equal influence on the

ecological health of extent.

Filed data and ground testing of GIS data was carried out however this was done at a

relatively small scale. This means that the data collected is not reliable. The report could have

been significantly strengthened by examining the ecological process and health from the field in

more depth, and quality. It would be interesting to analyse in the field a patch from each

category of health awarded. Then the correlation between field and this report’s GIS

outcomes could be reviewed.

There are many factors that influence ecological health that have not been investigated. This

investigation is limited by only using the approach of one model. The patch corridor model is

widely adapted however there are also contemporises to this approach. There is much writing

on subjects such as the variegation model. (Lindenmayer & Fischer, 2006)

The spatial approach to this report is very relevant. Maps such as core to patch ratio,

connectivity, matrix health directly relate to habitat size. This puts a significant percentage of

the overall health assessment based on habitat size. Access to suitable habitat is essential to the

survival of all species. (Lindenmayer & Fischer, 2006)

A large area of the extent features a soft matrix. This is the area to the west and north of

Albany. The land is mostly farmland featuring sprinklings of tress, bush corridors and patches.

This increases connectivity and in turn biodiversity. Habitat connectivity requires the retaining

appropriate vegetation cover throughout the matrix. (Lindenmayer & Fischer, 2006) The matrix

health map shows the matrix adjacent to patches as ecologically healthy.

To sustain or improve the current health of the landscape within the extent the following

strategies should be applied. The large and structurally complex patches of native vegetation

need to be maintained and restored. Maintenance and restoration of the matrix is also important.

The matrix should be directed so that it is structurally similar to that of native vegetation.

Sensitive areas should be identified. Buffers should be placed around these areas and they

should be maintained or restored. The corridors and steeping stones identified from this report

need to be retained. They should be maintained and or restored. Landscape heterogeneity needs

to be maintained or restored in areas where it is lacking. Land use intensities should be

distributed evenly across a range of environmental gradients. (Lindemayer & Fischer, 2006)

In summary this report concludes the environmental health of the extent as good. However

there is a level of uncertainty to this conclusion as the investigation has many limitations and

assumptions.

Works Cited Collins English Dictionary. (2003). Collins English Dictionary - Complete & Unabridged 10th Edition.

HarperCollins Publishers.

Issues and Perspectives in Landscape Ecology. (April 2005). Cambridge Studies in Landscape Ecology .

Janssen, H. (2006). Bush Viality Assessment: growing common futures. Wellington: Rainbow Print Ltd.

Lindemayer, 2., & Fischer, 2. (2006). Managin Landscape Pattern to mitigate the decline of species and

assemblages.

Lindenmayer, D., & Fischer, J. (2006). Habitat Fragmentation and Landscape Change: An Ecological and

Conservation Synthesis . Island Press .

Wiens, J. A. (1995). Landscape mosaics and ecological theory. London: Chapman & Hall.

Xiuwan, C. (n.d.). Buy now Using remote sensing and GIS to analyse land cover change and its impacts on regional

sustainable development . International Journal of Remote Sensing , 107 - 124.

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Patch Scores

Appendices

Patch corridor matrix data

Tables for scoring

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-Appendices